Troubleshooting High Rev

[ccdsg]

I recently rebuilt the top end of my KDX200. I started it the first time a few days ago and I was able to ride it and then it revved really high to the point I killed it in 4th gear, and then it did not start. Today I started it and it idled for 1:30 and then revved very high. It did this again but after 30 seconds, and then immediately the 3rd time. The video under "High rev" is the 3rd time.

Normal idle:



High rev:



Before rebuild this did not happen.

[John_S]

I would make sure the throttle cable or slide isn't hanging up but its likely an air leak. That'll make a 2 stroke rev like that. Search on this site and also youtube for 2 stroke leak down test.

[ccdsg]

I would make sure the throttle cable or slide isn't hanging up but its likely an air leak. That'll make a 2 stroke rev like that. Search on this site and also youtube for 2 stroke leak down test.

the throttle cable is ziptied to the frame and has all the means to move as necessary. It only seems to happen when the bike gets warm enough. Now that you say air leak, I believe my carb holder is a little dry rotted. It wasn't all the way through before but maybe it is now.

[bufftester]

Definitely sounds like an air leak somewhere. The carb boot is a major suspect, I would also look at your reed cage. A leakdown test will rule out (or confirm) crank seals or base gasket.

[ccdsg]

Definitely sounds like an air leak somewhere. The carb boot is a major suspect, I would also look at your reed cage. A leakdown test will rule out (or confirm) crank seals or base gasket.

All the gaskets in the topend are completely new moose racing gaskets. I was really baffled at first. I assumed it was air leak but I wanted another opinion. Thanks.

[KDXGarage]

Check the boot.

air leak is probable


Quick check is wrap, wrap, wrap it with electrical tape. If it stops, then it is time to break out the wallet.

[bufftester]

Flex seal for the win!!!

[KDXGarage]

Flex seal for the win!!!

HI! Phil Swift here!