To replace cast piston or not?

[NZ500]

I have a stock cast piston in my '90 k5. The cylinder has been sleeved and measures up like new (86.03). The piston looks like it's had quite a bit of use but only measures 85.90mm. The Clymer book says new is 85.905-85.920. So it's only just out of new specs. Service limit is 85.76.

Are the specs in book ok to go off? 85.76 seems like a lot of wear for service limit?

I've spent a lot of money and time on this and just not sure how safe it is to run. At least there isn't to much piston to bore clearance? Would it be possible that the piston is a used one off an earlier KX that is bigger from new?

[bleeding green]

if you have already spent big money on this then why not be safe and put a new piston in. seems like cheap insurance to me. just my 2 cents. good luck and happy holidays!

[Motorrad]

do a quick search on here regarding what happens when cast pistons get to the end of their service life...   

[Motorrad]

here...   looked it up for you..

http://www.kxriders.com/forums/index.php/topic,3327.0.html

[NZ500]

Thanks for your replies.

Re bleeding green, sounds like a good idea. It's just gotten rediculous is all.

Yeah I've already seen the horrible pictures, other wise I wouldn't have been concerned about running it. The piston and bore does measure up close to new specs is the odd thing. The piston had bad blow by marks. I wonder if it had a guts full of sand or was used before the cylinder was sleeved. I'll swap it out because I couldn't handle having this blow up now.

Did the Wiseco pistons ever get that cavity on the outside removed or was it just the custom ordered ones with the window in them?

Thanks and enjoy your Christmas.

[Polar-Bus]

I've spent a lot of money and time on this and just not sure how safe it is to run.

This is your most important comment. Far too many people "jump over a dollar to save a dime" . Replace the piston and ride worry free thereafter.

[sandblaster]

+1