YZ125 cutting out

[tussock]

Hi, my yz125 2000 runs perfectly at low revs and into the mid range but when I rev it right out it cuts out. It still accelerates but it's like the spark stops and restarts 3 times a second. Has new plug, clean air filter etc etc.

[eprovenzano]

Hi, my yz125 2000 runs perfectly at low revs and into the mid range but when I rev it right out it cuts out. It still accelerates but it's like the spark stops and restarts 3 times a second. Has new plug, clean air filter etc etc.

Well to diagnose we need some more details.  If this a new to you bike?  Has it always done it, so did it just start recently.  Has the weather changed in your area, and have you changed anything on the bike?

The reason I ask is it sounds as though your main jet is too small or partially plugged.  To me without any more info it seems as though your bike's not getting enough fuel at full throttle.

[tussock]

It has been doing it from the day we got it (months) in all sorts of weather. It's not a surge like it's running out of fuel and no engine rattles or pinging . It's  very violent almost like a rev limiter on a four stroke. Does it have a two stage stator and the second stage has sh*t it's self ? Cheers Tussock.

[TMKIWI]

Stators have high and low speed windings and yes 1 or the other can fail.

[gpnewhouse7]

Check that the power valve is installed correctly a friend of mine once bought a cr 250 that did the same thing, plenty of low and mid but went really flat on top and could be out dragged by 125's. He went through almost the whole bike before he realized the power valve was upside down, ran a lot better once that was sorted.

[Redski-jr]

The problem could also be caused by a sticky reedvalve I think,
Friend of mine had his bike running good when stationary, but when hitting the gas it started to run very bad, replaced the reed --> problem solved