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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
TT carb
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<blockquote data-quote="greg brillus" data-source="post: 142763" data-attributes="member: 597"><p>Hi there John, yes definitely the SG has an affect on the levels.......its worse on alcohol fuels as you find the levels are higher than petrol........Similar but different to altitude.......Running at higher altitude results in a richer mixture, so this has to be taken into account when tuning. The big helper for me with setting up the Gardner is the use of a fuel/air meter........Actually mine is set for Lambda........I quickly found the ratio on my racer was way too lean, the needle in the carb more suited to petrol than methanol.........As an example, the needles for methanol are 4 mm diameter brass rod.......this has a taper machined down one face of the needle, this taper facing towards the inlet valve........On full throttle the needle width at that point was 2.7 mm across.......To get the full throttle mixture rich enough to be safe....... I had to shave the taper so that at full throttle the needle is 1.5 mm thick.........So to visualize this, imagine a circle at 4 mm in diameter, then cut this down so the circle looks like a capital "D" then shave the flat face down thinner until it is only 1.5 mm thick, that is all that is left of the 4 mm diameter needle on full throttle.......Remember as this is a road race bike i do run a large float bowl (SS1 Dellorto) this gives a more constant delivery to the carb, as opposed to a speedway engine or sprinting engine that would not use a float bowl at all on this carby, just the fuel hose directly from the large bore fuel tap to the carb fuel inlet fitting.........in this instance you need to be very careful not to open the throttle if the fuel taps are on and the engine is not running.</p></blockquote><p></p>
[QUOTE="greg brillus, post: 142763, member: 597"] Hi there John, yes definitely the SG has an affect on the levels.......its worse on alcohol fuels as you find the levels are higher than petrol........Similar but different to altitude.......Running at higher altitude results in a richer mixture, so this has to be taken into account when tuning. The big helper for me with setting up the Gardner is the use of a fuel/air meter........Actually mine is set for Lambda........I quickly found the ratio on my racer was way too lean, the needle in the carb more suited to petrol than methanol.........As an example, the needles for methanol are 4 mm diameter brass rod.......this has a taper machined down one face of the needle, this taper facing towards the inlet valve........On full throttle the needle width at that point was 2.7 mm across.......To get the full throttle mixture rich enough to be safe....... I had to shave the taper so that at full throttle the needle is 1.5 mm thick.........So to visualize this, imagine a circle at 4 mm in diameter, then cut this down so the circle looks like a capital "D" then shave the flat face down thinner until it is only 1.5 mm thick, that is all that is left of the 4 mm diameter needle on full throttle.......Remember as this is a road race bike i do run a large float bowl (SS1 Dellorto) this gives a more constant delivery to the carb, as opposed to a speedway engine or sprinting engine that would not use a float bowl at all on this carby, just the fuel hose directly from the large bore fuel tap to the carb fuel inlet fitting.........in this instance you need to be very careful not to open the throttle if the fuel taps are on and the engine is not running. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
TT carb
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