Amal StayUp float adjustment redux

This afternoon I installed the amal StayUp floats in my 932 carbs and adjusted them so the fuel level in each carb bowl is precisely 0.21 inch from the top of the bowl, as per instructions included with the floats, and on Amal's website. This brought the fuel levels up quite a bit from my old floats' fuel level settings. I also replaced the float bowl gaskets with the new ones provided with the StayUp float kits. I knew right away I would be also adjusting the air mixture and idle screws because of the higher fuel levels. I primed the carbs and noticed they tickled up immediately, instead of the old 2 second wait with old floats. Bike started and first thing I notice is that it is surging at idle, then going to adjust the screws I see that the outside of the carbs are wet with fuel, and I see that the fuel seems to be coming out of the primer holes. Got the screws set OK,engine surging ended but still exterior of carbs are wet. Three possibilities come to mind: the new bowl gaskets need time to seat, the shaking of the engine at idle is splashing the higher level of fuel in the bowl and it is seeping out of the primer holes, and/or Amal's recommended fuel level of .21 inch is way too high for the Amal carbs on Commandos due to the forward tilt of the mounted carbs. I will let the gaskets seat themselves overnight, and if there is still fuel weeping out of the primer holes, I'm going to lower fuel levels in the bowls tomorrow. Anyone else experiencing wet carbs with the Amal recommended fuel levels?

singring said:

This afternoon I installed the amal StayUp floats in my 932 carbs and adjusted them so the fuel level in each carb bowl is precisely 0.21 inch from the top of the bowl, as per instructions included with the floats, and on Amal's website. This brought the fuel levels up quite a bit from my old floats' fuel level settings. I also replaced the float bowl gaskets with the new ones provided with the StayUp float kits. I knew right away I would be also adjusting the air mixture and idle screws because of the higher fuel levels. I primed the carbs and noticed they tickled up immediately, instead of the old 2 second wait with old floats. Bike started and first thing I notice is that it is surging at idle, then going to adjust the screws I see that the outside of the carbs are wet with fuel, and I see that the fuel seems to be coming out of the primer holes. Got the screws set OK,engine surging ended but still exterior of carbs are wet. Three possibilities come to mind: the new bowl gaskets need time to seat, the shaking of the engine at idle is splashing the higher level of fuel in the bowl and it is seeping out of the primer holes, and/or Amal's recommended fuel level of .21 inch is way too high for the Amal carbs on Commandos due to the forward tilt of the mounted carbs. I will let the gaskets seat themselves overnight, and if there is still fuel weeping out of the primer holes, I'm going to lower fuel levels in the bowls tomorrow. Anyone else experiencing wet carbs with the Amal recommended fuel levels?

Click to expand...

I was thinking about getting those float so I'm watching with interest...

Don't know noting about them fancy floats, but sure sounds
like fuel level is too high for your ride. The cockey engine
attitude may well be reason to fudge from instructions. ?
My simpleton brain just diddles fuel-float level till pilot screws
have effective adjustment effects and then some more
till best idle ~1.5 turns out.

You do have C02 or other type fire Extinguisher near by, don't ya.
Can you imagine the results of over tickled carbs when the
points or magneto was mounted directly below and the whimpy
cover with a nice big vent hole in it.

On this note if you do get a fuel fire going, start putting
it out from the ground up, NOT THE OTHER way.

hobot



hobot

I'll make sure my extinguisher is close at hand...even with a Boyer ignition one can't be too careful with open fuel...thanks hobot. Actually, with the fuel level that high, I wonder if priming the carbs is really necessary. I will first try starting the engine without priming tomorrow. If the primers still weep at idle, then it's back to setting the levels lower.

I found setting the fuel levels is very easy with these StayUp floats. I used a length of 1/4" fuel line, attached it to the banjo, mounted the bowl in a bench vise, leveled it cross-ways in two directions, then ran the fuel line to a funnel above the bowl clipped to my rolling tool cabinet. I first tried marking the 0.21" level in the bowl, but found it was impossible to see the fuel level with the StayUp floats intalled. Easier way was to take a straight pin, then caliper measure 0.21"from the pin head up the pin shaft, and mark the measurement with a thin length of electrical tape. That way you insert the pinhead down along the interior wall of the bowl until the tape edge rests on the float bowl top face. With a led flashlight, you can then easily see if the pinhead comes into contact with the fuel level...then adjust accordingly. I used a turkey baster to dribble fuel into the funnel. You have to remember that everytime you need to remove the float from the bowl to make an adjustment, you need to unclip the funnel and drain any fuel remaining in the fuel line into a container first before you remove the float, otherwise that remaining fuel will spill into the bowl and flood over the bowl edge onto the bench.

Just thinking as as type...I can now see that although setting the fuel level height in the float bowl is easy, setting the correct level according to the mounted carb body tilt, by trial and error, will be a giant pain with removing and reinstalling the carb bowls to the carb bodies after each and every adjustment. OK OK OK, complete brain clarity kicks in....it's all starting to make sense that the original 1966-1972 Amal recommended fuel level, used well for years, where the top of float should be 0.08" below the top of the float bowl is MOST appropriate for our Commando engines, as it allows for the tilt of the mounted carb body. Tomorrow I will first experiment with that goal in mind...I will set the left float top to 0.08" below the top of it's float bowl, then measure the fuel level height to top of float bowl. I will then use that fuel level height as my baseline to set up the right carb bowl fuel level. Then, I will install the bowls and floats back onto the carbs and see how that works. At least the fuel levels in both carbs will match....and failing that, I will determine the fuel levels using my original floats, match them, and use that level to set up the StayUp floats, as my original fuel levels seemed to work just fine.....I love the smell of gasoline in the morning...O, bother...

Will post the results

I discovered that the original floats were very low in the bowls according to the 0.08" Amal recommended setting and I thought it would be easier to match the fuel levels in the carbs without having to reset the float valve seat. I did find that setting float heights are very easy with the StayUp floats. My previous post details the fuel levels are now too high using the latest Amal setting recommendation, because of the mounted carb tilt, and what I will do to resolve.

The stock amals with stock floats on a stock 850 Commando work great with end of the float set .080 below the top of the bowl, set as per the directions in the AMAL information re moving the seat. I don't see any reason to rig up some sort of way to check it "wet."

OTOH, since the stay up float is different than the oem float, it's quite likely that the same float level setting results in a different fuel level in the carb. Unless the instructions for the stay-up specifically addresses this, then I would think that you would have to do a wet check on both the original float and the stay up to compare the difference. IOW, if the oem float is set at .080 and the SU float is set at .080, do they both produce the same fuel level? You would need to know that before adjusting the SU float because if you duplicate one of the oem float level recommendations, you may end up with the actual FUEL level being quite different.

Yep, I thought of that, so first, for reference, I'm going back to the original floats, check the fuel levels, and see how they jibe with the StayUp float levels.
Will probably end up using the StayUps, but will set fuel levels according to original floats...at least that way it will be easier to make fuel levels in each carb an equal value.

Hehe,
if carb don't need tickle or choke to start cold then set too rich.
If don't take but an instant to tickle over flow then fuel level too high
and will spill out in road loads splash.

You've got a built in bike specific monitor of correct float level,
the pilot screw response that tends to settle on 1.5 turn as best.

hobot

The stock floats aren't adjustable, if you like them, good, if you don't then Stay-up-Floats are your reality.

On my '75 Mk III the stock floats (new Amals) took 20 seconds to prime and the bike needed quite a bit of extra throttle to get moving, the air screws were out about 1/4 turn.

Enter the Stay-up-Floats. I adjusted them to the .21" specification and found that I had leaking float bowels. I went back to the garage and set the floats to be parrallel with the float bowel gasket surface ( a slight depression from the bowel surface), while just touching the float needle which was just touching its seat. This worked perfectly, the air screws came out to about a 1/2 turn, go figure, but the machine runs perfectly on it idle circuit and transitions smootly to the needle. I am gettimg about 43 MPG in mixed riding (1/2 in town 1/2 steady cruising) with a slightly modified engine (cam, porting and CR+). I have 220 mains, 3.5 cutaways, 106 needle jets and 32mm bores.

I have another set of Stay-up-Floats on order for my '72 Combat build, I do like adjustability.

I do remember the days when the stock floats worked fine, apparently much has changed since the early '70s...

RS

I readjusted the floats...first, I checked the fuel levels using the old original floats. Oddly, although the left float would seat the valve at a much lower height than the right float ,when doing the old dry method on each bowl, when I used fuel to find the respective fuel levels in the bowls, at full valve seating the fuel levels for both bowls were almost the same....
I averaged the two levels and applied the the mean fuel level height, which was .33" ( just under the lower tolerance value of .25" that Amal now recommends for 1972 carbs and up) to the fuel level setting for the StayUp floats. After the bowls were reinstalled and air screws set to 11/2 turns out, priming took 2 seconds, and engine started at first kick.
There was no leaking from the primer holes, and after some warm up time, I found that idle was smoothest and steady at 11/4 turns out of left and right air screws, and , left and right throttle speed screws also match exactly, from a synchronizing I did last week.
When quickly rolling on the throttle, then releasing, there is no exhaust popping.
To sum up...the StayUp floats work well, in that they allow for easier setting of the fuel levels in the bowls. Just don't use Amal's recommended 0.21" fuel level
setting, as it is way too high for Commando carbs.

Educational feedbacks to me.
Anywho besides fudging for each bike engine or float type configuration,
the new gasoline with lean-burn oxygenators added may
require a bit richer float level than past manual instructs.

While in there might try cutting some notch out back side
of spray tube in 750's for more accelerator type response.

hobot

RoadScholar said:

The stock floats aren't adjustable, if you like them, good, if you don't then Stay-up-Floats are your reality.

On my '75 Mk III the stock floats (new Amals) took 20 seconds to prime and the bike needed quite a bit of extra throttle to get moving, the air screws were out about 1/4 turn.

Enter the Stay-up-Floats. I adjusted them to the .21" specification and found that I had leaking float bowels. I went back to the garage and set the floats to be parrallel with the float bowel gasket surface ( a slight depression from the bowel surface), while just touching the float needle which was just touching its seat. This worked perfectly, the air screws came out to about a 1/2 turn, go figure, but the machine runs perfectly on it idle circuit and transitions smootly to the needle. I am gettimg about 43 MPG in mixed riding (1/2 in town 1/2 steady cruising) with a slightly modified engine (cam, porting and CR+). I have 220 mains, 3.5 cutaways, 106 needle jets and 32mm bores.

Click to expand...

Old thread but I find it interesting that I had the exact same experience. Set per the StayUp instructions, I had leaking float bowls and the air screws were virtually all the way in. Setting the floats almost parallel, about 1/2 to 3/4 turn out but a very good idle (although not quite perfect).

There's an old thread on floats here.. new-amal-floats-t5220.html?hilit=float . Unfortunately the link to the Amal site isn't working, anybody got a updated one? What their instrucions said, if I can recall correctly, was that float heights for different years should be at different levels, this was due to the fact that the float seat in the bowl was set at different heights from the factory according to the year, so what was the correct float level for one year , say .080" was not neccessarily the correct level for a different year.
I'll try and find the tech note that Burlen sent out and was on their site, it was to do with the new floats too.

Set it to the ' Tide Mak ' measure it if you want to know it in measurements .

Surgeings wet stutterings lean.Gee Monoblocks carburated better.Fit a real carb

D.C.O.E. or D.H.L.A. or Mk IIs ( with chokes or itll never start cold)
The 45 Weber , Ducatis use Astonand Lanchia carbs , IDAs and IDFs and suchlike
though there downdraft. The Capri V-6 pommie 3 litre carbs good
but youd need to cut the bottom out of the tank .

Quite a few old dungers ran the side draughts , Lotus'es, Esprites and the like,
and Jensen Healeys. Not hard to find.Waste of time if theres much internal
corrosion though , as fuel / air pasages are METREING CIRCUITS.
Irregular passas from corrosion are a waste of time. Like 6 Volt Coils ! :wink:

For info - I bought a stay-up float for the 34mm Mk2 Concentric fiited to my 850 Mk2A - the carb flooded (i.e. piddled petrol everywhere) if I attempted to set the height as specified - it appears that the float was touching the underside of the main body before it could shut off the fuel - I tried various settings all to no avail and ended-up resorting to the old float. The stay-up float is subsequently in a drawer in the garage - - - - - -

Put a set in my 932's last fall. .080 as instructed, no problems w/ flooding.
Runs great and won't sink that's the selling point.
I replaced them as I did a complete overhaul.
I had the bodies trued and slides resleeved, so figured why cheap out on 37 y/o floats.
Although they still were boyant I upgraded. I ride this machine and didn't want any road side suprises.
Get em set to spec's and they tickle right up and work great. We have a tendency to overthink this stuff
with Nortons. :wink:
Marshal

I had good luck with the stay up floats. I did also had to set them down a bit to keep them from dribbling.

Dave
69S