D
Deleted member 12676
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Both of these carbs have design flaws that can be corrected for a more perfect jetting (not rich or lean) from closed to wide open throttle. I prefer to just replace them with the Mikuni VM18 but some people need to be as conservative as possible with their money. Using my jetting calculator I came up with these suggestions but unfortunately they are mostly for engines with reed valves fitted to them. I need to put a Speed carb on a piston port intake engine and see how the jetting compares. Any way here is the url for my sites newest page and I hope some people find it useful: http://www.dragonfly75.com/motorbike/cheapcarbs.html
By the way by using the jetting calculator I realized that the Mikuni I have is with an incorrectly sized needle jet, one too small which throws the jetting off. It came from Treatland with a N-0 needle jet instead of the needed O-0 jet. The N-0 overly reduces the free space between the needle and the jet when the throttle is mostly closed (well, up to about 30% open when the needle taper kicks in). I had previously tried to compensate for it by installing a really big idle jet which helped somewhat but still it was off. I'm disappointed that Treatland sold me the carb that way. Normally the VM18 is sold with an O-0 needle jet.
By the way by using the jetting calculator I realized that the Mikuni I have is with an incorrectly sized needle jet, one too small which throws the jetting off. It came from Treatland with a N-0 needle jet instead of the needed O-0 jet. The N-0 overly reduces the free space between the needle and the jet when the throttle is mostly closed (well, up to about 30% open when the needle taper kicks in). I had previously tried to compensate for it by installing a really big idle jet which helped somewhat but still it was off. I'm disappointed that Treatland sold me the carb that way. Normally the VM18 is sold with an O-0 needle jet.