Problem with 98 TZ250

[Luckystrike]

I have this problem. Hopefully someone can help me out with this or atleast give me an idea of what might be wrong. I went out on my first practice session to find that the bike wouldn't rev. So I pulled in and checked the plugs to find that they were wet. So I went down two jet sizes and went out again. Still the bike wouldnt rev but if you hold the throttle wide open for about 4 seconds, the rpm would shoot up extremely fast to 13k with no power. I pulled back in and checked the plugs again and once again it was wet. went 2 sizes leaner on the mainjet and went out again. Same symptoms. Came in pulled the plugs and pulled the head off to find that the head was went with oily deposits. At about this time I also found that the clutch was burnt out hence the reving to 13k with no power. Put a new clutch on and went out for a 4th session. Yet the same symptoms persist. Someone told me that Tranny oil might be leaking into the crank and fouling the plugs and causing the bike to have symptoms of being extremely rich. I'm using Nutec GP2 with A747 at 32:1. What do you guys think could be causing this?
Any help will be greatly appreciated.

[ysr612]

do you think crank seals

[nicoloff]

I would definitely do a leak down test in or to see if the crank seal is leaking. If your changing jet sizes and no difference I would look for something besides jetting.

[TZ925]

If you use a quick shifter, try disconnecting it or checking for loose linkages. I had a similar problem where the bike would rev to 10,500 or so and the vibrations made the linkage pass the interrupt switch making me believe we were way rich. Hope your problem is something easy like this.

Monty

[CharlieM#90]

Originally posted by nicoloff:
.. If your changing jet sizes and no difference I would look for something besides jetting.

Could still be jetting.

Symptoms of not pulling along with wetness can be indicative of too large a nozzle jet.

And at 32:1, he could be a bit rich. Might want to lean it out to 28:1 or even 24:1 to see what happens.

Could even be float level in carbs.

My '99 (essentially the same motor), loves a mix at 28:1 with nozzles at R5 or R4.

He also says he was "pulling in" to check plugs. Unless he's doing a real plug chop, it's a meaningless exercise. If you just "pull in" and examine plugs/heads, they'll _always_ look rich.

And check your power valve solenoid - if it's not functioning properly (staying shut), it won't rev out and will give false plug readings.

Charlie Mc #90

[TwoCycler]

Charlie's right, it really sounds like a nozzle. Try an R5 or R6 and quit going down on mains (try a 350-370).

Rocky