weird yank... thingie

[strom]

OK, here's what happens sometimes.
While I'm riding (in 3rd or 4th gear at bout 4-6k rpm), sometimes the bike jerks a bit... under moderate acceleration, like a momentary loss of power. Made me think a bit today... shaft drive gears slipping, gearbox (kida doubt it), the dampener on the secondary shaft or something?
Camchain and primary chain were replaced bout 8000 miles ago with new ones, so were all the bearings in the middle drive,...
I was kinda thinking in the ways of broken pick-up wires. Anyone had this problem?

LP

PS: 78E offcourse.

[skids]

Re: weird yank... thingie

Like surging from a vacuum leak or something?

[strom]

Like something missed a tooth or something. Or a complete electrical shutdown for 1/3 of a second. When the power comes back is the same as before, no exhaust pop or something present (which I would almost expect if it would be electrical).

LP

[ratbyk]

Sounds like a check of the PU coil wires are in order.
Ken/Sooke

[T748]

My XJ is doing something like that too. When I "get on it" with a fairly hard throttle, the bike will have that "jerk". It's like you twist the throttle and the bike starts excellerating nicely. as the throttle climbs for a few seconds there is just a spot where that little "tug" happens. The engine doesnt sound like its cutting out, it sounds fine. I hav'nt noticed it happening in 1st or 5th, but in 2 ,3 or 4th gear. I will try and make it happen in those gears (1 and 5) sometime this weekend as a test. It's not at any particular rpm either.To me it feels almost like a slight bind that tugs the power back for just a split second. I had a freind with alot more riding experience than me ride it. He thought that it's something coming from the middle drive area. Everything is great on the bike. It rides like a dream, cruises without a flaw. the only issue left is finding and fixing whats causing this. Maybe a lack of proper lubrication at one of the bearings? -Tom

[TopCatGr58]

Hey Strom,

Try pulling and plugging the vacuum advance and then run it in the same rpm and see if it behaves the same....IF not skip, then it very well could be the pickup coils, the vacuum advance will be rotating the advance plate just a moderate amount with very little load, but it will still be rotating MORE than if it's plugged! And so with some rotation the PU coil wires may be partly breaking connection, but then reconnecting as the plate rotates further, more throttle or higher rpms!?
T.C.

[Dennyz]

Sounds like a 3rd/4th version of the 1st/5th gear problem. My brother's SH did this. I turned out to be worn shift dogs and fork.

[TopCatGr58]

Hey DennyZ,

I didn't think about that as much, cause when I rebuilt/dremmeled mine, I found that the 3rd gear dogs were actually undercut at the factory compared to the others, so I would think it even less likely for them to wear out as fast as the other gears, especially the lower ones that are used more often and under higher stress?? But, yeah, anythings possible with these machines.

Perhaps another ON ROAD test would be to shift into 3rd, and then hold the shift lever up...don't reset the pawl, so that the fork is holding the gear in place, and then try the rpm range to see if he experiences the same surge/stutter. IF so....then it's probably not the gears, but if it doesn't do it while holding, but then does after he releases the shift lever, then most likely it IS the gears...relatively simple test without tearing down the engine?!
T.C.

[strom]

Originally posted by Dennyz
Sounds like a 3rd/4th version of the 1st/5th gear problem. My brother's SH did this. I turned out to be worn shift dogs and fork.

I got to the same conclusion... sometimes I find a false neutral when shifting from 3rd to 4th. The problem occours while in 3rd gear. I guess I'll have to take it easy till the end of the season, then another engine session. I got camchain tensioner on the list, this problem, oil drain bolt needs threads fixed, tripple tree and swingarm replaced and repainted,....

LP