Quote:
Originally Posted by Ralgha
Factory engineers also have different requirements than we do though. For example, emissions, which is something most people don't have to worry about here with a motorcycle. The newgen 250's exhaust is undeniably limiting power, and they are undeniably set rich from the factory. I'm sure the engineers had their reasons for doing so, but the end user can easily put a new exhaust on, tune the carbs, and get some not-insignificant extra HP out of it, while also improving the general operation of the engine. I see no downside, unless you have to pass emissions.
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Some requirements for any major manufacturer is ease-of-use, reliability and durability. Not sure on exact terms, but I suppose 80-100k miles lifespan would be in ballpark. They'll tune engine on rich side intentionally in case owner runs across low-octane crappy petrol in boonies somewhere. Combined with hot day and that could spell disaster with knocking & pinging which will destroy head-gasket and puncture holes into pistons easily. So some extra fuel in 10-11:1 AFR range at WOT high-RPMs serves to cool down combustion, lowers NOx emissions and lowers peak-HP. Rich mixture also makes engine run smoother, something prospective buyers and owners would notice subconsciously.
For me, I only need engine & bike to last just ONE season and that's it. So I run high 13.0:1 compression with max-power 13.5:1 AFR on ragged edge of pinging/detonation and destruction. Bigger cams help high-end power and reduces dynamic compression to ward off knocking. Engine still requires 100-octane petrol (M+R/2) all the time. I think I may have detected some pinging at super-toasty 105F+ Thunderhill last year. I backed off ignition couple degrees just to be safe.