TRX250R - Doesn't have any top end

I will post this here, hoping maybe someone out there has run into a similar problem.

The engine pulls pretty strong in a very narrow rpm range (mid range), but will not rev out cleanly. Due to other mechanical issues, it has a complete new engine (including carb, stator, reed cage, etc) but this problem has remained. The only pieces remaining are the FMF pipe/silencer and the ignition coil/wire/ignition box. Before I spend more money chasing this demon, has anyone else out there experienced this with a 250R?

Thanks guys!

well what size carb did you put on it?? I was runnin a 38mm airstrker on mine when it was stock, and it wouldnt pull at all, but once I got an esr trx 5 and a k&N filter and some other stuff it ran fine, you may want to think about selling that fmf and looking into the esr trx 5 pipe, it is the best all around pipe for the 250r

As above you need to give more detail. What size carb, what main jet? I run a 37 smooth bore on mine but I also have a ProX 310 kit. If you have the airbox lid on the bike can't breathe very well. That would be the first thing I'd check. Run it with the lid on then run it with the lid off. See if it gets better or worse. Will help you fiqure out which way to go on your main jet at least. Sounds like it may be real rich.

It used to have a larger than stock carb on it, though not sure what it was. When it was on there, I tried going back and forth over a pretty wide range on the jetting, to no avail. I picked up a used, bone stock carburetor for it, and started with slightly richer than stock jetting (it has the FMF and a K&N cone filter), but the problem is almost identical as before (first ride was yesterday). It does feel stronger in the very very narrow midrange, but the end result is still the same. Plug is always resonably clean, depending on how far I jack the jetting around.

Thanks for the replies guys!

Do you hace a spark arrest.? If so it may be plugged.

Are you running the stock cylinder without any kind of porting modifications? If so, I think you might be limiting yourself. The FMF pipe is kind of a cheaper pipe in my opinion. It doesn't match the stock porting very well and seems to fall flat on its face when revved higher. That pipe does seem to work well with longer exhaust durations though, and it revs out surprisingly well. If you don't want to start cutting your barrel, I suggest trying the ESR pipe. It has less tapered cones and matches the stock porting better.

That could be it, I am out of ideas. The engine is bone stock. The problem has existed on 2 engines now, with different carbs/reeds/stators/etc. The only carryover parts have been the pipe/silencer and ignition system. I just have not had time or money to swap them out.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now