Wiseco Piston Comparison

[geezagillard]

I had the chance to compare these in the shed whilst I had things apart.

The 559MO5600 is being used in my track bike and I had to reprofile the combustion chamber to suit the dome shape.... but as you can see the 540MO5600 is much closer to standard and will be the piston I use in my next rebuild so I dont have to modify anything, a straight replacement by the looks.

Thanks to Caesar Gonzales via Facebook for the info

[KR-1R]

559PS/559M0 is 1986-1988 YZ125 ring pin 6 o'clock position (boost centreline)
540M05700 KX125 (+1mm oversize) is drilled for centre bridge holes - I'm not sure which other are drilled and which are blank
.
540M05600 KX125 1986, domed crown
http://www.wiseco.com/Catalogs/Powersports/Kawasaki.pdf

i think these are all 55mm long (skirt)
KX125 1986 540M05600 replaces 540PS which was a centre drilled skirt


KX125 1987 555M05600 defo centre drilled


KX125 1988-89 566m05600 single ring, undrilled, slight dish down


KX125 1989 578M05600 dual ring, undrilled


KX125 1990 589M05600
BACK view......FRONT view(centre bridge cylinder)


KDX125SR piston 13001-1346 ¥5,500 ea bare - ring, pin, clips are $ separate,
55mm skirt ~145g couple gram heavier than KR




with £3 cellphone endoscope Aliexpress 640x480 ... or get the £7 HD 1280x720 version
Lubrication holes are 40mm apart, less than KR (~43mm)


piston clearances
Wiseco 0.051mm
Wossner 0.06mm

WOSSNER piston comparisons
viewtopic.php?f=19&t=7562&p=72706

[Gerrit]

Bear in mind that if the piston skirt is too short on the exhaust side the exhaust port will be directly open to the crankcase around TDC with possible contamination of the fresh charge with exhaust gas as a result. Not good.

[geezagillard]

For better or worse I didn’t bother drilling any new holes to lubricate the liner between kips and exhaust ports and dont remember considering the length of the piston skirt. I do remember discussing the lubricating holes with “Wobbly” (my Two stroke tuner go to guy) and he said not to bother. To be fair I have completed about 6 to 7 track days with this setup and no issues with wear on the bore between the exhaust ports to report so that rings true. Power wise I am definitely on par if not a little ahead of most NSR250’s I come across so expect it’s somewhere between 60-65hp but haven’t confirmed with a dyno. I run no filter with race fuel otherwise standard.