50 year old floats sinking!

[JimNH]

Shocking! One tickles very quickly so float is probably down.

Anyway, I ordered a couple of aftermarket stay-up as well as O'haul kits. I recall some controversy about installation and float levels with them and figured I'd ask for tips. MKIII.

Thanks

 

[L.A.B.]

Setting Fuel Level on Amal Mark 1 Concentric Carburetters | AMAL Carburetters

Guidelines for achieving optimal fuel level in Amal Mark 1 Concentric carburetters. Covers fuel level measurement techniques, & more.

amalcarb.co.uk

 

[MexicoMike]

It important to do the fuel level/clear hose thing as described because the stay up float does not produce the same fuel level as the OEM float did if you set the float the traditional way. IOW, if you set both an OEM float and a stay up float to the same setting per the "vintage" procedure, the actual fuel level in the carb will be quite different.

 

[baz]

Has anyone actually had an original Amal concentric float sink or melt or anything like that?
I think it was on "triples online " someone did a long term test with amal floats submerged in ethanol laced petrol with zero ill effects

 

[daveforty]

Has anyone actually had an original Amal concentric float sink or melt or anything like that?
I think it was on "triples online " someone did a long term test with amal floats submerged in ethanol laced petrol with zero ill effects

once, but many years ago and pre ethanol petrol, and outside an MOT garage (it had passed).... The float had leaked and there was petrol inside the thing and thus the carb was flooding. It was fine on the ride to the place, so no idea what had happened in the meantime.

 

[L.A.B.]

Has anyone actually had an original Amal concentric float sink or melt or anything like that?

Yes, it split along the seam. I emptied the petrol out and melted over the crack with a soldering iron as a temporary fix.

 

[marshg246]

Has anyone actually had an original Amal concentric float sink or melt or anything like that?
I think it was on "triples online " someone did a long term test with amal floats submerged in ethanol laced petrol with zero ill effects

Yes, I had one on a Trident and one on a Bonneville. In both cases they were about partly filled with gas. Both were likely originals.

The Trident happened while riding and to make it fun on the road, it was the center carb.

The Bonneville happened while sitting and I had not shut the petcock off - gas everywhere - never made that mistake again!

 

[baz]

Yes, I had one on a Trident and one on a Bonneville. In both cases they were about partly filled with gas. Both were likely originals.

The Trident happened while riding and to make it fun on the road, it was the center carb.

The Bonneville happened while sitting and I had not shut the petcock off - gas everywhere - never made that mistake again!

Was this with ethanol fuel?

 

[MexicoMike]

FWIW, automobile carbs with foam floats - like the Premiers have - often became "waterlogged" with fuel over time and we didn't like them at all compared to the brass floats that they replaced on some brands of carbs. So I'm not convinced that the foam "stay up float" is actually better - or even as good - as the original plastic float. But time will tell...

 

[marshg246]

Was this with ethanol fuel?

Bonneville, no. Trident, I had only had the bike for a week when it happened. It was E10 when I was riding, but I have no idea what the PO used.

 

[L.A.B.]

But time will tell...

It's been around fifteen years since the Stay-Up floats were introduced.

 

[marshg246]

FWIW, automobile carbs with foam floats - like the Premiers have - often became "waterlogged" with fuel over time and we didn't like them at all compared to the brass floats that they replaced on some brands of carbs. So I'm not convinced that the foam "stay up float" is actually better - or even as good - as the original plastic float. But time will tell...

You've been mentioning this since at least Jan 2010. Have you ever heard of an Amal StayUp float failing?

 

[ludwig]

I found that, when setting the fuel level at 5mm below the top of the bowl (and slightly tilted carbs), there is a risk that the float hits the carb body when rising, causing flooding.
That's why I increase the weight on the old floats from 7 to 8 gr with a brass strip:



The newer alloy needle will probably have the same effect.
I don't know the weight of the stay-up floats.

 

[MexicoMike]

"You've been mentioning this since at least Jan 2010. Have you ever heard of an Amal StayUp float failing?"

No, I have not. Maybe I should change my opinion of foam floats...

It's hard to overcome many years of experience in engine building where non-floating foam floats were a recurring problem. OTOH, my 1976 Honda CB400F has the four original foam floats and they still float! But it's a HONDA so what else would we expect?

 

[Mart UK]

It's too early to change your opinion. There are brass floats still working at 50 years old. Stay-Ups have only been going 15 years. We should ask again in 2060.

 

[marshg246]

It's too early to change your opinion. There are brass floats still working at 50 years old. Stay-Ups have only been going 15 years. We should ask again in 2060.

Comparing against brass floats has no meaning talking about AMAL concentric carbs. The question is are the AMAL plastic or StayUp floats better. For me the answer to that is obvious given the method required to set the float height with the plastic floats.

 

[Torontonian]

Has anyone actually had an original Amal concentric float sink or melt or anything like that?
I think it was on "triples online " someone did a long term test with amal floats submerged in ethanol laced petrol with zero ill effects

Yes I've had the original plastic float ( only one of 2 ) fail and fill up half full of fuel , this was many years back . Replaced both with new and no problems . When the black stay - ups came out I was the one of the first to order them in , only to find out the first stampings of the metal flange were bad and they would occasionally hang up with the square stamped cut , when it should have been a rounded edge . Plenty of problems with that , until I dressed down the corners with a needle file .
Enjoy .