Hi 1940 model 8 500 OHV. When tuning the carby what position should the adv/retard be. Also threads in the tank are 3/8" UNF. What size and thread should they be BSF or BSC. Is there enough meat to heli-coil them
thanks
carburettor tuning
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Re: carburettor tuning
Hi Simon.sbrock wrote:Hi 1940 model 8 500 OHV. When tuning the carby what position should the adv/retard be.
When static tuning the pointed pilot (air) screw on an AMAL carb with the bike upright I leave the A/R in its normal position for starting, i.e. partially retarded, aiming for a slow steady tickover and clean pick-up. When adjusting the screw you should start with it about one and a half turns open (unscrewed) and end up with it somewhere between 1 and 2 turns open.
Just as a guide, if you end up with the pilot screw less than one turn open you may have an air leak at the carb/cylinder head interface. If it ends up more than 2 turns open it may be that the float level is too high.
Or it may be none of the above.
The main jet and slide cutaway are not 'adjustable', except by substitution with alternatives after road testing.
Here's a guide on carb tuning
http://www.hitchcocksmotorcycles.com/mo ... to-tune-up
Can't help with the thread question but wasn't there an article in a recent 'Jampot' mag about repairing tank fixing brackets?
Last edited by SPRIDDLER on Wed Feb 17, 2016 12:14 pm, edited 4 times in total.
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Re: carburettor tuning
In the petrol tank you should find 26 TPI cycle thread except for the petrol taps which are a Gas thread.
Check the parts list of the threaded tank fittings, it gives the sizes.
Check the parts list of the threaded tank fittings, it gives the sizes.