Bare with me on this description. It is a specific situation when I am getting the missfire. Sometimes i get engine miss when almost coasting. At that point when you are going down hill but just giving enough throttle to maintain speed. There are only a few hills around where I live that I get to exprience this on but it is annoying. I have changed the plugs and that didn't help. Starting to think it might be a timing issue. Because like the miss I occasionally get a really loud backfire when letting off the throttle going into a coast. Any Ideas?
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back firing , can mean a lean (popping on deceleration) or a rich mixture backfiring a lot , . check your connections at the headers and your carb to engine , and carb to airbox ... air is getting in , . look at your air filter .... look at your exhaust for blockages ... if this is the exup (power valve ) model then check the valve actuator , as it can lock closed , ... either remove it or wire it open
Hi, Anonymous for this situation I would call my local dealer or reputable shop's service/parts department and inquire about any possible quick fix, answers, or parts inquiry. If necessary, transport your bike to the dealer or shop and have a professional technician take it for a test drive, if it is in running condition, and give you a written estimate of repairs and answer any specific questions you may have about your issue. For more information about your issue please visit the website below. Good luck and have a nice day.
Backfiring out of the exhaust is usually an ignition problem. Unburned fuel is getting into the exhaust system because it's not being ignited in the cylinder. When the engine fires on that cylinder again, it ignites the raw fuel in the exhaust causing the pop that people call a backfire. I'd investigate the ignition system. Connect a timing light to each of the spark plug wires if it has a single fire ignition or either of them if the ignition system is the stock dual fire. Start the engine and watch the timing light to tell if the engine is missing as the light will miss a flash.
it probably isnt a firing order problem, or it probably wouldnt run
one coil fires 1 & 4 cylnder, the other coil fires 2 & 3 cylnders, as the pick up gets its signal from the crank, it sends a spark to each cylnder on the exhaust stroke as well as the compression stroke, ignition timing also doesent change as it is electronic and cant drift out like when points wear.
a short in the ingnition or kill switch can occasionally cause a backfire
Backfire can also be caused by
lean mixture, dirty carbs, loose carb clamps
leaking inlet or exhaust flanges and gaskets
tight valve clearances, burnt valves
make sure everthing is clean and tight, good air filter and exhaust, check valve clearances ,and give it a compression test, check the valve timing, incase it has been assembled wrong,(they rarely jump a tooth unless the chain and tensioner are completely stuffed)
The engine misses the firing as there is a faulty electrical issue or a fuel mismatch on the settings.
Now if this happens ONLY on the lower RPM,But there is very good performance at higher RPM then it is possible that the timing is set or is offset. It will best to have the engine tuned with the correct timing using the right equipment. Check the engine firing at low RPM Make sure there is no gasket leak on the manifold/exhaust that would change the firing.