milling the bottom off my pistons??

I was putting a new cylinder head gasket on my 81 KZ1100 but I broke the tail off one of the pistons. I ordered a new used one, it never showed up. I ordered 2 more new old stock. When they got here they were 107 instead of 961. Can they be used together? They seem to weigh the same. If I can find another 961 (my 1st choice) I'll put it in. But if the I find 2 more 107s (2nd choice) will they work? Or would my 3rd choice work?? Mill all four of the original pistons down. This is because I have seen some really short pistons in engines of that era. I mean almost 1/2 as tall.   

My personal opinion would be "no" to milling the skirts as this area controls the piston running "square" in the bore so reducing it may allow the leading edge of the crown to contact the cylinder wall. "Slipper pistons" you speak of are specifically engineered to work with with a reduced skirt and overall weight and are not modified stock items (as I say, only my opinion)

I think your rite. Any opinion on the 701 vs 961 pistons. They are both 75mm, 701s are heaver and have a harder alloy above the rings.
 

I leave that one to the guys on here that are intimate with these motors - generally speaking "lighter is better" with any moving part 

What model are the heavier pistons from ??
For the road the weight doesn't matter as long as all four pistons weigh the same so that the pairs cancel each other out and maintain balance.
 

GPZ1100

MB wrote:

GPZ1100

GPZ1100B model i presume.
As long as they aren't GPZ1100A unitrack ( which won't fit ) they will do the job.

I looked at the box they have the same part number. The new ones have the number 107on them, they weigh 10.1 grams. The original ones have 961 on them three of them weighed 10.3 grams (including the broken one). And one of the of the original pistons weighed 10.4g. The broken one might have weighed 10.4g before it broke. 

The numbers on them are just casting batch numbers and the weight differential will be within factory tolerances.
You will hardly ever find a production bike that has precision weight matched components.

From what every one has to say, there are the same.Those are just quality control numbers, batch/factory/shift. and the couple grams differences are within speck. Unless I want to go drag racing. Too old for that.