Backfire before startup??


Information and questions on GL1100 Goldwings (1980-1983)
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thefrontsight
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Motorcycle: 1982 GL1100I Interstate

Backfire before startup??

Postby thefrontsight » Thu May 03, 2012 12:40 pm



On cold mornings, It sounds like the motor backfires before it starts. Like a loud choking. when its warm this problem doesnt exist. any ideas?
Michael



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WingAdmin
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Re: Backfire before startup??

Postby WingAdmin » Thu May 03, 2012 12:49 pm

Are you sure it's a backfire (up through the carbs)? Or is it out the exhaust? If the starter turns the engine enough to get some unburned fuel in the exhaust, it can light off with a bang once it does start up.

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thefrontsight
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Location: vancouver,wa
Motorcycle: 1982 GL1100I Interstate

Re: Backfire before startup??

Postby thefrontsight » Thu May 03, 2012 12:54 pm

WingAdmin wrote:Are you sure it's a backfire (up through the carbs)? Or is it out the exhaust? If the starter turns the engine enough to get some unburned fuel in the exhaust, it can light off with a bang once it does start up.


no im not. can i email you a video of it? or post it here?
it sounds like a huge screech and is difficult to describe.....perhaps premature ignition in the cylinder.....???

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WingAdmin
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Re: Backfire before startup??

Postby WingAdmin » Thu May 03, 2012 12:59 pm

If you post a video to Youtube, you can easily embed it in your messages here - just post the link in your message, and it will automatically embed it.

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thefrontsight
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Re: Backfire before startup??

Postby thefrontsight » Thu May 03, 2012 1:09 pm




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WingAdmin
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Posts: 17046
Joined: Fri Oct 03, 2008 4:16 pm
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1998 XV250 Virago (sold)
2007 Aspen Sentry Trailer

Re: Backfire before startup??

Postby WingAdmin » Thu May 03, 2012 1:22 pm

Wow, I don't know that I can identify that. Perhaps an intake valve not quite closing? Or starter slipping? Can you locate where the sound seems to come from?

I do notice your tach isn't working. :)

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thefrontsight
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Joined: Wed Mar 30, 2011 9:29 pm
Location: vancouver,wa
Motorcycle: 1982 GL1100I Interstate

Re: Backfire before startup??

Postby thefrontsight » Thu May 03, 2012 1:28 pm

WingAdmin wrote:Wow, I don't know that I can identify that. Perhaps an intake valve not quite closing? Or starter slipping? Can you locate where the sound seems to come from?

I do notice your tach isn't working. :)



yeah the tach has never worked....though id like it to....i think it needs a new tach cable.

i have a new starter, new battery and new solenoid. i dont think the starter is slipping.....if i hold down the starter button I can (though i dont) chug my way through this rough choking......valve adjustment in my future???

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Re: Backfire before startup??

Postby virgilmobile » Thu May 03, 2012 3:14 pm

Now I remember where I heard that.....A suzuki 500cc single with a compression release.....
Come to think of it,my bosses Harley uses the same thing so he can start his Milwaukee vibrator :lol:
Question,have the timing belts been changed?
Did the bike always do this,and if not,did it start after something was repaired in it?
Timing really won't change unless the mechanical advance and/or vacuum advance system rusted up.
These can be checked using a timing light and a vacuum pump.
It does sound like it is blowing compression back into the plenum.
Sounds like a intake valve is not closed all the way or leaking.
For a real quick test of things,first from cold.Start the bike and idle for 4-5-seconds.Do not rap the engine up...JUST idle.Shut it down and lightly tap each header to test for heat.They should all be the same.If one is colder,that's the cylinder with the problem.Either timing belt off,valve adjustment too tight or not the valve is not sealing.
The valves do have dual springs on each valve and I've seen the inner one break leaving a poor operating valve.




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