Engine build, looking for input

Nsmith212

Nsmith212

Location
Concord ca
I have a r&d built 760 ish flat top piston motor. 27cc drop down domes.
84.40 mm flat top wiseco pistons
46mm buckshot carbs riva intake
Vforce2 reeds
Enhancer bpipe 10/16 skat

Still rips hard but only 130/140 psi. I want to rebuild this tired motor but pistons are no longer available. A 750 Kawi piston would work with a ring moved to clear ports according to r&d but I'm thinking of going with an 85mm Yamaha piston and going back to regular domes.
Does anyone know what would be better?
It was built for racing but I've since turned this into my freeride ski.
I'm curious if r&d has done anything with port timing, but a taller piston would only lower the port timing and thus cater more to freestyle type riding? Just sort of spit balling but any info would really be appreciated!
568959941d38460f8c37550efdc6144f.jpg



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Blue

Blue

Judging your cheapness
Location
St Cloud Florida
Are you sure that it is borable to 85mm? If its a 61x cyl it would need to have custom sleeves in it to be able to go up to 85mm pistons.
Its difficult to say what can be done since there is no way to know if the port timing was changed without disassembling it and inspecting it closer. Worst case get a new cyl and have it ported and switch out the domes.

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Pablo

Pablo

sqeez bth levrs & lean bk
Site Supporter
Location
georgia
Like Blue said. Not sure on R&D stuff. I had a completely Dasa built flat top big bore with a 61x jug and I had it at 85mm with Kawi pistons. Worked/ran like a beast for its size.
 
Nsmith212

Nsmith212

Location
Concord ca
I believe it's re sleeved, I was told that I could go down to 80 thou cylinder thickness safely and it's currently way thicker than 2mm


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Blue

Blue

Judging your cheapness
Location
St Cloud Florida
Ok thats good then. Your best bet is to send it to someone to have them check the port timing and give you options as to which way is most cost and power effective.

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Nsmith212

Nsmith212

Location
Concord ca
Here she is, got some 85mm Pistons coming. It has been resleeved, still have 125 thou left in my sleeve thickness. Currently 84.40mm


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