Something Failed, let’s find it! Transmission Analysis.

[barbagris]

I do have to own this, I am heavy footed in 4-5 downshifts using a NORMAL shift pattern. I can remember fairly aggressively kicking down a gear from 5th to 4th when I was using the normal shift pattern (now think about what a 4-5 downshift is using GP shift, its an UPWARD movement, you absolutely cannot generate the same force going up).

So no road racing with a heel/toe shifter.!

 

[albertaduke]

@albertaduke Finally a good news story!

I’ve identified the clack/slap/ feel and it’s innocuous and a false danger sign!!

It comes from the way 5th gear is undercut. All the gears and dogs besides 5th are designed differently so he can fully backcut the height of the gear side of the interface.

5th is different. See the pics below. 5th has a weld at the base of the gear teeth. It’s not back cut into the weld, but the dog can extend further in that the weld. What’s happening is the back cut shape is drawing in the 3/4 dogged gear closer to the 6th input gear, it slides over the weld and slips. Then it meets up with the back cut shap and slides over the weld and repeats.

This explains why more throttle makes it stop and more RPM. Increased speed or load will lock the dogs and prevent it from riding up the weld. Yours is 2500 vs my 3000 issue, this will be dictated by torque and the angle of the cut on the back cut.

Ride on, worry not, it’s a non issue. I should say, if he were to back cut it more, the gear's strength would be in question because he'd be cutting into the weld material. Basically, he did the best he could to provide lockup without compromising the strength of the teeth, given the way the stock gear is manufactured.

I believe the reason it stopped on my bike over time, was the faces wear into each other and fully seat. Once seated fully they provide better lock up over time giving it more grip between dogs/teeth and preventing it from riding up the welded portion.

this explanation is way over my pay grade as I would have never figured out something that complex however I take your answer as the best news I read this morning ,if you do not mind I am going to print and give my wrench a copy of your investigation for his benefit as he was also baffled by my problem ( twice)
again thanks a lot for lifting that weight off my shoulders ....and saving me $$$$

 

[Claviger]

@albertaduke

I was reading an old thread by you regarding slapping in your trans before you had it rebuilt. I found that after I had made that post. Is the current ongoing slapping exactly as it was before it was rebuilt?

The slapping you're experiencing may be different than what I had going on. In my case, it was the provided explanation.

In your case, if it occurred PRIOR to the rebuild and undercut work and persisted afterwards, then the above explanation is not consistent with your exhibited symptoms.

If that is the scenario, there are only 3 possible remaining likely causes in my mind:
Clutch
Bevel Box
Torsional Output Damper

I think I'd read you'd replaced the Torsional Output Damper with the revised version.

 

[Claviger]

A minor miracle occurred today:

3-4 Input gear
3rd output gear
and #21 the splined bushings that ride under 3rd and 4th output gears

WERE IN STOCK IN THE US?!

I'll have them in hand on Tuesday next week. So I can ship Robinson the whole Trans plus new gears to undercut and get this done relatively quickly.

Triumph of Seattle prices are better than Bike Bandit, just a heads up!

 

[warp9.9]

Ok did i miss something like you cracking the case so we can see what might have happened? Just curious as I've been out digging a ditch

 

[Claviger]

Yes warp. It’s all done and trouble shot

 

[warp9.9]

Ok went back and got caught up. Yes the warp threshold can cost money. Don't ask me how I know. I do have a spare grenade left if you need it


Keep going brother there is more to break. It just depends on how awnry ya want to be
Been there broke that

 

[albertaduke]

@albertaduke

I was reading an old thread by you regarding slapping in your trans before you had it rebuilt. I found that after I had made that post. Is the current ongoing slapping exactly as it was before it was rebuilt?

The slapping you're experiencing may be different than what I had going on. In my case, it was the provided explanation.

In your case, if it occurred PRIOR to the rebuild and undercut work and persisted afterwards, then the above explanation is not consistent with your exhibited symptoms.

If that is the scenario, there are only 3 possible remaining likely causes in my mind:
Clutch
Bevel Box
Torsional Output Damper

I think I'd read you'd replaced the Torsional Output Damper with the revised version.

yes the slapping noise is exactly as previous occurrences the best way to describe the feeling is to imagine two steel bricks slapped together intermittently the resulting noise and shock is what I feel in the footpegs. . I would tend to eliminate the bevel box as the footpegs transmit that slapping in a manner that preclude apparently the distance from the rear of the bike,what I mean is when it occurs I sense it strongly coming from close to the footpegs .


here is also the proper timeline for my situation
in 2011 I replaced the bearings in the output shaft on my 2006 r3 classic like many other riders experienced, the bearings were in pieces . sold the bike in 2015 . bought a 2013 roadster same year traveled across the US in summer 2016 when it developed this "slapping"
the shop worked on the trans back in the early winter 2016 replacing #4 gear with a OEM and a shifting fork . then my garage burned everything went up in smoke in feb 2017 , bike cars the lot so I never had a chance to test if the work did the magic, and bought a 2012 roadster spring of 2017 .
when slapping developed on that 2012 model I figured take it to robinson,'s and have it undercut .might solve the problem .....not.
the so called slapping is still there albeit not so pronounced and not in 4th anymore . I have spent enough for now so my solution stay away from 5th gear when riding uphill or stay out of the 2500/ 3000 rpm range when it comes to motor trans and electrics I am a basic wrench, hence my solution but the next service ( 20 000kms) I will ask about the possible cause you mention starting with the clutch although one would think if it happen at around 2500-3200 rpm it should be felt in every gear? I am discounting the outputshaft for the same reasons, as well as the bevel box as the noise and shudder occurs definitively within an area of the engine block

 

[Claviger]

Ok, thanks for the catch up and detail that it’s now only in 5th.

I suspect your current bike had two separate events, strangely I have also had both.

Initial slapping as you describe on mine back in 2015 was the rounded fubar 2nd gear. That got fixed and slapping was gone.

Post Robinson I had 5th slapping which faded over time and is my earlier explanation.

I believe if yours is only in 5th at a certain RPM that my earlier theory holds true on your bike and 5th is indeed fine to use.

 

[albertaduke]

Ok, thanks for the catch up and detail that it’s now only in 5th.

I suspect your current bike had two separate events, strangely I have also had both.

Initial slapping as you describe on mine back in 2015 was the rounded fubar 2nd gear. That got fixed and slapping was gone.

Post Robinson I had 5th slapping which faded over time and is my earlier explanation.

I believe if yours is only in 5th at a certain RPM that my earlier theory holds true on your bike and 5th is indeed fine to use.

I will be gentle when in fifth and staying away from the RPM range when loading the trans... when we ride the RAAwest you will have to ride my R3 and see for yourself if you still come to the same conclusions..