Hard to start with cold engine..

[Krossipoiss]

Hey.Having prob. with my 87' kx125.It goes to work with cold engine only by pushing it with 1gear,when engine is warm,then it goes from 1. kick.
With cold engine it hits to carb some bangs and then goes to work,but quite hardly.
Compression is good,just rebuilt all engine,new piston,rings,all seals,bearings.
I suspect reeds,but don't want to waste another 50£ when i'm not sure in problem.
I have tried with 3different carbs,spark plugs...

 

[dirt bike dave]

I also suspect reeds.

Hard to start when cold is a classic symptom of a bad reed. Usually it gets gradually worse. Eventually, even push starting will be tough.

 

[Krossipoiss]

But why its "backfireing" to carb?