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General Category >> Rubber Side Down! >> Backfiring when the bike shuts off
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Message started by Suzukisavvy on 02/16/15 at 12:06:46

Title: Backfiring when the bike shuts off
Post by Suzukisavvy on 02/16/15 at 12:06:46

OKAY! The bike is running and and riding like new... But when you shut off the bike you get a loud BANG. how can I fix that embarrassing bang? ;D :o

Title: Re: Backfiring when the bike shuts off
Post by verslagen1 on 02/16/15 at 12:10:57

several ways...
turn the idle mixture screw a little richer...
or pull out the choke when you shut off...
or let out the clutch when you shut off so it don't run down as long.

or clean your carb.

Title: Re: Backfiring when the bike shuts off
Post by Suzukisavvy on 02/17/15 at 07:32:32

the carb is clean. why does the savage even give that one last pop when you shut it off? design problem?

Title: Re: Backfiring when the bike shuts off
Post by Serowbot on 02/17/15 at 07:36:59

That's not anything to do with how it's running... It's just one last cylinder full of unspent fuel that gets chucked into the exhaust after you shut off the spark,... the heat in the pipe ignites it and "Boom"...
It's better to learn how to prevent it using rider technique than to try to tune it out...
(tuning for a shut-off engine is kinda' nutty)... :-/...

Just letting the bike idle for 5 or 10 seconds before shutting off will often prevent it....

Title: Re: Backfiring when the bike shuts off
Post by Dave on 02/17/15 at 07:58:13

As Serowbot suggested....it is a fuel/hot exhaust issue.

When you turn off the ignition or hit the kill switch - you are shutting off the electrical system and there is no spark at the plug. However - the spinning engine is still pulling air through the carb where it picks up fuel, and the engine then pumps this unburned fuel into the hot exhaust system. As the fuel/air mixture is heated up by the hot exhaust - it reaches the point at which it ignites...and "bang".

Letting the engine idle just a bit before you shut off the bike can allow the exhaust system to cool down a bit and the bang may not occur. I have not tried this....but opening the throttle wide open just after you turn of the ignition may allow the throttle butterfly to stop the flow of fuel out the idle fuel/air circuit, and may reduce or eliminate the bang....just be sure not to open the throttle before the ignition is turned off as you want the engine spinning as slowly as possible when you turn it off. (When the throttle butterfly is wide open the vacuum will not be concentrated at the 3 small holes where the idle fuel/air mix comes out).

You can also leave the bike in gear and as you turn the bike off let the clutch out to stop the engine down a bit faster. (Wait a minute....it takes the left hand to run the clutch and the key.....so you would have to simultaneously hit the kill switch and let out the clutch - and then remember to turn off the key).

Some of these bikes make a really loud bang....mine just makes a little bit of a "woof" if I turn the bike off before I let it idle and cool for half a minute before I shut it off. If a bike is running a bit lean the bangs seem to be a bit louder - however you should jet to make the bike run correctly, and not to eliminate the shut off bang.

Title: Re: Backfiring when the bike shuts off
Post by Suzukisavvy on 02/17/15 at 09:11:48

okay thanks for the tips guys!!

Title: Re: Backfiring when the bike shuts off
Post by Rembrandt on 02/27/15 at 17:51:51

Pulling out the choke is foolproof for me for eliminating gun-shot bang on shut-down, but unless I'm pulling in somewhere, including my home late at night, I love the big bang sound. I gave my riding buddy grief when he let the little choke secret out to my wife. The big bang bugs her just a bit and until fairly recently, I didn't know about the choke thing. He told my wife that I now have a way to soften the shut-down....grrrrrrr...lol

Title: Re: Backfiring when the bike shuts off
Post by justin_o_guy2 on 02/28/15 at 01:13:18

Pull in the clutch, rap it up, heel on the kick stand, heel off the stand,, Kerr_POW,