bike cut out at WOT

[utah250r]

I have a 250r that I just put a brand new top end in a different cylinder then I had before. After I broke it in as soon as I tried to get on it it falls on its face at WOT. I ran this cylinder before a few years ago and I had a 185 main jet.

I went all the way down to a 165 main and it got a lot better to where I could actuaaly ride it but still acted like it needed less gas. the only thing I have changed is that I switched from an ESR airbox elminator kit to the stock 250r intake tube without the airbox.

Is it possible that I need to keep going leaner on the jetting or is something else the culprit? I also have a 5 year old 2001 Cr250 ignition that I bought brand new on it. Hope this helps. Thanks guys for any input.

[utah250r]

I just went out and checked the spark and it had good color but it seemed to jump all over the place. Anyone know what would cause this?

[wilkin250r]

I don't want you to feel discouraged about the lack of responses. It's not that we don't want to help, it's that we don't have a good answer for you.

Cutting out at WOT seems to be a common problem recently, and there have been a variety of solutions. I've personally seen it attributed to broken flywheels (the magnets inside break apart and rattle around, most likely from being dropped), poor wiring connections, and bad gas. I've heard also of bad CDIs, bad stators, and spark plug issues (often an incorrect gap).

I would also imagine the culprit could be a combination of any of these factors.

If you suspect jetting issues, then a plug reading should point you in the right direction. Otherwise, it sounds like a trial-and-error fix :(

[utah250r]

so I guess maybe my question should be whether or not a 162-165 main jet is definitely too small?

It seems like the other guys with the same problem the bike ran the same no matter how they changed the jetting.

Mine is improving as I lean it out but I just have a hard time believing it would ever be jetted that lean which makes me believe it may be something else??

In case anyone was wondering its a ported 91 CR250 cylinder, ESR reed cage, 38 airstryker, TRX5 pipe and the stock 86 intake tube with no airbox.