Posts
13
Joined
10/28/2016
Location
Lexington, KY
US
Alright, so I'm not the most mechanically inclined but I somewhat know my way around 2 strokes. I have a 2002 yz125 that will start and run pretty crisp for about 1-2 minutes on the stand, then I put in first, take off and before I can even make it a lap around the track it bogs out bad and just dies. Won't start back up after that unless I give it a few minutes and tip it over and let all fuel drain out of the overflow. I have jetted it back to stock as I have no idea what the guy before me jetted it at. I'm at about 200ft elevation here so stock shouldn't be too off even with it being around 50 degrees here now. Air screw on carb is stock at 2.5 turns out. Just replaced reeds. Carb is spotless and blown out ever inch with air. Stock everything on this bike basically at this point. Gas mixture is 40-1 with 927 and pump gas. Gas regularly comes out of overflow even if the bike has been sitting a while so don't know if the float is actually working like it should or not. Don't thing the float is sticking though. Anyone have any ideas? Power valves maybe? I also happened to be filming when this issue started so I'll put the link to the video. The video shows right when the bike started running real bad. Just seconds before the video the bike sounded and felt good and crisp. So I already know the bike sounds like crap in the video. https://youtu.be/HfVhv0V-lRo
The Shop
Along with that I suspect that your carb vent lines may be clogged. No air = no fuel flow.
Reset the float level to factory spec's
Paw Paw
That was what you said.
That plastic part is the tank vent. It lets air into the tank, but does not allow fuel to spill out. They go bad.
Paw Paw
One of these is disappearing at some point.
My guess is wet plug, he gets it to run again with plug and unflooding/leaning bike.
Probably not compression, but easy to check in 48 seconds. It should blow you finger off the hole when kicking.
Fuel? Lean? I would ride with choke on and fuel cap almost loose and see if it keeps running without stalling.
Rich? Flooding? This is probably the culprit because a new plug helps it start again? Is the plug wet?
Proper diagnosis happens before a single part is replaced, you must find out what is missing when it dies,
fuel, air, spark, keep it simple.
Keep a spare plug in your pocket, when it dies pull over and pull plug cap, put extra plug in cap and kick bike over to see if the spark stopped when the stator got hot, takes 20 seconds.
If the bike is flooding then holding the throttle wide open while kicking might give you a sign, if it keeps trying to start with the throttle wide open then that is showing the engine is fuel flooded.
My guess is that you are losing spark because the plug is so wet from fuel it won't fire.
Maybe the float has a pinhole, see if it floats in water? Shake the float and listen for fluid inside.
Good luck
And man, knowing that thing is going to cut out or die and still jumping it. Not this guy.
Pit Row
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