Backfire on deceleration chinese moped?

Hello so I have a taotao 150 powermax. It ran great tell my exhaust broke off. I drove it maybe less than 25 miles without my exhaust trying to get it home and than like two other times due to emergency situations. Than i parked it since winter came for like 8 months. So now i bought a new exhaust and got it running and replaced my spark plug, oils, and fuel filter. But now it backfires when i slow down unless i feather the gas. Ive tried adjusting valves. I was told its running lean well i pulled my plug that is new and its black so that means it's running rich right? I did a valve adjustment and that helped alot but still backfires. I have a feeling ive burnt my exhuast valve out but what is your guys opinion and what should I start with?

Also im running a "performace" CDI and coil. I was also told that it could be that too.

Re: Backfire on deceleration chinese moped?

Dirty30 Dillon /

Yup, sounds like burnt valves from running no exhaust

Re: Backfire on deceleration chinese moped?

Cory Willis /

Okay thanks. I had a gut feeling it was the vavles. I can just replace the valves right? Will my head still be okay or should i just replace all of it.

Re: Backfire on deceleration chinese moped?

I'd do a compression test first . If you have a burnt valve , it's very likely it wouldn't run very well , if at all .

It only backfires on deceleration , which indicates an air leak in the intake .

The stock carb for that scooter looks like it may have an air cut valve . If so and that valve diaphragm is defective , it would allow decell backfires .

As a test , try turning the pilot screw out a few turns , if it has such .

Re: Backfire on deceleration chinese moped?

Cory Willis /

It runs great. I have no issues on the performance. Its a stock carb so unfortunately everything is sealed including my air fuel mixture screw. The valve diaphragm thats the black rubber thingy that holds my carb needle?

Re: Backfire on deceleration chinese moped?

Cory Willis /

Oops nvm i did a google search and found out what you meant.

Re: Backfire on deceleration chinese moped?

1-Is there a gasket between the head and the header pipe? If there is, make sure it's installed properly.

2-Re-torque the nuts/bolts securing the pipe to the head. Slightly loose connection can cause your symptoms on some 4-strokes.

Re: Backfire on deceleration chinese moped?

Anytime you have an airleak in the exhaust at the cylinder head the leak causes the popping/ backfiring....NEW exhaust gasket or donut...or...pin hole in pipe is the cause...

Re: Backfire on deceleration chinese moped?

Cory Willis /

I replaced the gasket with just the basic circular one. I have a premium gasket just need to find longer studs to make it fit. And when i did replace the gasket it stopped back firing nearly as bad. Ill double check everything again tonight but im like 99% certain there isnt an air leak from where my exhaust bolts into the head. And if there was a pin hole leak in my exhaust would it still shoot flames out the end of my exhaust?

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