Motorcycle Repair: motorcycle engines, carburetor jets, 2 stroke engines

Question
I have a 1975 keg 175 Kawasaki dirt bike and it is backfiring thought the carburetor what does this mean


Answer
Dale, backfiring comes from a number of sources. Usually carb backfires come from a lean mixture or incorrect ignition timing.

I am not a Kawi expert, but I think you have a 2 stroke KE175...?

2 stroke engines can get air leaks at the ignition/generator side of the crankshaft seal. Other lean conditions come from  dirty carburetor jets, cracked intake manifolds and in bad cases, damaged piston/rings.

I don't know if those bikes had electronic ignition by then or not. If you still have points and condenser ignition, then the points could be dirty or have closed up the gap, so the ignition timing is way off or you have a weak spark because of dirty points. A bad or loose condenser will cause all kinds of ignition timing issues.

Try a new spark plug, check spark plug cap for 5k ohm resistance and hopefully the ignition coil is still good. If the bike has a magneto ignition, it is not dependent on the battery. If not, then a dead/dying battery may cause misfiring problems, too.

Get a compression check done, clean up the ignition system components, be sure that the carburetor and whole fuel system is clean and functioning properly. Gas caps have vent holes that plug up, restricting fuel flow in some cases.

Bill MrHonda Silver