Backfire through air cleaner - Harley Forum

#1 05-24-2009, 07:13 PM

I have an 05 Sportster 883L. It started having a backfire through the air cleaner. Especially bad from a stop on acceleration. If I keep the enricher out slightly, it stops completely. Replaced plugs and air cleaner. Yesterday, replaced the vacumn piston and turned up the idle a bit. What should I try next? All is stock.

HarleyCruiser · #2 05-24-2009, 07:23 PM

Did you replace the air cleaner with a free flowing one, and put on aftermarket exhaust, before the problem started?
It sounds like a classic lean mix problem, getting too much air and not enough gas.
That or you have an air leak in the intake.
If you have added the air filter and exhaust with out re jetting, that is where I would start.

Quote:

Originally Posted by hawk63

I have an 05 Sportster 883L. It started having a backfire through the air cleaner. Especially bad from a stop on acceleration. If I keep the enricher out slightly, it stops completely. Replaced plugs and air cleaner. Yesterday, replaced the vacumn piston and turned up the idle a bit. What should I try next? All is stock.

#3 05-24-2009, 11:53 PM

Can the air mixture be affected if the air cleaner housing isn't fitting tight? Such as the gasket that goes up to the carb?

#4 05-24-2009, 11:55 PM

I did not change the air filter type or exhaust before this happened. It seems like it happened after I changed the carb top cover with a chrome one

JCourneyaP · #5 05-25-2009, 02:27 AM

You didn't happen to tear that rubber diaphram did you?

frisco-rigid · #6 05-25-2009, 05:44 AM

HC thought the same thing I did when I read the post,,, that you went to a Hi-Flow AC and now are a wee bit lean..

No,,, any air leak between the AC and Carb will not affect A/F mix..
It will simply Not get filtered.. Not that big a deal really..
An air leak between the Carb and Manifold or manifold and heads Will certainly affect the A/F mix and HC referred to that..

If there is a Prob after a Mod is performed, such as that chrome cover you installed,, that should be the first place to look for a solution..
It's Not sealing correctly or maybe that diaphram that JC mentioned..

#7 05-25-2009, 04:09 PM

Thanks, guys. I just found a tear in the rubber on the vacumn piston. Going to replace it and take a test ride. If not that, guess check for leak at intake manifold - right?

#8 05-25-2009, 09:14 PM

Put in a new vacumn piston with rubber - had to replace the whole thing. Anyhow, runs like a champ! Thanks again for the help;

JCourneyaP · #9 05-26-2009, 05:29 AM

Hey Hawk. I tore my diaphragm a few years back and could not just replace the rubber. Sucks. How much did they nail you for it...Around 40 bucks?

That was one expensive Chrome cover you got. Live and learn. We all do.

Like the time I dropped a driver bit in my intake and started the bike up.....

#10 05-30-2009, 10:45 PM

They nailed me $50 for it. Seems it is wise to buy the genuine HD chrome cover!