backfire issue

[tistoni]

Hi, I own a 98 vmax and I"m having some backfire issues.
When coldstart with choke on it backfires untill choke is off, then it runs ok.
When warm it only backfires on decelleration. What could be the problem?
I synced the carbs with carb pro. What could be the issue, a/f mix or vacuum leak (I sprayed the carbs with start fluid no change)
It's a pop in the right front exhaust. (Doma exhaust)
Does backfire do any damage by the way?

Thanks for your help.

 

[HyperPete]

I would start by checking for exhaust leaks, particularly at the headers.

 

[Diablotin]

It happened to me it was an exhaust leak but where the muffler connect.

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[tistoni]

Ok, I'll check that, thanks!
By the way, did you just tighten the bolts?

 

[tistoni]

Is there a way or procedure on how to find the leak? (Like the start fluid procedure on the carbs)
I've been reading here on the forum but couldn't find it.
Thanks

 

[Diablotin]

I found mine by hand but a soap test could work as long as it's not hot. Mine was obvious and easily accessible.

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[tistoni]

"I found mine by hand but a soap test could work as long as it's not hot. Mine was obvious and easily accessible"

Ok thanks, I'll try that!

 

[Redbone]

you could use a "smoke stick" (used for home leak testing) or if you're a smoker, cigarette smoke might work. I have a fireworks dealer nearby so I use "punks".

 

[HyperPete]

You can also check all of the bolts to see if they are torqued to specs (or at least tightened snugly.) After doing so, if you are still getting backfiring, then you can continue by smoke testing, or even holding your hand near each connection point to feel for exhaust leaks.

Sometimes it's as easy as just looking at the exhaust system. You may see exhaust deposits where it has been leaking.

 

[tistoni]

Well I was thinking of smoke myself, I'll buy an extra pack when I start!
Thanks for the help guys

 

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I felt air escaping with my hand. Careful. The exhaust heats up pretty damn quick!

 

[Redbone]

I felt air escaping with my hand. Careful. The exhaust heats up pretty damn quick!

Yes it does, brings back a painful memory when I thought one of the rears gasket was leaking!