backfire

hi ive a 250 4stroke shineray was running great and has just started backfireing the other day , will start first time and tickover all day but will not rev up without bacfireineing please help its driving me mad:taz:

I also have Shineray 250 Supermoto - XY250 GY-2.
Mine backfires only when let of the throttle, so no problem with power just a bit annoying sometimes. Not sure how to cure it.

http://forum.motorcycle-usa.com/defa...?f=18&m=398516

Here’s is some good dialogue on the matter….

Backfiring is really a timing issue and the ignition being premature and backing firing through the carburetor. The other end is consider popping and is about unspent fuel igniting in the exhaust, the use of the term backfiring is or gets confused often. Backfiring through the carburetor or exhaust?

Quote:

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Originally Posted by MJH

...Backfiring is really a timing issue and the ignition being premature and backing firing through the carburetor. The other end is consider popping and is about unspent fuel igniting in the exhaust, the use of the term backfiring is or gets confused often. Backfiring through the carburetor or exhaust?

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Mine is popping then - Backfiring through the exhaust

Check for a loose exhaust at the manifold….

I have a similar problem with missing and backfiring with flames from exhaust. Have read so many
possible solutions and having tried most am now utterly confused. A clear path to follow would be great

check your valves

Yeh done that, Its driving me nuts, almost ran ok but not quite after some messing with the carb so a bit more messing now cant even get back to what it was. Just wont rev without popping and spluttering except if I give it a tiny bit of choke then popping stops?

Sorted, even though the plug was black indicating too much fuel I drilled the main jet out bigger and it now runs fine, I also increased the size of the other jet but only one size. I have had this problem before and it is a pain because it can be any number of things, loose connections, faulty plug, faulty coil. My policy now will be to start with the wiring and replace the battery leads with thicker ones then check through, then do the carb and plug.