My 50 Vincent Comet (Ex EFX 585, now California Year of Manufacture 35 471) came with two carbs, the original brass pre monoblock carb (Amal 229/1L2) and a new Mk1 Concentric. I have decided to run with the original brass one because I like the look. Hooking up an Innovative LM-1 AFR Meter using their mounting device yielded initial measurements on the order of 35 to 45 lbs of air per pound of fuel, which is leaner than a popcorn fart. I was surprised that the measured AFR was that far off, the goal being around 13.8. I adjusted the needle, moving the slide from the top notch to the bottom notch. I also noted that the needle jet is 200, the throttle valve is perhaps a 2. When I remounted the carb and started the bike up again, the AFR dropped to the order of 20 to 23. Still too lean. I can make the meter read down to 14.7 and less if I partially cover the carb air inlet cone with my hand. When the Comet is shut down, the AFR reading rises to 20.9% O2 within a minute so it seems to be operating correctly. I plan to pull the muffler off tomorrow (Friday) and move the measurement point to the exhaust pipe outlet. Probably will scare the gardeners and the old lady across the street!!!
Other things to note about the carb installation is that I placed a layer of metal tape around the mating surface with the carb to positively close off any air leakage at that point. Clip ring is tightened before testing. The adaptor to head piece has the correct gaskets and are sealed with a high temperature permatex to eliminate air leaks there. The throttle and choke entries into the top of the carb have also been sealed off with permatex. In short, I do not believe that I have air leakage at the inlet.
I am really surprised by the lean readings, all of the jet, clip placement and slide numbers appear to be at the recommended points. My starting point for adjusting the air screw is one and a quarter turns off of bottom. Failing to obtain the desired readings, my next step will be to obtain a larger needle jet, I assume that one on the order of 250 can be obtained. I have all of the requisite literature to reference (Richardson, Stevens, Irving, Owner's Manual) and am going through that. The questions to the membership are, am I overlooking anything obvious, or have you had similar experience and, if so, how did you resolve it?
Thanks in advance for your input.
Other things to note about the carb installation is that I placed a layer of metal tape around the mating surface with the carb to positively close off any air leakage at that point. Clip ring is tightened before testing. The adaptor to head piece has the correct gaskets and are sealed with a high temperature permatex to eliminate air leaks there. The throttle and choke entries into the top of the carb have also been sealed off with permatex. In short, I do not believe that I have air leakage at the inlet.
I am really surprised by the lean readings, all of the jet, clip placement and slide numbers appear to be at the recommended points. My starting point for adjusting the air screw is one and a quarter turns off of bottom. Failing to obtain the desired readings, my next step will be to obtain a larger needle jet, I assume that one on the order of 250 can be obtained. I have all of the requisite literature to reference (Richardson, Stevens, Irving, Owner's Manual) and am going through that. The questions to the membership are, am I overlooking anything obvious, or have you had similar experience and, if so, how did you resolve it?
Thanks in advance for your input.