I have a 02' yz125 and i was riding it the other day and i noticed when i am in 4th or 5th mid half way through the RPM's the bike makes a flapping noise in the engin but when you get on the gas more it stops making the noise. This is only the case in the higher gears and mid RPM's. No power loss or n e thing just this noise is causeing me concern. Is it nothing or somethin loose. I took the top apart nothing i took the reed valve apart nothing. I checked bolts on the bike to see if it was something else nothing, so i think that it is in the engin. I recently had it ported and polished and had a slight seeze on a piston but no damage to cylinder. I have no clue what is making this Noise.
Engin Noise
- Thread starter yz125_894
- Start date
- Oct 20, 2000
- 2,969
- 2
I think I would do a plug chop and see what the jetting looks like, you may be running on the lean side especially if you seized it.
Yes probably like LOL said running lean can make 125's fluff on mid to top revs. Also might be the power valve fluttering at those exact revs as it opens up??? I know Kawasaki put a stronger power valve spring on later model 250's to stop this uneven reving as the valve opens
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