Posts
52
Joined
2/12/2020
Location
USA
Just put a new top end in my bike and figured I’d do pipe and silencer as well. Not sure if it’s caused by the pipe but just before power band my bike starts to knock if I’m rolling into the throttle, if I hit it hard there’s nothing I can notice. I’m not sure of jetting. I mix 40:1 and do a 5gal mixture of 3gal 110 octane and 2gal of pump 93. Thinking i might try straight race gas, from what I’ve heard 250xs are hit and miss with some needing 110 and some liking pump. Anyone have similar issues? Any recommendations?
I would say your needle is the issue. I know there a particular one some members are found of. You should not need more octane. It may just be a matter of moving the clip. The pipe may require a pilot change as well but you will have to play around.
I just put a fatty and shorty on my 2024 yz250 with stock jetting, ran the same. Rich. I threw the jd jet kit in and it took the on/off switch away and runs great. I guess what I’m saying is the pipe/silencer makes little difference.
YZ squish numbers all over the place from the factory. I’d send it to someone reputable to get it cut for the fuel you plan on running, and then start chasing jetting. Incorrect squish will have you swapping brass like musical chairs.
Did you use all OEM gaskets when you rebuilt the top end?
I used a vertex kit for all the gaskets. I’ll start looking around for someone to do the head.
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Does it make that much of a difference?
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