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Float Level 276's

rfriedman

Website User
Non-VOC Member
I have worn 276's the float needle has been trued and lapped to the seat, but now the float level is incorrect. I expect I can arrange the washers on the float to body banjo bolt such that my level is where I want it. And is that level as high as can be with out causing the carburettor to drip from the large threads on the bottom? If the bike is upright and the fuel taps on, should I expect zero drips from the carbs? If I put the bike on a side stand, should I expect drips?

Thanks
 

nkt267

Well Known and Active Website User
VOC Member
Yes they drip when on the side stand,and sometimes when they are not:D
Is your fuel level too high or too low since lapping the needle seat, and is it the front or rear carb or both?..john
 

Prosper Keating

Well Known and Active Website User
Non-VOC Member
I'd expect the float level to be too high as a result of wear and/or lapping in of the float needle and feed tapers. Experimenting with fibre washers of varying thickness between the carb and the float chamber is one solution. So is experimenting with washers of varying thickness between the jet block and its retainer, which screws onto the bottom of the carb body. You can also play with the height of the retaining clip on the front carb float although this is not really an option with the top-feed set-up on the rear carb.

One thing is sure, though: you should find a spare bottom bolt, the one clamping the float chambers to side-float carbs, drill it, fit it with a stub to take a length of flexible, transparent tubing - model aircraft engine fuel line is ideal - to act as a standpipe. You can fit this to a carb mounted on or off the bike to ascertain the actual fuel level in the float chamber. It should just come up to the level of the air or pilot adjustment screw. Just 'kissing' the bottom of this horizontal drilling. If higher or lower, then you must find a way of rectifying this to obviate excessive low down richness or weakness.

Leaking carbs are not only unsightly but much more expensive now, given the price of petrol. You wouldn't throw 30 year old single malt whiskey on the ground, would you? LOL! However, sidefloat Amals will tend to drip when canted over. They will sometimes drip when level, if the float is sticking, which is when you tap the carb with your steel-capped boot.

PK
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Float levels on 289's.

I've been plagued since i got my twin by a front pot much sootier than the rear. I'm now running 180's in both, rear plug looks good, front is as black as the Earl o' Hell's waistcoat. Something Big Sid said about float levels, and the twin difficulties of finding out 1) where exactly the float level is, and 2) the apparent impossibility of finding out where it ought to be in terms of the carburattor itself, prompted an experiment. I tilted the front carb on its stub so that whatever the level had been, it was now 1/16" lower. Encouraged by results, I tilted it further (anti-clock looking into the bellmouth) to drop it another 1/16". Bingo, eureka, what a bloody difference. The motor was noticeably smoother, and the front plug was now brown, albeit dark brown.
 

rfriedman

Website User
Non-VOC Member
I'd expect the float level to be too high as a result of wear and/or lapping in of the float needle and feed tapers. Experimenting with fibre washers of varying thickness between the carb and the float chamber is one solution. So is experimenting with washers of varying thickness between the jet block and its retainer, which screws onto the bottom of the carb body. You can also play with the height of the retaining clip on the front carb float although this is not really an option with the top-feed set-up on the rear carb.

One thing is sure, though: you should find a spare bottom bolt, the one clamping the float chambers to side-float carbs, drill it, fit it with a stub to take a length of flexible, transparent tubing - model aircraft engine fuel line is ideal - to act as a standpipe. You can fit this to a carb mounted on or off the bike to ascertain the actual fuel level in the float chamber. It should just come up to the level of the air or pilot adjustment screw. Just 'kissing' the bottom of this horizontal drilling. If higher or lower, then you must find a way of rectifying this to obviate excessive low down richness or weakness.

Leaking carbs are not only unsightly but much more expensive now, given the price of petrol. You wouldn't throw 30 year old single malt whiskey on the ground, would you? LOL! However, sidefloat Amals will tend to drip when canted over. They will sometimes drip when level, if the float is sticking, which is when you tap the carb with your steel-capped boot.

PK
If I adjust the float level to be at the bottom of the pilot air adjusting screw, doesn't that include a leakpath elsewhere in the jet block system. I am not sure, but I recall fuel leaking from the jet block retainer nut area, and that union is below the pilot air screw.
 

Prosper Keating

Well Known and Active Website User
Non-VOC Member
Good question. Offhand, I would imagine that the runoff to which you refer would not come into play when the motor was running and sucking fuel into the works. It would be there in order to reduce any risk of the fuel leaking through the pilot system into the motor, which (a) risks washing oil from the bores on start-up and (b) contaminates the engine oil. Once the motor were turned off, there might be seepage or drops until the fuel level fell below this runoff. This could explain the old-fashioned habit of turning the fuel taps off shortly before arriving at one's destination. I am going into the batcave tomorrow morning and will scrutinise and perhaps even photograph a 289 in pieces so we can see what's what. I will also play about with the 289 on the bike to see how it leaks.

PK
 

methamon

Well Known and Active Website User
Non-VOC Member
If I adjust the float level to be at the bottom of the pilot air adjusting screw, doesn't that include a leakpath elsewhere in the jet block system. I am not sure, but I recall fuel leaking from the jet block retainer nut area, and that union is below the pilot air screw.

Hi, I don't have a 276 to hand but I seem to recollect that there are two variants as regards the construction of the jet block. If I recollect corectly one type has (2?) small holes which can be seen when looking into the base of the bellmouth, one being for pilot air. The other has two small horizontal and diametrically opposed holes through the main body (& jet block) immediately above the threads for the jet block union nut that allows air to be drawn for pilot air. If my recollections are accurate the latter type could flood and presumably make its way out of these two holes and give the symptoms you describe.
If it is any consolation I am being tortured with similar problems on type 6 carbs except these differ in that they draw air through four 1/8" radial holes through the main body (& jet block) immediately above the threads for the jet block union. When the carbs flood fuel issues freely through these holes; how irritating! I also have a very sooty front cylinder and jerky power delivery which I suspect is related to carburration problems of this ilk. The petrol level is obviously critical and I'm sure these things worked properly to start with.
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Float level

I've used the method of having fuel seep out of the pilot jet. It worked OK, but what gives me pause for thought is that on a GP, Amal actually specify where the float level should be, and it is at the bottom of the 1/4" circle inscribed concentrically with the pilot jet. This suggests that the level should be 1/8" BELOW the pilot jet.
On the event, I used suck-it-and-see on the front carb of the twin, and while it is notoriously difficult to evaluate one's own brainwaves objectively, there was a noticeable improvement in the smoothness of the motor, AND visible evidence on the plug (traces of dark brown) that it was less rich than before.
Just as "calibration" the plug on my Manx is best described as "dirty white", whereas the rear pot of the Vin is light brown. Race bikes of course spend much of their time at full throttle, but there are many who believe that one should just "lean it out until it "pops" on the over-run", then either take the chance and leave it, or richen it one. (I used an exhaust sniffer.) Whatever, the plugs are usually virtually white, and the inside of the mega grey.
 

wld50

Well Known and Active Website User
Non-VOC Member
276 carburettor throttle stop thread

I have worn 276's the float needle has been trued and lapped to the seat, but now the float level is incorrect.
Thanks

I've inherited a worn 276, in this case the throttle stop screw thread in the carburettor body is no longer viable. (I've read somewhere that the steel screw when unscrewed would have destroyed the thread in the alloy).

It seems worth trying to remake the right thread in the first place, I've been told by Hitchcocks that the thread is 1BA, (Can anyone confirm the thread/ size?) and Armacoil make 1BA helicoil inserts but only available in 50 packs, about a pound per piece.

Has anyone already invested/ wants to do the same and would like to share the pain ?

Alternatively, does anyone know a commercial organisation which offers a rethreading service for a 1BA thread into an alloy carburettor on a reasonably fast turn around?

As a temporary expedient I've used another, larger bolt, but it wobbles around, can't be good for the long term.

wld '50
 

clevtrev

Well Known and Active Website User
VOC Member
I've inherited a worn 276, in this case the throttle stop screw thread in the carburettor body is no longer viable. (I've read somewhere that the steel screw when unscrewed would have destroyed the thread in the alloy).

It seems worth trying to remake the right thread in the first place, I've been told by Hitchcocks that the thread is 1BA, (Can anyone confirm the thread/ size?) and Armacoil make 1BA helicoil inserts but only available in 50 packs, about a pound per piece.

Has anyone already invested/ wants to do the same and would like to share the pain ?

Alternatively, does anyone know a commercial organisation which offers a rethreading service for a 1BA thread into an alloy carburettor on a reasonably fast turn around?

As a temporary expedient I've used another, larger bolt, but it wobbles around, can't be good for the long term.

wld '50
If you`ve used a larger bolt, you`ve probably B_______d it up for a helicoil.
 

CollingsBob

Well Known and Active Website User
VOC Member
If the threads are badly buggered..then the material can be welded ...it is a lead/zinc casting alloy - same stuff as modern carbs, fridge door handles and the like...very low melting temperature, soft/large flame..and a skilled welder - gas, not tig or mig
 

vapide

Well Known and Active Website User
Non-VOC Member
There are all sorts of aluminum/potmetal low temperature welding (brazing? soldering?) rods available on the net. The original was Lumiweld, but it has many imitators and knock-offs now. On a small item like a carb you can do it using a propane gas torch, though Mapp gas if available is quicker. Bigger stuff need oxy-actylene

I've had really good luck with the stuff. It's only flaw is it turns zinc gray, which may be a problem with aluminum but not on standard carburettor bodies.

BTW you can actually put a bolt in a stripped hole, then dribble this stuff in, then remove the bolt after it cools, and have a perfectly threaded hole, since it will stick to aluminum or pot metal, but not steel.

If the threads are badly buggered..then the material can be welded ...it is a lead/zinc casting alloy - same stuff as modern carbs, fridge door handles and the like...very low melting temperature, soft/large flame..and a skilled welder - gas, not tig or mig
 

wld50

Well Known and Active Website User
Non-VOC Member
Larger bolt but sloppy, not destroying more thread

If you`ve used a larger bolt, you`ve probably B_______d it up for a helicoil.

The throttle stop thread in the body really isnt any worse now than it was when I found it, trev, the bolt's very sloppy.

I had the carburettors 'renovated' by Amal, but they didnt deal with this - even though they charged a vast sum, £12.30, - (well it was a fortune in 1974.)

It's been a long rebuild - but now she runs like a twin rather than a Comet -and back on the road after the last owner took her to pieces in 1964.

Reading the other two posts: Collinsbob, Vapide, many thanks for your suggestion(s): it sounds worth trying the 'low temperature weld' method than a Helicoil.

Many thanks (unless someone in the UK knows a source for the materials mentioned)

wld '50
 

wld50

Well Known and Active Website User
Non-VOC Member
Possibly expensive blobs on carpet


Got it!

I found this fifteen year old link by someone who had obviously tried Lumiweld with limited success.

[FONT=&quot]http://www.users.globalnet.co.uk/~pattle/nacc/arc0151.htm[/FONT]

[FONT=&quot]"This year's Vincent Club 'Riders Rally' was to be held quite near to my home and even by my lethargic standards it was time to fix the problem and put it back on the road in order to attend. With nothing much to lose I decided to attack the bits with 'Lumiweld' the low temperature aluminium welding stick which is widely advertised (and copied). I don't know what alloys cyclemotor carbs are made of, but it looks more aluminium based than the bigger Amals whose zinc-based material can be welded by Lumiweld experts but turn rapidly into blobs-on-the-carpet for the rest of us. I had one successful job behind me - look at the ally hinge on xxx next time you see it, repaired in desperation when it cracked in half some years ago - it isn't a flush and invisible joint but it has held. Smaller jobs are actually harder, and differences in section between the parts to join also make life harder as they do with all forms of welding, because the lighter item melts before the heavier one gets hot. [/FONT]"


wld '50
 

The VOC Spares Company Limited

Well Known and Active Website User
VOC Member
Amal repair

Word of caution on the 'weld repair' solution, the fill metal is usually harder that the parent material so when re-drilling and tapping there is a real danger of running off the repair into the softer body. My brother used to be a distributor for Lumiweld we did quite a few trials of different repairs and thin, zine rich alloys were the worst to work on.
Ian S
 

CollingsBob

Well Known and Active Website User
VOC Member
A method that I have used is to tap the softer metal oversize...then take a coarse thread bolt that fits into that oversize hole....place it in a lathe and drill and tap it to fit the original size bolt..in effect - make your own helicoil..thread the custom insert into the part to be repaired with a healthy glob of loctite and then replace the original bolt...the repair is just as good as the original..and if you use a brass bolt to make your thread insert from - its easy to turn in a lathe..
 

methamon

Well Known and Active Website User
Non-VOC Member
Trick turning

A method that I have used is to tap the softer metal oversize...then take a coarse thread bolt that fits into that oversize hole....place it in a lathe and drill and tap it to fit the original size bolt..in effect - make your own helicoil..thread the custom insert into the part to be repaired with a healthy glob of loctite and then replace the original bolt...the repair is just as good as the original..and if you use a brass bolt to make your thread insert from - its easy to turn in a lathe..

Bob, that sounds a slick solution. Forgive me, I can do basic macining on a lathe but how on earth do you get hold of such an awkward shape easily and present the work in the correct axis without making elaborate & time consuming jigs? The art of holding awkward shapes would be nice to have.
 

CollingsBob

Well Known and Active Website User
VOC Member
ok....you don't put the part to be repaired in a lathe..I had to fix my kickstart cover - the threaded hole that takes the clutch adjuster ET27/1AS was partially stripped...so I drilled and tapped it to accept a coarse threaded bolt using hand tools...In this case I used a steel bolt..I then took that bolt and cut the head off..put the bolt part in a lathe - drilled and tapped the bolt - so what I ended up with is essentially a threaded piece of pipe - with threads on the inside as well as the outside...I then cut a small slot on one end with a hacksaw to allow me to insert it into the case with a common slot blade screwdriver..with a dollop of loctite...the threads on the inside are fine thread - retaining the fine adjustment feature of the original.....The only trick I can think of for repairing a carb would be the duplication of the original thread size..and I dare say the repair is stronger than the original..I would use brass as that material has the same, or similar "stiction" as the original alloy...I used steel on my kickstart case because I wanted the insert to resist wear...
 

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