276 Float Height

[maxwelton]

My bike has never really run right; it would never idle when cold and warm idle has always been a struggle. The adjustment screws didn't do anything, really, though obviously you could set the slide to sit up high enough to give the bike some sort of idle (incredibly variable) when it was hot.

Recently, it would flood when the gas was turned on, not a great sign. So I thought I'd take the carb off to see if anything obvious was wrong. This is a new reproduction 276 (well, it was new in 2002!) and has been off for investigation before, but we've never found any issues.

First thing I noted was that the float bowl was absolutely choked with sediment. I hope this is related to my old (cork) taps giving out a couple of years ago and not something which is currently going on; I'll take it off again in another hundred miles to be sure.

I cleaned everything and check to be sure the float hadn't sunk (it was fine) and even lapped the needle and seat though they looked ok. As I was putting it back together I assembled it just as it had come from the factory, and did some sophisticated  "blow" tests with my mouth to make sure the float needle was seating. It wasn't! To make a long story tolerable, the float needle in this carb has two height positions, and it had come with it set on the higher one, and I had never checked or changed it. This meant the tickler was constantly letting a small amount of gas through, not to mention the height of the fuel in the carb.

I reset it to the lower setting, which did allow the float needle to seat fully (and still allowed the tickler to work) and jeebus, what a difference. It fired right away and completely shocked me by idling when stone cold (with the slide lowered, of course). I still need to work through the hot idle adjustment, but I'm confident I can now find the sweet spot for that.

I went on a ten mile test ride and came back to find I was leaving an oil trail, uh oh. The banjo fitting just below the oil tank had broken where the line leads up to the head. So now I need to find one of those...

[muskrat]

 I know what you mean Max. We get a bike and look over it but don't realize the prev owner has changed something.
Things like kickstart cotters in wrong way, LH con rods around the wrong way, and so on. So we think this is the norm and don't bother with it till something goes amiss. I've learnt more here in a few years than the other 30 of BSA ownership.
Do yourself a favour and clean out the tank.
Cheers

[maxwelton]

I suppose I should now note the bike no longer starts when hot.  I guess I'll reset the float height and shim the tickler, maybe. I'm very very very very very very very tempted to ditch the 276 and use a monoblock. I live somewhere where I have to take a ferry a lot, and if I can't reliably get the bike going when hot it limits where I can go. This is reminiscent of my spark plug leads issue but I don't think it's electrical this time, nothing has been changed there.

[Housewiz]

I just read 276 floats are not adjustable - don't have one (or two) yet to verify that claim.

Thanks,

Steve

[wilko]

Pull the jetblock out and you will find a tiny pinhole which is the idle passage way, you will find it is blocked. And whenever you tickle one of these until it spews out of the top it will keep dribbling out of the jetblock area until it finds the right level again.So let it settle first before you assume the needle isn't sealing.

[LJ.]

Remember there is a big difference when bike is on side stand and when on centre stand. If bike had been on side stand then carb'll need a tickle... I find this with all three bikes that have the 276 although funnily not the star twin with twin carbs, with that bike there is a lumpiness when started until the offending float finds its correct level, what happens here is that the bike starts on a flooded opposite carb.

The 276 is not a happy carb on bikes with side stands.

[Clive54bsa]

Hi Max, I've buggered about with my 276 on my '54 Golden Flash for a couple of years, pulling the carb off, cleaning, blowing with compressed air, and what I've found is that after I'm absolutely sure I've cleared every orifice, my bike will not start hot on the prop stand, it has to be fairly level to start, I also followed someone else's advice from this forum by sealing the flange where it bolts to the head with hi-temp silicone, and wait a good 48hrs for it to cure before starting. This helped enormously with the idle. Make sure you don't over do the silicone and get pieces inside the inlet tract.  I sealed all the banjo joints with the Blue Hylomar, which stays soft,  I get no fuel leaks now, unless I park the bike on the prop stand with the fuel tap left on. Don't give up on it, you will get it right if you persevere, I've had a few friends tell me to go to a Monobloc, or a JRC, but I like the look of the 276, and I'm staying with it.
Good luck with yours

[Housewiz]

LJ & Clive,

I am planning on putting two 276 carbs on a twin carb 650 head.  The bike is a '58 SR.  My questions are what have you learned that is specific to those carbs?   Have either of you (or anyone) had experiences with new 276ers from Amal?  Haven't had much luck finding a matched used pair.  Do you guys know the throat diameters of the 276ers you have installed?  Do you still have the original slides or is there an upgrade you have had luck with?  Are you guys running filters and air box or open trumpets?

LJ - what is your maintenance & tune-up routine on the star twin?  Did you mount the float bowls on the outside of the carbs?  What throttle cable set up are you using?  What manifolds are you using and how long are they?

Anything else you can think of that a rookie should know or be aware of would be greatly appreciated.

Thanks,

Steve

[LJ.]

Hi Steve...

Bear in mind that my twin carb set up is on my 'long-stroke' and not the later A7. Am I right in guessing that you are wanting to put the 276's onto a 58 super rocket?? The one thing I can reliably say is that I have not noticed any improved performance at all with my twins over the single carb. I regard my twin carb set up as mostly cosmetic and a talking point, does look really nice though. I'll PM you with a link to some photos of my set up.

After-care Maintenance and tune up? none if done properly in the first place, biggest problem is muck in the petrol tank.
On the long-stroke the float bowls 'have' to be on the outside because there is no room for the two in the centre. Interestingly the 276 is always on the outside on the M20/21 bikes so the petrol keeps cool. But on the B31/33 the float bowls are usually seen fitted on the inside, I've not understood why this is, the float bowls are easier to tickle and look nicer when fitted outside.

I use a throttle cable with a splitter, easily obtainable on-line. The manifold for the long-stroke is hard to get hold of but they do come up on eBay from time to time, I guess anyone who is handy enough could knock one up in his workshop.

Edit: Damn... Just realised I've hogged Max's thread. My apologies...