Porting/Polishing? thoughts?

[jdanthony]

I was looking at my 787 as I rip it apart and was wondering about porting/polishing? I already got oversized wisco pistons fit in.

 

[mikidymac]

Unless you know what you are doing and have actual test data and exact measurements do not port an polish you cylinders. There is no benefit to port and polish the factory cylinders like you would the heads on a car engine. When you port a 2-stroke cylinder you are actually changing the port timing and somewhat the shape. You have to know what you are doing and have test data and measurements or you will destroy the cylinder and performance. If you want to have it done send it to someone that knows what they are doing that has done the testing like Group K or other pros.

 

[jdanthony]

Yea, I don't think I would ever try it,,,,, well yea maybe I would. But really the only thing would be to increase compression to gain more HP till it blow up... Then drop in a 951

 

[red2blue]

uhm...you are talkin about porting/polishing the head..right? Seen lotsa pretty work done for 4-tecs...better intake/exhaust flow...small performance increases.

What would be any different in a 2stroke?

Dunno how you increase compression removing material.

 

[jdanthony]

not really sure,, was thinking if you open up the intake and exhaust ports and smoother them out..

 

[red2blue]

10-4...increased flow is a +

 

[jdanthony]

ive heard of a 951 stroked to a 1200,, can you stroke a 787?

 

[purple_people_eater]

ive heard of a 951 stroked to a 1200,, can you stroke a 787?

biggest 951 i've heard of that lived for more than 1 hour was the 1050 builds that mel miller designed, and he was still having issues with heat and detonation. and yes you can stroke a 787 crank, but you can't just get a stoked crank and throw it into a set of cases. you're changing the heart of the motor, so everything else around it is gonna change too... plus at the very least you've got to clearance those cases so the rods don't contact them lol

 

[AdamXP800]

Any update on your R motor build?

 

[jdanthony]

Still doing research.. One big one is how much I can put into it and not blow the bottom end to pieces

 

[mikidymac]

not really sure,, was thinking if you open up the intake and exhaust ports and smoother them out..

You are still talking about a 787 correct?

Two strokes do not have intake and exhaust ports in the head. Your ports are in the cylinder walls. You can mil the head to increase compression but you better have someone do it that knows how the recut the squish correctly or it will detonate itself apart.

 

[Seadoodoc]

You are still talking about a 787 correct?

Two strokes do not have intake and exhaust ports in the head. Your ports are in the cylinder walls. You can mil the head to increase compression but you better have someone do it that knows how the recut the squish correctly or it will detonate itself apart.

some of the best reading is on Group K under 787 rec engines. Harry Klemm does a great job of detailing out rec riding versus race engines.