SuzukiSavage.com /cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Inspecting Transmission Gears /cgi-bin/YaBB.pl?num=1670528313 Message started by DragBikeMike on 12/08/22 at 11:38:32

Title: Inspecting Transmission Gears Post by DragBikeMike on 12/08/22 at 11:38:32 I’ve been having trouble with my transmission.  The higher gears pit.  On my 97mm Flat-Top engine, 5th gear pitted and the debris from the gear-teeth got into my cylinder.  The cylinder was damaged.  No more rebores on a 97mm.  Then, on a smaller engine (94mm Flat-Top), 4th gear started pitting.  I caught that failure before any serious damage occurred to other components.  I suspect these gear failures are related to overload.  As Armen says, “You find your limits by exceeding them”. To prevent another gear failure, I built a new engine using an old 4-speed gearset from a 1987 LS650.  The gears, for the most part, are wider than the 5-speed gears, and they appear to be beefier.   I’ll be doing a report on that engine soon.  It’s a bit different.  It makes a lot of power and should be a good test of the 4-speed gearset.  I also have plans to add a separate lubrication system for the gear teeth.  It’s ambitious, but no guts no glory. I needed a way to inspect the gears without tearing the whole engine apart.  The only way I’m gonna learn anything is to keep trying, and an inspection routine is a must.  I already had a cheap borescope that I got at Walmart, but the camera is too big (9mm), it can’t capture a photograph, and the resolution sucks. A good friend of mine turned me on to DEPSTech Endoscopes.  They make these cool endoscopes that connect to your smart phone or iPad via Wifi.  They take still pictures and videos.  The resolution is decent, but glare is a problem.  With a bit of effort, and a little patience, you can get a good idea of what’s goin on in your engine. About $43 bucks on Amazon.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/08/22 at 11:39:21 This is the type of resolution you can expect to achieve with this camera system.  Again, not perfect but certainly useful.  It’s about the best I could achieve in an environment that’s as friendly as you can get.  No oil, natural light, plenty of room, etc.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/08/22 at 11:40:02 I had the new engine opened up for a clutch repair.  Like I said, it makes good power.  That gave me an opportunity to try out the endoscope.  This is a picture of 4th gear that I took with the endoscope.  Lots of hob marks but no pits yet.  The endoscope is inserted through the port just below the clutch, 4th gear is on the right, 2nd gear is on the left.  The gears are on the input shaft.  Haven’t figured out how to access the output gears yet, but the failures seem to be confined to the input gears.  I think this will work good.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/08/22 at 11:40:37 The old engine with the failed 4th gear was sitting on my workbench, so I took a look at it.  I accessed 4th gear through the port just below the alternator rotor.  This shows that pits will not be hard to identify with this tool.  Not perfect, but certainly good enough.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/08/22 at 11:41:11 To get consistent pictures of the transmission gears and make setup easy, I made some fixtures to hold the camera in just the right location.  You tape the camera to the fixture, insert the assembly into the appropriate hole in the case, and you are ready to go.  The gears on the input shaft rotate freely when you turn the rear wheel, so 360°inspections are easy.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/08/22 at 11:41:47 Here’s the right-hand fixture installed.  It is used to inspect top gear (4th on a 4-speed, 5th on a 5-speed).  I made a similar fixture for the left-hand side.  It is inserted in the port just below the alternator, and is used to do 3rd gear on a 4-speed, or 4th gear on a 5-speed.  Removing side covers is waaaaaay easier than tearing the cylinder off.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/08/22 at 11:42:31 Camshafts are another component prone to pitting.  Would be nice to be able to check the lobes for the emergence of pits.  I threw together a top end with an old, pitted cam.  This will give you an idea of what to expect.  I feel that I will be able to identify the onset of pitting using this tool.  This is a shot of the exhaust lobe.  Even though there’s a lot of glare (due to all the oil), it’s still easy to identify pits.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/08/22 at 11:43:14 The intake lobe was a little harder, but with some effort you can make out the pitting.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/08/22 at 11:44:01 After practicing a bit, I was able to get some good pictures of the 97mm Big Bore 4-Speed DR650 cam.  I think these shots are a lot better.  Much easier than removing the head cover for inspection. This is the DR650 intake lobe.  Still looks great.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/08/22 at 11:44:39 Here is the DR650 exhaust lobe.  You can see some very small pits.  Not too bad for 28,990 miles.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/08/22 at 11:45:21 One of the areas that interest me is the cylinder bore.  The front side of the bore starts developing vertical, linear, marks from the debris getting wedged between the piston and cylinder.  If left unchecked, the debris eventually wrecks the cylinder and the rings.  It’s not the clearest picture, but I can see the vertical lines in the front of the cylinder.  Access via the spark plug hole is easy.  The camera is only 3.9 mm, goes right in and allows you to form the flexible shaft to get the angle you need.  Don’t know why I couldn’t get a clear shot but it’s better than nothin.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/08/22 at 11:48:18 I’m glad I got this tool.  It will make life a whole bunch easier moving forward. I hope some of you find this info useful.  If you are into hot rodding your Savage, the DEPSTech endoscope will come in handy. Mike

Title: Re: Inspecting Transmission Gears Post by Armen on 12/09/22 at 06:02:13 Very cool! I’ve been waiting for these gizmos to get small enough and cheap enough for me to justify. Sounds like it! I’m not clear about which one to get. One is listed as 2 Megapixtels, one is 5 MP, and yours uses a different rating. Obviously, 5 MP is better than 2, but how does yours fit into the ranking? All else being equal (except the price) I’d like to buy the best one. As always, thanks for your hard work and thorough documentation. Hope all is well, and Happy Holidays!

Title: Re: Inspecting Transmission Gears Post by justin_o_guy2 on 12/09/22 at 17:56:05 Any idea why the gears are taking such a beating? What oil are you using?

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/11/22 at 08:53:46 Armen, I don't know much about mega-pixels.  The device I got (WF070) is rated at 1920*1080px.  I'm not sure exactly what that means but seems to be the same numbers used to define a laptop video display.  I got it primarily for the small camera.  The camera is 3.9mm diameter which is really small.  It has lights in the camera.  It's not the greatest resolution, but with a little practice you can get a decent picture.  I really like the feature that allows me to take still photos and videos.  You can also zoom in & out, and rotate the picture.  I'm sure the resolution is fairly low because the files are small.  This thing creates a file on the order of 200kb while my iPad files are usually at least 2mb. Justin, I wish I knew exactly why my gears are failing.  I call the failure "pitting", but the correct term is "spalling".  Spalling is an extreme form of pitting and is defined as "destructive failure".  It's a fatigue failure associated with cyclic stress due to overload.  The obvious solution is "reduce the load" (not an option I am willing to accept, yet). There are a few things I can do to try and prevent pitting/spalling.  Reduce the load (not on my list).  Provide more lubrication (I'm workin on that).  Increase quality and viscosity of the lubricant (I run Mobil 1 V-Twin 20W-50).  Increase the contact area (the 4-speed gear set does that).  Increase hardness of the contact surface (that's a tough one).  Improve surface finish of the contact area (New England Gear Polishing).  So far, the 4-speed gear set seems to be holdin up.  Have to see where things go. This final comment will probably raise the fur on Armen's back.  I have a suspicion that the mini flywheel might be associated with the gear spalling.  I have noticed that the engine struggles to maintain high speeds in 4th & 5th gear.  It really struggles if an incline is involved.  When faced with a challenge like a 6% grade at 4500 rpm, I have a tendency to attempt to overcome the obstacle (twist the wrist).  Without the stored energy of the 6-pound flywheel, it doesn't wanna carry through the parasitic strokes (exhaust, intake & compression).  So, in order to maintain speed and/or accelerate, you have to develop a lot more BMEP than necessary.  In other words, the push you have to apply on the power stroke must be a lot greater without the flywheel.  The gears have to deliver that push.   I'm currently runnin the big wheel.  It would be nice if I could test the theory, but my resources and energy are limited.  I would have to do long term tests with and without the mini-wheel.  So, for now, it's the shotgun approach.   The heavy flywheel was easy.  Wider gears were a bit harder.  More oil will be challenging but I have a plan.

Title: Re: Inspecting Transmission Gears Post by justin_o_guy2 on 12/11/22 at 13:12:09 The ad just popped up. IDK hoot about the quality. https://qiihong.com/products/usb-endoscope?utm_source=taboola&utm_medium=referral&tblci=GiBtfDjwYdmNbyO27_7LaT0orFUt2MIexGAtfQQ21RFN1CCogFsohr29qParsuWxAQ#tblciGiBtfDjwYdmNbyO27_7LaT0orFUt2MIexGAtfQQ21RFN1CCogFsohr29qParsuWxAQ But the price is right

Title: Re: Inspecting Transmission Gears Post by verslagen1 on 12/11/22 at 14:40:58 My BIL just got me a inskam (only brand name I can find) It has 1600x1200 resolution with a 8mm cammera. The good thing about it is that it has a wifi/bluetooth adapter so you can port it to whatever you got.

Title: Re: Inspecting Transmission Gears Post by TheSneeze on 12/11/22 at 18:12:29 I bought an endoscope for my cell phone when I had to clean the inside of my KZ750 fuel tank.  I haven't used it in a while, so I can't give specs on right now.  I haven't been in my shop for a week - been down with a nasty case of the flu.  When I get back out there in a few days I will report back the specs on which one I got.  Mine works well. I had already made the decision for my hot rod motor to stay with a stock flywheel.  Looks like it may have been the safer choice.

Title: Re: Inspecting Transmission Gears Post by Armen on 12/11/22 at 19:30:00 Hey Mike, As always, thanks for the info. I bought exactly the same one you talked about. Should have it this week. No worries about not liking a lite flywheel. :-) Wondering if there is a way to increase the oil volume being pumped?

Title: Re: Inspecting Transmission Gears Post by Gary_in_NJ on 12/12/22 at 12:23:37 Mike, I have wondered about your gear wear issues since you first brought them to light many months ago. I found it strange that it only affected the higher gears and not the lower ones - the ones that typically fail - and then I thought about your test routine. You generally don't provide 0-60 or 1/4 mile trap speeds - you usually provide roll-on acceleration. This is a very practical test for sure, but it is this testing that may cause your issue with gear wear. While I have never ridden with you, I get a feeling that a typical ride for you includes a lot of WOT applications in high gear. When the engineers were designing the gears they did so for an engine that made ~30-40 lb-ft of torque. You have well exceeded this and there is a very good change that the Rockwell number used in the material just isn't correct for your application. I'm sure you have exceeded any margin that was built into the design. You may find alternative gears (and ratios) by looking at Suzuki's vast parts database. Or, you may be able to lessen the impact of gear wear by limiting the high gear roll-ons to testing only.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/12/22 at 13:22:22 Hey Armen, yes I have considered increasing oil volume.  I have a bunch of the stock pumps and I have been looking at stacking up pumps.  Make a longer shaft and then stack an additional pump onto the original. I wasn't considering pumping more oil through the stock circuit.  I was thinking I could fabricate some internal piping and use the discharge off the second gerotor to spray oil directly on to the overdrive gears (4th & 5th).  Like right into the mesh between the input and output gears. More oil through the stock system does not look like it would be of any benefit.  The gears are not dip lubricated.  The gear mesh gets all of its lubrication from oil thrown off the rod.  The rod on the Savage is not in alignment with 4th or 5th gear.  So, I would be just pumping more oil into the sump.  Probably would overwhelm the oil control rings too. This picture shows the problem.  The oil is thrown off the rod as shown by the green arrows.  The orange circle is around 5th gear and the yellow circle is around 4th gear.  Looks like 5th gear really gets the short end of the stick, but 4th ain't much better.

Title: Re: Inspecting Transmission Gears Post by Armen on 12/12/22 at 13:31:15 Hmm Oil is being fed through the trans shafts, right? And there is a restrictor on the right side of the case. Assuming the oil goes thru the shafts, then ends up on the gear surfaces by way of being splashed all over. Or am I missing something? Maybe increase the volume and remove the restrictor? Might also help the top end oiling problems.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/12/22 at 13:54:14 Hey Gary, my sentiments exactly.  The gear spalling is confined to the overdrive gears (4th & 5th), and I have been doing a lot of WOT testing using those gears (especially 5th).  Those tests subject the gear teeth to the maximum load since the wind resistance is highest under those conditions.  It's an exponential function so the stock design fades fast as the speed goes up.  I'm makin a lot more power than stock.  To add insult to injury, the overdrive input gears rotate at the highest pitch circle velocity, so centrifugal force is throwing oil off as fast as it can be applied.  Failure seems inevitable. One issue I have a little trouble with is 4th gear.  That particular gear is not part of my test regimen.  To be sure, I do hit 4th pretty hard sometimes, but it's not a regular part of my testing.  The pitting occurred on two different transmissions.  The first failure (5th gear) was on my original stock bottom end.  I pretty much know everything that gear set was subjected to.  The second failure (4th gear) was on my spare engine.  While I have beat that baby up pretty good, I have no idea what the prior owner did to it. The gears that failed are between 45 and 50 HRC.  I checked them with some special files.  Pretty neat tool.  My reference material on gears indicates typical hardness of 47 HRC.  That's not to say that a set with the hardness up around 50 to 55 wouldn't be better, it just indicates that the hardness is typical for a mass-produced gear.  One interesting feature is some of the gears look ground, and some are clearly hobbed.  A smoother finish would be better so would be nice if they were all ground.  The 4-speed set that I'm running now is about 10% wider so that should reduce the contact pressure a bit. From a practical perspective, I think it would be best to try and achieve reasonable durability without investing a ton of money.  I want to learn new things for sure, but having custom gear sets manufactured would simply be too expensive.  So I'm gonna see what I can accomplish using junk eBay parts and Yankee ingenuity. I want to try and run the drain oil off the cylinder head onto top gear (4th on a 4-speed, 5th on a 5-speed).  Maybe even possibly onto 4th gear on a 5-speed.  That won't take any lubrication away from any other components.   This is a picture of those files.  I also want to try and make a rebound tester.  It's kind of a bouncing ball contraption.  More info is always better.  BTW, the button says "Choose File", I love it.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/12/22 at 14:04:23 Armen, I think the oil being pushed through the trans shafts is to lubricate the gears that idle on the shaft (un-splined), and to lubricate the clutch basket bushing.  I really doubt that much, if any, finds its way to the mesh.  It's just gonna run up the side of the gear and end up in the sump.  I could be wrong on this but seems logical to me. You might have something on that orifice though.  If I doubled up the pumps and ran all the output through the stock circuit sans the orifice it might find it's way to the problem areas.  If the oil pressure remained right about where it is now, it would indicate that all the excess was going to the trans and clutch.  Hmmmmm! What do you think about using drain oil off the cylinder head?

Title: Re: Inspecting Transmission Gears Post by TheSneeze on 12/12/22 at 14:07:43 The endoscope I bought is a Nidage brand.  Here is the spec sheet.  It works very well, and has great resolution with some patience applied.  Yes, you can get blurry images if you are not careful

Title: Re: Inspecting Transmission Gears Post by Armen on 12/12/22 at 14:09:43 Honda blew up a gazillion V-4 motors in the early 80s. They lubed the top end with low pressure, dirty oil from the gearbox. A few band aid fixes were around, but the only real fix was a complete redesign of the motor, giving clean, cool oil to the valve train. Don’t think I’d use oil after it went North.

Title: Re: Inspecting Transmission Gears Post by Armen on 12/12/22 at 14:18:30 Mike, I can’t tell exactly from the parts blow-up, but it seems that 5th gears are on bushings. If I’m reading it right, they get driven by their adjacent gears-in this case 4th gear. So, power travels thru the 4th gear set, then gets transferred thru dogs to one of the 5th gears. So, load on 4th gear teeth as well as 5th. Or, am I looking at it wrong?

Title: Re: Inspecting Transmission Gears Post by Armen on 12/12/22 at 14:35:58 Scratch the gear wear theory. I looked again, and my previous guesses don’t hold water (4th/5th).

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/13/22 at 09:29:45 Armen, I can understand why you wouldn't want to use low pressure, unfiltered oil from the sump to lube the top end (cam, rockers, valves, etc.), but a typical manual transmission lives in a slurry of ground up shift dogs, syncro trash, and gear tooth debris.  The dip lube units seem to hold up OK and that oil is straight out of the slop bin.  I've never seen a manual trans with a filter.  Granted, the oil our transmission currently receives has been through a filter, but it still contains wear products off the rod bearing, and I suspect it's also mixed in with sump oil that's splashing all around.  I don't get your aversion to using drain oil off the top end.  I'm sure it will contain wear products, but I doubt they will be much worse than what's already goin through the mesh. I was planning to run the drain oil through a simple cooler device and locate neodymium magnets in the cooler to trap ferrous wear products. After thinkin a bit about stacking pumps and running the discharge through the stock circuit, it dawned on me that the filter probably won't be able to handle all the flow.  At best, the bypass relief will lift, at worst the filter will collapse.  That would be a very complicated modification.  I wonder if the drive gear could handle twice the load.

Title: Re: Inspecting Transmission Gears Post by Armen on 12/13/22 at 09:59:04 Hey Mike, Do you have a pic of a stock oil filter internals? Thanks

Title: Re: Inspecting Transmission Gears Post by Dave on 12/18/22 at 03:27:36 Would it be possible to reroute the drain oil from the left front cylinder stud to the transmission case above 4th/5th gears?  That way you wouldn't need a pump and gravity would do the work. I don't know if that would provide sufficient oil flow to be of any benefit.

Title: Re: Inspecting Transmission Gears Post by verslagen1 on 12/18/22 at 07:31:14 Dave, I think that's actually on the right (clutch) side as it flows down over next to the oil fill port. I think that a high pressure relief valve at 50ish psi could bleed off a little bit of oil and spray it on the gears at a time most needed.

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/18/22 at 23:12:03 Armen, I don’t have any pics of the filter cut open.  I should do that on my next filter change.  I’ve been meaning to make a test rig to see what pressure the bypass relief lifts. Dave, that’s pretty close to what I’ve been planning.  Take the oil off the valve spring pockets and dump it on 5th gear.  That way nothing gets robbed from any of the pressure fed components.  Left front stud hole serves as the drain for the exhaust spring pocket.  The intake spring pocket simply spills over into the cam chain cavity.  I’m planning to plug the stock drain port for the exhaust pocket (left front) and drill a new drain laterally.  Make a lateral drain for the intake spring pocket (left side).  Then connect the two drains and run the drain oil through a small cooler with magnets inside.  Then direct that oil over the top of 5th gear.  I don’t think I can place the flow directly into the mesh.  Most likely it will have to dump on the top of the output gear. Versy, that’s an interesting suggestion on the relief valve.  If I increased pump capacity (tandem geroters) and installed a pressure relief valve, I could plumb the escape piping to discharge on to the overdrive gears.  Mighty complicated job but I bet it would be fun.  Quite a juggling act to get the filter bypass relief and a pump discharge relief to work as intended and end up with a filter that isn’t continuously on bypass.  Another good reason to build that test rig and see where the filter bypass lifts.

Title: Re: Inspecting Transmission Gears Post by Armen on 12/19/22 at 05:35:17 Hey DBM I meant pics of the oil pump, not the filter. My bad. Just trying to think of ways to increase volume. Thanks

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/20/22 at 17:12:38 Sorry Armen, I don’t have those photos right now.  I will try to post later.  I can tell you that it’s a typical gerotor pump and both the outer and inner rotors are easily removed.  I’m fairly confident that I could make an extension for the housing and stack another rotor set.  That would essentially double the capacity.  The ideal option would be to grind the additional rotor set to about one-half the original thickness.  That should increase capacity to 150%.  I don’t have access to a surface grinder.  I don’t think I could do it with a tool bit.   Then, could install a relief valve in the plugged hole in the engine case.  All this would depend on the filter bypass set point.  The filter bypass set point has to be significantly higher than the relief valve setting.  Actually, doesn’t need to be a relief.  Could be a fixed orifice.  Just adjust the size of the orifice to set the flow so that my current oil pressure could be maintained.  If the new oil pressure (as measured at the head cover) remains close to my current pressure, then all the additional flow should be goin to my gears.

Title: Re: Inspecting Transmission Gears Post by Armen on 12/20/22 at 17:32:24 Many a bike has been modified with bigger or smaller oil pumps. Finding someone with a surface grinder shouldn’t be that hard. Make sure the passages on the feed side are ‘full figured’. BMW had problems with cavitation when they started spinning the race bikes to 10,000 rpms. Can’t wait to see how this project progresses! How about an oil jet to the underside of the piston (while you are at it)?

Title: Re: Inspecting Transmission Gears Post by DragBikeMike on 12/22/22 at 05:57:57 Good point on cavitation.  I assume by “feed side” you mean suction side.  The suction foot and screen look like they could be easily modified, but the casting with the suction channel might be difficult.  It’s clearly an engineered shape with a gradually decreasing cross section.  The pumpage is very hot and there’s zero suction head, it’s always lifting the pumpage. It would also be wise to enlarge the discharge channel in the right side engine case, not sure about the discharge & suction ports for the geroter, they look like they are timed.  Not sure, I don’t know much about gerotor pumps.  Time to light off google.

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