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Message started by hersh1992 on 07/03/15 at 11:05:34

Title: popping backfire
Post by hersh1992 on 07/03/15 at 11:05:34

hi everyone I am new here I just bought a Suzuki s40 with 500 mile great shape
though it has some popping sound, I adjusted the air/mixture fuel valve. to 2 turns counter clockwise to richen it still there a little popping sound, anything else should I do .. :)

Title: Re: popping backfire
Post by verslagen1 on 07/03/15 at 11:11:48

1st read, then post.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1120506946

Title: Re: popping backfire
Post by verslagen1 on 07/03/15 at 11:15:40

6D716F6D606F35373731070 wrote:

[edit]If you turned it 2 CCW, that's leaner ooops that's wrong.[/edit] and you're about to bottom out.
be careful there, sometimes it will stick if you turn it down hard.

Visit the tech section and look up serowbots carb tuning.

But 2 full turns out from a factory adjust and the needle is likely to vibrate out. 3 turns out and you should go up a jet size. -v1

Title: Re: popping backfire
Post by Dave on 07/03/15 at 17:53:12

The adjustment of the idle screw is not done when the engine is turned off....it is like tuning your guitar - it has to be done by sound!

Get the bike thoroughly warmed up on a about a 10 minute ride....then drop the idle speed down a little bit....and make the adjustment as shown in the following video.

https://www.youtube.com/watch?v=zm5mB3R8Ucw

If you can turn the mixture screw in almost all the way and the engine still runs fine - you need a smaller pilot jet.
If you need to turn the screw out more than 2 turns - you need a bigger pilot jet.

Once you get the setting so the engine runs smooth, turn the idle speed back up to 1,000 - 1,100 rpm. You now have the proper idle fuel mixture.

Popping through the exhaust when you close the throttle is not an indication there is anything wrong with your bike....big singles do that. You can turn the mixture screw out an additional 1/4 turn and see if it helps - but don't go much farther or the idle mixture will be too rich. You can learn to hold the throttle open just a tiny bit off fully closed when you shift or are compression braking, and this will cut down on the popping. This is not a fuel injected modern engine....it is a primitive bike that takes a bit of rider participation to operate.....and a bit of learning how to ride the bike smoothly.

Title: Re: popping backfire
Post by Kris01 on 07/03/15 at 18:23:21

32090413020E151308000D12610 wrote:

Get the bike thoroughly warmed up on a about a 10 minute ride....then drop the idle speed down a little bit....

This helps to hear the difference in engine sound as you adjust the mixture screw.

Title: Re: popping backfire
Post by Dave on 07/04/15 at 11:41:44

4D746F753637060 wrote:

[quote author=32090413020E151308000D12610 link=1435946734/0#3 date=1435971192]Get the bike thoroughly warmed up on a about a 10 minute ride....then drop the idle speed down a little bit....

This helps to hear the difference in engine sound as you adjust the mixture screw.[/quote]

Yes...and at higher idle speeds it is possible that the slide and needle are just beginning to operate - and that can make adjustment of the idle mixture impossible.