Hi all
Having trouble with my '66 Spitfire.
Trying to keep the GP carbs . Everything cleaned and updated the throttle slides to 5 1/2 from no.4 as recommended.
Bike will only start of I choke by hand over one bellmouth (hot or cold) and then is liable to stall when opening throttle.
I have to have air screws set very rich to stop this. Float level correct and fuel enrichment slides make little difference.
I read somewhere of a tweak to aid slow running that you can drill a tiny hole the throttle slides above the pilot hole to make things better but this was pre internet.
Bike has been rebuilt with Pazon ignition and a rebore .
Bike hadn't been run since 1980 but must have started easier then.
I've been building stuff for along time but this has me scuppered.
Thanks Micky.
Where did the slide recommendation come from? 4 to 5.5 is 3 steps in slide changes. Stick the 4s back in and see how you are with them and go from there.
On a different note, your carbs will be gp2's which Amal no longer make, where did you source your slides from?
Recommended in bsa service sheet no 27 I think.
The previous owner had the slides but never fitted them
I put the no. 4 ones back and pick-up is better. Still need hand choke though.
Flooding via tickler makes no difference.
Only other thing is have you adjusted the pilot mixture screw? On the gp (I'm sure your aware) you adjust the fuel mixture and not the air mixture as per other Amal carbs. There could be a blockage on the pilot circuit?
On the GP 10 it's an air screw, the pilot system was 're designed to the rear of the carb. But thanks.
I cleaned the pilot fuel jets again and starting getting better , but will have to look at internal drilling as the carbs y are still not responding as they should.
All sorted, the drillings had rubbish in them from standing for 40 years. A bugger to get the blanking screws out though.
The small hole forward of the slide was getting blocked intermittently.
I'd have to have a look at my GP's to familiarise myself with them but I'd think you'd have a tiny hole either side of the wall of the slide. The one closer to the head is the slow running mixing feed, if there's one Under the slide then it will be for the transition between the slow running circuit and the main carburettor.
Well found though despite the headache of sorting it.