engine

Pull a plug next time it will not start and hold it in the head and kick over bike checking for spark. Do you have the heat insulator spacers between carbs and manifolds.

Worth checking for possible clogged filters in the fuel tap or carb.  

Also......the older Boyers would happily let an engine start and idle even if the pick-up wires were reversed by mistake. But as soon as the revs started to rise above idle speed the electronics would put the advance in reverse direction ie serious retard and kill the motor. Check the timing.

Pilot jets could be wrong size in new Amals (too small). If newer Amal premiers used fit correct jets or if old style Amals fitted open fixed jets out to .45mm.

Good luck.

When you start it, do you tickle the carbs and put the choke on? If not and it starts happily without choke, then it is probably running way too rich.

Tony

Your pilot circuits are blocked, usually its the jets but could be anywhere in the circuit.

Brand new carbs can include swarf in the galleries, old ones get blocked by today's fuel.

Might be worth releasing the petrol tank cap next time in case the breather is blocked preventing fuel getting to the carbs

The new compounds that they are adding to the fuel will cause the fiberglass (and other coatings) to melt causing the resultant goo to clog the carb(s).

Your best cure is to replace the fiberglass tank with one made from steel or aluminum.

Mike

Fibre-glass tanks are very susceptible to modern petrol and I believe that once they have gone soggy there's not a lot that can be done with them.  Best advice is from Michael above and that's to get a new tank made from steel or alloy.

In Australia we have a coating that seals up rusty steel tanks. I've got it in my Ford.

It might be worth trying this stuff in your fibreglass tank befor you bin it completely. 

You were lucky spotting it when you did, it can get on the valve stems and then jam the inlet valves open which then hit the pistons.

You now have to get rid of the resin. 

https://www.westsystem.com/instruction-2/epoxy-basics/clean-up-removing/

Clean epoxy resin or mixed epoxy residue with lacquer thinner, acetone or alcohol. 

Those small galleries and jets in the carbs will be all full of the stuff, you will need to get them soaked for a few days in one of the above fluids and cleaned ultrasonically. For the pilot jets drill out with a 16 thou drill for the old carb pilot bushes and 17 premier pilots, 18 thou drill for the 19 premier pilots.

Dan:

Can you give us the ID of the product that you have mentioned?

Thanks

Mike Sullivan