02 yz125 stalling

Y2Z

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#1
I got this bike in September, put about 8-10 hours on and it rean awsome. i went out riding awhile ago, it was a bit wet out and i was going down a road in 4th about 1/2 throttle, all of a sudden it started to bog and wouldnt fire again, i tried to bump-start it with the speed i had but still nothing. After i was at a dead stop i kicked it and it started right up ran fine, then half way down the road did it again, same thing. I know im not fouling the plug, and i thought it might be the ignition or somthing, the rest of the day it didnt do it. Went on a few more rides, all on warmer and drier days and it never did this, then just last week about 2 hours into riding (it was 5 celcius, and really windy) and it did it again, and it kept on doing it but this time it was when i would get to about 3/4 throttle, im pretty scared to ride it at a track because it is so unpredicable, i dont know if ill be aproacing a double in 3rd and it does this crap.
Could this just be the cold weather? should i fatten up the jetting? Is the float level messed up, seems like its not getting enough gas or somthing.

thanks for any help!
 
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#4
i had the same problem with my bike.... i would be pinned or just high in the gear and it would stall.... come to a stop and it would start first kick again.. checked filter, plug,gas and even took all ignition cables and cleaned them ..... the only thing that seemed wrong was gas was a little clearer then normal. so i started it again after i checked everything and it did the same thing... so i drained my gas...put new gas in at 32:1 and it was fine.... so make sure ur gas is mixed correctly bc that will do it to ya.... to this day im still not sure how that gas was mixed. i guess without enough premix there is too much friciton between piston and cylinder... but im not sure.... someone correct me if im wrong.... cya
 

Y2Z

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#5
that crossed my mind, but im sure i mixed it at 32:1, mabe i didnt shake the gas around enough? i hope this isnt somthing serious.
 
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#6
my 02 yz125 have got this problem, when I stalled it under hard riding, it wouldn't start up, even in neutral, i had to wait for a while before I can get it fire up.

what could be the problem? it was fine last time...
 
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#7
Podia, sounds like rich jetting to me. Overly rich jetting b/c you said you'd ride it hard, THEN it would stall. Maybe it wouldn't start back up at first b/c the spark plug fouled a little, but not all the way. So as you waited it dried and that was when you could re-start it. I've done that before. Fouled a plug and took it out and cleaned it. Fired right up.

Y2Z, sounds like a air & fuel problem. It could be alot of other things too though. Is whats weird is that it's an unpredictable thing. That could explain the fuel idea. B/c some of your gas could be good while some is bad. But that doesn't make sense b/c it'd fire right up again and run good all day. It possibly could be the float. Probably not though. I had a float problem and know what thats like. I only fouled plugs when I warmed up my bike and it ran 100% for the rest of the day. Keep at it. You'll figure it out!
 
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#8
rairden, sorry never mentioned about the brake.

i stalled it when i use my rear brake too hard, and it wouldn't fire up
even in neutral.

i have tried different needle position, change both main and pilot jets, but still same problem.
now i'm suspecting the float height, but i have never alter the height before.

hmm...what ya view?
 

Y2Z

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#9
im going to wait and see, when it gets warmer ill take it out, i think its just jetting or somthing because the bike ran fine in warmer weather, and i rode it 2-3 times inbetween it doing that.
 
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#10
Podia, not that its much help, but I have had similar problems on my cr with hard rear braking.

I checked the jetting, carb vents, fuel line, etc. and the only thing I was left to wonder about was my clutch. I doubt this would apply to Y2Z's problem unfortunately though.

What I suspected was that the clutch wasn't disengaging completely so when using the rear brake heavily it was increasing the load on the motor. I was able to partially verify this by shifting into neutral thenbraking hard and not being able to stall the bike.
 
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#11
gatorkdx,
for my case, i don't think is clutch dragging problem.

my bike should fire up immediately when i get it into neutral, but it didn't.

i gotta wait for a while and by the time it fired, the whole field have already pass me
 

Y2Z

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#12
ok guys, took my bike out for a spin today around the yard, it was about 1 or 2 C. It had some low end bogging, and i figured it was because it was to lean, so i changed the needle clip pos. 1 notch richer, worked awsome after that. i didnt get to do much wide open riding to test it out, but ill be riding tommorow and ill see what happens. also a guy at the dealship told me to throw a new top end in, this seems a bit soon seeing as how it only has 25 hours on it and 145 compression, and i really doubt that will solve my problem.
 
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#13
25 hours !! I dont think it warrants an answer as to what wrong with your bike. Anything over 15 hours with a stock yz piston is asking for trouble. The ring normally turns and causes serious barrel damage. As a rule, dont run the ring for longer than 8 - 10 hours. Try Wiseco - better quality.
Regards
Anton
 

Y2Z

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#14
antont, thanks for the advice. i just cant see replacing a piston so soon, mostly because i dont ride my bike hard at all. ill take the head off and check it out, if there is any damage ill put the top end kit i got. are the gaskets re-usable like on the new CR's?
 

Studboy

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#15
Since you say that it stalls when it is wet/cold maybe you are getting some moisture on your ignition components causing the bike to stall. Make sure that they are all sealed tight and clean.