5th Gear Problem?

[TopCatGr58]

I just reviewed the How the XS11 Tranny works tip in the Repairs section, and although 5th gear slides on the countershaft, it is splined and solidly connected to the countershaft, and spins all the time that the shaft spins. IT's dogs are NOT engaged when it is in 5th, they are only used for 2nd gear, so it's possible that either some teeth have gotten damaged on the outer edge of the 5th gear, or it's pinion gears as to cause your skipping symptoms?? Hopefully Yamanatic can enlighten us with what happens to 5th to cause it to fail during his road racing experiences!?
T.C.

[Yamanatic]

Hi All,

I don't know if possibly the referral was to my racing experiences with XS11's gearbox, but since my ears were burning...

The problem I encountered with the actual 5th gear wheel was the presence of a bushing where a needle bearing should have been to keeping the whole works spinning correctly under max load. I left a skid mark to behold at Daytona when my #5 driven gear locked on the shaft at about 135mph. Since the transmission is behind the clutch, when it locked up there was no way to disengage the rear wheel from the failure by disengaging the clutch, and I had no choice but to ride it out. It twisted the shaft, broke the engine case, and wore a nasty flat spot in the tire - but the gear held and did not shatter. In the new motor (the one with the turbo installed), I modified the gear by replacing the bronze bushing with a caged needle bearing. But please read on:

The drive cushion (that stack of big fat spring washers on the shaft the primary drive chain goes around) can weaken with age. The cushion face will actually ride completely up the ramp and "jump" back into the proper position 180 degress from where it was initially installed. It feels all the world like the 2nd gear skip, but is not the transmission loosing engagement but the cush drive exceeding design limits. Generally there is no damage caused by this very disheartening event, and the fix is quite easy - just install one more washer into the cush stack. Check the repair/parts manual and it will make more sense.

This event usually occurs in the upper gears because the cushion is exposed to the highest torque load and the greatest resistence by the drive train. The trans ratio/gear reduction is at it's lowest and there is no where for the applied load to transfer such as as through an increase in RPM or tire spin; the cush drive is now the weakest link. I experienced this on my track bike as well as on customer bikes - first time I saw it was on a 1978 full dresser customer bike that skipped only above 85 in a head wind. The couple that owned the bike probably weighed as much as the scooter, and they pulled a trailer besides. I was at a loss when I dismantled the motor and found absolutely nothing wrong with the gearbox. When I started looking at the primary chain for a possible problem, I saw the marks the drive side cush left on the driven side when it walked across the flats between the ramps. I called Yamaha, and the service rep agreed to cover the warranty because there was no bulletin on the failure; he explained the fix to be the inclusion of an additional washer in the spring washer stack.

The bike went back together with an extra $4 washer installed, $40 in gaskets and oil, and 5.5 hours of warranty labor; problem solved and a happy customer! First time it happened on my race bike I knew exactly what it was and kicked myself for not fixing it before hand - thankfully I learned my lesson on that customer bike and completed the repair in under an hour. This may not be what is happening on your scoot, but it would sure be worth a look. If it has happened a few times there should be marks on the flats on flats of the cush ramp, and signs that it has been over the top. You will need a hydraulic press to stack the extra spring-washer in and install the retaining clip, but will not cause any harm to the assembly or drive train with the mod.

Cheers,
Yamanatic

[TopCatGr58]

Awesome answer and explanation!!

Hey there Warren,

Thanks for that vivid description! And hopefully Gtrmn will see this soon...before he attempts to tear into his engine!

So...from what Yamanatic states it sounds like this is a probable normal sign of wear on the engine, and that to avoid it, you will probably just want to downshift a gear to get more leverage for the engine to get you going faster without putting as much stress on the drive cushion assembly! Cause, to repair it I would think WOULD involve splitting the cases to remove and R&R it with the extra washer!

So...you should be able to relax and enjoy your machine and just avoid full throttle rollons in 5th!
T.C.

[GtrMn]

Hey guys! Hmmm interesting...ok so what the heck is a cush drive? Anyone got a pic of it...etc. etc. It does "sound" like that may be the problem though....cause it only happens in 5th under a lot of load. I did notice the 5 1/2 hours of labor too...haha

[Yamanatic]

Hello again,

The cush drive fix can be done without removing the motor and/or splitting the cases; I unfortunately learned that hard way (5.5 hours is Yamaha flat rate to R&R the transmission). The drive end of the cushion can be seen as the smaller gear that drives the clutch, under the cover and towards the top front of the clutch basket, and extends through the big hump behind the cylinders.

The cush assembly is on a splined shaft that passes through the primary chain sprocket/gear; you can fish the shaft in and out using a dowel to line up the gear when reinstalling. I do not have a parts book, and it is a little tough to describe the arrangement exactly by memory, or what's left of it - lol. The engineering of this assembly is really quite nifty, and usually gives no trouble whatsoever. I never even knew this little widgit even existed until it acted up :-0

Cheers,
Warren, the Yamanatic

[GtrMn]

The drive end of the cushion can be seen as the smaller gear that drives the clutch, under the cover and towards the top front of the clutch basket, and extends through the big hump behind the cylinders.

Ok..from how I reading this the cush drive is attached to the primary gear drive that drives the clutch...that's a mouthfull..haha.
After removing the clutch does the entire assembly pull out or do you first remove the primary gear?

At this point I'm thinking my problem is one of 3 things....either the cush drive....a bent shift fork...or damage to the shift drum so that 5th gear is not engaging somehow as it should. I do know I've hit the false neutral between 4th and 5th several times.

Oh, BTW I did order all the transmission parts from a member here just so I could try and tell how everything meshes together...and possibly do the second gear fix etc. on the gears before pulling mine.

[Yamanatic]

Hi GtrMn,

If I remember correctly, the nut comes off the shaft behind the clutch, then the assembly is removed from the opposite/left side of the motor. In all honesty, I would have to look at an exploded diagram (or just tear into it) to get the exact procedure fresh in my memory again; my appologies but it has been many years since I have done one.

In 5th gear, the shift cam follower is at the end of the slot; seems it is less likely the cam grove is worn, but the pin could be worn or bent. Whatever the problem, it should be quite obvious as yamaha builds very straightforward and notably smooth gearboxes. The cush issue is not so obvious...

It sounds like you are ready to go for a complete disassembly, so possibly it would be best to look carefully at the cush drive when you are in there. If all looks well with the gear box, just add a cush washer as added insurance.

I really wish I could help you with the project, but unless you live near Eau Claire Wisconsin there is little I can do (plane ticket gladly accepted too). The problem living in the sticks is there is not a convenient shop to visit for a quick look at the parts list either :-(. Given the use my poor Turbo has received over the last 17 years, I will probably have plenty of opportunity to take pictures when I have to give my beast a similar renewal.

Please let me know what you find, and if possible, swing into the dealer and borrow their repair manual if you decide to pull the cush first. You know the beast is just toying with you, and wants some attention!

Cheers,
Warren

[TopCatGr58]

Okay Gtrmn,

First you can go to The Official Yamaha Online Fiche site and view exploded views of our machines, just go the parts secton, select motorcycle, year, model, and then section!

Apologies for the size of these images, they are "borrowed" from Bike Bandits version of the online fiche!

1st here is the Primary Shaft/chain. Part#16 is the large gear on the clutch side that drives the clutch basket!

The large section near the chain is the starter clutch assembly!

Part24, bearing case for Primary Shaft, on the gear shift side, it's the part just forward of the starter cover!


Starter Clutch, this is what the primary shaft fits into before it comes out the clutch side of the case!


So...apparently Warren/Yamanatic says that you can pull the primary shaft out the left hand side once you remove the large nut on the clutch side, and then the bearing cover on the shift side, and I guess you use a dowel pushed in from the clutch side to help push the shaft out, and hold the starter clutch and parts in place until you're ready to put the primary shaft back in! Just a shame we can't get access to the starter clutch parts this same way, or can we?
T.C.

BTW, I have hit false neutral many times as well, just have to be a little more forceful when upshifting, so you're experience is relatively normal!! Gtrmn, if your 2nd or 1st gear is acting up, then, yeah, I'd tear into it, but if it's just this 5th gear thing that you have described, which seems to match what Yamanatic has described, might be more work than what it's worth??

[GtrMn]

Thanks for the pics T.C! Wow..I 've never even seen some of these! Time to do some studying..

[GtrMn]

And thanks Yamanatic for your input...Still wondering one thing though...why wouldn't it do the same thing in 4th gear...with a bunch of throttle say at lower speed...

[GtrMn]

but if it's just this 5th gear thing that you have described, which seems to match what Yamanatic has described, might be more work than what it's worth??

Yeap it is ONLY 5th gear acting up...and then only with a bunch of throttle. It'll do it riding 2 up more so though at lower speeds and not as much throttle. Wish I could get it to do the same thing in 4th...I think then it would point directly to the cush drive.

[GtrMn]

Ok guys...let me know if I have this right. Looks to me like part #'s 5 and 6 are the two that come together and "could " make that "ca-clunk" sound if they were to come apart and spin. And the part # 7 that looks like washers is actually the spring damper that may be worn...so just add another spring damper then on the shaft there?

[Just In Case]

Yep, parts 5 and 6 are the cush drive, and 7 are the washers.

Dave

[Yamanatic]

Excellent diagrams; I concur with numbers 5, 6, & 7 being the suspect cush drive assembly items in the illustration. TopCatGr58, you are the Man! Thank you so much for the link to the parts list.

With the very few bikes I worked on that experienced the cush drive skip other than my own (only 3 total, 2 touring and one drag bike), the problem could only be reproduced in a lower gear by getting the motor well into the power band with the throttle WFO, and jumping on the brakes hard enough to force the skip. It took Max HP and a LOT of brakes, and still would only occasionally skip; 3/4 moon, barometric pressure at exactly 2.56 milobars, and Jupiter aligned with Mars - lol.

I studied the gearset illustration of the transmission in TopCatGr58's link, and the active engagement dog in Fifth is the small end of the double gear #5 sliding internally into gear #8 locking to gear #19. IMHO it would seem that if this engagement were to be compromized enough to cause the trans to jump under heavy load, the chances of re-engaging solidly under power are minimal - it should be a chronic failure.

I am probably being overly optomistic, but it would be nice to fix the problem with as little work and $$$ as possible; I tend to try the path of least resistance first myself. As an aside, I am way impressed by the collective knowledge and enthusiasm of the XS11 forum members, and you all have really got me fired up to get my bike back on the road ASAP too!

Cheers,
Yamanatic

[GtrMn]

I studied the gearset illustration of the transmission in TopCatGr58's link, and the active engagement dog in Fifth is the small end of the double gear #5 sliding internally into gear #8 locking to gear #19. IMHO it would seem that if this engagement were to be compromized enough to cause the trans to jump under heavy load, the chances of re-engaging solidly under power are minimal - it should be a chronic failure.

Can't wait to get the tranny parts so I can see what slides and engages into what...