AMAL 2932 carb main jet size with E10
Posted: Fri Oct 01, 2021 8:43 pm
This may be old hat to some on the forum, but I thought I should share the information.
In 'Chilton's Italian Motorcycle, Repair and Tune-up Guide', OCee Ritch, Chilton Book Company, Philadelphia, 1968. Page 102, part 5, final paragraph.
I was running a 210 main jet in the 450 MKIII and increased it to a 220 when using E5. Now that E10 has arrived, I have fitted a 230 main jet in the AMAL MKII 2932 and the plug colour is looking much better down the whole length of the central electrode insulator. I am also using Castrol Valvemaster, without octane booster at a rate of 1ml to 1l of fuel.
So, with a NGK B7HS plug. No air filter. Gold Star style exhaust shell with a "bowler hat" exhaust pulse disrupter, 10cm long absorption silencer element and a 25% reduction in exhaust area outlet cone, inside the exhaust shell.
AMAL MKII 2932 32mm carb. Short standard bellmouth.
Main jet 230
Slide No.3
Needle jet 106
Needle 2A1, clip in the 4th land from the top of the needle
Pilot jet 25
Cold start jet 25
Air jet 3
Air screw 1turn out from seated
Throttle stop screw set to achieve a steady idle @1,100rpm
Keep wearing the beasties out, Bill
In 'Chilton's Italian Motorcycle, Repair and Tune-up Guide', OCee Ritch, Chilton Book Company, Philadelphia, 1968. Page 102, part 5, final paragraph.
In the case of carburettors for engines running on alcohol fuel, considerably larger jets are needed. The main jet size will need to be increased by an amount varying from 50% to 150% according to the grade of fuel used. If the engine is run on fuel containing a small proportion of alcohol added to the fuel, a rough and ready guide is to increase the main jet 1% for every 1% of alcohol in the fuel.
I was running a 210 main jet in the 450 MKIII and increased it to a 220 when using E5. Now that E10 has arrived, I have fitted a 230 main jet in the AMAL MKII 2932 and the plug colour is looking much better down the whole length of the central electrode insulator. I am also using Castrol Valvemaster, without octane booster at a rate of 1ml to 1l of fuel.
So, with a NGK B7HS plug. No air filter. Gold Star style exhaust shell with a "bowler hat" exhaust pulse disrupter, 10cm long absorption silencer element and a 25% reduction in exhaust area outlet cone, inside the exhaust shell.
AMAL MKII 2932 32mm carb. Short standard bellmouth.
Main jet 230
Slide No.3
Needle jet 106
Needle 2A1, clip in the 4th land from the top of the needle
Pilot jet 25
Cold start jet 25
Air jet 3
Air screw 1turn out from seated
Throttle stop screw set to achieve a steady idle @1,100rpm
Keep wearing the beasties out, Bill
however having worked on dope burners in the past, mainly big Brit scramblers and more recently a Mk 8 Ktt Velocette 
I also thought I should consider a small increase in main jet size, I am hoping to not use e10 if at all possible and sticking to super unleaded e5 but I will certainly have a close look at my mixture when I am back on the road again.