Backfire on start-up

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Feb 11, 2006 | 10:41 PM

SKJOLD

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From: St. Petersburg Florida

Backfire on start-up

What would cause an engine to start backfireing on start-up all of the sudden. It has been doing it for a few days now. The plugs are not fouled, but the front cylinder does not seem to be fireing initially. After a few attempts to start which results in backfireing, then fireing on the rear cylinder, and then both very roughly until it warms up and then runs fine.

Feb 12, 2006 | 09:40 PM

pococj

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From: Texas! Ya mean there's someplace else?

RE: Backfire on start-up

Couple things to check, in no particular order - gap the points, replace condenser, check timing, adjust valves (pushrods).

Feb 13, 2006 | 12:10 AM

SKJOLD

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From: St. Petersburg Florida

RE: Backfire on start-up

I forgot to mention that I have electronic ignition. On startup, the front cylinder won't fire until the engine has been running for a few seconds, then you hear the front cylinder sputter and fire up. Then it runs fine after warmup.

Feb 28, 2006 | 03:37 PM

prooils

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From: San Diego, CA

RE: Backfire on start-up

Did you ever get the problem fixed? If the pushrods are out of adjustment on your front cylinder then it could be holding the coresponding valve open and allowing too much air in. After it runs for a bit, check the spark plug on the front cylinder and make sure it's not too rich or too lean. The Ironheads vibrate like crazy and it's not uncommon for the pushrods to need a little adjusting every now and then. I saw a thread somewhere around here that describes how to adjust the pushrods so I won't re-post it. Good luck!

Feb 28, 2006 | 11:09 PM

SKJOLD

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From: St. Petersburg Florida

RE: Backfire on start-up

How do you adjust the pushrods on these?

Mar 1, 2006 | 01:49 AM

pococj

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From: Texas! Ya mean there's someplace else?

RE: Backfire on start-up

Vewwy carefuwwy! It's not difficult, but you need talented fingers, 'cause you gotta manipulate 3 wrenches at the same time. Ya gots yer service manual handy?

Mar 1, 2006 | 03:54 PM

prooils

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From: San Diego, CA

RE: Backfire on start-up

Here's the link to the post that I mentioned earlier. Having your manual handy helps too if you have one. This post explains Ironheads, Evos, S&S, etc. It's pretty thorough. If you have any questions, just let me know.

https://www.hdforums.com/m_95088/mpa...s/tm.htm#95088