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I am new to the site and hoping someone can help. I have a 2006 CRF250X with stock exhaust that I purchased a while back and the previous owner had removed the baffle from the stock exhaust but gave it to me. Spark arrester was left in the stock exhaust. The bike runs great without the baffle and fires right up and idles great. I tried installing the baffle to make it quieter but the bike would not start with the baffle installed. Once I remove the baffle, it again fires right up. I removed the end cap and checked the spark arrester screen for blockage and it is totally clear. There are no other blockages in the pipe. Any help is appreciated.

Hello,
Any time you change inlet or exit flows on an engine that is metered with a carburetor you have to adjust fuel scheduling.
When you install the "baffle" try and adjust the fuel air screw in 1/2 turn [ CW direction ]. That adjustment will lean the start and idle fuel schedule and may get you going. But anytime you are backing up the exit pressures with a baffle you should lean the main jet & change the pilot jet. That is if you cannot get enough adjustment from the AF screw to compensate the start / idle circuit.

Hope that helps.

Hi Neil,

Thanks for taking the time to respond, I really appreciate the help. I'll try adjusting the fuel air screw in 1/2 turn [ CW direction ] and then try to start with the baffle installed.

Thanks again,

Aaron

Let us know how that performs. We can give you some guidance from there. Don't worry, jetting is actually pretty simple once you understand whats going on in there.

Hi Neil,

I adjusted the AF screw in 1/2 turn as you suggested and bike fired right up yesterday with the stock baffle inserted. Stock screw seems to have enough thread that it is still OK. Thanks again for the help. Let me know if I can venmo/zelle/paypal you a beer for your help. Hope you had a great weekend.

Aaron