Wiesco Piston

[Randy Kirkbride]

Does anyone know if a Wiesco piston (407P6), listed for a '77 - '82 KTM 175, will work in a '74 silver motor?
Thanks

[Kip Kern]

I am going to brush away the cobwebs and say no.  I messed up and tried to put later model pistons in a early jugs and all was well until I tried to set deck height and noted inches instead of thousands!  The later pistons are shorter than the early ones. Someone verify this as that happened last year and I have slept since then!

[Rocket]

The later pistons are approximately 10mm shorter than the early style pistons.  I know this for sure, because I happen to have a new style that came with a bike that needed the old style.  Cylindar got bored and then I figured out the problem, same as Kip, trying to set deck height.  Fortunately found early piston and clearance was perfect.
Rocket

[Randy Kirkbride]

Thanks Guys,
Just to make sure, this is not a piston for a black motor.

[imported_n/a]

Randy,

The long-skirt piston fit KTM 175s from '72 up to early '76 models, as I recall.  The short skirt, I believe, came about as the "new" 175 top end was based more closely on the KTM 125 that had just been released, also.  And until Al Buehner can get the long pistons remade, you will most likely not find one.  

Check with Dr.2stroke and see if he can help you.

Glenn

[Randy Kirkbride]

Thanks Glenn,
Are you saying that a piston for a black motor 72 would be the same as a silver motor 74?  This piston is for sale & we're trying to figure out if it will work before we buy it.

[imported_n/a]

Randy, a black motor '72 piston and a silver motor '74 piston are interchangeable.  Make sure the piston is really from the '74 and has the long skirt.  I don't know if you have the comfort of waiting, but I have two long-skirt pistons for engine projects.  I could measure the bottom of skirt to piston dome dimension for you, probably tonight, and let you know tomorrow.

Glenn

[Randy Kirkbride]

Glenn,
That'd be great if you'd do that & let me know.  
Thanks

[Larry Perkins]

That piston is the wrong part # for the 76 and back bikes.  It is definitely the later one and will not work in the 72-76 motors-silver or black no difference.

[Randy Kirkbride]

Thanks Larry

[Rocket]

Early 175 motors have 7 fins on the jug and the late model 175's have 6 fins.
Rocket

[Randy Kirkbride]

Thanks Rocket,
I was aware of the difference in the cylinders, but I thought they changed them when they changed the color to silver.  My goof.[8]