Motorcycle Repair: when its getting warm, no more power, check engine oil, vacuum hoses

Question
Model: GSX600F 1990 Katana

After about 10 minutes of running when it is getting warm it starts to loose power.

I've changed:
1. cdi - no changes
2. ht coils - no changes
3. carburetors - no changes
4. everything on the fuel path - no changes
5. sparks - no changes

I've checked:
1. compression - fine
2. electrical stuff - fine

The simptom is like i am out of gaz. Motorcycle will run in one cyclinder (i think). Anyway, without running, the rev will not rise after 4-5000 rpms.


Answer
Hi Baiazid,

Check the ventilation system on the fuel tank and fuel system.

Run engine with fuel tank cap ajar and note engine performance.

Check for pinched or collapsed vent and vacuum hoses.

Check carburetor vent hoses and passagesways.

Check engine oil level.

Respectfully,
Mark Shively