Rear wheel slipping at high rpm

[Ctopher87]

Well I've been busy on my 80sg. I've worked out a lot of gremlins but I've got one that showed up on my way to work this morning. The highway was clear for the next 3 traffic lights so I turned out in first gear and went wot. Up around 6500 rpm I felt a slight jerk coming from the rear. Shifted into second and it happened again in the same rpm range. I ran all the way to redline and the jerking started to get more noticeable. It's almost like a drive chain that is loose on a chain driven bike. Shifted to third it happened again. Got into fourth and went to redline without the slipping. By then I was going just a tad over the posted limit so I shifted to fit and let off the throttle. Does anyone have any idea what would be causing this? I'm stumped. I just replaced the tires and lubed up the sprockets on the rear wheel and the driveshaft. Tires are properly balanced and the rotors are straight. It's only happening under hard acceleration.

[BA80]

You have the second gear issue, first gear also. Not too hard to fix but time consuming.

http://www.xs11.com/forum/showthread.php?t=5090

[Radioguylogs]

3rd too?

Are you sure it happened in third gear?

That's the only thing that doesn't match BA80's diagnosis.

[motoman]

Are you sure it happened in third gear?

That's the only thing that doesn't match BA80's diagnosis.

Hmmm.......possibly some excessive speed-shifting up thu third in the past decades..........matches well with BA80's diagnosis and suggestions.

[Ctopher87]

Yeah it's all the way through third. I feel I could pull it all apart rather easily considering I've been wrenching since a was a kid. One thing I've been thinking about but I'm not positive it would work, could I swap the gears out of a later model xj? I know there were some changes between the two but I don't know if anything changed in the bottom end or not. I've been able to find a few for around a hundred bucks from the xj but no luck on the xs.

[Ctopher87]

It's not the first time I've stretched the legs on it but it's the only time I've had the issue in the 6k I've put on it since June

[BA80]

Never heard of 3rd gear skipping. No need to buy new gears, the dremel trick and washer swap work just fine. repaired min that way 5 - 6 years and about 70K miles ago and it's still working great. And I'm not nice to my transmission.

Read the forum link I provided in my previous post.

[TopCatGr58]

Well, it's rare but I HAVE heard of 3rd slipping also. We had one member who tore his down to fix 2nd, but didn't do 1st, and after he had it back together, 1st went out a little later. Tore it down,fixed 1st, back together and a while later 3rd started skipping. Had to tear it down a 3rd time to fix 3rd. That was the last time he had to tear it down. 3rd is less likely to skip because unlike 1st and 2nd, they WERE actually undercut at the factory, but given enough wear and tear, it too can fail.

The XJ gears are the same as the XS11's, the problem wasn't figured out by Yamaha until years later, and THEN they undercut the gear dogs/slots in the replacement gears, but they didn't make that many, and now are no longer available from Yamaha anywas. So either repair yours, or get some other used gears and treat them to make the swap go a little quicker if you want.

As a side note, I repaired mine (1st and 2nd) in 2000, and I didn't swap the washer. I've put on ~25K miles since then, had ~50K miles when the gears first started slipping/skipping. I don't abuse the bike, didn't do very many speed shifts, but do accelerate a bit farther in 1st and 2nd than many other folks...taking it up to 6+k rpms at times like you did..."spirited" acceleration. It had not given me any hint of any problems this past year prior to my recent rebuild and frame swap. BUT on my rally ride/trip, it actually started occasionally skipping in 1st gear again! Wish it had shown up BEFORE I had swapped frames and had the engine out, would have made it easier to work on than now that it's all back together. Will be curious to see the appearance of the dogs and slots. I have a spare set of gears from another engine that I could work on that have NOT had any prior grinding/treatment vs. retreating my original gears which did have a fair amount of rounding off and required a considerable amount of material to be removed to get back to a square and even a slight undercut profile!

There was also a member who actually had one of the dogs I think it was on 2nd gear that actually broke/sheared off after performing the dremel repair...don't know if it was that he left too sharp of an edge at the base of the dog...or if he didn't get all 3 cut even enough so that the 1 dog was put under more stress than the other 2 which might have contributed to the stress crack/failure?? Once the surface hardening has been penetrated with the grinding...they don't necessarily need to be micrometer level even because they will mash/beat/mold themselves together to an even stressed position. The key is to ensure that you put a good undercut into the contact surfaces so that they PULL the gears together under stress. It was this action that occurs with engagement after the dremeling that led me to not swap the washer on 2nd. Folks have tried it on 1st, but didn't work and caused engagement problems with the other gears shifting the secondary shaft too far.

And the washer swap is only for 2nd gear. For some reason the earlier models 78-80 develop the 2nd gear skip first...whereas the later model years...81-82 seemed to develop the 1st gear skip first, as well as the 2nd gear. This may be just a manufacturing tolerance in the dogs/slots of the gears...don't know....the transmissions are essentially the same. There was a change in the size of the bearing and spacer for the countershaft gears shaft, but the parts are supposed to be the same otherwise.

T.C.

[hamjam]

"Got into fourth and went to redline without the slipping. By then I was going just a tad over the posted limit"

just a tad over

my bike the " buick " exceeds the speed limit anywhere in Canada in 2nd

[3Phase]

[...]
And the washer swap is only for 2nd gear. For some reason the earlier models 78-80 develop the 2nd gear skip first...whereas the later model years...81-82 seemed to develop the 1st gear skip first, as well as the 2nd gear. This may be just a manufacturing tolerance in the dogs/slots of the gears...don't know....the transmissions are essentially the same. There was a change in the size of the bearing and spacer for the countershaft gears shaft, but the parts are supposed to be the same otherwise.

T.C.

I think the more frequent 1st gear problems in the later models happens because Yamaha stopped putting the kicker idler gear in the later engine cases. The kicker idler gear rides on the 1st gear wheel and doesn't just give the kicker something to turn and start the engine, it also stabilizes it.

The 1st gear wheel is relatively huge, heavy, is put under serious loads and it rings like a bell when you shift into 1st, especially if it clunk-shifts. The idler gear damps some of the, "CLUNK! (boing-oing-oing-oing)(wobble)(wobble)(wobble)" at the gear but removing it saved some more money for Yamaha since they had already deleted the emergency kicker assembly and the lever and most of the new XS11/XJ11 transmissions would still last until the warranty expired. Unfortunately letting the 1st gear wheel wobble on its bushing wears out the bushing so the gear wheel and its slots can tilt away from the 4th gear wheel dogs and they both start to wear/chip/crack/whatever.

Once the dogs and slots are worn it's like lowering the setting on a clicker torque wrench. If it used to take 90 ft/lb to make the wrench click but the gearing only ever needed 80 or 85 ft/lb to accelerate you and the bike and all of your gear then it would never click. When the parts wear and they start to break away/click with less torque then it just gets worse from there.

[Ctopher87]

I think I'll order another gear set considering the bike is currently my only means of a to b. If I need any help I know were to find it. Thank you all

[DiverRay]

That seems like a good idea. I've done three of these now, and not all on my machines. If you have a set of gears you can set up the counter-shaft assembly, and then do the swap in one weekend as the first time, and usually in one day after two or three times.