Some reason my 1986 TRX250R is sputtering on top end, really bad. It's very hard to even drag race any one for the occasional time. I would like to know how to fix this problem? Do I need a bigger carb?
So I will tell you what I have done so far. My bike has a FMF fatty pipe, intake spacer, K&N, ATC head gasket, the motor is bored .75, or .80 over, and still has the stock carb. (not ported)
As of right now the carb. has a 190 jet, and the rest is still stock pieces in it. Please help!!! I know this thing can run it has awesome midrange. ( anything can help to be faster though)
By the way the whole motor is new wiesco piston, and new bottom end, and cases.

 

A 190 main jet sounds rich for your setup. Try a new plug and a 165 jet. This may still be rich depending on elevlation of kansas but should run a lot better.

 

That about sounds what happened to mine 86 250r. It ran good on bottom end then wonce it got to high rpm's it fell flat on it's face. At first i thought it was my carb but then after further inspection i pulled the pipe off and looked up the cylinder and i saw a scar in the piston and sure enough part of the piston was gone and the top ring was gone too. Luckly i found it in time before it realy caused much damage it did not even scar the piston walls so i just put a new pro-x piston kit in it.

 

I have seen that before. Double Check your air cleaner, if it is really dirty, it is restricting your airflow. Which causes the rich condition you describe.

 

Hey 86 250r,i know this is off topic but how do u like your bills pipe.Im thinking about getting one?does it have good mid range?Does the plating look nice? thanks

 

190 sounds way too rich for an unported engine.

 

Unless you are at or bellow sea level a 190 main is WAY to rich.WHen i had a stock motor with a Paul Turner pipe I was running a 148 with the air box lid off and it was a nice coffee color(2500FT Elevation)Burning av gas fuel 50to1 redline mix.I race moto x and never have had a problem yet.

 

try jets in the 150's

 

Hey trx250rman, yeah i like my bills pipe and silencer. In fact i sold my fmf to get the bills. I like the plating ALOT more than the fmf. I thought that the fmf got that ugly gold color after awhile and the bills has not changed color and i have had it for like 4 months. It was also pretty inexpensize too, i paid 230 for pipe and silencer. Yeah i love the mid-top end power. I had the fmf toqure pipe and it pulled well aff bottom but the mid is not as good as the bills and neither is the top end. So yeah i would recomend a bills pipe

 

Sorry to pop in for my own personal question but you 250R guys seem to know about jetting so I will ask. I have an 86 punched out to a 265cc and a full FMF exhaust, 39mm Keihin and a Boysen reed cage. Fryed the top end last summer and am just now getting it back together, I was running a 172main with a 42 pilot on the middle clip does this seem lean to anyone else considering the 39mm carb? I am at sea level and run Bel-Ray MC-1 50:1 with no lid and a K&N with outerwears?

Thanks,
Brad