carb overflowing

htown16 · Dec 9, 2022

Original amal concentrics but refitted with stayup floats and aluminum needles. Set both carbs the same using utube fuel level at .21" on cold carbs. Took it for about a 5 mile ride to get up to temp. Head temp about 225F, float bowls identical 118F. Right carb is pissing out fuel around the tickler. Didn't do it on first start up only when up to operating temps. After the bike cooled removed the bowl on rh carb and reset the fuel level at slightly lower than .26, the low limit according to Amal. Tested it several times on the bike. Took it on the same ride and still pissing fuel. I've done this a number of times on other bikes and l've never had the fuel level this low and still have a leak. Only does it onced warmed up but the carb temps are the same on both sides and the lh side is fine at .21. Also with bike shutoff and but hot it still does it. I'm afraid of lowering the fuel level anymore on setup.

ashman · Dec 9, 2022

Sticking float, float needle not closing could be a bit of gunk in the float needle to stop it closing.

Tornado · Dec 9, 2022

Unlikely to e float height setting as it would need to be very high to lead to tickler overflow and should appear before startup. Yes it could be a problem with the gasket catching the float or its hinge....might only appear during the shaking/rattling from the engine. Perhaps carb heating and something expanding enough to make a sticky float stay open. Or perhaps some debris/residue in the float valve seat. New or old? Can try to polish the sealing area with a q-tip in a power drill and some AutoSol or similar (carb off obviously).

bluto · Dec 9, 2022

My bike did that when I bought it, turned out the new floats the PO had installed were slightly too wide at the pivot, I filed them down a bit and no problems since. HOWEVER before that the bowls overflowed a good bit when I tickled the carbs once and when I started the bike it caught fire

I'm guessing a tiny spark from the alternator wire junctions did it. (the PO put the wires is split loom which caught some gas and helped the fire start I'm sure). Anyway, I'd carry a fire extinguisher until you get that fixed, I was able to beat the fire out with my gloves but I easily could have lost my bike.

concours · Dec 10, 2022

Polish the seat.

texasSlick · Dec 10, 2022

concours said:
Polish the seat.

I agree, Concours, but how? Seems to me, it would to too easy to make it worse by getting off axis.
If you can share your technique, it would be beneficial to many.

Slick

Carl H · Dec 10, 2022

Q tip. Semi chrome. magnifying glass to look at it.

texasSlick · Dec 10, 2022

Carl H said:
Q tip. Semi chrome. magnifying glass to look at it.

I think you mean 'Simi Chrome' an aluminum polishing compound.
Makes aluminum look like chrome...... for awhile.
I suppose you are recommending it as a gentle buffing agent for float needles.

Slick

marshg246 · Dec 10, 2022

htown16 said:
Original amal concentrics but refitted with stayup floats and aluminum needles. Set both carbs the same using utube fuel level at .21" on cold carbs. Took it for about a 5 mile ride to get up to temp. Head temp about 225F, float bowls identical 118F. Right carb is pissing out fuel around the tickler. Didn't do it on first start up only when up to operating temps. After the bike cooled removed the bowl on rh carb and reset the fuel level at slightly lower than .26, the low limit according to Amal. Tested it several times on the bike. Took it on the same ride and still pissing fuel. I've done this a number of times on other bikes and l've never had the fuel level this low and still have a leak. Only does it onced warmed up but the carb temps are the same on both sides and the lh side is fine at .21. Also with bike shutoff and but hot it still does it. I'm afraid of lowering the fuel level anymore on setup.

To come out around the tickler the fuel level is higher than the top of the bowl. So, either the float is being held down (gasket fuzz, binding on the pivot, warped bowl, etc.), or the float needed is not seating (unlikely since it only happens when hot), or the gas is boiling (unlikely at 118F - if running E0, try some E10 which boils at a higher temp).

BTW, it's bad for the engine since you are dumping fuel into it any time it is high enough to come out around the tickler.

Consider taking the bowl off, glove on hand, hold down the pivot pin, and fill with hot water (around 118F) to see how high the top of the float is. If higher than the rim of the bowl at the front either you have it set wrong, or the float is bad. I've never had a bad stay-up float but then are a few on here that insist that they have.

seattle##gs · Dec 10, 2022

I always use a wet Q-tip with Ajax or Comet.

htown16 · Dec 10, 2022

Okay, took the bowl off. Under magnifying glass saw a small piece of crud just below the needle seat. Polished the seat, good shot of carb clean and replaced the needle with a spare. Rode it around the neighborhood. No leaks. Runs smoother. Now having problems with it not wanting to idle when hot. Engine only has about 15 miles on a rebuild. Seems like on other rebuilds the hot idle is hard to set until the engine has some miles on it. I suspect some vapor lock when it tries to idle. Head temps were up to 335 and float bowl temps were around 130.
thanks for the input

Carl H · Dec 10, 2022

texasSlick said:
I think you mean 'Simi Chrome' an aluminum polishing compound.
Makes aluminum look like chrome...... for awhile.
I suppose you are recommending it as a gentle buffing agent for float needles.

Slick

For the float seat, the float needle has a "rubber tip" . Semi chrome does a nice job on most all metals.

seattle##gs · Dec 10, 2022

Now go back to checking your float levels again. Make sure the are correct and match each other.

RoadScholar · Dec 10, 2022

Technically you set float height by lowering or raising the seat. A heat gun and a suitable drift works well.

Best.

L.A.B. · Dec 10, 2022

RoadScholar said:
Technically you set float height by lowering or raising the seat. A heat gun and a suitable drift works well.

StayUp floats are normally adjusted by bending the tangs to adjust the fuel level.

Optimising Amal Mark 1 Concentric Fuel Levels | AMAL Carburetters

The Optimising Amal Mark 1 Concentric Fuel Levels page for the AMAL Carburetters website.

amalcarb.co.uk

"The new Amal 'Stay Up' float has stainless steel tangs which can be bent to alter the fuel level."

concours · Dec 10, 2022

texasSlick said:
I agree, Concours, but how? Seems to me, it would to too easy to make it worse by getting off axis.
If you can share your technique, it would be beneficial to many.

Slick

Chopsticks. Or a wooden kitchen match. I use Mothers Mag, abit faster, more aggressive.

carb overflowing

htown16

ashman

Tornado

bluto

concours

texasSlick

Carl H

texasSlick

marshg246

seattle##gs

htown16

Carl H

seattle##gs

RoadScholar

L.A.B.

Moderator

Optimising Amal Mark 1 Concentric Fuel Levels | AMAL Carburetters

concours

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