Cam gear and crank nose gear gap

[malmac]

Duane Ausherman indicated that the gears around 0 were marked 0-, 0, and 0+. This indicated that something could be slightly less than 0 and another could be slightly more than 0. Seems like per what Dave said, adding the two "numbers" together doesn't get 0 but even more less than 0.

Mal, what is stamped on the outside of the engine case?

I had someone else do the bottom end on my R69S. Here's a picture of the cam gear. I don't see any numbers on it. There doesn't seem to be anything on the crank gear. The number on the engine case is +1. Nothing was changed during the engine overhaul. What should I make of that?

Kurt

I didn't fully respond to your post.

Given your case is marked +1, then the "0" cam gear had to be fitted after the bike left the factory, to get the correct backlash. I guess it is possible that the crank gear is the original +1 gear and a "0" cam gear matched and remedied a worn cam gear (obviously prior to the most recent work). But hey I am guessing.

Mal

[schrader7032]

Mal -

I'm the first person to have ventured inside my R69S engine. I checked the invoice for the work and no gears were purchased, so the ones I have are still the originals. Here's the crank gear.

[jwonder]

=jwonder post_id=79580 time=1639699354

James

I am just concerned that if my gearset expands when hot, faster than the engine case expands, that my new gears will damage each other and flood my newly rebuilt engine with ground up aluminium particles.
The gears run smoothly but there is not a surplus of clearance.
Basically, how close is too close?


Mal

The crank gear is ferrous so it will not expand much and the camshaft gear is fairly thin. The crankcase will expand more due to its mass. Also remember there is a lot of oil up there being sprayed directly on the crank gear that keep them lubricated and cool.

My new R 50 S gears when I measured them were perfect, and when installed I could feel no backlash but they moved freely. I have close to 300 miles on it now with 4 oil changes. All good.

As long as the backlash is right they will be fine. They will wear in together.

[malmac]

Mal -

I'm the first person to have ventured inside my R69S engine. I checked the invoice for the work and no gears were purchased, so the ones I have are still the originals. Here's the crank gear.

Kurt

Well I was a believer that the factory always fitted the gear set that corresponded to the number stamped on the engine case.
Your example indicates that was not what always happened. I have heard that towards the end of the model run, parts were used up and so strict adherence went out the window.

Also the number etched into the crank gear, if there is one, would most likely be obscured by the nose bearing in your photograph.

Mal

[jwonder]

Mal, also many crank gears don’t have a number on them either.

[malmac]

=jwonder post_id=79580 time=1639699354

James

I am just concerned that if my gearset expands when hot, faster than the engine case expands, that my new gears will damage each other and flood my newly rebuilt engine with ground up aluminium particles.
The gears run smoothly but there is not a surplus of clearance.
Basically, how close is too close?


Mal

The crank gear is ferrous so it will not expand much and the camshaft gear is fairly thin. The crankcase will expand more due to its mass. Also remember there is a lot of oil up there being sprayed directly on the crank gear that keep them lubricated and cool.

My new R 50 S gears when I measured them were perfect, and when installed I could feel no backlash but they moved freely. I have close to 300 miles on it now with 4 oil changes. All good.

As long as the backlash is right they will be fine. They will wear in together.

James

That is good news re your new timing gears. I don't quite understand your two statements.

1. "when I measured them were perfect"
2. "when installed I could feel no backlash"

I was working on the assumption that .01mm~.02mm backlash would have been the criteria for perfect
and "no backlash but moved freely" would have constituted, inadequate backlash.

In the photograph you posted the cam gear was etched with "-2", does that match the number on your engine case? Also I am assuming that engine is not your R50s engine?


Mal

[jwonder]

All great questions.

.02mm is 0.00078“ and my gauge is in .001” increments. So, the backlash dry and clean was under .001 and looked in range, so i call that fine with my measuring instruments.

Installed in the engine with oil there was no perceivable backlash and it was very easy to spin and was very smooth. In fact one of the more easy ones I had to spin. Sorry I did not specify with oil. I am on my phone typing with my thumbs.

The engine and gears shown are from an R 68 and they are not matched gears to the motor nor to each other. The cam gear is a -2 and the crank gear is a -3 and the backlash is perfect. They look great and that’s the way it was running. Still not sure what to do with that and still trying to decide.

I was told by several knowledgeable people that especially for the 20 degree gears you can run a mismatched set that gives the right backlash. If they had already run together and are fine on the backslash your good to go. I am still not fully comfortable with that and I am doing more research.