my sons bike yz250 run well for about an hour then cuts out and won;t start until we put a new plug in it the plugs not the problem as we can use them in my other sons bike no probs yz125 we can go through 4/5 plugs a day what could it be when running it.s not hard to start first kick
2007-11-24 15:15:34 · 7 answers · asked by terry l 1 in Sports ➔ Motorcycle Racing
You have some good answers here. Having the wrong fuel mixture can foul out a plug pretty quick. If your plug is the wrong one, then it can explain why it fouls out in your 250, yet doesn't in your 125. Compression would also explain this, well the lack there of actually. I would suggest looking for some information about the plug specs first, then if it turns out your plug is the correct one, then you need to look elsewhere.
You can used a compression tester to see what yours is like and compare it to what it's supposed to be. If that is ok, then the spark isn't hot enough to burn off all the oil. Good luck.
2007-11-28 12:34:01 · answer #1 · answered by Anonymous · 1⤊ 0⤋
I had this problem with my yz. it turned out to be the magneto. dont ask me how but once i changed it the bike ran fine and i didn't have to change plugs anymore. But before you do that make sure the gas/oil mixture is right. it could be that it is too rich in the 250 and just right in the 125. Good Luck, hope this helps.
2007-11-25 01:32:46 · answer #2 · answered by beezzis 3 · 0⤊ 0⤋
I'm going with barry's answer - top end rebuild (cylinder, piston & rings).
Low compression won't fully burn the oil in the pre-mix and eventually foul the plug.
Throw in a new plug and zing-za-zing-zing-zing, away you go.
The other bike probably has better compression.
Good compression would allow the engine to run with a semi-fouled plug.
2007-11-26 23:10:44 · answer #3 · answered by guardrailjim 7 · 0⤊ 0⤋
Maybe the wrong plug in the first place?
My advice: NGK Spark plug BPR8EIX
They cost more then most, but are well worth it.
2007-11-25 07:32:06 · answer #4 · answered by Anonymous · 2⤊ 0⤋
change your gas/oil mixture.your running to rich and it foul's the plug.don't go to lean either or you'll sieze the motor.also check the plug wire.sound's like a bad connection maybe!
2007-11-25 23:49:53 · answer #5 · answered by blueeyiz702 1 · 0⤊ 0⤋
could be a carb problem. It sounds like it is fouling the plug.
2007-11-25 05:10:52 · answer #6 · answered by SWT 6 · 0⤊ 0⤋
When was the top end last rebuilt, Ceck the coil.
2007-11-25 15:15:51 · answer #7 · answered by barry m 5 · 1⤊ 0⤋