2 stroke miss??

[racer94]

i have a 250r,the problem im having is when i crack the throttle wide open it sounds like it is hitting a rev limiter,in which 2 strokes do not have.i have never seen anything like this before,so im stumped.from bottom to half throttle it runs perfect idling,but when i get on and ride it it will hardley even go.motor is freshly rebuilt.anyone got any ideas.would a fouled plug do this?

[400eXr1d3rZ]

If you plug was fouled it wouldnt run, but check your jetting, thats usually the issue, or your air/fuel screw.

[bradrenea]

It's probably just the plug. Contrary to what the last poster said, I have had that happen several times due to a fouled plug.
If the plug does not fix it, check your jetting. If you did not make any major changes during the rebuild your jetting should not have changed, so check to make sure the reed cage and carb boot and stuff are all sealed up good.

[bradrenea]

Also, how long have you owned this bike? You do know that you have to "clean out" the motor on some two strokes on a cold start, right? I had one that was jetted a little rich and it took forever to get it to clean out and run good. It would fall on its face until it got warmed up and ran wide open for a distance.(Usually wide open until 4th or 5th)

[mattonln]

definetely sounds like a fouled or wet plug. Make sure you turn your fuel petcock off when your not going to ride for a while because if it has a slight leak, which most older do, it will slowly leak fuel into your cylinder which can coat your plug and make it run shatty. my buddy has this same problem on his shee whenever he forgets to turn the fuel off.

[05trx400exridr]

my friend used to ride a yamaha blaster and it was doing the same thing. it turned out that there was a broken spring on the parking brake cable(which didnt work anyway) and the parking break would stay on (but didnt slow the bike down because it didnt work anyway). the mechanism on the clutch lever was not fully disengaging and we guessed that there was some censor telling the motor to miss every other time, because if you pushed the mechanism on the clutch lever forward, it would run fine.

[racer94]

i have had this bike for about 6 months.i bought it not running and put a new piston in it,that is the only thing i have done to it besides i did clean the carb from it setting.the motor starts on the first kick and runs fine setting in the garage from the bottom to half throttle it is very crisp and smooth,but when i crack the throttle wide open it sets there like it is bouncing off of a rev limiter.when i get on it and ride it the bike will barely go anywhere and i have to hold it wide open to get it to go and it will still only go maybe 35 mph..like i said i am stumped.i will change the plug and see what that does.by the way this is a cr125 motor that we have in a 250r frame for my son.thanks

[DieselBoy]

how's your spark? ...check it...

[racer94]

changed the plug,didnt help at all.i checked the spark and there is plenty of that also.this is crazy!

[GPracer2500]

Make sure your jetting is at least close to correct.

[86 Quad R]

whats the gap on the plug set at?

[juanki]

i think its the jetting, the 250r revs pretty fast and at the top end sometimes it doesnt get the fuel needed, but in the ohter hand in the mir and low range you ar good, since its a 2 stroke and cries to be reved, you shoud go with one size more, so when at high revs the carb gets the fuel that it needs.

when i do xc i use 185 size and for mx 165 and play with the needle to get the carb to work rigth, also i change tires from 22 to 18". i think that those are the jetting that i use, well i don doit but my mechanic does.

[GPracer2500]

Remember, he said this is a CR125 engine.

[bada440ex]

my 250r has been doing this to like a rev limiter and on top end it goes ba ba ba like it is hitting a rev limiter or running out of gas