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converting to 4 mill?


VictorK

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my current motor set up is, standard 20cc domes, welded stock crank, and hjr port for my t5s. Do I only need new domes or does the porting need to be changed? Also what would the difference be and how drastic?

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my current motor set up is, standard 20cc domes, welded stock crank, and hjr port for my t5s. Do I only need new domes or does the porting need to be changed? Also what would the difference be and how drastic?

 

 

yep,porting need changed and you need new domes cut for a sleeper engine,and ther will be a noticable difference and a little more torque.

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Yep that is what sucks about going from a ported stock stroke to a ported 4 mill. You have to get new cylinders and have them reported. I am sure your cylinders have had the port hights raised to much for them to be corrected for a 4 mill crank. When they port for a 4 mill the start by lowering the ports roughly 2mm since the piston falls 2mm down in the bore. Then they raise the roof's of the ports. Since your ports have already been raised when the drop the floor's 2mm the ports are way to big and to far advanced.

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I was just curious. I think next year I might do cheetah cub cylinders. For around here my hjr ported cylinders are the fastest thing around but I have this power and wonder how much fun a cub would be. I still have stock carbs, which I think a upgrade to better carbs along with a lockout and higher compression domes would be a good difference. Maybe that would do it for me.

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