Back Firing

[Anonymous]

Hey guys its been a while, but finally rebuilt the carbs on my 81 gs 1100e. now i sync'ed them the best i could and turned the air (or fuel) mixture screws out 2 turns. Now the bike starts up fast and doesnt smell like gas all that bad (like last time) but now it seems to back fire while idleing but when i rev it it doesnt do it as much . Can someone give me the list of all the things i need to go through. To make it easier i own a manual but i need a place to start and an idea if i did something wrong or not. I dont really care to pay suzuki a million dollars to fix something i can probably do myself. Thanks guys and god bless our soldiers.

[Anonymous]

does it only backfire when its warming up?

[Anonymous]

A wild guess is to check your number 2 plug to see if it is burning rich 8O

[nabrams]

I had mild back-firing during idle, warm-up, and higher revs - just as you do. In my case, everything was running too lean (my plugs were VERY light gray). I had to do ALL of the following in order to totally get rid of the back-firing:

1. Adjust the mixture screw for max RPM at idle (I had to remove the tamper-proof caps). They should be between 2 and 6 turns out from bottom.
2. Clean idle and main jets with a copper wire (spraying tons of carb cleaner through them didn't quite get all the gunk out).
3. Install a proper foam air filter element (mine had disintegrated).
4. Seal ALL air leaks (no matter how tiny) at all boots and at air box lid.

Steps 3 and 4 above are just as important (perhaps more so) as steps 1 and 2.
Do all of the above and then move on to other areas if necessary (coils, timing, etc.).

[Anonymous]

I rebuilt the carbs already, they are as clean as i could get them all the holes were cleaned. It backfires on warm up and when i am riding. Mainly at idle but also when reving. How would i go about checking for airleaks? Also the needles are 2 turns from bottom. Dont smell the gas so much any more but sounds like it could run better. What am i looking for as far as the second plug running lean? And thanks guys for the help. It has a v&h 4 to 1 on it. But is running a little rich but not as bad when i synced them.

[Anonymous]

gs850 back fire

most back fires come from lean conditions. checking for them is easy all you do is start engine and spray carb cleaner around suspect areas and if there is a leak your engine will rev up. remember to put rags down to protect the paint also try to isolate the cyl you are checking by raping rags around the other carbs. if you do have leaks check ever thing and replace as needed. if you do not have leaks check valve lash a tight valve will also cause a back fire, as well as ignition timing. also check your fuel for being dirty good luck reg

[nabrams]

You mentioned that the problem is mainly at idle. In that case you should probably at least try backing out the mixture screws a bit more. My bike idled considerably better after I set my mixture screws out to 4.5 turns. If that still does nothing, then re-check your jets. I also thought I did a good job of cleaning them out, but idle wasn't smooth. Then I scraped them clean with a copper wire. It made a huge difference.
Also, check your floats to insure they're not stuck. Another guy on this forum just gently tapped his carbs untill the floats came loose and then his bike ran well.
The suggestion from reg wiebe on how to check for air leaks is good, but it will be most effective if you do it at various RPMs (not just idle) due to the varying degrees of vacuum at different RPMs.