Ear Shave and Backfire when starting with engine warm/hot - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 8 (permalink) Old 10-22-2012, 12:10 AM Thread Starter
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Question Ear Shave and Backfire when starting with engine warm/hot

I did the ear shave procedure about 6 months ago. I re-jetted and everything per the instructions. I believe I read a post that after this procedure, you could have difficulty re-starting the bike when the engine is warm/hot, but I can't seem to find the post.
Anyway, my bike DID have this problem. After riding for a while and stopping the bike, it wouldn't struggle to start again if the engine was still warm/hot. It would try to turn over for about 3-5 seconds, then a LOUD backfire would occur. After the backfire, it would start up immediately with no problem.
I've been dealing with this problem up until now, although it is quite embarressing when at a gas station or parking lot with people around. So the other day I rode my bike home from work (about 20 minutes on the highway at 70mph). After being home for about 15 minutes I went to start my bike again. Same issue...after 3-5 seconds of trying to turn over, a very loud backfire...yet this time, it still would start. I tried again for another 3-5 seconds, and then a second backfire, but this one not as loud as the first. I gave up at that point because I was in a hurry to get to my next destination, so I just drove my truck.
Does anyone know what I can do to alleviate this backfire issue?
Thanks!

1993 VN750 stock
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post #2 of 8 (permalink) Old 10-22-2012, 04:46 AM
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Try doing the Ignition Coil Relay Mod

and Gaping the pick up coils.

also change out to an AGM battery if you haven't already, make sure your grounds are tight and clean ... especially the frame to engine ground
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post #3 of 8 (permalink) Old 10-22-2012, 11:53 AM
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check to make sure your fuel tank vents are not clogged.

Read about "POOGS" and see if that helps.

At one time I had a partial clog in the vent line and it did the same thing to me. All the other things mentioned above will also help.

fuel starvation....wears down the battery....big bang!!
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post #4 of 8 (permalink) Old 10-22-2012, 06:08 PM
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Quote:
Originally Posted by knicol View Post
I did the ear shave procedure about 6 months ago. I re-jetted and everything per the instructions. I believe I read a post that after this procedure, you could have difficulty re-starting the bike when the engine is warm/hot, but I can't seem to find the post.
Anyway, my bike DID have this problem. After riding for a while and stopping the bike, it wouldn't struggle to start again if the engine was still warm/hot. It would try to turn over for about 3-5 seconds, then a LOUD backfire would occur. After the backfire, it would start up immediately with no problem.

Does anyone know what I can do to alleviate this backfire issue?
Thanks!
Bet if you pull the plugs, they are wet. Backfire is probably ignition of unburnt fuel in exhaust.
Check the plugs
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post #5 of 8 (permalink) Old 10-22-2012, 06:21 PM
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It is ussually the battery.

02 honda sabre 1100
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post #6 of 8 (permalink) Old 10-22-2012, 07:46 PM
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Youre not by chance twisting your throttle when cranking, are you ? That would cause gas from the float bowls to enter the cyl and could cause similar.



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post #7 of 8 (permalink) Old 10-30-2012, 01:46 PM
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Is the Air fuel mixture screw turn out 2.5 turns or more?


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post #8 of 8 (permalink) Old 10-30-2012, 02:22 PM
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Quote:
Originally Posted by niterider View Post
It is ussually the battery.
yup.mine does that when the battery gets low.put it on the charger for a while and she starts fine

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