Backfireing help
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Joined: Aug 2012
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From: manassas va
Backfireing help
I have an 03 sportster 1200 with 10k on it on Friday I stopped and got gas 93 bike was running fine tried to restart the bike would not start just starting backfireing out the exhaust. Turned the gas off let it sit for a few then tried it again after about 10 min. Retried for a bit and it finally started up got the bike home pulled the plugs they were good running a little rich. So I went to the Harley shop and picked up 2 new plugs gapped them to 40thousands. Did a compression check with hot engine 110psi installed new plugs fired up ran it around the block came back shut it off tried to restart it same problem backfireing. Pulled the carb off cleaned it no dirt in the carb cleaned all the jets no dirt nothing the air fuel mixture screw was 4 1/2 turns out looked online found its set around 2 1/2 to 3 turns out on a hd performance page. Drained the tank refilled with new fuel. Took out today since repair and still doing it what could it be?
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From: Boynton Beach, FloriDuh
I have an 03 sportster 1200 with 10k on it on Friday I stopped and got gas 93 bike was running fine tried to restart the bike would not start just starting backfireing out the exhaust. Turned the gas off let it sit for a few then tried it again after about 10 min. Retried for a bit and it finally started up got the bike home pulled the plugs they were good running a little rich. So I went to the Harley shop and picked up 2 new plugs gapped them to 40thousands. Did a compression check with hot engine 110psi installed new plugs fired up ran it around the block came back shut it off tried to restart it same problem backfireing. Pulled the carb off cleaned it no dirt in the carb cleaned all the jets no dirt nothing the air fuel mixture screw was 4 1/2 turns out looked online found its set around 2 1/2 to 3 turns out on a hd performance page. Drained the tank refilled with new fuel. Took out today since repair and still doing it what could it be?
Unless you ran out of gas and pushed it into the station, the carb bowl and fuel fine were still full of "old" gas that would need to be used up running the motor before the "new" gas entered the system. If it was a gas issue, the bike would have started and run for at least 30 seconds before the motor started burning the new gas.
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From: manassas va
I just did a cold compression test and it's 115 psi removing the tank now and checking all the harness connectors rechecked spark as well not much there spark wise clean the connectors at the coil and see where that takes me
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From: manassas va
Is there a reason the front exhaust pipe is not pushing out hot exhaust and the rear is the bike runs great after you get it started when cranking it to start it acts like its to much compression and the starter starts to slow up let off the button then good for a little while when cranking do these engines have an internal decompression release valve or what would be causing it to be doing anyon this?
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no internal release.sounds like a timing issue to me.but one thing that happens is a weak battery can cause ignition module issues allowing some weird timing to go on.Also when its not pushing exhaust its not got fire to that hole so you know you have compression so it has to be fuel or spark.Eliminate from there
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From: manassas va
Rechecked coil with an ohms meter and I'm reading 2.9 ohms across the 2 wires once I realized that you half to have one of the plugs grounded out while checking the other with a spark tester I have good fire I'm getting gas and have fire and have compression = should run the timing on this engine is ear driven off the crank for the cams so how could it be out?