Stalling when coming to a stop

[bombshelter13]

Hey guys,

For a while I've been having a problem where, when coming to a stop, the idle RPM will frequently drop down to an abnormally low speed and within a couple of rotations the engine will stall.

Normally, I have the idle set fairly high, to about 1400 or so. When the stall problem happens, the idle RPM will drop down to about 700-800 or so before stalling. If I give the throttle a twist before it stalls, there's usually an audible sparking noise - this makes me think that one of the cylinders is cutting out, and is firing back up when I give it some gas. Does that sound correct?

The bike has never stalled while accelerating/moving at a steady speed, this only happens when I'm coming to a stop. I don't think the clutch is dragging, because shifting into neutral as I come to a stop doesn't seem to make a difference, the chances of stalling seem equal when in neutral.

My bike's a 2007 model, jetted with 132.5 mains and 20 pilots (stock mid-mains), air-fuel mixture screws set 3 turns out. I don't think any extra washers have been added to the needle.

Things I've tried in attempts to resolve the problem include:

- Running a couple of bottles of Seafoam through it (one at a time, not all at once).

- Changing the spark plugs. I've tried both the iridium and regular ones, same behaviour.

- Cleaning the carburetors, specifically: Removed the bowls, unscrewed all the jets and soaked them overnight in carb cleaner. They didn't look too bad, but I scrubbed the insides out a little with a nylon brush to be sure. When held up to a light I can see nice round holes through all of them, with no visible obstructions. I also sprayed a little cleaner into the air ducts on the back openings of the carbs. Slides seemed to be moving nicely, and seemed to make the sucking/thunking noises that some videos I watched on cleaning carbs told me to listen for. I was not brave enough to open up the top of the carbs.

Possibly related issue: When cold starting the bike, this happens: With full choke, after the starter button is hit, the idle wants to stay relatively low (<2K RPM) until I give the throttle a twist. Once I give the throttle a twist, it'll 'catch' at about 4000 RPM or so and stay there, after which I'll usually close the choke to back it down to the Suzuki recommended warm-up RPM of 3000.

Any ideas on what could be wrong would be appreciated. The bike's still usable, but this problem's certainly annoying.

[termlifed]

Check your valve clearance. When I had toolottle clearance I was stalling at every lighy and havong trouble startong up.

[mass-hole]

Is it only on hard stops? My bike was doing that and my instructor from my Motorcycle Riders Safety Course told me it was because it was too rich. It was worse if the choke was on which was pretty much my entire riders course since it was constant starting and stopping.

[bombshelter13]

mass-hole, the hardness of the stop doesn't seem to be a factor. The speed I'm going at before stopping seems to have some impact - if I'm on a slow road, going 25 MPH or less, it seems less likely to happen than if I'm going faster, but how quickly I stop doesn't seem to change anything.

termlifed, I'll try to do a valve check maybe next week, once I get some money to buy a spare valve cover gasket.

[bombshelter13]

Bump... people have given a couple of ideas, but I'm sure more must be out there. Any other ideas would be great.

[jestercinti]

Could be any one of the following:

1.  Air cleaner dirty, or non-stock?  This could be messing up the mixture.  Take out your air cleaner.  Go on a short ride.  Does it still happen?  That could give you an indication of too rich/too lean.
2.  Valves (already been covered).
3.  Exhaust leaks causing lean conditions.
4.  Idle speed needs adjusted when engine is nice and hot.  Not sure if it was originally adjusted when 'hot'.

EDIT...Got ahead of myself.  Saw the jet settings and idle screw settings in your original post and adjusted my answers.

[bombshelter13]

Thanks! That gives me at least one more thing I can check (air box). It looks clean, the filter was replaced 2000 miles ago, but taking it off to do a test is pretty simple.

I'm not really sure how to test for an exhaust leak, though. I'll try to look it up, but any tips on how to do that would be great.

[Bluesmudge]

How many miles since the last valve check? I say tight valves. Same thing happened to my GSF when the exhaust valve clearances were <.03mm

[00sanchez]

I had this happen as well, but I had fuel leaking through the air box. It ended up being the needle valve seat in the carb. Your floats might need to be adjusted as well. An easy thing to check would be to see if you have enough spark. If you have a weak spark, it may start and ride, but on a stop, if your floats aren't working correctly, this can dump gas in and the weak spark wont be enough to deal with the extremely rich mixture.

[Juan1]

How many miles since the last valve check? I say tight valves. Same thing happened to my GSF when the exhaust valve clearances were <.03mm

This is my guess as well.