YZ250 surging when warm (over rev off throttle)

Are the cases completely sealed with yamabond, or other case sealer? Ticking in that video is really weird though. Timing and all that is set properly?

mattyhamz2 wrote:

Are the cases completely sealed with yamabond, or other case sealer? Ticking in that video is really weird though. Timing and all that is set properly?

Definitely a lean condition... also the oil ratio while richer in oil to gas ratio is actually leaner in the air/fuel sense... I would definitely look for an air leak somewhere... you can do the old carb cleaner trick around all the mating seams and seal areas to see if you can pick up th idle to find the leak... also maybe the timings set a little (advanced... but I’d check for an air leak first... you can run the bike with the left side cover off and dust a little carb cleaner by the crank seal too to see if it’s leaking since it sounds like u don’t have the tools to pressure check it at the moment

Apparently nothing was wrong with my bike. I took it to the mechanic and he said if was crank seals or a gasket somewhere it woukd do it every time the bike got hot enough. He rode around for about an hour yesterday and it never did it once. I went and rang it out behind his shop and it never did it once either. I tried and tried... so i took it home. I an thinking it may be jetting or something along those lines now... i do ride up in the NC mountains everytime i ride unless its in SC. Maybe too lean of a pilot? I am going riding tomorrow and will update here i guess afterwards. Kinda stupid the bike wouldnt do ANYTHING but run normal while at the shop... lol

Maybe the pilot had a piece of dirt in it that was restricting the flow.

Also, sometimes the vent tubes suck dust up them, and over time the slide area can get dirty enough that it makes the slide stick. Maybe that was the problem?

CSAR FE wrote:

Maybe the pilot had a piece of dirt in it that was restricting the flow.

Also, sometimes the vent tubes suck dust up them, and over time the slide area can get dirty enough that it makes the slide stick. Maybe that was the problem?

No idea but he also said he messed with the air fuel screw. But i rang the dog s**t out of it and it never did it. When i change the oil and get my shock rebuilt next week i will pull carb off and clean it for peace of mind.