SuzukiSavage.com - Cam timing?

Armen Serious Thumper Offline Half-Witted Wrench-Jockey from Jersey Posts: 1452	Cam timing? 10/07/16 at 14:45:20 Anyone try playing with the cam timing? On a stock bumpstick or one of the aftermarket ones? Webcam has a decent section in their catalog on the voodoo, but that is assuming one can just play with things like offset Woodruff keys. Just a quick look tells me it'd be a real PITA to alter. But then again, happy cam timing makes for a happy motor. thanks, -Armen
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Dave YaBB Moderator ModSquad Offline SuzukiSavage.com Rocks! Posts: 18099 Camp Springs, Kentucky Gender:	Re: Cam timing? Reply #1 - 10/07/16 at 17:23:45 So far nobody has fooled with the cam timing.....although we all see how far behind that timing notch becomes as the cam chain wears/stretches. There isn't anyone that has created a way to alter the timing....there is a pin that locks the gear in place on the cam....and no options to adjust that (yet).
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Re: Cam timing?
Reply #2 - 10/07/16 at 18:17:53

verslagen1 wrote on 03/17/07 at 23:35:13:

replace the chain if it stretches beyond .07" over 5". Reshape or replace the guide if the tensioner extends beyond 18mm with a good chain.

You can go further with either but at risk. .07" stretch will retard the cam timing by 7°. Apparently, this type of chain is meant to float on the gear teeth anyway. So a worn chain doesn't effect the teeth of the sprockets like chains in the final drive.

The forward side of the cam chain run is straight.
As an alternate method to taking up slack in the cam chain, OF proposed this...
Oldfeller--FSO wrote on 01/29/11 at 02:21:01:

That's OK Justin, all input is appreciated. Sounds like you had a failure of the left hand (rear) normal moving adjuster guide piece during a second life (or was it third life?) after hand bending it strongly to take up the same slop I am taking up by gently single bending and reinforcing the right hand (front) guide.

You bustulated the other one, not the one I am messing wid.

Now, did you have any major damage to the inner gears, etc, or jest a bunch of noise when yours went?

I'm asking because second (and third) life re-use of the cam chain guides is taking place a lot during these here hard hard recessionary times.

And that left hand large bottom sheet metal guide piece does jest hang out there in space with the cam tensioner spring telling it all the time to go that-a-way and the moving cam chain itself saying go this-a-way and it has a right rough row to hoe by the time it gets to the end of its second or third use life ....

And remember as you go through your various cognitive processes, there is 1/2" hardwood dowel stock, 5/8" hardwood dowel stock and 3/4" hardwood dowel stock all readily available at your local hardware or artsy craftsy store.

I used 1/2" diameter because I had it on hand and I was jest fiddlin' with the idea.
5/8" would likely be about the ideal size with 3/4 being kinda too big diameter wise but a small flat could be put on each side to keep it properly centered with the guide.

Length needs to get shorter as dowel diameter goes up -- larger diameters are stronger and less flexible (if that's what you think you want).

This is probably overkill taking up the slack and nets 3° advance cam timing.
But there's the idea.

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Ruttly Serious Thumper Offline Thumpers Rule Posts: 5106 Manteca , CA Gender:	Re: Cam timing? Reply #3 - 10/07/16 at 19:38:18 Really ! You would run your engine with a wooden dowel in it , just for 3 degrees of cam timing !
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Ruttly Serious Thumper Offline Thumpers Rule Posts: 5106 Manteca , CA Gender:	Re: Cam timing? Reply #4 - 10/07/16 at 19:47:30 Armen , Why not machine off a fin or two on forward side of cylinder at cam chain galley to create a flat area drill & tap fab up a adjuster with copper washer & locknut ! Very simple for someone with your skills
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Armen Serious Thumper Offline Half-Witted Wrench-Jockey from Jersey Posts: 1452	Re: Cam timing? Reply #5 - 10/08/16 at 04:03:49 Hmm... Interesting. Have to sit in front of the motor and scratch my head a bit. I was hung up looking at the cam sprocket. Drilling new holes in that would be high on the 'no fun' list. thanks, -Armen
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Armen

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Re: Cam timing?
Reply #6 - 10/08/16 at 05:13:51

Another thought:
Verslagen stated that a totally stretched out cam chain would retard the timing by 7 degrees. Not so stretched means fewer degrees.
The cam sprocket has 38 teeth, so each tooth is about 9.47 degrees of timing at the cam, which is 4.735 at the crank (cam moves at 1/2 of crank speed).
So, if someone is running a stretched out cam chain with the extended cam chain tensioner, probably moving the chain one tooth on the cam sprocket would bring the cam timing pretty close to stock.
Thinking out loud here...
-Armen

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verslagen1 YaBB Moderator ModSquad Offline Where there's a will, I want to be in it. Posts: 28886 L.A. California Gender:	Re: Cam timing? Reply #7 - 10/08/16 at 10:08:40 has been done... accidentally. and it doesn't work. common complaint is won't go past 50. and you're comparing .070" of chain stretch vs. 1 tooth at .250" in pitch. I say .01 is ~1°, you say 1 tooth is ~10°... I don't think so.
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Armen

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Re: Cam timing?
Reply #8 - 10/08/16 at 16:17:38

Verslagen,
You had said a stretched chain would retard the timing about 7 degrees.
There are 38 teeth on a cam sprocket. If there were 36, each tooth would represent 10 degrees on the cam. There are 38, so each tooth is 9.4737 degrees of the cam circle.
A cam rotates at 1/2 of crank speed. Two turns on a crank make one turn on the cam.
So, 1/2 of 9.4737 is 4.737.
That is the number of degrees of crank rotation for one tooth on the camshaft.
If the cam timing (as you said) is retarded 7 degrees for a slapped out chain, then advancing the cam timing 1 tooth would result in correcting the cam timing 4.737 degrees in the right direction. With said clapped out chain, the timing would still be a bit retarded.
If the chain wasn't so clapped out, it might bring the timing back to stock.
I mention this because so many folks seem to have clapped out cam chains and use the longer cam chain tensioner.
Unless I'm missing something obvious.
-Armen

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verslagen1 YaBB Moderator ModSquad Offline Where there's a will, I want to be in it. Posts: 28886 L.A. California Gender:	Re: Cam timing? Reply #9 - 10/08/16 at 16:53:50 That's great, you can type out all those digits. I'm not going to. I'll have to see if I can find the file I used to calculate the numbers.
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batman Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 3806 osceola new york Gender:	Re: Cam timing? Reply #10 - 10/08/16 at 17:06:47 I wonder how far the valves move down when fully open,if you do place a shim behind the front guide is there a chance of the valves strikeing the piston,how much is too much?
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Armen Serious Thumper Offline Half-Witted Wrench-Jockey from Jersey Posts: 1452	Re: Cam timing? Reply #11 - 10/08/16 at 18:58:26 Good question Batman. When I change cams, I usually dummy up the motor with a real soft spring, set the valve clearance, rotate the motor and push down on the valves periodically to see how much piston-to-valve clearance I have.
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Re: Cam timing?
Reply #12 - 10/09/16 at 04:03:12

I wonder how accurate the notch on the cam is placed by Suzuki? If it is only to allow the cam to be set on the correct tooth - it might not be accurate enough to used for precise cam timing. If you are going to the trouble of "timing" the cam....then it would be time for a degree wheel and dial indicator......and some advanced motor and math skills! (I am not saying the results wouldn't be worthwhile....it is however more advanced than most of us have done).

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Re: Cam timing?
Reply #13 - 10/09/16 at 04:52:27

Dave,
Exactly. If/when I do the timing, I'll def drag out my whole cam timing voodoo kit (degree wheel, piston stop, dial indicator, etc).
Just wanted to be able to do something if I found the timing to be off.
FWIW, I've never seen a stock motor where the cam timing was within 2 degrees of what the factory said it should be.
Sometimes you are lucky and the cam timing can be altered with offset cam keys. I have those for Ducs and Airhead BMWs. But with these scooters, not so easy.
To add to the entertainment value, when I do the big motor, I'll measure up combustion chamber volume and measure squish clearance. If i end up skimming a bit off the top of the barrel to tighten up the squish clearance, that'll retard the cam timing a tiny bit.
In my abundant spare time Roll Eyes

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Steve H Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 1223 Spartanburg, SC Gender:	Re: Cam timing? Reply #14 - 10/09/16 at 09:24:30 One problem with your figuring of degrees of crank rotation. The cam turns at half the speed of the crank. The deg of rotation on the crank will be twice, not half, of cam rotation.
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