Posted: 10/9/2006 6:37:29 AM EDT
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I have a 06 honda shadow 1100, that I unfortunately laid down about 3 weeks ago. WHile doing a check ride yesterday I noticed significant backfiring when I rolled suddenly off the throttle at high speed. The bike has never done this before and I'm concerned that I may have damaged more then the cosmetic items when I laid it down (slow speed right turn, bike fell and slid about 10 feet) What causes an engine to backfire? |
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I did fall on the pipes side, there is some chrome scrapage on the pipes at the back, but I think my leg got most of the fall. I'll check to see if there is leakage at the pipe header. WIll it cause damage to the engine to run it like that, or just the annoying backfire? |
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It is considered normal if a bike backfires when closing the throttle quickly after being run at a high rpm. Is it more of a pop, pop, pop or a BANG!!? Backfires are excessive unburnt fuel exploding in a hot header or an exhaust valve still open when teh plug fires. Does the motor run fine under normal riding? If its a light pop pop pop on decelleration, I really wouldnt worry much. Dropping a bike sometimes causes carb problems that usually clear themselves out after running for a bit. Float could be sticking slightly higher or lower than recommended. Hard to say without seeing the bike. |
Normal. Have you considered that it might have been doing it all along and you have somehow "opened" the exhaust, for lack of a better term. Maybe an exhaust leak is not causing it, but it's simply allowing you to hear it now. |
| I believe your bike has a secondary air system which some also call an (get this) anti-backfire valve. Check for anything unhooked or unplugged under the seat or rear of the motor area. It's job is to let air into the exhaust to help burn any left over unburned fuel (especially on decel) in the exhaust. IIRC. |
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I agree with the lean suggestions. Check the air filter and boots. If the air filter got knocked out of position or if it's boot to the carbs got pulled off in the fall it will be sucking more air than it should. This will result in a lean condition and backfires. I hope that between all of us, someone will have the 'lucky guess'. goodluck |
But that causes drivability problems on acceleration. HE said its fine accelerating. Just pops on decel. |
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I reseated the air filter and still there is considerable backfiring when rolling off the throttle. At 70+ mph I can usually get 3-4 loud pops, and at slower speeds I get one or two. I'm concerned that I may be doing damage to the bike by continuing to ride it. Any more ideas as to what it could be? |
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Bike is lean on the cross over from the pilot jet to air/fuel screw (depends on the carbs). On single cylinder dirtbikes this lean condition is usually resolved by richening the idle circuit ~1/8 turn. The Shadow is a multi-carb bike, correct? Try richening it up just slightly on each cylinder. Brian |