Too much gas at high RPM

[Hooner33]

I have a 98 Rm 250 with about 20 total hours on it and it has only been rejetted once due to a Bills pipe upgrade. there are no other engine improvements made. Since then, I have rocket at low to mid rpm range but very little top end.

I sounds like its running rich at the top end. So I changed the main jet to a 170 from a 172 and I was thinking of moving the clip position one notch to the lean side.

My question is, "Should I keep the clip position the same nad only change the main jet or move both to improve the whole top end power?" Or only change one at a time to see the improvement?

Thanks for your interest, Brendan!

 

[76GMC1500]

Going to the 172 jet made the bike richer. How does your plug read?

 

[kx125412]

He said he went to a 170 FROM a 172. Going down one size isnt going to hurt anything expecially if the 172 is stock. Try moving your clip one step leaner and see how it goes, and then lean out the main. Also make sure your powervalve is functioning properly.

 

[Hooner33]

Well I changed the main jet to a 170 and put it back together and it ran strong at high r's. the stock setting is a 175 main. It still runs a little rich at the top though. I'll move the clip to the lean side it see if that makes it any better. BTW the plug has a little carbon on it but not bad at all. I have never fouled a plug since I have owned the bike. Ill return with the progress.

 

[76GMC1500]

Do you know the current clip position? You may even go a tad leaner on the main jet and then a lower the clip on the needle to richen the mid-throttle, if necessary. Remember, the needle has no effect on the mixture at full throttle. That's why if you really lean out the main jet to get the full throttle mixture right, your mid throttle may be too lean and you'll need to raise the needle/lower the clip.