17-05-2018, 05:06 PM
Hi JonE
The H1 is a 1 and 1/8 inch carb, the 1 referring to the number of eigthths of an inch above 1 inch. I run a fully refurbished original one (From a M****s 8), with a '37 head and a sidedraught alloy "log" style manifold not too different to the Nippy style downdraught but without the hotspot. Power and all other aspects of running are an improvement on the Zenith, but this may be due in part to the less restrictive manifold. I use a GG needle which seems to work well, but I make no claim that this is optimised. This carb has a weighted dashpot but no spring, so one less thing to fiddle with. I suspect that the carb is a little oversized for a road engine with only a standard cam and valves which maxes out at about 4000 RPM, so a 1 inch type might also be a worthy contender if you can find one.
Cheers, John
The H1 is a 1 and 1/8 inch carb, the 1 referring to the number of eigthths of an inch above 1 inch. I run a fully refurbished original one (From a M****s 8), with a '37 head and a sidedraught alloy "log" style manifold not too different to the Nippy style downdraught but without the hotspot. Power and all other aspects of running are an improvement on the Zenith, but this may be due in part to the less restrictive manifold. I use a GG needle which seems to work well, but I make no claim that this is optimised. This carb has a weighted dashpot but no spring, so one less thing to fiddle with. I suspect that the carb is a little oversized for a road engine with only a standard cam and valves which maxes out at about 4000 RPM, so a 1 inch type might also be a worthy contender if you can find one.
Cheers, John