Bought new wiseco piston,

[ryanfoley]

A while ago i bought a wiseco piston for my bike(99 yz 125). SO i go to instal it every things smoothe and then i go to start it, klank,klank, klank, klank, klinke. i hit the kill switch as fast as i could. this was a loud clanking, VERY VERY BAD SOUNDING. I tore it down about 4 times and double checked every thing and could not firgure out what the problem was. SO i ended up instaling the old piston with a new ring on it. The bottom of the new wiseco pistons has a small indent on the back side of it, so im guessing it was hitting the rod or case? but they both pistons seemd to be the same size. I know that the wiseco piston is a one size fits all, as far as, A, B, C, D clyinders go, could the piston been too small and i should have waited for it too expand? Do you guys have any clue as to what might have been happing?

 

[podia]

on the older weisco piston set, i think the ring got some marking for which side up?

is ya power valve still in place?

my 02yz125 have got rattling sound, but much quieter than ya.

i can't figure it out yet, will tear down this weekend, will watch ya thread as well

 

[Moto Squid]

The piston/cylinder clearance should be 2-3 thousandths...did you spec your cylinder??? Did you even glaze the cylinder....

 

[jmics19067]

What do you mean by a notch in the back side?

If you have a mark in the piston on the bottom of the skirt where it would try and ride over the intake port I would strongly suggest measuring your cylinder bore and checking piston to cylinder clearance.

If the piston is too small or the cylinder worn out your piston can be racking in the cylinder catching a port.

 

[ryanfoley]

you know i really dont know what it have hit to make that dent on the piston, i got a micrometer? i just know its the right tool to measure the bore but it doent have millimeters so im gonna get one with millimeters, does any body know the correct conversion? thanks, im gonna rip into it now.

 

[A-RustyDemon]

Wisco Piston.. #726PS Piston Size 53.94mm x 0.03937 = 2.124"

 

[ryanfoley]

hey thanks alot rusty now i just gotta figure out how the heck to read this thing