What causes backfiring? - Victory Forums - Victory Motorcycle Forum
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post #1 of 16 (permalink) Old 10-01-2014, 05:56 PM Thread Starter
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Default What causes backfiring?

My new used 2008 Vision has the Stage 1 upgrade. It backfires occasionally. Is this due to a rich gas mixture or a lean gas mixture? Should I take it in to reflash? I run premium 91 octane.

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post #2 of 16 (permalink) Old 10-01-2014, 06:47 PM
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Are you talking about backfiring (which is thru the carb) or exhaust popping (thru the pipes)? If its the latter, you may be too rich. Or you "chop" the throttle between shifts. Try being a lot easier with the throttle and make less movements when shifting.

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post #3 of 16 (permalink) Old 10-01-2014, 06:59 PM
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Let me guess... 1750 rpm on deceleration?

The fuel injectors are off on deceleration... they come back on at around 1750 rpm... BANG!

In your case you have no way to tune it out. The first thing to do is unplug the O2 sensors in the exhaust pipes. Just follow the wire up to the connectors and unplug them. There will be no FI light or issue.

You can also try this:
http://www.lloydz.com/store/item_vie...itemid=1000078

Or this will definitely be worth doing:
http://www.lloydz.com/store/item_vie...itemid=1000125
http://www.lloydz.com/store/item_vie...itemid=1000131


Other causes are:
Exhaust leak at the header connections (failure to use new gaskets if the pipes were ever loose).
Intake vacuum leaks
Bikes as old as yours... the cap-offs on the throttle body may be rotted, or you may need to replace the rubber throttle body adaptor (rubber intake manifold). Rubber parts don't last forever.

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post #4 of 16 (permalink) Old 10-01-2014, 07:07 PM
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Quote:
Originally Posted by half_crazy View Post
The fuel injectors are off on deceleration... they come back on at around 1750 rpm... BANG!
Good reason to keep the revs above 2,000.

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post #5 of 16 (permalink) Old 10-01-2014, 08:01 PM Thread Starter
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Quote:
Originally Posted by RICZ View Post
Are you talking about backfiring (which is thru the carb) or exhaust popping (thru the pipes)? If its the latter, you may be too rich. Or you "chop" the throttle between shifts. Try being a lot easier with the throttle and make less movements when shifting.
I'm hearing it through the pipes, so I figure it is the pipes. Rich running may make sense, cuz if you idle, I think it's loading up with too much fuel.

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post #6 of 16 (permalink) Old 10-01-2014, 08:07 PM
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Quote:
Originally Posted by KingpinRider View Post
I'm hearing it through the pipes, so I figure it is the pipes. Rich running may make sense, cuz if you idle, I think it's loading up with too much fuel.
Disconnecting the O2 sensors and installing the Lloydz adjustable idle air valve will help reduce exhaust popping. I had some explosive popping and the above, along with the Lloydz adjustable timing wheel, has all but eliminated it.

2010 Midnight Cherry XR. 7Jurock, Lloydz AF, ATS, AFR tuned VFCIII, IAV, and T-6 and locally repacked pipes = big smiles. SOLD to a dear friend, so it's still in the family."
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post #7 of 16 (permalink) Old 10-01-2014, 10:00 PM
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when shifting "don't" close the throttle all the way to the stop.
Other wards try doing a mild speed shift. Closing the throttle all the way cause it. We have a poor vacuum system that doesn't respond fast enough

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post #8 of 16 (permalink) Old 10-01-2014, 10:35 PM Thread Starter
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Quote:
Originally Posted by visionjohnny View Post
when shifting "don't" close the throttle all the way to the stop.
Other wards try doing a mild speed shift. Closing the throttle all the way cause it. We have a poor vacuum system that doesn't respond fast enough
Will give that a try. It's not continuous or every ride.

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post #9 of 16 (permalink) Old 10-02-2014, 07:01 AM
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This is why I am contemplating keeping my exhaust stock . I realize its ultra quiet but I can not stand the popping .

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post #10 of 16 (permalink) Old 10-02-2014, 07:13 AM Thread Starter
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Quote:
Originally Posted by LILMAGS500 View Post
This is why I am contemplating keeping my exhaust stock . I realize its ultra quiet but I can not stand the popping .
I left my Kingpin stock and it was quiet and never had a backfire. Not a bad idea. I had thought about undoing the Stage 1 if anyone had the stock pipes. Will try a few of the other suggestions. Didn't have a single backfire this morning. I ran a little SeaFoam through and that probably wasn't helping the situation.

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