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General Category >> Rubber Side Down! >> Backfire when key is turned off
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Message started by rayce on 08/18/15 at 20:13:04

Title: Backfire when key is turned off
Post by rayce on 08/18/15 at 20:13:04

My S40 has a really loud backfire when i turn the key off. That is the only time it does it. i replaced the petcock with a raptor one. that is the only mod on the bike.

Title: Re: Backfire when key is turned off
Post by Kris01 on 08/18/15 at 20:17:02

Sounds normal. What year? Stock jets in the carb? You can tune out most of the backfires but not all of them. Learn to like it.

Title: Re: Backfire when key is turned off
Post by old_rider on 08/18/15 at 20:21:23

Some folks pull the choke and shut it down (I have never done that), some just pull up in first gear, clutch in, and put down the kickstand (it will kill it when in gear most times without a bang), then turn everything off.
I turn off the gas..... let it idle for about 30 seconds or so, then shut off the key...8 times out of 10 it won't pop loud.... just go "poof"....
But I've done the spacer mod and adjusted my fuel/air needle....

Title: Re: Backfire when key is turned off
Post by Kris01 on 08/18/15 at 20:43:06

You can also hold the brake and let the clutch out slowly to slow the engine to the point of dying. It will just shut off with no bang.

Title: Re: Backfire when key is turned off
Post by chasethorn on 08/19/15 at 19:53:43

Mine does this all the time. Wont back fire while riding but right when I kill the bike after riding for a little while it will back fire. just like a fast "ssss thunk" sound

Title: Re: Backfire when key is turned off
Post by 1st2know on 08/19/15 at 22:31:32

726179636562000 wrote:

i replaced the petcock with a raptor one. that is the only mod on the bike.

Check to make sure the vacuum port on the right side of the carb is properly plugged.

When I did the raptor conversion, the cap I put on it fit tight, but would still leak. I put some RTV sealant around the nipple, put the cap back on, let it cure overnight and my (((loud))) backfiring went away. It still went 'poof' on shutdown, but not a bang.

Title: Re: Backfire when key is turned off
Post by Super Thumper on 08/21/15 at 07:07:46

Two things cause a bike to backfire or "Pop" when rolling off the throttle or on shut down. One is the carb is jetted too lean as with our stock Savage carb. The other is a straight pipe or straight through muffler with NO internal baffle......they ALL backfire when you roll off the throttle unless you jet them very rich which isnt good for performance or economy. Some mufflers with an internal baffle have a smaller hole straight through the baffle....these will still "pop" and backfire on deceleration or shut down but not as bad as an open pipe.

Kudos to Dave for posting the S&S You Tube video.....it tells you all you need to know about jetting carbs and open mufflers/pipes.

Just in case you missed it - here it is again...............

https://www.youtube.com/watch?v=KjKUKhHQLHg