TOPIC:

It's hot, humid and gloomy outside. This is the time around here, work is done on the bike. Bossie's shed has A/C and soon I will be tearing her down to install the pistons at long last. I decided to weigh the new piston and compare it with the other's I bought two years ago. I was thinking I could make them all the same. They already are. Then I weighed the cast forged K 1015 Wiseco piston from 78. Big difference. Then a stock 903 66mm piston. Wow. It is said Kawasaki made their crank shafts heavier to compensate for the heavier pistons. Judging from the 903 piston I don't think this is the case or maybe it is. The billet Wiseco's are much lighter than even the 903's. When I take out the stock 1015 pistons, I will weigh them to compare.












I've been gathering the paint needed to do my tank. That will be in another thread. What not to use to clean you tank.
Steve

Just for fun.... slide that Wiseco wrist pin out a little further and start it into the ART piston... look and see how much (if any) higher the piston ring and top land are, vs the stock piston.

I've been comparing them to the 66mm piston. I'll show that too. Also I compared all the pistons with what John sent me from his Z2 site. I'll have to set something up inside to compare them all. I can't find my metal rule in this mess I call a office. Time to clean it up.
I'll take pics of all to compare with my Mic.
Steve

Here ya go. The top land is identical, the second is much lower and the oil rings are much different. We knew that. It looks as if the deck height will be the same.
Steve

What I'm finding hard to understand is, if the 903 piston is 8.5/1 and the 1015 is 10.25/1, they don't look that much different. Yeah the valve pockets are deeper but the dome isn't as radical as others I've seen.
Steve

The dome on the 750 is 10mm, taller than the 903. That being the case, wouldn't it make the displacement smaller too?
Steve

Displacement is just bore and stroke...from the top of the cylinder deck to the bottom of the stroke vs bore.
Combustion chamber doesn't come into play with displacement.
Are you sure your 1015 kit is 10.25:1?
Below is a stock 1015 ART piston vs a Wiseco 1075 10.25:1 piston.
The bigger Wiseco, both with pins installed, still weighs about 1 oz less then the OEM.
Just almost exactly 9oz for the Wiseco and 10.1oz for the OEM ART piston.






I removed the rings after this photo to weigh the ART piston......

Also, note that in my middle picture, the top flat of the piston, above the compression ring land and below the start of the actual piston dome, is about .015" higher then the ART piston.

The 1015 pistons are 2mm taller than the 903 66mm piston, 8.5/1. I know the are 10.25/1. The 750 Z2 piston has a 10mm dome. I'll try to measure the others with my mic.
Steve

I've used lots of Wiseco pistons over the years in tons of 2 stroke bikes (dirt and street) but only a few 4 stroke ones.
And, I sold all those bikes off well before there was 5,000 to 10,000 miles on them.
With respect to average street riding, city lugging, street blasting, WOT on the open road juking (etc) .... I wonder what the life span the 4 stroke Wiseco pistons are...?
Anybody have any with say +20,000 miles on them.

swest wrote: The 1015 pistons are 2mm taller than the 903 66mm piston, 8.5/1. I know the are 10.25/1. The 750 Z2 piston has a 10mm dome. I'll try to measure the others with my mic.
Steve

The extra length could be just a few mm of additional skirt length.... unless you meant from the top of the wrist pin hole to the top of the piston flat before the dome. ??

swest wrote: What I'm finding hard to understand is, if the 903 piston is 8.5/1 and the 1015 is 10.25/1, they don't look that much different. Yeah the valve pockets are deeper but the dome isn't as radical as others I've seen.
Steve

Bigger bore, even with same crown height / profile as the smaller piston still means more CC's being compressed in to the same size combustion chamber hence higher compression ratio.
All very basic stuff.

missionkz wrote: I've used lots of Wiseco pistons over the years in tons of 2 stroke bikes (dirt and street) but only a few 4 stroke ones.
And, I sold all those bikes off well before there was 5,000 to 10,000 miles on them.
With respect to average street riding, city lugging, street blasting, WOT on the open road juking (etc) .... I wonder what the life span the 4 stroke Wiseco pistons are...?
Anybody have any with say +20,000 miles on them.

Yes, the piston on the left is from 78 when I bored it out the first time. It's a forged cast piston. They don't make them anymore. Still within spec. At least 50,000 miles.
I guess crown is the best term for what I was talking about. the 750 crown is 10mm. The 1015 are around 5mm. I was playing with them on my coffee table. I'll take better measurements this morning on my bench. Too damn hot after noon.
Steve