400ex just giving me problems

[greco400]

The thing will not start i have to jump start it seems to me no compression, Some times it will run like a champ and some times just out of the blue not rev past 1/2 trottle it cuts out. My plug is carbon but not wet?? I tried down sizing the main jet but didn't work seemed to run worse tried cleaning it out nuthing


Should i rebuild it and then try to get the jetting right or get the jetting right now

[DieselBoy]

1. compression test (must maintain 100-125 psi)
2. clean carb; inspect
3. leakdown test if compression test appears correct.

from there you can then decide if it is time to rebuild, but if your plug's dry & cutting out past half throttle.. could be plugged jets, float stuck, or other carb problems.

[greg_gorrell]

your floats may need adjusted