I just tore down a stock bore motor with one of these "CP 14:1" pistons you guys are talking about. I'm going down to the factory that I do machine work for. They have a gram scale that reads to the thousandth of a gram, its a very accurate scale. I have several other pistons to weigh so I can give a complete rundown if anyone would like. Everybody is quoting about 3 grams difference between the HPR and RW.

 

cool, that will be interesting.
I'll have my motor apart this coming weekend, and I'll weigh my old first generation Pami 11.2:1 piston on a gram scale as well. I bet its a ton in comparison. and also the stocker. but my scale only weighs to the .01 gram.
lets be sure to weigh them all with their own wrist pin as well, since they are all no doubt different in length and wall thickness.
also when my piston comes in later on this month, I'll weigh it to see if its the same as the version you have.
how many circlips, one, both, or none? so that we maintain exacting conditions...

 

Just out of curiosity, what kind of diference are we talking about when it is only 3 or 4 grams???

Also, Mister HP that still would be good to know for inquiring minds.

 

less than 1/4 oz. - the weight of a nickel, aka a one finger bag!

 

[img]i/expressions/face-icon-small-smile.gif[/img] I was looking for what kind of power difference???

 

Tire pressure, barometric pressure, a headwind, the need for a haircut will all make far more difference than the weight difference in these two pistons.

Ron

In retrospect I am currently re-evaluating my understanding of piston weight. I do look forward to finding out which is lighter.[img]i/expressions/face-icon-small-wink.gif[/img]

 

Well darn it, our gram scale does not go high enough to weigh any of the pistons.
So I weighed on a digital pound scale that reads to the .001 decimal place.

Stock piston - 2.225 lbs.
Pami 11.2:1 (5 year old so called "boat anchor") - 1.090 lbs.

Now this scale has a pretty high capacity, not certain how super accurate it is at weights this small, but I did weight them both twice and the results were the same each time, and regardless of accuracy I do have faith that the pami is lighter than the stocker, in spite of the higher dome.

I won't have the 14:1 for a few more weeks.

EDIT - OOPS - I have no idea how I did this, but the above is a typo - I meant 1.225lbs on the stock piston [img]i/expressions/face-icon-small-confused.gif[/img][img]i/expressions/face-icon-small-blush.gif[/img] and also as mentioned the weight may not be accurate due to the scale used but the identification of which is lighter holds true.

 

anyone care to grab their spec. sheet on these pistons, the gram weight should be listed ???

Also, what is the diameter and length of the pins used on these pistons ? Just curious.

 

400 grams or 14.2OZ.

 

As I am reading, the above new lightweight pistons are gas ported , any feedback on how long the rings are lasting, as I have been told that gas-porting is terror on the rings, expect less than one season before re-ringing, hear the results are good but becomes 2-stroke like maintenance doing top-ends all the time, feel free to inform us on the pro's and con's on gas-porting please.