So would the backfire be more likely to occur with an overly rich mixture? I'm still trying to wrap my mind around the normal condition. Would a by the book tuned bike with minimal upgrades (less restrictive exhaust and K & N filter, larger main) be likely to backfire when shutting off the throttle?
REgards,
Leonard
Well will your air cooled lawn mower pop when you suddenly close the throttle from fast to slow in a hurry after mowing for awhile. It's is caused by the same dynamics and considered perfectly normal. It is always more pronounced in a single cylinder engine, and the larger the engine or the freer flowing the exhaust the larger the pop.
Can't say that it ever has, no. It does sometime backfire if I turn off the ignition too quickly before it idles down a little bit. Same thing I suppose.
I don't want to belabor the subject, my bike doesn't normally backfire when I shut off the throttle and I like it that way. I was just trying to understand why it would be considered normal when everything I have ever heard claims that a backfire is not a good thing to happen.
Best,
Leonard
--Leonard
Trust me, I'm not saying there is anything wrong with the bike not back firing. If it is a stock Enfield, you wouldn't hear it if it did due to the over enthusiastic silencer that is in place. If you put a free flowing exhaust on don't be surprised if you hear an pop through the exhaust pipe. That is normal. But normal is a relative term, every engine is different, as with anything in life moderation is a good thing. If it is continuous, better check your ignition timing (overly retarded, firing way after TDC ), exhaust valve clearance (not enough clearance can hold open the exhaust valve), or your valve timing, which can be change slightly on the Enfield's by adjusting the valve gear backlash (if the valve backlash is improperly adjusted it can cause the exhaust valve to open to soon).
If you watch NASCAR on television, during the short track races (they back off the throttle a lot more than on the super speedways) you will notice flames coming out the exhaust, watch the shots of the right side of the race car, when they enter the corner and back off the throttle. You will see flames coming out the exhaust headers, that is in reality a backfire. If you were standing at that point in the track, you will hear the popping. Which is more like a rumble with multiple cylinders being exhausted so close together