gs1200ss backfireing

[firebird]

Hi all out there, Im looking for some advice on a backfireing problem on my suzuki GS1200SS. This bike was brought new about 5 months ago and has been giving me problems with backfireing through the carbs mainly when cold but on a recent trip it gave problems for 80km plus till i turned the idile up just to keep it running.Next day it was fine again. Now as it is new i have had into my dealer twice now and they stripped and cleaned the carbs. This helped but problem didnt go away entirely. Next stop a bigger dealership who i thought would have more info on road bikes and they said , no shes running fine and some backfireing was normal for a carbed bike. It was after this i had the stalling and generally running like bag of arseholes, next day fine again with minor backfires. All this is about 1200 to 2000rpm.
I would have thought in this day in age this wouldnt be normal at all, i dont remember any other of my bikes doing this. It has been about 10 years since i have owned a bike so im not familier with things anymore. I have been told there is a bit of a problem like this with the gs but should be fixed with a carb clean. Im looking for some advice so i can go back to my dealer with some info.
Hopefully someone may have had simaler probs as i am having and be able to help, thanks, firebird.

[Wheeliemonsta]

Firebird,
Your backfiring is certainly not normal... Has the bike been modified in any way i.e a can, different airfilter etc etc...??? (be honest, it will make the problem easier to diagnose...)

The SS was always what they called a "cold blooded bike" meaning it needed truck loads of choke to keep the thing running when cold... it sounds to me as though you may have one or several choke circuts in the carbs still closed
even though you've put the choke right away (off)

What sort of time frame did the bike spend at the dealers whilst the carbs were being stripped ?... to do the job properly would be a days labour + on/off parts time

In standard form they should run like a swiss watch, they always had what could be best described as a "loping/lazy" idle...

The other area's worth checking very carefully would be the pilot jets for blockages and the pilot air screw settings, as both these will effect the "idle" "off idle" and "low rpm" running...

If your in Auckland I'd be happy to have a look at it for you, I also have a set of std 32 mm Mikunis off my old one if you cant find a satisfactory outcome...

Cheer's

C U

[Sensei]

There is NO WAY it should be back firing through the carbs !!! Leave the bike at the dealers till they get it sorted . Eg make it backfire so they can see for themsleves what its doing .

[firebird]

Thanks to those who have replied allready, No the bike is bog stock standard, it spent a couple of days at shop but i wasnt in a hurry for it so who knows how long it took. Also as it is under warrenty im not charged of course. I will take it back but these guys deal mainly in farm bikes etc and dont have alot to do with road bikes, i brought it through them to support local dealer.
Also as i said i took to a dealership in invercargill and they said its fine and normal. This prob has been with me since new, it just took some time for me to figure out what the prob was, it wasnt till i actually seen and heard at the same time what was going on. in the beginning it almost sounded mecahnical and as it was new i thought it might just be a run in issue, tight etc, but i did discover it was indeed this backfiring issue.
apart from this issue it runs great and strong, a good bike to my bearings again after 10 years off bikes, its now done about 5300km in 5 months.
thanks for the advice and it will be noted for the dealer to look at and thanks to wheeliemonsta but im at the other end of the country, ie gore,
cheers , firebird.

[rogson]

Backfiring through the carbs at low engine rpm suggests to me the idle/low speed running is lean. At small throttle openings (idle up to about 1/8th throttle) carburation is controlled by the idle and low speed jetting. You can increase the richness of this circuit by winding-out the mixture screws (You should find them underneath on the engine side of the carbs). Firstly, check the current setting. I don't know what it should be on your bike but usually its between one and a half and two and half turns from fully in. Also, it should be the same on all carbs. If its not the same then set them all to say two turns and try that. If it still backfires then wind them out another turn. The mixture screws can be a bugger to get at so if you can't or don't want to then maybe suggest to your dealer that this could be the problem and get him to fiddle with it.

[Lou Girardin]

Pilot jets have sensitive adjustments, adjust 1/4 to 1/2 turn at a time. Standard setting on Bandits is 3 turns out.
Mine gives the occasional spit through the carbs in colder weather, but only in the 1st few seconds of starting.

[vifferman]

I know very little about the GS1200, but I do know that backfiring is not normal for carbed bikes, and that apart from insufficient fuel supply (idle mixture set too lean, blocked jets or idle circuits, etc.) lean running can also be caused by air leaks and even by exhaust leaks. But one would expect the dealers to have chacked this when trying to solve this problem.

[firebird]

Thanks guys for the replys to my backfiring problems, interestinly i approached my mechanic on friday and he did mention pilot jets and settings so ill take it in this week with the advice you guys have given me as well.
so itll be interesting to see how it comes back this time. took it for short ride over weekend and popped around abit when cold but warmed up it was fine agian, you just cant win sometimes but itll still go in as i dont think it should be doing this at all really. thanks agian. firebird.