Idle surging... 1st ride after break in... yz250 help?

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5/12/2018 4:42 PM

So i broke my freshly rebuilt yz250 in over the week and took it riding today to see how it would do riding. It did great... until it started to surge when decelerating. It was not doing to badly at 1st but it was something i went back to the truck over. Anyways, i adjusted the air/fuel screw in and out and it got a little better but once i started to warm it back up and ride it, it started doing again to the point of annoyance and it being pretty audible to my riding buddy.

Before we even started the bike after it was rebuilt to do the break in, we added gas to the carb and it poured out of the bottom of the bowl. After fixing that issue it held fuel with no problem. Before the rebuild, we ran 40:1 93 octane fuel. We did switch it up though to 36:1 since we had the can already mixed together in 5 gallons.

I plan on taking the carb off and reed cage out next week and reinstalling them to see if it helps since we may have not gotten the carb boots put on good enough...

What would you guys suggest? Anyone else have this problem with their yz? How did you fix it?


5/12/2018 5:31 PM

Since it started after rebuilding the bike I'm going to say you didn't clean the base gasket surfaces off good enough and your sucking air, Or you have a bad crank seal.


5/12/2018 5:58 PM

Air leak or a crank seal isn’t seated properly. I believe you can push one too far in.


If you're not mixing gas, you're not haulin ass.