backfiring

[ridgie]

hey all i bought my gf a pit bike 125 semi auto and everytime just before it starts it backfires what could b causing it

 

[bulldog93]

Define backfirer.

Check valves:
- http://www.miniriders.com.au/motor-tutorials/24965-how-set-valve-clearances-horizontal-engines.html

Could be too much air going through or fuel.

 

[ridgie]

yea its pretty hard to start as well

 

[ridgie]

yea its pretty hard to start to

 

[sean01]

did you buy brand new?

back firing can be from a few things...
shit fuel
bad cdi
bad cam timing
bad carb or air leak
valve clearance may need looking at

 

[Thumpstar Pro]

On new bikes it doesn't take long for the inlet valve to zero out.

I have a feeling this may be it as it will cause hard starting and backfiring through the carb.

 

[clunky64]

mate is it backfiring through the crabi or exhaust or is it just kicking the kickstarter back up against your foot,also are you finding top dead centre before you try to kick start it