piston size
- Thread starter blaster64
- Start date
there isn't any other letters or numbers?. that could mean its for a .050 over bore?. most of the time when its a stock pistons they put std or some thing on it i do beleav .
In my experience, .050 would be .050" oversize. Stock bore being 66.0mm, then a .050" oversize piston would be 67.25mm (every .010" equals .25mm)
If it truly does have ".50" stamped on the piston crown, then it's a .50mm oversize and would be a 66.50mm (pay close attention to where the decimal point is).
I wonder what brand of piston it is, since Wiseco (in my experience) always has the model number of the piston written on it. Wiseco's are easy to read too; the last four digits of the piston model number is the size (example: 573M06600 is a stock 66.0mm bore Wiseco piston for the Blaster).
After you've bored your cylinder oversize, you may be curious about your new displacement (# of cc's). Here's an easy way to figure it out...
Bore (mm) x Bore (mm) x Stroke (mm) x 0.7854 / 1000 = # of cc's
For a stock cylinder bore with stock crank, 66 x 66 x 57 x 0.7854 / 1000 = 195.008cc
If you're boring your cylinder to .060" then you'd have 67.5 x 67.5 x 57 x 0.7854 / 1000 = 203.973cc
For a Vito's +3 stroke crank, change the 57mm to 60mm, and for the Hot Rods +4 stroke crank, change the 57mm to 61mm.
I hope this is more helpful than confusing...
Yes, someone has been in there before and bored it oversize. You bore and hone the cylinder liner if it is worn and no longer "true" or to clean up damage to the cylinder liner caused by part failure.
I'd have a machine shop check your current cylinder bore to make sure that it's okay. There's a reason that piston shattered, and you need to make sure that it wasn't because of a worn cylinder bore.
Years ago, back when I was young and dumb, I rebuilt the top-end on an '85 Suzuki LT250R Quadracer. The piston that I took out had a broken skirt on the intake side. The cylinder looked good, so I had it honed, installed the new piston and gaskets, and put it back together. The quad ran for a couple of weekends and then broke another piston skirt. I knew there was something wrong at that point, so I took it to a machine shop. Turns out the middle of the cylinder bore was about .010" (0.25mm) bigger than the top and bottom of the cylinder bore. Since there was so much extra clearance in the middle of the stroke, the piston was able to rock back and forth and finally it hooked the bottom edge of it's skirt on the edge of the intake port. The lesson here is to get your bore checked out so this doesn't happen to you.
when ur piston says 0.50 it is NOT a 50 over bore... the .50 means half a millimeter meaning .020 over.... ur piston is a 20 over next size would be .030 or .040, .40= a millimeter(67.00)
In your last line, you meant to type .040 = a millimeter (67.00)
Absolutely right...these over bores we're talking about here are fractions of an inch increases in bore diameter, we're not adding 50cc's when we bore these cylinders .050" larger.
The machine shop will inspect your current bore and let you know what size they will have to bore it to.
