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Message started by Timbo6 on 12/03/16 at 10:05:11

Title: Backfiring
Post by Timbo6 on 12/03/16 at 10:05:11

My LS650 has a tendency to backfire every time I shut it down. It runs well and has plenty of power. Sometimes popping the choke on shut down stops the backfire.

Other bikes I have had did not have this issue.

Anyone know of a fix for this issue or what causes it?

Thanks in advance for your info

Title: Re: Backfiring
Post by Kenny G on 12/03/16 at 11:41:59

Tim,

Let the engine idle for a minute or 2 before you shut it down.

Kenny G

Title: Re: Backfiring
Post by Kris01 on 12/03/16 at 16:47:58

This topic has been discussed to death. You can search this site for a lot of options.

Have you rejetted?

A trick that works for me is to sometimes hold the brake and release the clutch lever to slowly allow the engine to come to a stop. Works every time.

Title: Re: Backfiring
Post by Dave on 12/04/16 at 03:18:58

This is a common situation with the Savage....it was also a problem with a lot of lawn equipment a few years back, and they started to put an electric fuel shut off switch on the carb on mowers.

The engine is a pump, and the cylinder has an intake cycle that pulls fuel and air in the cylinder, there is a compression stroke, then the spark plug ignites the mixture and you have a power stroke, then the exhaust valve opens and the burned gasses are pumped out of the engine.

When you turn off your ignition you have eliminated the power stroke as the spark plug doesn't ignite the mixture - but the other 3 strokes are working as normal....and you are pumping unburned fuel/air through the engine and into the exhaust system. When the fuel/air mixture is pumped into the hot exhaust system - the heat is enough to ignite the mixture, and you have an explosion in the header/muffler.

Several things can make this explosion louder. If your engine speed is too high at idle, you can pump a lot of fuel/air into the exhaust system. If you idle fuel/air mixture is lean, the explosion is louder than if the mixture is correct. If you pull off the highway and instantly shut the ignition off, the header and muffler are still hot and can/will ignite the unburned fuel/air mixture.

Make sure you idle speed is not too high - but you do need to keep it above 1,000 rpm so that you have good oil pressure at idle. Rejet your carb if it is lean.....does the engine have any "surging" or unsteady acceleration at low throttle settings? And do let your engine idle for half a minute or so when you get off the highway.....if you were just riding around in town at low speeds you most likely won't get any benefit from a short idle period.

If your bike just makes a small "poof" there really isn't any need to worry about it - but if it sounds like a shotgun blast....that can get a bit annoying.

Title: Re: Backfiring
Post by HAPPYDAN on 12/05/16 at 11:17:44

+1 on "Discussed to Death". When new, my 2012 had a very loud "BOOM!" Scared folks at the gas station. I popped out the brass air screw cap (called many other things) and did the recommended adjustment and that helped. Pulled the choke out on shutdown to stop it altogether. Then, my HD buddies told me it was the ethanol, to use straight gas or STA-BIL. Now at 5,000+ miles, using STA-BIL for the last 2 years, I barely get a "POOF". Something about air cooled, large displacement, low compression engines that don't like ethanol. It doesn't always burn completely in the combustion chamber? :-/

Title: Re: Backfiring
Post by Timbo6 on 12/05/16 at 13:54:41

Thanks to all who gave me some good ideas. I think I will try the STA-BIL
trick and see how that works.

Question for HappyDan, how much STA-BIL did you add to your tank and do you add it everytime you fill up?

Thanks,
Tim