variable exhaust port

snorks · Feb 28, 2015

Perhaps a bit beyond the scope of the average home tuner...has anyone ever considered a variable exhaust port on one of these engines?
The first time I sawit was back in the 80s on the yamaha twin RZ250 I think.
Just felt like mentioning a few more two stroke hot ups beyond porting and the more common go fast tricks.

Cheers
Simon

frank66 · Feb 28, 2015

the heat is bad for the power valves. so is the carbon buildup. we dont even have correct exhausts.

2door · Mar 3, 2015

frank66 said:
the heat is bad for the power valves. so is the carbon buildup. we dont even have correct exhausts.

What is "power valves"?

Tom

GoreWound · Mar 6, 2015

just leaving this here

I may or may not have been rolling this idea around in my head for years.

snorks · Mar 6, 2015

2door said:
What is "power valves"?

Tom

Its a rotary valve that is integrated on the exhaust port of some racing two strokes. As it opens and closes it adjusts fhe exhaust port height and alters the port timing. Usually they are servo driven and connected with cables.

Cheers
Simon

frank66 · Mar 6, 2015

gorewound i really like that one u posted. that reminds me i made one out of a nt carb because it fits perfectly on a silencer. but i realized it would not be enough size and that the stinger and silencer sizes were also limiting factors somewhat. lost interest a little. but maybe.... i even looked at boring the carb out because it fit well and had a spring loaded slide that could go to a lever..... it was pretty juicy actually till the size seemed to small.

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variable exhaust port

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