Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Carb slide sticking

So the bike has been in a bad mood for days now. Figured on giving it a wash to cheer it up. Curious thing happened. Washed it as usual by giving it a spray with degreaser and a hose and brush off.
It decided not to start at all. Figuring I had flooded it, I wide opened the throttle to pump it over and the slide in the carb stuck open. This has happen before in similar cercumstances. Backed off the carb to head bolts and CLICK it freeded off. I have a Tufnol spacer between carb and head, does this swell with the degreaser?
BSA B44 1967, new carb a year ago.

O rings swell with degreaser, a good tip, use nyloc nuts and spring washers, just tighten til the spring closes.

Maybe you tightened the bolts too hard and bent the flange. That can damage the carb and make the throttle slide get stuck.

Peter

It never ceases to amaze me that people will call anything that comes out of the far east "crap". Yet they treat with reverence and praise the piece of sh1t produced by AMAL. A carb that cannot be tightened past finger tight, a carb without a proper cold start system, a carb that wears out within a few thousand miles

Loosening the carb bolts and having the slide free means you over tightened them and warped the body. The O-ring should be barely proud of the flange and the spacer dead flat. Micarta is a good material for the spacer because the faces are flat and it insulates the carb from heat.
If the slide sticks at full up position you can unwarp the body by using a pair if slip joint pliers. Take the carb off and remove the top. Raise the slide until it sticks then gently squeeze the body in different positions around the slide until it drops. Very carefully squeeze the top of the body a little harder then try the slide again. Best to build up the squeeze from where the slide still sticks until it moves free.

Nice.
How thin could you go and still achieve proper insulation?

p.s. someone is looking for you in the "Adjustable P/R Tubes T140V" thread.

Bit of Exaggeration there Andy, never known one to wear out after a few thousand miles. The Mk2 is a better carb but they are a later carb also. The Bing I had on my canam was almost identical to a mk1 apart from the card start system and that was troublesome, the choke slide was far better in my opinion, ok a crude design and second to the butterfly chokes on my Keihins.

An improvement would be to convert them for rubber mounting, not only to aid insulating the carb from heat but to reduce frothing also.

I honestly don't know why they didn't rubber mount them when they introduced the premier series

I used 2 pieces of 1.6mm (total 3.2) compressed asbestos fiber gasket material on the carbs of the a65 .......worked well .........but good luck being able to buy asbestos gasket material now .......all the whale-huggers have taken it off the market

you simply cant get a better thermal insulator material than that

Agree.
But it seems the Micarta is more rigid and would be less prone to allowing carb body warp.
And thinner = more space between air cleaners and everything else.

Brings to mind a bit of commentary seen on a bog wall.
"Nuke a gay whale for Jesus. Covers all the issues."

Yeah it is pretty obvious that the bolts were too tight, the question is why? The bike had been running fine and the carb working as well as an AMAL does for around a year or more. The only change was spraying, perhaps with a little to much Gusto, with degreaser. New carb, new studs, new nylock nuts new Tuffnol spacer about a year ago. I only backed off one nut to free the sliderand that was only less than one flat. I know nuts shake loose (I own a BSA after all) but I have never heard of one shaking tight so the question remains, what swelled up?

The O ring swells if you get solvent cleaners on it.

yes correct ......but i kind of like SAVE THE KRILL nuke the whales

I take your point and "when you have eliminated the impossible, whatever remains, however improbable, must be the truth", but how in the name of all that is holy could the degreaser get to the O ring unless the carb was positively sloppy? plus a swelling O ring has enough power to bend metal? (assuming you call that stuff AMALs are made of "metal").
Will take the O ring thing under advisement and file the incident under "Magic" and "Don't Do That Again".

Stripping the head next week end so will examine carb closely at that point.

FYI. bike no longer in bad mood, starts first kick and pulls like a train.

I put "half thick" rubber washers on the 2 mount studs
so that when there is enough O-ring Crush
the mounting stress is shared onto the 2 extra washers .

Not sure what you mean by "half thick" rubber washers, but I was considering making a rubber gasket and ditching the whole O ring thing.
Any comments?

If the carb is correctly mounted it should barely kiss the O ring indeed you should be able to move the carb ever so slightly , degreaser if applied will easily penetrate around the flange, at 4 lb ft or so the nuts are barely more than finger tight.
If you dont use good nyloc nuts then be sure to use a wee dab of blue loctite on the mounting nuts.
Theres no need for a home made gasket , the o rings work fine so long as the flange isnt bowed. check that it is flat with a straight edge. If its bent there is a cunning tool to press out the distortion. dont be tempted to sand/ file the flange flat , that will not fix a distorted body.

They really should've published a clearance spec between the carb and the manifold instead of a torque spec for the nuts. But, nobody would've paid attention to either.
Oh wait, there is a spec given in Triumph service bulletin #25.
"DO NOT over tighten as there should be some flexibility at the mounting studs. This can be measured by checking the gap between the carburetor flange and the mounting adapter with a feeler gauge. This gap should be at least .030"."

I believe there is a thick o ring for the triumphs although I have never found one listed.

Going back to the original post, Concentric carbs are prone to sticking when exposed to water

" Concentric carbs are prone to sticking when exposed to water" !! Ye Gods! and these things were designed in England?

they are prone to sticking when exposed to motorcycles. I had a huge smash in the 80s from which i was lucky to walk away because they both jammed wide open ......bet i wasnt the first

get new Concentric premiers get micarta type heat insulators do not overtighten nuts do not ride bike if even slightest chance of slide sticking everything I just said I learned the hard way is your life worth a few hundred bucks?

Might be worth giving the carb cable and handlebar throttle some lube, these often neglected items can get sticky and cause the problem you describe.

Just a reminder ………….
All within the last year or so:-
New premier carb,
New tufnol spacer
New studs and nylock nuts
New throttle cable (nicely lubed a couple of weeks back)

All performing well until I washed the bike. Slide stuck at top of travel, freed off by slacking of one nut by less than one flat. All good ever since.

I was just wondering how the carb got tighter when I washed it!
Seems I have two options ……1) keep it dry, luckily I now live in a semi arid climate and 2) Don't use degreaser on the carb, perhaps carb cleaner?