93 250...power problem. Is it just jetting?

[SpectraSVT]

I know theres lots of jetting posts but none seemed to cover a problem this extensive. So here it goes. I rode my buddies bike last weekend and the power was horrible. 1st thru 3rd the power cut out and missed constantly. No smooth part at all. I thought it was jetting so I went up 1 main and it cleaned up slightly in 3rd but 1st and 2nd were still useless. 4th and 5th absolutley ripped hard with no probs.

I'm picking up his bike thursday to look it over cause no one should have to ride a bike like this. He bought 1 more size up on the main so far. My intitial thoughts are that the bike is really lean everywhere. But with 4th and 5th running so clean I'm not so sure anymore.

From previous posts it looks like I need to clean the carb and vent hoses. Plus check reeds. Other things I thought of was maybe float bowl is off but I don't know how to check that or what happens if its off. What do I look for with powervalve and would that be messing up stuff?

Top end has about 7-8 rides on it. He is a beginner rider and spends most of his time in 2nd and 3rd. The bike is all midrange.

Any thoughts or something else I should check?

 

[SpectraSVT]

ttt

 

[Matt Fisher]

I had a similar problem with my 92. Turned out that when I rebuilt it, the ring didn't seat, so compression was a little low (150psi @ 3200 feet). This caused it to run pig rich, and I was fighting jetting issues big time. Because it was so rich, the power valve began to get sticky in just a few hours.

Slapped in a new ring (now 185psi), cleaned the power valve, and wala- much, much better. The mid's still a tad rich, but it's in the ballpark. New needle should make it perfect.

Your friend's 93 has a Keihin 38PJ, much better than the Mikuni that my 92 has. Check compression, then pull the little preload cover off the powervalve to make sure it responds right away when snapping the throttle.

Stock jets on his bike should be:
Main-180
Needle- R1471NS
Slow jet- 45
Air screw- 1 1/2 out
Float height- 16.0 +/- 1mm.

 

[SpectraSVT]

THx...are those specs for the 93? He don't have the manual so I didn't know what the float height should be. He has 180 main, needle in 3rd clip and 55 pilot. This is the reccommended starting point for an FMF fatty according to FMF site with exception to the main (FMF=178).

I pulled the reeds and 1 corner was straight instead of round and both sides were not sitting flat on the reed cage surface. Supposed to get new reeds on Thurs and I hope that fixes it. I didn't know reeds could cause the power to freak out like that.

On the float checking, I turned the carb upside down and the needle clip is not touching the little tang at all. Needle not compressed at all by the floats. Is that correct? SHouldnt
there be some contact?