My 87 honda 250x runs great all day long....except when i stretch it out on a straight away...it dies out at the end...Any Tips????

 

sounds like its not jetted right

 

So it runs fine at high throttle and every other way, until you are on heavy throttle for a while?

In that case, I'd wonder if there's a screen in the fuel petcock thats clogged up, or the float valve is partly obstructed.

 

Sounds like fuel or fuel tank vent/hose plugged or pinched ..

 

Sounds like it's not getting enough air for the amount of fuel it's getting. Needs more air or less fuel. I had a racing go kart that did the same thing, but I didn't bother fixing it because I was never on the gas for long stretches. Oh, BTW, that kart & me won a regional championship.

 

This is exactly what happened with our 90, you would make a long full throttle run and when you let off it would die. I ended up taking the fuel petcock of and just ran a single line with a shut off valve and plugged the other tank hole. I also increase the gas line size and inlet to the carb.

 

Sounds like the vent line to me.

 

Yeah, I sould have also thought of the vent line.

Easy way to check: when it acts up, loosen the gas cap to let some air in. If that fixes it temporarily, you've got a blockage in the gas cap or vent line.

 

Once again Thanx for all the help....but i might just forget about it cause im gonna get a 400ex...but feel free to give me some tips and points on aftermarket for it

 

They seem to be solid machines, if given a little care. Leaving it mostly stock would probably give you the most fun for the money, and reliability.

May as well get the 250x sorted out, so you can sell it or take a buddy riding, or whatever.