Yz250 Stuttering problem

SO I have a 05 yz250, bought it used a few months ago and after about 5 rides where it ran perfect it starts to stutter at high rpms, almost like it wont maintain its power. I havnt even finished my 5 gallons of gas through it yet. I run 100 octane aviation fuel at 32:1 with spectro premix. Any thoughts, a few people have said it could be my reeds because it sounds like fluttering and the guy at the shop said I have to run vp race gas but thats not going to happen, 100 is good enough.

SO I have a 05 yz250, bought it used a few months ago and after about 5 rides where it ran perfect it starts to stutter at high rpms, almost like it wont maintain its power. I havnt even finished my 5 gallons of gas through it yet. I run 100 octane aviation fuel at 32:1 with spectro premix. Any thoughts, a few people have said it could be my reeds because it sounds like fluttering and the guy at the shop said I have to run vp race gas but thats not going to happen, 100 is good enough.

I would suggest checking the case reeds and make sure there's not cracks or rough edges on them first.  Then see if there are any air leaks, make sure all hoses and seals are good to go.  That should be a good starting point :) hope that helps!

Sounds a bit like its running lean. Check for air leaks around the boot, chipped reeds and correct jetting.

 

Then check the plug colour is nice dairy milk chocolate colour and if it is, replace it anyway. Its a million dollar fix for $5.

instead of sounding like this:

BRRRRAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAP!

 

Cracked reeds sound like this:

 

BRRRRAAAAAAAA   AAAAAAAAAAAA     AAAAAAAAAAAA    AAAAAAAP!

Stuttering is rich. Lean is a hesitant or surging type of power.

 

First thing I'd check are the basics: Clean the air filter. Install a new spark plug. Pop the fuel lead off the carb and ensure fuel pours out fast.

 

If just the new plug fixes it, then to avoid a repeat, consider going leaner on the jetting. Which might mean a leaner #8 slide part, but start with one size smaller main jet.

 

Next I'd remount the coil to the frame to ensure good grounding and re-seat all the wire connections to the coil.

Edited by numroe

Plug chop at full throttle

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