I hate starting yet another carb related thread as the info already available is very thorough.  I am a fairly competent mechanic and have experience tuning carbs on other bikes.  I'm hoping someone can save me some time and lessen my learning curve with the LS650 carb by giving me some pointers to help me figure it out quicker.

My bike is an '02 with the stock exhaust/intake and stock carb.  When I got it a few years ago I thoroughly cleaned the carb and did a refresh on it replacing jets, float needle etc. all with stock parts.  I adjusted the idle air screw properly or so I thought.  It's been a while so I don't remember exactly what I set it at.

Now onto the symptoms I am experiencing. FYI it has run this way since day 1 when I refreshed the carb so this isn't a recent problem.  I just dealt with it by having a slightly higher idle speed and am now getting around to doing something about it.  Off idle and up it runs SWEET!  So no complaints there.  
  1) If I am coming up to an intersection and go from part throttle cruising (constant speed) to close the throttle (engine braking) I get a LOUD shotgun blast backfire.  This doesn't seem like it should be normal.  It's not really a problem since I usually pull in the clutch, close throttle and roll to the stop.  Also if I slowly close the throttle, ie. gradually slow down I don't get a backfire either.
  2) Choke (fuel enrichment) doesn't seem to work very well.  The first stop out will keep the engine running but idle is still very low.  2nd stop out causes it to sputter and die.  
  3) Bike warmed up and idle set at 1100RPM.  When rolling and I pull in the clutch idle drops to 900-950RPM range but comes back up to 1100RPM when stopped.  When doing the same on a freeway exit ramp it drops as low as 800 and usually stalls.          

I'm assuming for #1 it's the increased engine vacuum pulling excess fuel thru the idle circuit that then pools/ignites in the hot exhaust.  Not really sure what I could do about that other than hope it's not normal and goes away when I fix the other idling issues.

For #2 I speculate that I'm not getting enough air from the idle circuit and the choke adding more fuel just smothers the engine.  Possibly I didn't adjust it right when I rebuilt it?

I'm at a loss for #3.  

The reason I let it go so long was a lack of time to deal with it and that turning the idle up to 1400-1500RPM yielded about a 1100RPM idle when cold and eliminated stalling issues.  I plan to start by removing the carb and disassembling looking for any passageway blockage, Checking whether or not I shimmed the needle valve (I think I did to richen up the mid throttle), and then starting over with tuning the idle circuit.  I am guessing that if there aren't any plugged passages, when tuning the idle circuit I may need to crack the butterfly with the idle screw to get more air at idle for proper choke (enrichment) function and proper idle function.  If anyone has any experience with the symptoms above I'd greatly appreciate hearing how you corrected them.  

As an aside I think this bike needs an idle when warm of not be less than 1300.

eau de sauvage wrote on 08/16/17 at 02:27:36:

If that indeed is the case then maybe I don't have a problem.

Quimrider wrote on 08/16/17 at 06:46:21:


That's very possible. Maybe take a look through this thread...

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1496795234/0

Adjusting the idle is so easy that I do it while riding.

Haven't done that yet.

I think 1000 rpm is absolute minimum. I run mine nearer to 1400.

Quimrider wrote on 08/16/17 at 06:43:22:

let's say I'm on the freeway going 75.  I slow down to 70 as I'm getting onto an exit ramp.  As I hit 70 I pull in the clutch to coast to the end of the exit ramp.  Engine hits idle at 65.  

Why in the wide world of sports would you pull in the clutch at 70 mph to coast to a slower speed? This is just a bad technique.

Oh, like others have said, an idle of 1,100 rpm is too low.