Stalling out

[moosehead]

1981 R100

Lately, every time I come to a stop this bike stalls out unless I'm feathering the throttle on deceleration, No big deal but wondering what can do to fix it. Never had this happen in the past. This happens even when bike is good and warmed up.

Reconditioned carbs last winter (gaskets, rings, new needles and needle jet holders in both carbs etc). Idle set about 1100 rpm, sync'd and balanced. Was running great this spring and never really noticed the stalling out except when not warmed up. Wondering if its the float levels being set too low??? I usually do the standard with float heights (shut off at parallel to carb body) but maybe I set them maybe too low this time. Worse is when I decellerate quickly and come to a stop. I usually feather the throttle all the time on down shifting for stopping . Would float level be cause of this??

No biggie...just annoying and wondering what might be causing this.

[Duane Ausherman]

I would be doing a short cut carb adjustment and hope to find clogged idle jets. I am not there to hear it run, so this is just a guess.

[ME 109]

Will it idle normally when hot and stationary?
Have you tried increasing idle speed
Sounds like you are rolling to a stop with the clutch pulled in?
Does it stall rolling to a stop using engine braking?

[Kurt in S.A.]

The best way to set the floats is to measure the amount of fuel standing in the bowl when the floats shut off. Snowbum lists the heights for fuel depending on carb type:

32mm - 24mm
40mm - 28mm

Let fuel flow for 5-10 seconds. Shut off petcocks. Drop the bowl. Measure in the center of the well.

Kurt in S.A.

[ME 109]

Kurt, do you think there is any concern with the fuel bowl measurement as the bowl is removed from the carb?
That is to say that the fuel in the fuel line below the Petcock will flow into the bowl as it is lowered from the carb.

Perhaps it is an insignificant amount.

[dwerbil]

Run a tiny wire through the tiny holes in the carb throat near the throttle plate. You can do this with the carbs detached but with the cables still hooked up. These little holes when clogged can cause the same symptoms.

[Duane Ausherman]

One can get a good estimation of float bowl level without any measurement at all. Remove the bowl and raise the float by hand until it just barely touches the needle. The casting line on the float should be parallel with the bottom of the carb body casting.

In the expensive shop labor rate, we can't waste your money on official measurements every time. Short cuts are mandatory.

[barryh]

Low float level certainly can do it. Happens to me sometimes when I'm just about to run on reserve. Just cruising along at low speeds I don't notice the effects of low float level until I come to a stop. I would feel the effects of low float level much sooner at sustained high speed and that is the usual test of low levels.

I did an experiment to determine how the engine ran at lower than usual float levels and how close my setting was to being too low. During a ride try turning off the petcocks at different distances from home so that by the time you roll up the drive you can just detect the signs of low fuel i.e. the idle is low or it stalls when you come to a stop. Whip the bowls off and measure the levels. I measured 21-22mm and I then knew that 21-22mm was too low for proper running. I was expecting to find something significantly low like 15mm and was surprised to find the difference between the proper level of 24mm and significantly reduced idle speed was only 2-3 mm. My idle mixture is set quite lean though.

A low float level has to affect the mixture right across the range but not neccessarily in a linear fashion. Don't know how true this is but I read that the effects of 1.5mm reduced float level is equivalent to one size down on the main jets.

[Kurt in S.A.]

Kurt, do you think there is any concern with the fuel bowl measurement as the bowl is removed from the carb?
That is to say that the fuel in the fuel line below the Petcock will flow into the bowl as it is lowered from the carb.

Perhaps it is an insignificant amount.

Personally, I've never been concerned about it. If you want to rule that out, consider some hemostats to pinch off the line coming into the carb and then maybe pull the line off before dropping the bowl. It would be interesting to know what we're talking about it, but I've never bothered to worry...

Kurt in S.A.

[Deleted User 62]

One can get a good estimation of float bowl level without any measurement at all. Remove the bowl and raise the float by hand until it just barely touches the needle. The casting line on the float should be parallel with the bottom of the carb body casting.

While that method works most of the time, I had a carb continue to leak after setting it that way, the floats were old and had perhaps absorbed some gas and gotten heavier. Setting it with the float ever so slightly lower fixed the problem.