Backfiring??

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Aug 3, 2010 | 08:42 PM

RaceFace

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From: Ladera Ranch, CA

Backfiring??

As I mentioned in the other Ness Big Sucker thread, I'm learning about my first Harley here. I am pretty knowledgeable about motors and consider myself a gearhead, BUT this is my first V-twin. My RK has V/H Dresser Duals on it and it backfires quite a bit when I'm not full throttle in the lower gears. On the freeway in 4th and 5th its fine, but accelerating from a red light nice and mellow, it backfires. The bike is an '05, so its injected. I did some research on here and other forums and people have said backfiring is caused by an exhaust leak. I have double checked everything and I don't see anything. It starts nice and easy, idles fine, and runs great at freeway speeds, but just riding from red light to red light in town, it backfires a lot. I can't imagine that this a characteristic of the pipes. It's a tad embarrassing.

The bike still has a warranty on it but I don't think it would be covered since it has aftermarket mufflers on it, so I'm afraid to take it in.

Any advice would be deeply appreciated.

Thanks!!

-Scooter

Aug 3, 2010 | 08:48 PM

dawg

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From: Vermont

Just because it's an 05 does not mean it's injected. HD's had carbs up until 06 so you could technically have a carb unless you're sure it's injected. In any event, yes intake and/or exhaust leaks can cause exhaust popping. If it is injected, do you know if there was just a stage 1 dealer download or is there a tuner on it? A poor tune or no tune can cause popping and backfiring.

Aug 3, 2010 | 08:57 PM

RaceFace

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From: Ladera Ranch, CA

Quote:

Originally Posted by dawg

This thing is definitely injected. I questioned primary jetting as I was riding it, then got into it and looked, no carb. I have no idea about the tuning. I have gone through the receipts and I don't see anything regarding tuning or any adjustments. In dealing with the previous owner and his 'knowledge level" my guess would be no, he did not have anything done.

I know it hasn't been ridden since at least December, possibly even more. Tags are due in December on it and they had not been put on the bike yet. The gas didn't smell bad, but I added fresh 91 to it, but haven't ridden it yet with the fresh gas in it.

Aug 4, 2010 | 12:33 AM

cjairplane

Cruiser

Joined: Aug 2009

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Interesting. I have some decel popping, which I guess is not uncommon after a stage 1 job. The only time I've heard of it on accelerating is with a bad tune or carb issues.

Aug 4, 2010 | 12:49 AM

Lama

Road Captain

Joined: Jun 2007

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Change your sparkplugs and sparkplug wires first.

Aug 4, 2010 | 05:05 AM

VETERAN75

Road Warrior

Joined: Nov 2009

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From: SC

blow some sort of smoke around your exhaust connections to make sure there is no leak. It is unburned fuel fumes burning in the exhaust pipes as they exit. You probably do need a tune adjustment to lean it a little to alleviate this. But still check the exhaust to be sure on that end. Thats my opinion.

Aug 4, 2010 | 10:21 PM

RaceFace

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From: Ladera Ranch, CA

Well I got into it tonight and the exhaust system did take some more snugging off the motor and at the mufflers, so I re-torqued them. I also pulled the plugs. The front plug looked ok and the electrode was bridged and clogged with something hard. It looked like the plug was barely working. I cleaned the plug but haven't had a chance to ride it yet to see if it fixed the problem, but it makes total sense that the backfiring was unspent fuel mixture igniting in the pipes. I will buy new plugs tomorrow just to make sure.

By the way, whats the gap on the plugs?

Thanks!!