amal problems again

seattle##gs · Jun 6, 2023

A few months ago I fit a pair of 930s to a 750 after swapping the useless #17 pilots for 19s. Today I turned on the gas for the first time and discovered no flow. After checking all the other possibilities I discovered the brass needle seats were so badly adjusted that they only let in approx a teaspoon of fuel. I made up the drifts to push the needle seat higher or lower so it's not a big set back. But imagine the poor bugger with limited knowledge of Amal spending around $300 apiece and trying to make these work. Please Burlen...a little bit of quality control? And why do you keep putting in those stupid #17 pilots?
By the way, if anyone wants them I will give away about 10 #17 pilots. I am also looking for the old white plastic floats and brass needles. Will trade 6 of the stayup floats

kommando · Jun 6, 2023

You can drill out the #17 to be #19's but use a cobalt drill or a carbide end mill as they are made from steel not the brass type material of the old pilot bush. You are drilling out from 17 thou to 19 thou.

johnm · Jun 6, 2023

A friend found another new trick a month or two back.

He was fitting twin new premier concentrics to a prewar Lagonda Rapier car. Small engine DOHC 4 cylinder about 1100 cc I think.

He could not get two cylinders to idle and the problem followed the carb when he swapped them.

Eventually he found the bore for the throttle was parallel for the top half but flared out several thou at the bottom. So much air was flowing around the slide the idle would not stabilise.

He sleeved the brand new carb and the problem was solved.

Fast Eddie · Jun 6, 2023

seattle##gs said:
A few months ago I fit a pair of 930s to a 750 after swapping the useless #17 pilots for 19s. Today I turned on the gas for the first time and discovered no flow. After checking all the other possibilities I discovered the brass needle seats were so badly adjusted that they only let in approx a teaspoon of fuel. I made up the drifts to push the needle seat higher or lower so it's not a big set back. But imagine the poor bugger with limited knowledge of Amal spending around $300 apiece and trying to make these work. Please Burlen...a little bit of quality control? And why do you keep putting in those stupid #17 pilots?
By the way, if anyone wants them I will give away about 10 #17 pilots. I am also looking for the old white plastic floats and brass needles. Will trade 6 of the stayup floats

The float height settings between plastic and stay up floats is different. This isn’t part of your issue is it ?

baz · Jun 7, 2023

Fast Eddie said:
The float height settings between plastic and stay up floats is different. This isn’t part of your issue is it ?

I've never used amal stay up floats but I'd assume you bend the tangs on the float to adjust the float height ?
The same as you would with mikunis

L.A.B. · Jun 7, 2023

baz said:
I've never used amal stay up floats but I'd assume you bend the tangs on the float to adjust the float height ?
The same as you would with mikunis

Yes, but the float height (should be fuel level) can still be adjusted by moving the needle seat.

Fast Eddie · Jun 7, 2023

Key point is the level is set different for the different floats, I was / am curious if that is why the OP saw an incorrect level?

baz · Jun 7, 2023

L.A.B. said:
Yes, but the float height (should be fuel level) can still be adjusted by moving the needle seat.

Yep I'm not saying it can't be adjusted by moving the needle seat up and down
Just wondering why anyone would bother if you had a stay up type float and the ease at which it can be adjusted (if it is the same as a mikuni type float of course) ?

L.A.B. · Jun 7, 2023

baz said:
Just wondering why anyone would bother if you had a stay up type float and the ease at which it can be adjusted (if it is the same as a mikuni type float of course) ?

Similar, but not exactly the same.

I don't know what seattle##gs's motive is for doing so but it has been said that bending the StayUp tangs reduces the range of float movement (and that can only be when adjusting to lower the float/fuel level) but I found that adjusting the needle seat by the same amount to lower the float also restricts the float's range of movement and, in both cases, the resulting float/fuel level would be below that recommended by Amal.

seattle##gs · Jun 7, 2023

I have adjusted fuel level many times by pressing the seat up or down. I made a small drift for this purpose which is driven by a C-clamp. It allows for fine adjustments. Has always worked. Not this time. The brass seat would not budge even with a little heat. It is very difficult to see but it appears that the seat is bottomed out in the float bowl. I resorted to bending the tab on the float. It took about 4 tries per side, each try was a micro-movement. I am now in the ball park, will see what the level stabilizes at when running.

Madnorton · Jun 7, 2023

Valve seat in new Amals is fixed I believe. If fuel delivery is not correct using the brass float needles then swap to the alloy type.

seattle##gs · Jun 7, 2023

It came with alu float needles. One carb fills faster than the other.

acotrel · Jun 9, 2023

I never worry about float levels, as long as it is the same in both carbs. You still need to go through the jetting routine, whatever the float levels might be. I do not use jets of sizes which are recommended by other people, except as a rough indication of what might work - a starting point ? Four things work in combination for optimisation - comp.ratio, fuel (- octane ratio and latent heat of vaporisation ), and ignition advance and jetting. Most motors are different from each other. Set rhe first three, then jet to suit.
Unless you have a dyno, then there is another way which involves an oxygen sensor.

amal problems again

seattle##gs

kommando

johnm

Fast Eddie

baz

L.A.B.

Moderator

Fast Eddie

baz

L.A.B.

Moderator

seattle##gs

Madnorton

seattle##gs

acotrel

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