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Old 09-29-2004, 12:29 PM   #16
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No,that is not what he mean.

Mp 777 means that lower the port is wast of time as it is prooved that it is better for engine if piston goes .5-.6 mm lower than exhaustport in BDC. You should remeber one moore thing. If you lower ehaust port to much you can have a problem with fresh gasses going past piston and out in exhaust system while piston is at TDC. Never mesured it but it can happend.
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Old 09-29-2004, 01:04 PM   #17
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I was talking about that, if piston goes below bottom line of exhaust port it will not hirt at all ( but should be certain number).
Exhaust timing will have nothing to do with that ( exhaust timing counting from top line of exhaust port).
Actualy underpiston induction ( when gap is open at piston in TDC position) is using widely in couple classes in airmodeling ( if they not prohibited). In cases where carb diameter is restricted-underpiston induction is very good solution. In our case it will not unfortunately work due the presents of idle.
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Old 09-29-2004, 08:30 PM   #18
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Quote:
Originally posted by Top Gun 777
I was talking about that, if piston goes below bottom line of exhaust port it will not hirt at all ( but should be certain number).
Exhaust timing will have nothing to do with that ( exhaust timing counting from top line of exhaust port).
Actualy underpiston induction ( when gap is open at piston in TDC position) is using widely in couple classes in airmodeling ( if they not prohibited). In cases where carb diameter is restricted-underpiston induction is very good solution. In our case it will not unfortunately work due the presents of idle.
THanks for clearing that up guys, i get it now hehehe

I also have another question regard exhuast port height. if you raise the exhaust port hieght on the sleeve, then you would have to raise it also on the crank case right? What happens when i replace the sleeve to a new one with the stock exhaust height. THat would meant that the exhuast port height on the crank case would be higher than that of the sleeve. Would that jeopardize the engine's longivity or reliabiliy or power? Would the sleeve start to warp or blow out at the top of the sleeve exhaust port because there's no reinforcement from the crank caes due to its exhaust port being higher than that of stock? Have i lost you guys yet?
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Old 09-29-2004, 09:37 PM   #19
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Quote:
Originally posted by noobatron
THanks for clearing that up guys, i get it now hehehe

I also have another question regard exhuast port height. if you raise the exhaust port hieght on the sleeve, then you would have to raise it also on the crank case right? What happens when i replace the sleeve to a new one with the stock exhaust height. THat would meant that the exhuast port height on the crank case would be higher than that of the sleeve. Would that jeopardize the engine's longivity or reliabiliy or power? Would the sleeve start to warp or blow out at the top of the sleeve exhaust port because there's no reinforcement from the crank caes due to its exhaust port being higher than that of stock? Have i lost you guys yet?
I glad that we were able to help.
How much higher exhaust makes sence to raise? 0.1 mm is equal 2 degree. Even if you raise 10 degree exhaust it is only 0.5 mm-don't touch crnckcase, leave it as stock, nothing will change.
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Old 09-29-2004, 11:48 PM   #20
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I would try that ^^^^^
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Old 09-30-2004, 01:12 AM   #21
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Quote:
Originally posted by Thunder racer
I would try that ^^^^^
Please if you try that, don't forget to compencate pipe lenght. It is sort of issue with raised exhuast. Exhaust timing must to be compancated by pipe lentght, otherwise pipe will be too short.
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