Britbike forum Forums Thread Like Summary - A65 Starting issue

I've got a rebuilt 1971 A65 with new Amal carb and Boynton ignition. Cold start -Tickle carb and it starts 1-2 kicks. Ride bike, runs great. Upon returning I can shut it down and immediately restart it with one kick. If I let it sit 10-15 min. it won't start. 4-5 kicks and I'm done.... If I try to tickle it, it spits and sputters out the tickler as if it's pressurized. Is that a heated carb issue? Should I have an insulator between carb and manifold? Anyone experienced anything like this?

Yes , there should be an insulator between the carb and manifold.
It may be getting too hot.
Go through all the normal checks, ignition timing etc if it's too far retarded
it may behave as you say.
Normally when hot you need a little throttle to start.

A word of warning I learned the hard way on my DBD and 36 mm Concentric. Some of the insulating spacers are soft and can distort, allowing the “ears” of the carb flange to bend even more than usual, leading to all the familiar Concentric problems with slide sticking and wear, etc. The answer seems simply to be, exercise restraint when tightening it, especially when using a non-metal spacer.

There’s various sizes, some folk are now listing ones which are 1/16” thick (1.5mm) avoid these are they are too thin to do anything. Most original ones were 3/16” thick (4.5mm) these work fine as a minimum thickness but I find anything 1/4” and up works better when we do eventually have some
Stinking hot days in the UK.

ALL BSAs need a thermal insulator between the carb and manifold. These are NOT an Amal part, and therefore DO NOT come with new carbs or the Amal rebuild kit. However, not all thermal insulators are equivalent. Some won't seal, some are too thin. Problems abound which usually mandate a fuel-proof sealer, AND a very calibrated way of fastening the carb... lest the mechanic use too much torque and distort the carb body... causing more air leaks.

All things considered, the BEST modern solution may be the Triumph carb mounting solution. This design uses a fat o-ring to seal the carb to the manifold. The o-ring is so big in cross-section that the carb does not physically touch the manifold, providing thermal insulation and a BETTER seal (without using sealers). Then, smaller rubber cushions go between the mounting nuts and the carb body on the air filter side of the flange. In effect the carb is now rubber mounted at 3 points, with a 100% seal to the manifold and WITHOUT distorting the carb body.

You can see the effect in this photo of a Bonneville....




Again, these 3 new "rubber" parts are NOT Amal parts. They are purchased separately, but they need not be sourced from Triumph. O-rings good enough for this job can be sourced at any local hardware or plumbing store.

Hope this helps.