Super Jet What domes to run with R&D Dominator 85.5mm top end??? R&D Wiescos

[cjbchopper]

So I have a 61x cyl with R&D sleeves and custom R&D 85.5mm weiscos. We ordered an ADA head with their flat top domes. Bolt it up and there is only 125# compression, the squish is way too large. Are these pistons lower than kawi flat top pisons?? Not sure what to do here. We are thinking of decking 3-4mm off the top of the cylinder to get the compression where we want it. Or we could get some Kawi style flat top pistons and put those in?? Any advise would be awesome!

 

[Waternut]

The dominator and kawi flat top pistons have the same dome angles to my knowledge. When I rebuilt my engine last time, I was told that I either needed dominator pistons or I could get kawi flat tops but the kawi pistons would have to be machined to clear the crank webs. I'm almost positive I have the ADA flat top domes with 85.5mm dominators and my engine puts out about 200psi but my cylinder was decked pretty heavily.

Maybe the wrist pin to the top of the dome is lower on the dominator - kawi pistons than on yamaha. I don't know... Do you know who built your engine?

 

[cjbchopper]

Yeah, We are figuring out that the R&D pistons are roughly 4mm lower than the Kawi style flat tops. The distance from the wrist pin center to the top of piston is shorter on the R&D dominator style piston. Anyone know why they did this? We are thinking of decking 3-4mm off the top of the cylinder to get the .05 squish we were after.

 

[GIL]

The pin height on the Dominators is the same as the Kawi Wiseco flatops. Been there done that, Waternut IS correct-both pistons have 2* angle on the piston tops. Kawi pistons do require extensive machine work to the skirts to clear crank webs. Keep the Dominators and get the correct domes!

 

[lerott]

Hi Gil,
I have an old cast r&d cylinder 7 port pv stroker +8mm and crankworks crank +8mm with 133mm rods. I've built my engine with kawi pistons and I haven't cut the skirt because pistons don't hurt crank webs at LDC. I've had riva pistons in hand, I've seen pics of Dominator pistons and side of skirt (and notch for boost port) on both aren't designed like kawi one. I'm wondering if I need to machine kawi piston skirt to clear properly transfert at LDC and what I need to know to be careful (and keep my engine safe when I'll press start button lol )
Thanks for the help you can give me and for the others building their own engine.

 

[GIL]

Hi Gil,
I have an old cast r&d cylinder 7 port pv stroker +8mm and crankworks crank +8mm with 133mm rods. I've built my engine with kawi pistons and I haven't cut the skirt because pistons don't hurt crank webs at LDC. I've had riva pistons in hand, I've seen pics of Dominator pistons and side of skirt (and notch for boost port) on both aren't designed like kawi one. I'm wondering if I need to machine kawi piston skirt to clear properly transfert at LDC and what I need to know to be careful (and keep my engine safe when I'll press start button lol )
Thanks for the help you can give me and for the others building their own engine.

As far as cutting skirts on the Kawi pistons it's not that hard-just VERY time consuming! The fastest way to do it is to cut the majority of the metal off and then finish with a dremel and then 600 grit sandpaper. From what I know about cutting the skirts-the only reason we cut them is to clear the crank webs. I have run 5 sets of Kawi pistons until
this year and now I am running Dominator pistons. The Dominators only required minimal grinding to clear my webs of my RAD 5 mil crank.

 

[tricky1]

Hi Gil,
I have an old cast r&d cylinder 7 port pv stroker +8mm and crankworks crank +8mm with 133mm rods. I've built my engine with kawi pistons and I haven't cut the skirt because pistons don't hurt crank webs at LDC. I've had riva pistons in hand, I've seen pics of Dominator pistons and side of skirt (and notch for boost port) on both aren't designed like kawi one. I'm wondering if I need to machine kawi piston skirt to clear properly transfert at LDC and what I need to know to be careful (and keep my engine safe when I'll press start button lol )
Thanks for the help you can give me and for the others building their own engine.

The Kaw pistons can be used right out of the box on +8mm 133 rod setup..

 

[lerott]

Thank you Jason and Gil.

 

[cjbchopper]

Gil, you mentioned getting the right domes for my setup. Where would I find "in-set" domes for this?? I called ADA, they had not heard of these pistons. They sold me domes for Kawi flat tops, 24cc, they said it would make 200# compression. It only makes 125#s due to the piston not making it to the top of the cylinder. We are currently decking down the top of the cylinder to get the squish to .050. Seems like the best option. I am guessing that ADA sold me flat top domes for OEM style Kawi pistons?? Not Wiesco style Kawi pistons??

 

[tricky1]

Are the domes you have marked YAK86-24 ?