back fire...
 

Hello... I use an xt600 motor in a sidecar mx outfit. I had the carbs sonic cleaned and now i have a small backfire through the slow running carb? any idea's?

Backfire or sneezing through the carburetor
 

Backfiring usually indicates a lean running condition, stumbling or sputtering indicates its running rich. I'd pull a spark plug and see what the color indicates to be sure though. If it's doing it at a specific rpm range, use the kill switch while it's happening if you are using brand new plugs and you'll know for certain. If the exhaust or intake has been modified and the shop put the carburetor back to factory settings it would make it lean.

If its popping under decel it could be the diaphragm on the left side of the carbie (small dome size of your thumbnail) its job is to prevent popping when you shut the gas off.

Mezo.

backfire
 

This diaphragm was replaced after the cleaning.... The backfire is when the bike is sat at tickover,..

Leaks in your exhaust system will also cause popping backfire. Block the exhaust with your hand will the engine is running, and listen for leaks.

sure the carb rubberes are seated properly as if its leaking or split it will give the backfire

My xt was backfiring when the carbs intake rubber were cracked, or leaking.

Just a thought

Mine did it when the exhaust headers were pinholed with rust. It just looked like corrosion from the outside, but there was enough air getting in to ignite the unburnt mixture on a closed throttle. New headers, problem gone.