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Tree Monkey MS462 - PART 2

CJ Brown

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On the upstroke, low pressure in the crankcase draws in fuel/air mixture into the bottom of the crankcase. At the same time, fresh air is ducted around the piston and into the top of the transfer tunnels, thereby filling the tunnels with fresh air, while the crancase holds the rich mixture. On the downstroke, the transfers open, releasing the fresh air in the tunnels, followed by the rich mixture, into the chamber.
 

Deets066

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Notice stratos engines are never dual port? I’d tend to say that they need bigger crankcase volume to store the fresh air and still have enough mix in the crankcase to fill the chamber effieciently. That being said, quads seem to run better than duals with less case compression.

Just an observation
 

tree monkey

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If you gut the strato (remove the divider), the tunnels are still filled, but with mixture rather than fresh air.

yes to some degree, and any fuel that gets mixed with the fresh air does not lube anything.

So do the transfers and stratos all need to open at the same time?

the strato does not open until the piston opens the transfers, the piston creates a passage from the strato to the transfers. the strato port opens at the piston before the piston opens the transfers. you can't time the transfers by eye.
 

Deets066

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Let’s say you ran a standard piston and drilled holes in the intake side of the skirt to just open the stratos into the crank case.
What would be your prediction of how it would run?
 

tree monkey

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Let’s say you ran a standard piston and drilled holes in the intake side of the skirt to just open the stratos into the crank case.
What would be your prediction of how it would run?

the skirt of the piston would not be wide enough to cover the strato ports.

you could fill the strato ports and put in a std intake port
 

huskyboy

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I was surprised stihl went to quads like older huskies and husky went to duals like older stihls. Interesting.
 

tree monkey

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brad said there wasn't enough time for the fuel to mix with just a gutted boot. he said I needed to hog out the ports in the cylinder.

the strato port window can not be made bigger, so you have to give it more time. can't shorten the time either.

so why make a big hole in front of a small hole, makes no sense to me.
 
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