580 bored .060 over

[gmcarroll1]

I have a 1992 sp with a white 580 rotax. this maybe a stupid question, but i just bored my motor .060 over and didn't know if anyone know off the top of their head what size it would make the motor. i know u can measure stroke and bore to get the size. but i dont have any measuring tools or specs on the motor yet.

Thanks Greg

 

[brcombs]

Funny, just did this a couple of weeks ago after a ring failure on a 76.5 piston failed. Your 60 thou oversize is 1.5mm over. A=pi*d^2/4 x stroke = Vol

You can't just take the increased diameter, you need to figure the displacement of the entire new volume and subtract the old volume. See this excel table (Vtotal is Vmm x 2 pistons):

D A Stroke Vmm Vtotal(mm) Vcc
D1 76 4534.2 64 290186.2 580372.5 580.4
D2 77.5 4717.3 64 301906.8 603813.6 603.8

Difference = 23.4 cc increase over stock bore.

Oh, one thing I ran into, I have a WSM head w/ 35mm domes, and found once I torqued down the head, the new Wisco pistons were now hitting the edge of the head (pistons too wide for the domes) at TDC. I had to take head to machine shop to mill down (make wider) the edge of the domes so piston would fit. Be sure you check this out after you torque head down before you try starting motor!!

 

[gmcarroll1]

Thanks

Wow u really know what your talkin about. me , would get lost in a heart beat.lol


Thank you for the info. Greg

 

[gmcarroll1]

Carbs

After boring the 580 .060 over. Would it be better to convert over to twin carb or should i just leave the one?

Thanks Greg

 

[gmcarroll1]

Hey

Today i was assembling my motor and after i install the head i rotated the motor by hand and found that the forward piston hits the head, Just like u(brcombs) said.

This week i will take the motor to the shop so they can mill the head so the pistons don't hit.

Thanks again Greg