Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties Meshing NOS Cam Gear Set

Meshing NOS Cam Gear Set

Moderators: Curt!, Pa

Post Sat Jan 28, 2012 7:22 am
Pa Site Admin

Posts: 5774
Location: Ohio USA

Was wondering what you folks do to mesh the teeth on a set of NOS cam gears so they all turn freely when installed without teeth binding. I've been fitting a set to a set of cases. All cam gears turn freely when installed individually. None of the cam gears turn freely when installed in pairs, threes, or all four. I can turn them though. Idler gear teeth bind with front exhaust gear teeth when installed as well. I know the teeth of the nos cams and nos idler gear are the issue here because there are spots during rotation where one, two, three, or all four turn freely until I feel slight to moderate tooth restriction between cam gear teeth. same goes for the idler gear. Again...all cam gears and idler gear are nos. I do not wish to hand dress the teeth if I can avoid it. Any suggestions or tried and trued methods of correcting this binding ?? Thanks, Pa

Post Sat Jan 28, 2012 9:31 am

Posts: 140
Location: USA
Hey Pa,Tom here,I know this may sound bad and I hesitate to even suggest this out in the open forum to avoid a huge uproar but,would it be a possible solution to coat the gears with valve grinding compound and rotate the gears until you work out the interference ? Was that what Jerry Branch did on his racing motor to achieve minimal restriction and internal interference ? Know doubt after reading this you you will be convinced of my mental instability but I have also encountered a similar problem trying to match up an generator idler gear.I had two gears both appeared identical,same teeth,same pitch,same dimensions,but for some unknown reason one would spin and one would not.Anyway lets see if someone has a solution.The older I get the less I know. :D :D

Post Sat Jan 28, 2012 9:34 am

Posts: 426
Location: Tucson Arizona

Are you installing the cam gear cover? This is a must when installing gears. If you just install the gears and try to turn them without the cover they try to "climb" on each other and then bind. I've had sets returned because of this very issue and when I installed them in my bikes they worked just fine.

The other thing is, did you have your case bushings replaced? This has always been an issue with people whom I've sold gears to. They size the bushing, but it throws out the location and then the cams bind. I believe Eric made a fixture for this. Maybe Eric can step in here with a pix.

Then the final thing is the way the factory did it when they had gears that bind.....they just reached into a bin and found a size that fit. I was told the Sportster cam gears were color coded by size to help the installation process and read I believe on the Andrews Sportster cams if one was binding to send it back and they would supply another size.

Kurt

Post Sat Jan 28, 2012 11:52 am
Pa Site Admin

Posts: 5774
Location: Ohio USA

celticdodge wrote:
Hey Pa,Tom here,I know this may sound bad and I hesitate to even suggest this out in the open forum to avoid a huge uproar but,would it be a possible solution to coat the gears with valve grinding compound and rotate the gears until you work out the interference ? Was that what Jerry Branch did on his racing motor to achieve minimal restriction and internal interference ? Know doubt after reading this you you will be convinced of my mental instability but I have also encountered a similar problem trying to match up an generator idler gear.I had two gears both appeared identical,same teeth,same pitch,same dimensions,but for some unknown reason one would spin and one would not.Anyway lets see if someone has a solution.The older I get the less I know. :D :D


I have considered that Tom but was hoping to get more views and opinions before proceeding with teeth lapping.

Post Sat Jan 28, 2012 11:59 am
Pa Site Admin

Posts: 5774
Location: Ohio USA

Kurt wrote:
Are you installing the cam gear cover? This is a must when installing gears. If you just install the gears and try to turn them without the cover they try to "climb" on each other and then bind. I've had sets returned because of this very issue and when I installed them in my bikes they worked just fine.

The other thing is, did you have your case bushings replaced? This has always been an issue with people whom I've sold gears to. They size the bushing, but it throws out the location and then the cams bind. I believe Eric made a fixture for this. Maybe Eric can step in here with a pix.

Then the final thing is the way the factory did it when they had gears that bind.....they just reached into a bin and found a size that fit. I was told the Sportster cam gears were color coded by size to help the installation process and read I believe on the Andrews Sportster cams if one was binding to send it back and they would supply another size.

Kurt


Cam cover on completely with all screws in place. Yes, all bushings replaced and line bored on a horizonal mill to location. A used set of decent cams and idler gear spin easily but this nos set of gears has tight spots which feel like teeth binding in places. The binding is not at all spots of gear rotation. The binding is also mild. I feel a click click click and then free motion as I rotate them. Visually I do see any rolled over edges on any of the gear teeth but something is not rolling against each other all smoothly.

Post Sat Jan 28, 2012 2:39 pm

Posts: 232
Location: Norway
PA, Since Tom dared to say it first, i`ll admit that i have used fine lapping compound to get NOS cams to run free
myself. First i would hand dress all edges of the teeth with oilstone though. Then again, i`ve ran into individual NOS cams that just won`t play nice with others whatever i`ve tried. Only replacing it with another NOS cam did the trick.
Malte.

Post Sat Jan 28, 2012 11:01 pm

Posts: 87
There are 3 primary considerations that could cause cam gear binding - the cam gears have mismatched pitch dia (too large, too small or mixture of both), the cam gears are not concentric (pitch dia varies at different locations around the gear circumference), or the bushings are incorrectly located. Since you mentioned that the used cams fit and rotate reasonably, this suggests that the bushing locations are fine. That leaves you to sort out whether all gears have the same pitch dia, or whether the pitch dia is non-uniform around the gear circumference. From your description of the tightness coming and going during rotation it certainly sounds like a concentricity issue where pitch dia varies at different locations around the gear.

Either way it sounds like you need a more uniform set of cam gears to correct the issue. So get your gauge pins out and let us know how they size up.

XR cam gear sets are all color coded, and I believe vary in pitch dia by 0.0005" or 0.001". You absolutely can not mix and match, or substitue a different color set or they will either bind or give excess gear lash.

Post Sat Jan 28, 2012 11:44 pm
Pa Site Admin

Posts: 5774
Location: Ohio USA

Thanks Guys ! I did not wish to measure pitch all over each gear but it looks like that is the only way to find the binds since I eliminated misaligment posibilities. If I do not locate a large enough variance in pitches, I may lube the bushings with grease and design and build a driver which takes the place of the pinion gear so I can power drive spin, using a variable speed drill, the set of with lapping compound.

Post Sun Jan 29, 2012 8:08 am

Posts: 640
Location: Wisconsin, USA
I use fine lapping compound to make the gears run easier and quieter in any motor where the tooth mesh is a little tight. 500 or 600 grit works well. You'll be pleased with how little effort it takes to make a big improvement.

Post Sun Jan 29, 2012 10:16 am
Pa Site Admin

Posts: 5774
Location: Ohio USA

amklyde wrote:
I use fine lapping compound to make the gears run easier and quieter in any motor where the tooth mesh is a little tight. 500 or 600 grit works well. You'll be pleased with how little effort it takes to make a big improvement.


I'm leaning that way Bro and thanks for the grit specs. Once I eliminate all possible errors not considered, I definately will.

Post Sun Jan 29, 2012 11:09 am

Posts: 391
Pa,
Take each gear out one at a time and rotate it about 90 degrees and reinstall. (ignore the timing marks for this). See if by changing one it eliminates the binding. If so you have found the source of the binding, an eccentric gear or similar. Then you may have a better idea whether to lap or replace one gear!
Robbie

Post Sun Jan 29, 2012 11:02 pm

Posts: 1027
Location: Ojo Caliente,NM,USA
I usually blue them and dress the high spots with a small diamond file.
Dusty

Post Mon Jan 30, 2012 10:19 am

Posts: 767
Location: CA USA
As Dave, I use blue, but then dress the high spots with an oil stone. Haven't progressed to diamond yet, probably quicker and easier tho.

Post Mon Jan 30, 2012 11:47 am
Pa Site Admin

Posts: 5774
Location: Ohio USA

Thanks again fellas for the great suggestions. The untimed gears sounds like another winner ! I had some machinist scrapers stashed away but cannot seem to locate where I placed them. I have not used them in several years.

Post Mon Jan 30, 2012 6:50 pm

Posts: 36
Don't use power drill to lap your cam gears. Lapping needs to be done with a back and forth motion and with the gears pulled out and the fine grinding paste moved back onto the face of the teeth every now and again. I did my new cam gears that way, rotated back and forth by hand, in1972 and they have been running good ever since.
It does not take long. In a slight case of drag in certain spots like yours, half an hour maybe? Maybe lots less even.

Post Mon Jan 30, 2012 7:09 pm
Pa Site Admin

Posts: 5774
Location: Ohio USA

Thanks Hopper.

Post Tue Jan 31, 2012 9:15 am

Posts: 640
Location: Wisconsin, USA
For more serious high spot removal I use a diamond impregnated laminate on a plastic handle from a company called E-Z Lap. They make them in various grits and you can grind away some of the plastic handle to get good access to the gear teeth. They are inexpensive and available from machine shop suppliy companies such as MSC. Once you have a couple of these, you'll find them to be very handy for many little sharpening tasks.

Post Mon Feb 20, 2012 3:40 pm
Pa Site Admin

Posts: 5774
Location: Ohio USA

Getting up to date.....I checked out all of the gear pitches. All were good. I reassembled one gear at a time for rolling freeness. All good. Now to study the gear teeth under a strong lense for burrs.

Post Tue Feb 21, 2012 10:46 pm

Posts: 1027
Location: Ojo Caliente,NM,USA
Just give up and blue every other gear them then rotate a few turns then it's easy to tell where to look.
Dusty

Post Wed Feb 22, 2012 10:22 am
Pa Site Admin

Posts: 5774
Location: Ohio USA

I've been doing that and it has worked successfully. Got all but one left to fit now :D


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