Jetting limits
- Thread starter RCJ
- Start date
alvin l nunley
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That sounds really baffling. By what criteria do you decide that a jet change is necessary? Are you using an air density gauge? When you say "not responding" what criteria are you basing your assumption on? I've been accused of hounding people when I suggest that an exhaust gas temperature gauge (EGT) is the best measure of fuel mixture.
We were on the dyno. The motor made more hp as I add jet , I typically keep adding jet till power falls. You could tell at a certain piont it stopped responding to the jet. I was using a completely stock carb so I ordered a .640 Holy Moses carb. The motor really like it. The guy that I am building this motor for wants me to build the carb to save some money.
You reach a point of diminishing returns when going richer with jets. The carb can flow "X" amount of air only, so when you up the gas concentration in the mixture, it's getting too rich for the air flow & power is lost. That's why people put larger carbs on motors (Mikuni VM 22-26, etc.) which can benefit from more air flow. The trade-off in carbs comes when there's just too much air flow for the motor. At lower rpms it will stumble off of idle if there's too much carb when you hit it hard out of a corner, so you need more motor, then...
It's the "Whiffle Bird" effect, a little bird that flies in decreasing concentric circles, faster & faster, until it flies up its own butt & disappears in a puff of feathers, too much of a good thing.
It's the "Whiffle Bird" effect, a little bird that flies in decreasing concentric circles, faster & faster, until it flies up its own butt & disappears in a puff of feathers, too much of a good thing.