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Message started by Steve H on 08/13/17 at 17:17:09

Title: What happened tensioner mods
Post by Steve H on 08/13/17 at 17:17:09

Curious about what happened with the different folks out hehre working on different tensioner mods.

How's Versy's seconday spring to allow a little more movement working out?

How's Batman's?? idea of no pawl and just letting the tensioner move? The only problem I might think of with this would be wear inside the tensioner bore since the tensioner isn't designed to move all the time.

Anybody else working on something?

Title: Re: What happened tensioner mods
Post by Armen on 08/13/17 at 18:09:05

I'm going to do a rod inside the spring that only allows the plunger to retract a certain amount. And remove the pawl.
I think no pawl and no other way of restricting movement would be a bad idea. The chain would try to become an oval as it gets thrown off the sprockets.

Title: Re: What happened tensioner mods
Post by batman on 08/13/17 at 23:40:31

Armen, the bottom of our drive final drive belts have slack in them (we twist them 90 degrees with thumb and one finger) how does that effect their performance ? all the tension is on the top of the belt .the cam chain is pulled over the cam gear by the drive gear on the main shaft with all the weight of the flywheel and alternator and is therefore under tension any time the engine moves from hitting the starter to WOT,the tensioner is merely picking up the slack on the back side of the chain which is still under tension (it's not flying around)and I believe if the main spring is strong enough to push the piston out it should be strong enough to act as a shock and prevent the chain from going oval coming off the drive gear .I believe it has for the last 11,000 of the 30,000+ miles I have on it to date,with about 90% reduction in chain stretch and no unusual wear on the guides thus far.

Title: Re: What happened tensioner mods
Post by justin_o_guy2 on 08/14/17 at 00:37:35

Going oval won't try to make it jump a tooth.
The spring doesn't keep the tensioner extended. It takes up slack when it's parked. The Pawl keeps the chain from
Going oval.

Title: Re: What happened tensioner mods
Post by Dave on 08/14/17 at 04:33:56

The big problem I see with having "no pawl", is what happens when the engine is at very low rpm.....the conditions that exist when you are starting the bike or it is coasting to a stop when you turn off the ignition. When the valve spring pushes on the back side of the cam lobe, it places a lot of force on the chain and will make the "backside" of the chain tight and the "front" side loose....there will be a lot of flopping around of the cam chain in those first or last revolutions.

Armen is correct that if you remove the pawl, you need to have something to limit how far the valve springs can pull on the chain at low speed.....and perhaps while running to keep the chain from coming off the sprockets - the existing spring is never called on to resist the forces of the chain, as the pawl does that. The spring pushes on the plunger and the pawl grabs another tooth when it can (perhaps too frequently), and I believe this likely happens at "startup" when the engine is cold.

I am very likely to try a "manual" tensioner this winter.......it should get me through until an updated design is completed by the "machinist" guys on this forum.

Title: Re: What happened tensioner mods
Post by norm92de on 08/14/17 at 08:25:33

I intend to do what Armen is planning. I only have 6K on my bike thus far but when the time comes removing the pawl and a suitable length of rod inside the spring which allows just enough back movement.

Batman seems to be happy with what he has done so far. His mileage seems to prove something!

Title: Re: What happened tensioner mods
Post by Dave on 08/14/17 at 10:06:16

2A2B36297D762021440 wrote:

If you remove the spring - but leave the pawl in place......the tensioner will likely stay at whatever setting you place it. Then when you feel the need to adjust it....a small tug will get another notch.

Title: Re: What happened tensioner mods
Post by batman on 08/14/17 at 11:05:53

Dave ,I don't believe the pawl will stay in place without the spring pressure,and I don't believe with the inertia of the drive shaft that the valve springs are strong enough to transfer slack to the forward part of the chain,under the conditions you state the main shaft is still spinning and therefore still driving the cam. the only time the slack could be transferred is when the engine is stopped, and only in a certain position .If this happens the slack is removed the next time the starter motor is engaged,while this may "snap" the chain ,(I have no indication of this ever happening ) how much damage can it cause compared to the chain being over stretched all the time,and knowing that the starter motor isn't even powerful enough to work all the time without a compression release.If people want to place a rod in the center of the spring to limit travel I see nothing wrong ,in fact it would limit the amount of slack tranfered to the front of the chain IF it happens.

Title: Re: What happened tensioner mods
Post by Dave on 08/14/17 at 12:08:40

56554059555A000C340 wrote:

Dave ,I don't believe the pawl will stay in place without the spring pressure.

If you leave the pawl spring in place - but remove the plunger spring.....the pawl will stay in place right where you set it. the orientation of the pawl and teeth will not allow the plunger to every go backwards. But without the plunger spring...there is nothing to push the plunger out any farther.

In the last bike I did I put a very weak spring in the plunger....that way it is not as "anxious" to grab another tooth on the plunger, and maybe the cam chain tensioner will allow a bit more time between adjustments.

Title: Re: What happened tensioner mods
Post by justin_o_guy2 on 08/14/17 at 12:56:56

I would like to hear from someone who is running a spring in the mount hole.
I'm hoping that slows down how fast the chain gets worn. If it works according to how I Think it will, when the Pawl catches a new tooth the spring will compress when the jug grows as it warms up, decreasing the tension on the chain.

Title: Re: What happened tensioner mods
Post by batman on 08/14/17 at 16:19:59

JOG,I believe you'll be waiting a long time. I don't think that idea is sound. Finding a spring of proper strength, in a size small enough to fit in the area, will prove almost impossible. The fact that the softer metal of the tensioner body has to slide back and forth against the mounting stud and the snap ring ,might also cause damage and metal grit entering the oil system.If the new spring is to weak the tensioner will be pushed back against the stud and act as it did ,if the spring is to strong,the pawl will advance ,but when the cylinder expands will the tension of the chain on the back side be strong enough to move the tensioner back ? If not ,there will be no gain either way.

Title: Re: What happened tensioner mods
Post by justin_o_guy2 on 08/14/17 at 16:48:07

It's been done.
Believe what you will.
Next time I'm in it, I'm doing it.
The spring has to be stronger than the tensioner spring.
The oval hole only needs to be elongated enough to let it move a bit more than the pitch of the teeth on the tensioner.

Title: Re: What happened tensioner mods
Post by batman on 08/14/17 at 18:58:06

I agree that it been done by at least one member ,but I've not heard that it has worked.I was once told "the proof is in the pudding" ,I've had 1mm of stretch in 10,000miles ,if you have the same results I'll be very impressed,and be asking if you have one for sale.good luck, and keep us informed.

Title: Re: What happened tensioner mods
Post by Armen on 08/14/17 at 19:13:25

What I did on our old SR500 racer was to convert the automatic tensioner to a manual one. Then I made a hole in the side of the cylinder about half way up the chain travel, on the rear (tensioned) side of the chain. I made a threaded bung and epoxied it over the hole in the cylinder.
This way, I had a way of 'reading' the cam chain movement as I was adjusting it, and could check it again when the motor was up to full running temp.
I just experimented until I found a good amount of slack when the motor was cold that would result in almost no movement when the motor was hot.
Have to take a look at the Savage and decide if the same idea will work.

Title: Re: What happened tensioner mods
Post by piedmontbuckeye on 08/15/17 at 15:16:17

455A5C5B4641704070485A561D2F0 wrote:

I did what you describe to my upgraded tensioner. The problem I had was finding a mount spring that was stronger than the plunger spring. I think that I did find one, however as I tested it on my make-shift fixture. When I installed it in my bike, I did do some pressure testing and it did allow the tensioner to go "backward" about .050" - the amount I elongated the mount hole.

I have had it installed now for over 3,000 miles and no strange anything. Bike runs perfectly.

Finally, I have not had the side cover off since installing it, so I can't attest to its effeciency.

Title: Re: What happened tensioner mods
Post by piedmontbuckeye on 08/15/17 at 15:22:03

56554059555A000C340 wrote:

Slightly disagree. I am not sure how the tensioner moving back and forth will create any such wear. Since the tensioner is under constant spring pressure from both sides, it is not just "flopping" back and forth.

Probably, if I had mine to do over, I would have thinned the tensioner mounting lug slightly - the same amount as the thickness of a washer that I would put on after the tensioner, but before the circlip just to make sure that the moving tensioner didn't work the circlip off the mount pin.

Next time I have cover off, I will do that.

See my previous post about what I did, and how it has worked up to now.

Title: Re: What happened tensioner mods
Post by justin_o_guy2 on 08/15/17 at 17:15:44

I think the OEM petcock internal spring will work great. Long enough to do at least two.

Title: Re: What happened tensioner mods
Post by batman on 08/18/17 at 16:41:27

The one factor about the way my tensioner is rigged is that the spring pressure applies the same constant force against the rear chain guard and thus the chain, no matter if the bike is stopped /running, cold /or at running temp, at idle or WOT .no other approach can claim the same ,there are to many variables .If I decided to make any change in my tensioner at this point it might be to add a second spring inside the present one to experiment with a bit more pressure and see if it causes more chain stretch. If one chooses to place a rod in the center of the spring ,how do you determine the length? Keep in mind that the guide is curved toward the chain ,but swings from a bolt at the top in an arc .If the chain places pressure on the guide as the motor warms ,in the direct center of the guide, the movement will be 4 times greater at the tensioner.

Title: Re: What happened tensioner mods
Post by piedmontbuckeye on 08/19/17 at 16:36:01

7D7E6B727E712B271F0 wrote:

I want to disagree here. I don't see how the "secondary" spring will vary pressure at all! It will remain constant better than when only the primary spring is used. The primary spring will reduce pressure over the long haul as the chain wears longer, because the spring will generate less and less pressure as it gets longer (Hook's law of spring rate).

On my test fixture, the factory primary spring took more and more pressure as I compressed it. Therefore, I had only to find a secondary spring that was stronger than the original spring had when it is fully compressed in the adjuster when the timing chain is new.

This means that any "back and forth" movement of the adjuster was only the amount machined into the mounting hole to make it a slot. I chose .050 elongation.

Title: Re: What happened tensioner mods
Post by batman on 08/19/17 at 17:24:48

How did you arrive at .050 ? How far is the guide pushed back as the cylinder heats up and the chain goes straighter? The force exerted on the center of the guide due to its curve(in toward the chain) is centered on the guide ,but the guide is bolted at the top and therefore the movement is 4 times greater at the tensioner ,is .050 enough or to much?Is your small spring being stronger than the main , going to increase stretch over time? 10,000 miles should tell.

Title: Re: What happened tensioner mods
Post by piedmontbuckeye on 08/19/17 at 17:32:24

5457425B5758020E360 wrote:

How did you arrive at .050 ?

By looking at the pawl's teeth spacing and just plain estimating as to how much movement I thought would be sufficient to counteract the heat/cold expansion of cylinder and head on the chain.

Title: Re: What happened tensioner mods
Post by batman on 08/19/17 at 18:01:01

Oh ,you guessed,(another variable), well I guess if I place a washer/spacer of 1 mm behind my spring I will have the same pressure I started with and again have the same result of 1mm of stretch in the next 10,000 miles, according to Hook's law of spring rate. Then again as I have not done this at 10,000 miles I have a decrease in spring pressure(slight) which means I may have even less stretch in the next 10,000 miles ,we shall see.

Title: Re: What happened tensioner mods
Post by Steve H on 08/21/17 at 04:42:48

Is that 1mm of stretch or 1mm of tensioner movement?

Title: Re: What happened tensioner mods
Post by justin_o_guy2 on 08/21/17 at 05:06:33

It's not easy to envision the cycle of wear the oem design causes, but I'll try to describe it, and then the way the spring mod changes that dynamic.

The jug grows when it warms up. The chain has only the flex in the guides to Give a little, and the tensioner won't give any. The tension wears the pins, stretching the chain. The tensioner spring is always trying to get another tooth, keeping slack outta the chain.
One day, after a ride, it cools down, jug shrinks, and click, the Pawl gets the tooth.

Now, if the whole tensioner was being shoved into the chain hard enough to keep the tensioner spring from being able to make that happen, then the Pawl doesn't catch a tooth and the next warm up cycle, instead of the chain being tortured, it just compresses the end spring.

Title: Re: What happened tensioner mods
Post by Steve H on 08/21/17 at 15:41:38

No chain should ever be stretched tight as it will go. There should always be certain amount of slack.

Look at the drive chain on anything as an example...Have you ever seen instructions that told you to tighten it absolutely as tight as possible?

I have seen instructions that state overtightening will cause the chain to wear faster.

I don't know but I'd imagine that super high chain tension isn't too good for the aluminum bearings either.

Any cam bearing inserts out there that would work to have the head machined for them when the bearing surfaces are messed up?

Title: Re: What happened tensioner mods
Post by justin_o_guy2 on 08/21/17 at 16:37:04

Nobody has found any.

Title: Re: What happened tensioner mods
Post by piedmontbuckeye on 08/25/17 at 14:27:08

6F6C79606C6339350D0 wrote:

I wouldn't call my process "guessing." All the tensioner needs is a little of "back-up" room when engine warms up to allow it to not be forcing the chain all the time.

Title: Re: What happened tensioner mods
Post by batman on 08/25/17 at 15:45:10

Ok, let's call it hoping ,but the truth is you don't know if the tension placed on the chain when the motor warms is even placing enough pressure, at a right angle ,to move the entire tensioner and compress the new spring.

Title: Re: What happened tensioner mods
Post by justin_o_guy2 on 08/25/17 at 16:07:23

Do you understand what a calculated best guess is? Why do you need to pretend it's stupid? What if a genuine engineer said it looked viable?

Title: Re: What happened tensioner mods
Post by piedmontbuckeye on 08/26/17 at 09:53:45

4F4C59404C4319152D0 wrote:

If it doesn't back up at all, it wouldn't be any worse than factory pawl set-up,

However, while it would take a lot of experimenting and work, I would bet that the chain when stretched tighter (when cylinder heats and expands) it would put a tremendous amount of back pressure on the adjuster assy. Else, why would the original design have the pawl assy. in there at all? The secondary spring I put in between the mounting post and the back of the adjuster body is only slightly stronger than the primary spring when it is compressed as when it would be with a new chain. Therefore, my "guessed" reasoning is that the assy. and chain WILL be able to push back on the adjuster and compress it some - thus saving the constant tight pressure always being placed on the chain as it was originally designed.

Title: Re: What happened tensioner mods
Post by batman on 08/26/17 at 21:30:54

JOG,I NEVER said it was stupid! I never said it can't work! I do have some doubts,but I wished him well,said it needed testing ,and that I would like to hear the result,and that if it worked I would be interested in in buying one to install myself . Don't be putting your words ,in my mouth!

Title: Re: What happened tensioner mods
Post by justin_o_guy2 on 08/26/17 at 23:33:20

How could I have inferred something so far from the truth?

Title: Re: What happened tensioner mods
Post by piedmontbuckeye on 08/27/17 at 07:24:35

4C4F5A434F401A162E0 wrote:

The one factor about the way my tensioner is rigged is that the spring pressure applies the same constant force against the rear chain guard and thus the chain, no matter if the bike is stopped /running, cold /or at running temp, at idle or WOT .no other approach can claim the same ,there are to many variables . If one chooses to place a rod in the center of the spring ,how do you determine the length? Keep in mind that the guide is curved toward the chain ,but swings from a bolt at the top in an arc .If the chain places pressure on the guide as the motor warms ,in the direct center of the guide, the movement will be 4 times greater at the tensioner.

Guess I don't understand how you determine this "4x greater at the tensionser" part?

If the timing chain is exerted to the curved chain guide directly to the guide it would be the same amount exerted by the guide to the tensioner. How do you come up with the 4x amount?

The mods suggested by Mr. Verslagen (If I understand them correctly) are to 1) keep the tensioner from falling apart when the plunger extends out too far, and 2) to eliminate the extra force caused by a rigid tensioner (due to pawl ratcheting assy. when extended during cold) and transferring that unforgiving force toward the chain as it and cylinder warm up and expand causing the chain to already be too tight.

The first one is easily taken care of by the pin/screw that prevents the tensioner from separating.

The second problem is the one in question. Some have just eliminated the pawl assy. which prevents the tensioner from becoming rigid, allowing the existing spring to keep pressure on the chain guide but allow it to compress back when the chain/cylinder heats up. I think this is great idea as long as the chain doesn't just "flop" back and forth if the spring may not be strong enough to overcome the flopping pressure. Also, according to Hook's law, the more extended the spring becomes, the less pressure it will be able to exert on the chain. The worst scenario here would be after the chain has worn (stretched) enough to be significant is also where the spring would be at its most extended point and thus the weakest pressure. But, with the double hole added to the plunger, and at this point moving out to the extended hole, the spring would then be re-compressed to near original compression and overcome this problem.

The second way of handling the second problem is to add a spring between the mount pin and the body of the adjuster. Here the dilemma is to get the second spring just slightly stronger than original spring ANDf have enough movement in the "slot" to account for the chain tightenung up after the engine heats up. I calculated .050" added to make the mounting hole to make it a slot with .050 of possible movement. If at the beginning of chain wear, the adjuster produces more pressure than my secondary spring has, I have no more than just allowed the setup to work as it originally did from the factory. If after some extension of the primary spring (thus entering a less-pressure situation), it would then allow the secondary spring to do its thing and allow the timing chain to push back a bit and allow the adjuster to also move back. This situation allows the chain some release from the rigid pressure of the original setup. I can't see why this wouldn't work! My problem is, is how we can actually "measure" how much would be beneficial, as to my knowledge, none of us is doing any sort of scientific" method of testing or measuring. What would constitute an affirmative that it (or any method) is "beneficial"?

Title: Re: What happened tensioner mods
Post by justin_o_guy2 on 08/27/17 at 10:12:25

What would constitute an affirmative that it (or any method) is "beneficial"?

If fifteen thousand miles allowed the tensioner to extend fifteen MM before the spring mod, but not after.

Title: Re: What happened tensioner mods
Post by piedmontbuckeye on 08/27/17 at 13:51:25

534C4A4D50576656665E4C400B390 wrote:

What would constitute an affirmative that it (or any method) is "beneficial"?

If fifteen thousand miles allowed the tensioner to extend fifteen MM before the spring mod, but not after.

Well, I didn't measure exactly where my plunger was when I changed mine over, but I think I have a good idea. I will measure probably when I inspect next spring/summer. 15mm = aprox. .590. At this time, I have over 3,000 miles on it with no issues that I know of. Runs quiet and strong with a lot of acceleration.

Title: Re: What happened tensioner mods
Post by justin_o_guy2 on 08/27/17 at 14:44:40

My figures are purely hypothetical.

Title: Re: What happened tensioner mods
Post by Dave on 05/17/18 at 04:29:28

I am dragging up this old thread, as I am doing some maintenance/improvements to my Savage Cafe', and one of the things I did was install one of Lancer's nitrided cam chains and make a change to my cam chain tensioner. When I had this bike apart at 1,200 miles the tensioner plunger was out 13mm....after another 8,000 miles it was out 15mm. I still had some life left - but since I was changing my cam I decided just to go ahead and swap the chain for the nitrided one at the same time.

I assembled the engine with the new cam and chain, and rotated the engine through several revolutions. The tensioner plunger extended to 10mm.

I then took the tensioner off and removed the pawl and pawl spring, and I made an aluminum spacer to install inside the tensioner body to limit the travel....I adjusted the length of the spacer so that the tensioner plunger cannot retract to anything less than 9mm.....this allows 1mm of movement as the engine warms up. The stock tensioner spring will provide tension on the chain guide as before - the only thing that is missing is the pawl and the tensioner will not automatically adjust and overtighten the chain.

This photo shows the tensioner and 2 spacers. The spacer is machined with a hole in the center for the spring.

http://i66.tinypic.com/300clrb.jpg

This is what the tensioner looks like prior to assembly.

http://i65.tinypic.com/w9bew5.jpg

Is 1mm of travel the "correct" amount?......nobody knows. It is however 1mm more than the pawl would have allowed, and as the chain is used and the slack gradually increases.....there will be more clearance available. Only time will tell if this change works and is worth doing, and I will likely pull off the clutch cover at the end of the riding season to see how much change has occurred.

Title: Re: What happened tensioner mods
Post by batman on 05/17/18 at 07:57:41

Dave ,I can't remember who but someone measured the difference in cylinder height at one time and estimated chain stretch to be 1.5mm between a cold and warm motor. ( but who knows?) I have run without the pawl spring from 19000 to at present 31500miles with no apparent problems ,the motor is otherwise stock ,except for tuned intake runner ,carb tuning , main jet (150) , a Dyna muffler ,and a 140/90 rear tire, it accelerates briskly and still tops out at 90 mph. I checked the tensioner last Spring at about 10,000 miles and found 1-2mm of extension , I be checking it again or this winter ,it should have over 15000 by then. As a side note ,I did my own home version of the Gadgetman Grove to my carb and I'm seeing a 9-9.7% increase in fuel mileage depending on if I'm riding two up or solo.

Title: Re: What happened tensioner mods
Post by norm92de on 05/17/18 at 11:26:08

Dave,
That will get it done. It is essentially what I proposed with my rod inside the spring but far more elegant, you broke out your lathe. :) I can't wait to see how it works over the miles

All manufacturers have mostly similar devices for maintaining cam chain tension. The Savage is the poorest design that I have experienced.

I cannot see any downside to what you have done. The screw/nut type devices are essentially fixed until the next adjustment.

Title: Re: What happened tensioner mods
Post by norm92de on 05/17/18 at 11:31:28

I'm stuttering again. ;D

Your cam bearings will thank you. The intermittent over- tension of the cam mechanism must be enormous. :'(

Title: Re: What happened tensioner mods
Post by verslagen1 on 05/17/18 at 15:33:13

53686572636F747269616C73000 wrote:

Is 1mm of travel the "correct" amount?......nobody knows. It is however 1mm more than the pawl would have allowed, and as the chain is used and the slack gradually increases.....there will be more clearance available. Only time will tell if this change works and is worth doing, and I will likely pull off the clutch cover at the end of the riding season to see how much change has occurred.

1 mm should be pretty close. I think we calculated.03" or thereabouts.

Title: Re: What happened tensioner mods
Post by norm92de on 05/17/18 at 15:46:44

Dave,
Maybe you have instituted a new maintenance schedule. Possibly 10K and then return the clearance back to 1MM. Time will tell.

Title: Re: What happened tensioner mods
Post by batman on 05/19/18 at 10:27:55

I've often heard that because I removed the pawl spring and my tensioner is just a spring loaded shock, that the chain many be flopping around. but consider for a moment that even at an idle speed of 1000 rpm that the cam is still being driven at 8 1/3 revs per second, (500 rpm).I believe the chain is still moving fast enough to maintain a constant pressure against the guide .After 12,500 miles of use, 31,500 total miles on my factory original chain , I have no indication in either noise ,wear ,vibration or performance, that any flopping occurs.

Title: Re: What happened tensioner mods
Post by norm92de on 05/20/18 at 10:40:05

Batman,
Do you still have the original plunger on your tensioner? i.e. no extension welded on. If so that is impressive mileage on the original chain.

Title: Re: What happened tensioner mods
Post by batman on 05/20/18 at 11:15:55

No ,My plunger was out 19mm at 19,000 miles ,I did an extension at that time and have since put on another 12,500miles to date without the pawl spring . I checked it last May at about 10,000 miles and found the piston had moved out about 1-2 mm at that time. I will be checking again at the end of this riding season when I should have at least 15,000 miles . If I had it to do over again I would have removed the pawl spring earlier, and saved much of the first 19mm stretch (about 50% of the" normal" chain life).

Title: Re: What happened tensioner mods
Post by norm92de on 05/20/18 at 12:23:15

What Dave has done is to hedge his bet so to speak.

I think we will all be doing away with the pawl sooner or later. It will be interesting to see what mileage can be achieved- on the chain- if someone removes it very early in the game before appreciable chain wear has taken place.

One thing is certain the poor chain and more importantly the cam bearings are taking a terrible beating after starting when a tooth has just been taken up by the pawl.

Title: Re: What happened tensioner mods
Post by Dave on 05/20/18 at 15:40:10

I got the bike back together and was able to ride 50 miles today.

So far so good! :)

Title: Re: What happened tensioner mods
Post by Armen on 05/20/18 at 15:58:22

Basically what I was planning on doing. We talked about how much the cylinder grows, and how much slack to allow.
On the next cylinder I mangle, I'll put a window on the trailing side of the cam chain so that I can check the tension hot and cold. I did that on our SR500 racer and it worked great.
Considering that the slack reduces by twice the amount the cylinder grows, maybe 1mm isn't enough. Can't be any worse than that pawl set-up. That has to be the reason the chains die a quick and painful death.
Gung ho for doing this. One day, I'll actually work on my own bikes when no one else is looking...
-Armen

Title: Re: What happened tensioner mods
Post by DragBikeMike on 05/22/18 at 01:06:48

I measured cylinder growth today. Ambient temp was 85 degrees F. Engine/cylinder temp before starting was 85 degrees F. Rode for twenty minutes. On return engine/cylinder temp was 285 degrees F. Total cylinder growth from centerline of crankshaft to just above the camshaft was exactly .025".

Don't forget that the chain is also growing as the temperature increases. The coefficient of expansion for steel is 51% of the coefficient for aluminum. Its a complicated problem. I intend to attempt an evaluation along with some critical measurements discussed in this thread. I think it will be an interesting project. There's a lot of interesting ideas discussed in here.

Title: Re: What happened tensioner mods
Post by norm92de on 05/22/18 at 08:06:39

I made some measurements of cylinder growth some time ago. Starting at about 60* F. My repeatable measurements were .020" from the base flange to one of the fins on the cylinder head.

Based on this I concluded that from the center of the crank to the center of the camshaft the cylinder growth would be about .025" This agrees very well with you measurements DBM

Title: Re: What happened tensioner mods
Post by Dave on 05/22/18 at 08:13:21

14121D61636460500 wrote:

Don't forget that the chain is also growing as the temperature increases.

And just to make this even more complicated.....I suspect the cylinder and head get warm and grow faster than the chain. The head and cylinder get hot from the combustion process - the chain only gets the heat passed as it travels from the head to the camshaft to the cam sprocket.....or from the piston though the rod to the crank to the crank sprocket......or from the oil splashed onto the chain. And the cam sprocket most likely gets a bit warmer than the crank sprocket.

I suspect the chain gets warm far slower than the head/cylinder, and it likely never becomes as hot as the head or cylinder.

Title: Re: What happened tensioner mods
Post by norm92de on 05/22/18 at 12:07:24

Dave,
I think your latest fix is easily the best compromise.

Combined with Batman's experience with no pawl at all and no restriction of backward movement I think we will see quite an improvement in cam chain life. I also think that your guess of 1MM is very close, and anyway, is a lot better than none as provided by Suzuki.

Title: Re: What happened tensioner mods
Post by batman on 05/23/18 at 22:45:10

When I first removed the pawl from my tensioner, Dave brought up a valid point that the valve springs being much stronger than the tensioner piston spring that at times (I'm thinking shutdown) that the cam could be rotated forward , moving the slack in the chain to the area of the front guide. while when restarting the bike the starter motor develops instant torque and snatches the slack from the chain and MAY cause momentary stress to the pins and possible wear ,this doesn't happens often. ( if the motor was very strong we wouldn't need decompression) What bothers me is what occurs on the other side of the chain, which is now stretched taut, In my case , if my piston was out dealing with 2-3 mm of stretch with only the spring holding it the piston simply retracts , and no extra pressure is applied to the chain . But what stress would occur if my tensioner was set up to retract only 1mm? It could be many times greater than the stock tensioner.Note DBM's statement below in his reply #55"as I continuied to rotate the motor backward, the plunger would retract 8 mm".I believe this same type of action takes place with forward rotation, a purposed limit of .050 (1/16) will not releave 8mm(5/16) placed on the chain , and due to the nature of the cam being in a certain place for this to occur, the stretch will happen in the very same section of chain each time. limiting the tensioner from full retraction , when the chain is already under stress from the valve springs, is like putting a thorn in its side.

Title: Re: What happened tensioner mods
Post by DragBikeMike on 05/23/18 at 23:17:17

I spent the day taking data on the chain tensioner assembly. I gathered some interesting info. Hopefully the info will help some of you make a decision on your own tensioner.

I have already posted that I measured cylinder growth from ambient to normal operating temp. I did that by setting up a dial indicator rig to monitor the distance between the surface just above the camshaft to a bolt hole in the case that is just about even with the crank centerline. The span of the rig is just about 13.5". I left the rig in place but removed the indicator, took the bike for a twenty minute ride, then reinstalled the indicator while the engine was idling, shut it down, zeroed the indicator, and immediately shot the temp. The engine was 85 degrees before I started, and 285 degrees when I shut down. It took about 6.5 hours to cool completely to ambient. Indicated travel was exactly .025".

Title: Re: What happened tensioner mods
Post by DragBikeMike on 05/24/18 at 00:02:33

The calculated growth for aluminum 13.5" in length with 200 degree delta T is .033". That's using .00001244 for the coefficient. I attribute the .008" variance to the steel studs that are restraining the cylinder and head. The coefficient for steel is about 51% of aluminum (.00000633).

The chain is also getting hot. I initially thought that it would run a bit cooler than the cylinder, but after careful consideration I have concluded (just my opinion) that the chain is running pretty close to the same temperature, possibly even hotter. The chain is encased in a cavity within the cylinder. I am measureing the temperature on the surface of the cylinder where it is exposed to ambient cooling air. The chain isn't getting any cooling air, not much cooling oil either. If your thinking the oil is cooling off the chain, remember the oil is about 220 to 250 degrees, ambient air was 85 degrees. So essentially, the chain is in an oven cooking at about 300 degrees. Just my opinion.

With the chain growing at about half the rate of the cylinder, the difference in length should now be about .012". So, with the pawl locking the plunger, I believe that the chain is under about -.012" interference at operating temperature. In other words the cylinder is about .012" longer than the length of chain running from the centerline of the crank to the centerline of the cam.

This .012" difference is the amount you want to compensate for if you decide to make your tensioner soft (i.e. remove the pawl). So I wanted to try and measure how much the tensioner plunger retracts for a given movement of the slack side of the chain.

I removed the pawl from the tensioner and set up dial indicators to read plunger movement vs drive gear movement at the tooth pitch line. I took a few crude measurements and determined that the chain sprocket on the crank is roughly half the diameter of the drive gear. The drive gear is about 3 inches so the sprocket is about 1.5", therefore, movement at the sprocket should be about 1/2 the movement at the drive gear pitch diameter.

I backed the engine up until the intake lobe was at a point where any CCW rotation resulted in movement at the plunger and zero movement at the cam. The valve springs are so strong that the plunger just backs off when you rotate the engine. When the gear pitch moved .050" the plunger backed off .100". I did this several times to verify repeatability. Since the sprocket is one half the diameter of the gear, .025" movement at the sprocket should retract the plunger .100".

The .012" chain interference is roughly 1/2" of .025" so it seems to me that the plunger needs to retract about .050" to make the chain and cylinder run at equal lengths at normal operating temp. One millimeter is .040", pretty close Dave. This data seems to confirm Dave's spacer length which restricts the plunger from moving back more than 1mm. Setting it up for .050" might be just a tad better but that's splitting hairs.

Title: Re: What happened tensioner mods
Post by DragBikeMike on 05/24/18 at 00:13:37

I wanted to see how stable things are with the pawl removed so I did some rotations and gyrations just to see how the plunger reacted. If I continued to rotate the engine backwards, the plunger would retract about 8mm. That's a lot. As the chain wears, and there's more slack, it seems to me you run the risk of jumping a tooth when you are performing maintenance. Note that the Clymer manual directs you to "rotate the engine clockwise as viewed from the left-hand side". That's backwards. Anyone know why they tell you to do that?

I greased up the plunger and rotated it through a few times, then took a pic to give folks a better idea of how much it moves.

Title: Re: What happened tensioner mods
Post by DragBikeMike on 05/24/18 at 00:26:56

I continued to fiddle with it to see how it behaved without the pawl when rotating in the normal direction of rotation. The plunger modulates about .09" as you rotate the engine, and at times can make excursions up to up to as much as .15". The valve springs really are a challenge for this thing. No way of telling what it's up to when the engine is running.

I noticed that the plunger is a bit rough when its close to fully retracted. The spring is bunching up a bit and catching on the edge of the chamfer. I pretty much eliminated that by rounding off the edge of the chamfer in the bore. I'm not too comfy with all that movin around so I reinstalled my tensioner with the pawl and stock spring.

I hope this data is useful and helps you decide what path to go down. There seems to be four or five to choose from. Here is a pic of that sharp edge on the chamfer.

Title: Re: What happened tensioner mods
Post by Dave on 05/24/18 at 02:28:21

56505F23212622120 wrote:

Note that the Clymer manual directs you to "rotate the engine clockwise as viewed from the left-hand side". That's backwards. Anyone know why they tell you to do that?

It has always been our assumption that they just made a mistake, and have recommended you turn the engine the same way that it rotates when running.

My 1mm was just a guess at where to begin (thankfully it is pretty close). My idea was that if I installed the tensioner in the stock form where it measured 10mm of extension.....it would never be less than 10mm and from there the plunger would begin the slow process of getting to 20mm over the next 10 - 20K miles. If I made the spacer allow an extension of 9mm there would be room for growth when the engine was warm, and if the cylinder wanted more growth it would overtension the chain as before....but not nearly as much as it did when the plunger was locked in at 10mm. From this point on my chain will begin to stretch and wear - but hopefully at a much slower rate than it used to.

DragBikeMike: Thanks for your creative work in resolving several of our long term issues (enrichment of the TEV valve, cylinder growth, etc.). I new that it takes a long time for our engine to cool down after running - 6.5 hours is a bit of a surprise! I have just installed a cylinder head gauge on my Savage, and it is pretty interesting to watch how the head temperature changes as the load, rpm and air temperatures changes. On the 70 degree days and backroad 50 mph rides the temperature of the head at the left rear cylinder stud is around 215 degrees.....so far 240 degrees is about the maximum temperature I have recorded when cruising on the superslab. When I had the Trailtech Vapor on the Savage a 95 degree day stuck in traffic in downtown Gatlinburgh resulted in 300 degrees!

Title: Re: What happened tensioner mods
Post by DragBikeMike on 05/24/18 at 11:26:51

After a good night's sleep I realized that I missed a very important point. Quite some time ago I had made a comment regarding "both sides of the chain". Both sides of the chain are being subjected to the interference. When the system is hard (pawl installed) it's a wash. Nothing can give so it's essentially .012 interference. But when the system is soft (no pawl), you have a condition where the cam rotates as the cylinder grows. During normal operation the drive side of the chain is fixed and the slack side of the chain is flexible, the tensioner takes up the slack, and the pawl locks things in place. With the pawl removed, the drive side remains fixed and as the cylinder grows the cam must rotate clockwise. So removing the pawl also results in your cam timing advancing just a bit as temperature rises.

With the stock cam, that's probably not much to be concerned over, but if you are running a performance stick, and you want to run a soft tensioner, you might want to do a good check of clearances. I haven't had the head off yet but from photos I can see that the intake & exhaust valves have lots of distance between them, so valve to valve clearance is most likely not an issue. But valve to piston might be something to be concerned about. If you checked that clearnce with the chain system hard, and then switched to a soft system, there's a good chance your valve to piston clearance may be altered because the cam will be at a different position at TDC, and as such your TDC lifts will have changed.

Title: Re: What happened tensioner mods
Post by batman on 05/27/18 at 07:36:36

DBM ,while it true that the cam will advance as the cylinder grows ,this may be more of a problem on a newer bike ,I f the bike already has some mileage on it ,the cam chain has already stretched and retarded the cam timing , so you may just be "braking even".

Title: Re: What happened tensioner mods
Post by DragBikeMike on 05/27/18 at 12:51:26

That's an excellent point Batman.

Title: Re: What happened tensioner mods
Post by Armen on 05/28/18 at 06:58:16

Dave
I think the reason for Clymer saying to rotate the engine clockwise is to eliminate the possibility of loosening the alternator bolt. hard to imagine it would loosen, but with the plug in and someone turning rapidly, who knows.

Title: Re: What happened tensioner mods
Post by verslagen1 on 05/28/18 at 08:48:11

But if you rotate CW, you engage the starter and risk breaking the case or the teeth on the gear.

Title: Re: What happened tensioner mods
Post by batman on 05/28/18 at 18:34:23

What Versy said! Even more true if you own a 1995 or older bike with straight cut starter gears .

Title: Re: What happened tensioner mods
Post by norm92de on 05/29/18 at 13:48:18

On a positive note: :)

Our cam chain tensioner may not be the best but the rear of the cylinder has a very clean look and a potential oil leak has been eliminated. Also, I think we are closing in on a scheme to get the maximum life out of the chain.

By the way, how many miles do other engines get out of their cam chains? Anybody got a clue?

I have never owned a particular bike long enough to find out but have never had a problem for 20k or so which I realize is not very many miles.

Title: Re: What happened tensioner mods
Post by Dave on 05/30/18 at 04:09:09

27263B24707B2D2C490 wrote:

On a positive note: :)

By the way, how many miles do other engines get out of their cam chains? Anybody got a clue?

I have never owned a particular bike long enough to find out but have never had a problem for 20k or so which I realize is not very many miles.

One fellow on the 250 Ninja forum got 86,970 miles on his original engine and replaced it due to the cam chain being worn out. On this engine the cam chain is in the middle of the crank between the 2 cylinders, and it requires taking the engine completely apart to replace the cam chain. It is far easier and cheaper to buy a good used motor - there are plenty of good engines from low mileage crashed bikes (that obviously will change as the years pass).

Quote from his post:

I did replace the original engine at 86,970 miles with a 1,700 mile '01 engine, due only to my decision that the camchain was getting excessively worn, and might break before long. If it did break, it might break the crankcase and ruin the engine. But at 86,970 miles the performance was still normal and the oil consumption was still nil, as it always was. The worn camchain was evidenced by being able to be pulled excessively away from the cam sprockets, and no more adjustment available on the adjuster. Probably the camchain guide strips were also well worn. Had it not been that camchain replacement requires the complete dismantling and reassembly of the engine, I would have replaced the chain and guide strips and continued to run the engine.

Link to his thread:
https://faq.ninja250.org/wiki/100,000_miles_on_an_EX250

Title: Re: What happened tensioner mods
Post by batman on 05/30/18 at 16:57:45

I don't believe changing the cam chain on a Ninja would be as hard as people think . The fact that the case seam is horizontal ,make s replacement a bit easier.