I have no idea what but I am sure it is bad

[streaks383]

I have a 2005 yz-250, eric gorr 295 kit, bike has been a dream until today. Now it has a surging thing going on rather a miss is happening, not a miss in the engine but a miss in the drive train somewhere but it is only in 5th gear and it is very consistent, it happens like clock work at constant intervals regardless of RPM or throttle position? The best way to describe the feeling is if you were to go at a constant rpm in 5th gear and were to fan the clutch. Any ideas?

[cnrcpla]

Sounds like the clutch is slipping... Its odd that its only happening in 5th though. I would take the plates out and inspect them. Look for warping, scratches, and make sure they are still in wear specs. Change the oil and see what happens after you inspect all the plates.

[Stusmoke]

Thats an odd issue... But like cnrcpla said maybe the clutch is slipping but strange that its only happening in fifth. Your oil level isn't too high? I've heard of people having similar issues and less oil solved it. My 2001 YZ 250 takes 700 mils of oil and shifts like a dream

[streaks383]

I am hoping it is the clutch.  It makes sense that it would happen in 5th gear first, that one puts the most load on it.  But what made me wonder is because in my experiences the clutch either slips or it doesn't, I have never had one that slipped and caught like this.  I pulled it out last night the plates are well in spec and look pretty good, the steels do have so discoloring from heat but I did not check them for warp yet, I cleaned every thing and the plates have been soaking in new oil over night.  Thanks guys.

[MetalMike1982]

I am hoping it is the clutch.  It makes sense that it would happen in 5th gear first, that one puts the most load on it.  But what made me wonder is because in my experiences the clutch either slips or it doesn't, I have never had one that slipped and caught like this.  I pulled it out last night the plates are well in spec and look pretty good, the steels do have so discoloring from heat but I did not check them for warp yet, I cleaned every thing and the plates have been soaking in new oil over night.  Thanks guys.

I had a Honda atc200x that would do exactly what your yz is doing . It would slip in and out like you were feathering the clutch in top gear and it ended up being the clutch . good luck

[Marco810]

I am hoping it is the clutch.  It makes sense that it would happen in 5th gear first, that one puts the most load on it.  But what made me wonder is because in my experiences the clutch either slips or it doesn't, I have never had one that slipped and caught like this.  I pulled it out last night the plates are well in spec and look pretty good, the steels do have so discoloring from heat but I did not check them for warp yet, I cleaned every thing and the plates have been soaking in new oil over night.  Thanks guys.

Clutches will do that when there worn. The work truck im using would do the same thing going up hills, just start slipping hard, would let off the throttle, then go back into and it would stop, replaced the clutch in it not long ago and its fine now. Not a wet clutch i know, but same principle

[streaks383]

It ends up it is not the clutch, it was doing it at perfectly timed interval not like slipping.  Now I just have to split the cases and see if I have a bent shift fork, worn drum, rounded dogs or rounded gears, fun times.  At least I don't have to worry about cams, valves, chains and such.

[cnrcpla]

Post up some pics. Should be interesting, but good luck with it 

[Recovered]

sounds like it could be either worn gears or even possibly a broken cog/tooth on the gear good luck

[cnrcpla]

sounds like it could be either worn gears or even possibly a broken cog/tooth on the gear

That's what I was thinking, but I thought it was a little far fetched, but now that we know it isn't the clutch, it is sounding more probable.

[Stusmoke]

if the clutch was slipping, you'd think that the revs would increase/decrease as the clutch engaged/disengaged. Is it doing this? If not it sounds like it might well be that fifth gear is missing a tooth or two

[TotalNZ]

How far apart are the timed intervals?
I can't imagine it's a broken tooth, you'd be having far more problems than an intermittent slip.
Are you sure it's not the clutch? maybe something in the selector fouling with the clutch rod or actuator or something.
I'm not really familiar with YZ gearbags.

[streaks383]

It's not the clutch, I put a new one in to make sure, its skips at very regular intervals and a couple times a second.  On another forum I was told the digs for 3rd and 4th may be worn causing 5th to not engage properly, shift forks could also be trouble as well as the shift drum itself.  I split the cases and took it to a shop I really trust so they can look at it and tell me what is out of spec.  The teeth on the gears themselves were in fantastic shape.  This bike has maybe 150 hours on it since it was  new in 05,  I think maybe those hitting those arenacross whoop sections in 4th and 5th may have bent something, I will keep everyone posted.

[TotalNZ]

Oh couple times a second, thought you meant further apart than that.
Yeah think you might be on the right track with the shift forks being bent or worn dogs.
If you've stomped the shifter real hard can bend a fork and it won't stay in gear properly like that.

[TMKIWI]

Worn dogs is my guess.