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Discussion Starter · #1 ·
Hi folks. Just found this forum tonight and now maybe I can learn a few things.
Some background-I have a '98 1500 Classic that I bought new. It now has 15000 miles. Back in '98 I had a Cobra Slashcut classic exhaust system installed and a jet kit which the installer said was necessary. The bike has ran great since I bought it but I have a problem that has come up. Upon decelleration, the bike will now pop and backfire. This condition has had no effect on the acceleration. This started happening overnight. It seems like it happened the day after I had two new tires put on. I know enough to change the oil on the bike but that is about it so I took it to a bike repair shop and they said the low speed jet was the problem and drilled it out from a 45 to a 48. After dropping $150 for this I picked it up and you guessed it.............popping and backfiring on the way home from the repair shop and this was after they said that they had tested it and the problem was gone. Not too much confidence in these guys now. :roll:
Anybody have any idea as to what the problem might be. I'm having these nightmares now that the bike will be in and out of the shop 5 or 6 times for 2-300 dollars a pop before the problem is diagnosed and fixed correctly.
Thanks for letting me rant and rave and I appreciate any advice.

Dave C.
 

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The popping/backfiring is caused by a lean condition usually. Meaning that your engine is not getting enough fuel. Sounds like they drilled it out to get more fuel to the engine(don't prescribe doing that)
A couple of things come to mind:

1. Vent line is blocked or pinched.
2. Carb is fouled up.
3. Float bowls not set at correct height - although not likely.
 

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make sure you AIRBOX is fitting correctly at all points (carbs,filter etc)
what does the airfilter look like ?
the first thing that came to mind was that you have a exhaust leak in the pipes somewhere at a joint (sucking air). make sure all the clamps are tight and the gaskets good. could be SUCKING air somewhere which causes popping in the exhaust.
good luck
 

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Discussion Starter · #5 ·
Thanks for the replies guys. I had forgotten about the marbling thing. I think my plan of attack is to check the air filter(although I don't believe this will be the culprit because acceleration hasn't been affected), remove and reinstall the exhaust to check for the proper seal, marbling the air lines, and if that doesn't do it I guess the Kawi repair shop will be able to make their next rent payment on me. :cry:
 

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Hey Wulf:

I think you are on the right track of checking the sealing between the exhaust pipe and the head. They had to remove the rear cylinder's exhaust pipe to gain access to the rear brake bracket bolt when they replaced the rear tire. In doing so, they likely reused or misinstalled the crush gasket and now it is leaking air into the exhaust pipe. I would install a new crush gasket ($7 for a Kaw part) and make sure it is fit up right. Torque the bolts evenly so not to **** the pipe.
If this fails, and you haven't lost your marbles (sorry! couldn't resist), then I'd search out the dyno shop and hook up the exhaust analyzer to check out the ratio...good luck.

T-man
 

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Discussion Starter · #7 ·
Sorry to bring an old topic to the top but just wanted to let those interested know that I changed the crush gaskets on the exhaust system and now there is no more popping or backfiring. And again, thanks for the helpful advice.
 
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