Backfireing

[Pogo]

Hi everyone. Back again. I need a little advice. The GY6 in my ASW Carbide is giveing me a bit of trouble. It has started to miss and backfire through the exhaust at mostly high RPM. It starts and idles absolutley perfect,you rev it up and it runs smooth as silk with no back fireing. But when you drive it at high RPM it starts to miss and backfire. it also does it sometimes at middle RPM. The backfireing is not really bad but it is only going to get worse.This is what I have done. Torqued the head to specs, adjusted the valves to 003 and 004 witch are specs. Changed the plug. The colour of the plug looks perfect. Light tan with maybe a hint of grey. Checked all the gas and vacume lines for cracks or looseness. Fuel filter seems ok. I put some alcohol in the gas in case there was any water from condensation. The thing starts and runs perfect except for what I mentioned. Can't do a compression test on it cause my tester won't fit the plug hole. I think it is electrical just by the way it is acting but a service guy says that a dirty carb can do that. I would certainly appreciate any help you folks can give me. Oh yea, it is under warranty so ASW will pay, but the dealer says they will not pay for a dirty carb.So if that's what it may be I will clean it my self. Thanks to all.

[GX150]

Have you checked for intake leaks by spraying carburetor cleaner around the intake elbow mating surfaces at idle? If idle changes, you have a leak.

Try going up and down one size on the main jet and report back how things change.

[Pogo]

I am going to do that this afternoon.Out of carb cleaner.

[Pogo]

I did that and know luck. So it does't seem to have a vacum leak. Any other ideas.