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Saw these used 1394 wiseco pistons on ebay. is drilling holes in pistons like these a good idea? and is it worth the effort if it goes right?
thx
Scott

Was wondering about this myself remembering Vance and Hines did it many a year ago on there early pro stockers.

While were on this subject how about piston porting for the top ring to seal better also?

Mainly on the street usage for me with a blast through the quarter several times a month.

KZB2 650 wrote:

Was wondering about this myself remembering Vance and Hines did it many a year ago on there early pro stockers.

While were on this subject how about piston porting for the top ring to seal better also?

gas porting? holes from top of piston to behind the top ring. uses the pressure from inside the combustion chamber to force the ring against the cylinder wall

gas porting, been there done that, dont think its the way to go, I would be scared about putting a hole in a skirt like that, seems like it would open up a chance of skirt failure to me

I've seen that done before, even cut skirt off the piston(leave very little of skirt left). Holes don't look big enough to hurt and spacing looks like it would be ok. I would be concerned if holes were bigger or there wasn't much space between the holes. I believe they call them Pro-Lites by Wiseco, but I could be wrong. R.C. Engineering used to drill holes in valve buckets the same way to lighten them.

heres a set of gas ported pistons,cant tell really good from picture:whistle: sawwy .we used to cut the windows in our dirtbike pistons to lighten them up but ive never tried it on a kz piston and would rather not try since there is a lot more to lose if something goes wrong!

I've never saw cut pistons like that. Gas porting is a good way to go if you're running loads of compression,keeps top ring sealed tight.

look at this full size. The gas ports are visible around the outside of the crown.

The skirts are pretty thin anyway. I can't see much weight savings from the holes. Thinking on it, I don't know if they would hurt or help oiling. Less surface(skirt-bore interface) means more pressure but more oil means less surface is needed.

Seller's photos are not good enough to tell if the skirts are scuffed/galled. If they are used and skirts are nice, then it's pretty clear that the holes don't hurt If considering purchase, I would want some much better photos prior to submitting a bid.

-Duck

Post edited by: Duck, at: 2006/11/02 08:58

Gas ported pistons are typically used for drag racing applications only ,general rule is an et pick up of up to 1/10th. sec but it does wear out rings faster as they are pushed out to cylinder wall by the pressure.

I remember the RC pistons with holes cut in the skirts.If it worked that well Byron would still be doing it and I have not seen a set of those type of pistons in many years.

Wiseco Prolites are actually slipper pistons- very small skirts.It's a way to keep big pistons lighter but they do wear out cylinders more quickly than full skirt type due to piston rocking in the bore.

You may want to check prices on a kit before bidding.since it will cost more per item when buying a set of jugs ,wrist pins, rings,head gasket.

KZ engine family has a rather long piston skirt when compared to the slipper type pistons in modern bikes.

Keep in mind that if you cut the skirt down that not all piston to cylinder clearances are measured in the same spot on all pistons.

Gas porting is definitely a plus for ring seal. Head over to www.rehermorrison.com/ , Tech Talk and read the article on Gas porting along with other tips from some of the best in the business.

larrycavan wrote:

KZ engine family has a rather long piston skirt when compared to the slipper type pistons in modern bikes.

Keep in mind that if you cut the skirt down that not all piston to cylinder clearances are measured in the same spot on all pistons.

Gas porting is definitely a plus for ring seal. Head over to www.rehermorrison.com/ , Tech Talk and read the article on Gas porting along with other tips from some of the best in the business.

OK,I take it back - If David Reher says gas porting is good and no accelerated ring wear,that's more than good enough for me.