SXR SXR backfire

[shank]

Hi,

The ski starts fine and runs at low RPM ok. However whenever it is given throttle it is backfiring in a single cylinder being the front one and the engine is dropping most of its power. Seeing it is CDI ignition system i dont think i can adjust the timing on the engine. It has new spark plugs, new battery and cylinder compression test is good. Ski has been running fine and used reguarly for several months leading up to this issue.

Any ideas of what i should check ?

 

[atvracer]

check the compression
you may have sheared your key in you flywheel and your timing is off

atv

 

[shank]

compression is good.

i pulled the carby off to clean it and checked the reed valves. I found one of the reed valves was broken in the cylinder that is backfiring so i will replace that and see if it makes a difference to the backfiring.