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Originally Posted by punishum808
Has anyone else had similar problems with the factory CR jetting? Thinking of going to 114, 112 or even 110s and have the needle set at #3 to start. Any input from guys who have had this same scenario would be greatly appreciated. Mahalo
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Bottom-line with power-generation is number of oxygen-molecules you can injest per intake-stroke. Then petrol is metered to match that oxygen-supply.
With pre-gens, it's extremely difficult to improve on engine's VE, it's so well-optimised from factory with max-power close to redline. There's minor restriction on intake, and you get a tiny gain with full-exhaust (unlike new-gen). Factory 28mm carb is way larger than tiny 15mm intake-ports, so you can increase carb-size all you want, but most-restrictive part is still inside head. Only way to make any major increase in airflow through engine is with boring and bigger pistons, installing larger valves, head-porting and cams.
So with not really improving air-flow any, adding massive carbs and humongous jetting will only result in super rich mixtures. Try going smaller-than-stock for power-increase since factory mixtures are already too-rich from factory. No factory engineer is gonna be crazy enough to set up bike with optimum max-power 13.5:1 AFR. That's just way, way too much liability. Out of factory, bikes are always super-rich in 10-11:1 range. Reports of upsizing jets and gaining power are due to people who've got dirty carbs and too lazy to fully clean them. Of course replacing
any clogged jets in dirty carbs will result in improvement, but only back up to factory levels.
BTW - good read is Dan Gurney's moment-canceling engine patent. Too bad he died before getting it mass-produced. Particularly notice intake tract design, very innovative, intuitive and simple. Makes me smack my head thinking, "
why hasn't anyone done this before?"