Mismatched pistons

So I get my cases apart, pull my crank and find this..... :blink:

:blink:

I just noticed the skirts being differant,what size pistons are they?

Check the Weight of the pistons, you want them all the same weight, hopefully within a gram, but at least 3. Big differences will cause vibration, Crank Issues.
Same bore size and Dome for even compression/ power/ force on the crank also.

Wireman- I'll measure when I get home from work and post the size.

Motor Head- Yes I planned on weighing them all with my digital scale once I make a wrist pin press and thanks for the tolerance estimates.

If all else fails Id say try to match 1-4 as a set and 2-4 as another according to the piston skirts

I just weighed up the ones I got in a bib bore kit. Pistons varied by 1 gram. Wrist pins by .5 gram. Mix and match to near zero difference.

Ive seen crazier shiz though. Thats proof many people have no business working on bikes. If someone is taking the time to pull a top end, they might as well do it right.(Im sure they got lucky regarding the weight issue) :whistle:
Thats ok, I have to pull the bottom case half off the motor in the bike I just bought cheap. They broke off 2 bolts on the lower case, JB welded crap and cross drilled the bolts trying to remove them. Time to EDM them I guess.
Some goof balls have no business working on anything.

This should be everyone's motto
"Lord grant me the bravery to fix things I know I can fix, the strength to accept the things I cant, and the wisdom to know the difference"

It seems like Im forced to tell some homeowner that the previous hack artist who did their plumbling/electrical work needs to be beaten with his own tools on just about every job I show up on these days!! :sick: :woohoo:

OldSchoolZ-It's funny you mention the broken bolts, I broke 3 of the main crank bolts and 1 of the bottom case bolts while preparing to split the cases. One hour later, after smacking each one with a pointed drift, drilling and an easy-out everything was kosher. I would also suggest heat if they wont budge, martin_csr suggested that for stubborn exhaust studs.

wireman-Measured the pistons with my crappy calipers and came up with 70mm.

OldSchoolZ wrote: Ive seen crazier shiz though. Thats proof many people have no business working on bikes. If someone is taking the time to pull a top end, they might as well do it right.(Im sure they got lucky regarding the weight issue) :whistle:
Thats ok, I have to pull the bottom case half off the motor in the bike I just bought cheap. They broke off 2 bolts on the lower case, JB welded crap and cross drilled the bolts trying to remove them. Time to EDM them I guess.
Some goof balls have no business working on anything.

This should be everyone's motto
"Lord grant me the bravery to fix things I know I can fix, the strength to accept the things I cant, and the wisdom to know the difference"

wireman wrote: If all else fails Id say try to match 1-4 as a set and 2-4 as another according to the piston skirts

That's what I thought since they run as sets.

Could you take a Dremel and shave the bottom of the skirts on the heavier ones?

Just curious.

I would take this as a sign that you need need a big bore kit,maybe even block :woohoo:
Wayne