Sputtering Backfire

[fishybusiness]

04 Zuma 1550mi

at top speed, scooter has a sputter, and backfires occasionally. Only happens over 32mph?

Any suggestions?
Thanks

[Carlson]

Could be too rich. The spark plug will tell you if you are running too rich. Heavy black deposits or if the plug is wet = too rich.

[gfmktm]

04 Zuma 1550mi

at top speed, scooter has a sputter, and backfires occasionally. Only happens over 32mph?

Any suggestions?
Thanks

lean out the air fuel mixture screw- turn it out 1/8th turns until it stops backfiring

[Jack B]

Your spark plug may be fouled. Replace it and see how it goes. Like Carlson says you may be too rich on the needle or main jet which would foul the plug. Usually the air fuel mixture screw only affects the first quarter or so throttle.

[fishybusiness]

OK, new plug today. keep you posted thanks

[Carlson]

What did the plug look like. If it had a black residue or was wet, then you are running too rich. It should have a light brown color on the anodes.

[125 Sumthnerudr]

Having issues with backfiring when running for a while. I live in Savannah Ga and the roads are terrible. Whenever I hit a bump and lift off of the seat the scooter dies. Sometimes it slows down and hesitates until it backfires (POW!) then it runs fine for a mile or so then put puts and shakes. I've taken it completely apart, gas tank and all, cleaned it checked it, am at a loss. Any ideas as to what it may be? The muff is rusted but no holes. Gonna pull the plug again and adjust the carb next.

[Old School]

Side kickstand engine kill switch...???

[125 Sumthnerudr]

I thought that might be it but when I took it apart I could not find any switch. I think it might be a short somewhere, maybe it's grounding out on an exposed wire. then again not many wires on it around the engine. I blew a fuse a few times so changed it out and snugged it next to the battery so it wouldn't move. Now it runs but runs rough. Next step is the shop but I really don't want them to screw me on something simple.

[mpathus]

Sounds like an electrical gremlin: spark cutting out, then a build up of unburned fuel collects in the pipe, and re-ignites when combustion gasses resume.

Check your battery's condition and wiring too; hot weather is hard on batteries as well.

I don't know if your fuel hoses are clear to see through but if there is an air bubble that might inhibit fuel delivery some, and may contribute to a lowered carb fuel level to cause a lean backfire.

[zeonsredcomet]

This thread is dead, I sold Fishybusiness my stock top end pretty much a year ago since he said he needed one.