Gotta agree wholeheartedly. You can't tell all about piston integrity just by appearance. As Gary mentioned, out-of-round is a somewhat normal wear issue on a piston like this, but it was probably fine in the matchng cylinder it came out of...not the new cylinder. Even on automotive street engines in very moderate hot rods I've had, I had the machine shop match each piston to its bore. On a KLX engine that goes to 10000 rpm, this will be even more critical. Not saying it won't work, but it's not worth the risk or at least diminished performance or life expectancy. This is one of those areas that is not worth trying to cut corners.

 

When I put new pistons in my '67 Triumph they were out of round. They were made that way.

 

thats right, they are cam ground, they should be round at working temp

 

you guys are spoiling the bet..
it was a WIN WIN.
The point is:
the skirts are most likely worn,,,if the bore in not matched to the piston it will slap causing premature failure because someone wanted to save money.
We can discuss all day how much wear is acceptable to re use a piston in a NEW bore.
Personally, i never would do it.
Just my $.02

 

RTFM

Page 167 from the manual posted here.

************************************************** ***********************************
Piston/Cylinder Clearance
• Subtract the piston diameter from the cylinder inside diameter to get the piston/cylinder clearance.
Piston/Cylinder Clearance Standard: 0.035 -0.062 mm (0.0014 -0.0024 in.)
*If the piston/cylinder clearance is less than the specified range, use a smaller piston made within the standard diameter or increase the cylinder inside diameter within the standard diameter by honing.
*If the piston/cylinder clearance is greater than the specified range, use a larger piston made within the standard diameter.
*If only a piston is replaced, the clearance may exceed the standard slightly. But it must not be less than the minimum, in order to avoid piston seizure.
************************************************** *******************************

You can also use a long feeler gauge in the cylinder with the piston you want to use.


Don't take a simple job and turn it into a blow job.

Measure the piston and bore.....

David

 

I will send the piston to Bill just to be safe but I dont see how its worn much as the machineing groves are all still there from top to bottom, any apreciable wear would surely be noticeable as rounding off or the groves gon completly. But flame away I dont mind.