ATV Florida Forum

My yz125 wont hit the power band and it runs good but it has no power and I replaced the Jug, Piston, rings, power valves, reeds, and I checked the timing and ajusted the carb and it still dose the same thing. Some guy said that it might be the coil . So what do you think?   thanks

Check the stator and make sure your packing is not clogged.

ok and ya i tryed to see if it would hit the power band even without the silencer on and it still did the same thing

STATOR

but if the stator was bad then would the bike even start? hahah

Yes it will have week spark and seem lik its loading up.

but it starts 1st kick every time

Your right its probably the piston or the top end orthe power valve or the reeds or a carb ajustment.Oh wait you already changed all those.HA HA

whats the plug look like is it wet? brown or black in color? it sounds to me that its to rich what mix are you running in gas/oil is the plug new or old? is the spark deep blue in color? what position is the clip in on the needle jet?

i just put a new plug in when I replaced my jug and everything.....and what dose your mix have to do with hitting the power band or not?

if your running to rich the engine will load up and not rev up. I run my kx at 32:1 gas oil ratio needle jet in the 3rd slot from the top but the zilla runs on 42:1 needle jet in the 4th slot from the top you must jet and adjust to what mods you have done every engine is differnt have also seen a leaking crank seal do this is it smoking alot from the exhaust (rich)or very little smoke (lean)?? have you removed the carb and inspected the jets to see if they are dirty or clogged? whats the air filter like clean or dirty and how strong is the spark??

he smoke is rich from the exaust....and ya I removed the carb and cleaned it out and  the airfilter is new....and the spark is really strong(starts every kick)

I dont think its a stator sounds fuel related to me if you pull the choke when its running dose it run better or worse? and check the needle thats mid range in throttle and ck the main jet that on at wot.when the engine is cold dose it run better then when its warmed up or better when its warm?? or same??

steve

Did it do this before replacing the cylinder?  I'm wondering, because powervalves sometimes have an adjustment, that controls when the valve opens up for that topend hit.  On my RM250, there was this cover on the cylinder that had to be cranked clockwise one and half turns, then tightened down, inorder for the powervavle to be adjust correctly.  By how little or how much you turn it, it makes the hit come up higher or lower in the RPMs.  If you have not taken the same precautions with your YZ125 (assuming there is a similar adjustment or something), then that could be why you're not hitting the powerband.  The powervalve is just staying closed and nothing is happening.  I'm also not sure how the powervalve is actuated or connected on your bike, make sure of that.  On my bike, it was like a pushrod that opened and closed it, if it wasn't connected, the powervalve wouldn't have any way of operating.

I would think the power valve was removed cleaned adjusted and checked during the rebuild

ya ...I put brand new power valves in and everything...and they open and close fine