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Yz444 Tuning: Building a Monster Torque Curve
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[QUOTE="Ol'89r, post: 825021, member: 17212"] Oops. Sorry Masterphil, I guess we didn't jump on this one fast enough for ya. :ohmy: Just kiddin. ;) What do you plan to use the engine for? Is it a race bike or are you just gonna pull tree stumps out of your back yard. Possibily a yz444 trials bike or a 1/10 mile drag bike??? Just wondering. By having two seperate cams in your engine you are able to change the torque curve without regrinding your cam. In my experience, building a torque engine requires narrowing the spread of the two cams. This packs the most charge into the combustion chamber. The amount of spread used is limited by mechanical clearances. (Valve to piston, or valve to valve.) Valve to valve is not a big factor in your engine due to the valve angles. Also, decreasing the spread too much will result in less working vaccum in the engine and it will not want to idle or carburate very well. The 104 degree center is a good place to start. I use a 105 center as a reference point to degree most cams in depending on what the engine is used for. Rather than use the stock cams, you may want to have a set ground. This way you can change the lift and duration and still have the ability to advance or retard each individual cam. Best of both worlds. Check with Web Cam, Hot Cams or Megacycle Cams for a regrind. Port design also plays a big factor in torque. A deep pocket port is best for a torque engine. In most modern engines there is not enough material in the port to reshape it very much. Your engine has a fairly straight port design. The problem with a deep pocket port is, the motor will stop pulling at a very low rpm. A straight port does not disrupt the flow and will rev to a much higher rpm. Usually a smaller diameter exhaust pipe will add to torque, but you need not go there until you have the engine built. IMO, exhaust tuning should be done on a dyno. Pipe diameter and length are both a factor. Doing it any other way is just guesswork. Intake manifold length is also a factor and that is also determined on a dyno. I would recommend using the Kibblewhite stainless valves. They will outlast the stock valves and you can get them in oversize and definitly use the ti collar and spring kit. Rich would be the guy to answer your fuel question. You might want to pm him if he doesn't respond to this thread. Hope this answered a few of your questions. :cool: Ol'89r [/QUOTE]
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Yz444 Tuning: Building a Monster Torque Curve
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