piston weight /engine balance

I recently bought a wiseco 1197 kit.the pistons are quite abit heavier than stock art kz 1000 pistons.about 17.6 grams to be exact.anyone have any ideas on how to lose the weight with out weakening the piston.lighter wrist pin? maybee. I guess I'm mostly worried about the engine balance. thanks for your time ,walt

as long as the piston weights are all close which they should be,dont worry about it.

Inline four cylinder engines are "self canceling", meaning if all the components weight the same, it is in balance. The pistons could weigh 100 lbs each, but as long as they were exactly 100 lbs each, it would be in balance.

Wiseco pistons are very close to each other in weight.

Jay

the pistons are heavier because there bigger, all that extra horse you get will far out way the extra piston weight. I thing they grind, machine or file the bottom of the skurt to balance

thanks guys,I'll just get them all done to the lightest piston on my paint scale. I just tig welded the 900 crank [didn't add or lose any material, just stirred it around alittle] everything should be in pretty good balance at the bottom. the next thing willbe the valve springs[I've heard it is quite important to have them all close to the same spring rate and pressure] any ideas?

buy a set from APE to match your cams;)

jimmybon wrote:

the pistons are heavier because there bigger, all that extra horse you get will far out way the extra piston weight. I thing they grind, machine or file the bottom of the skurt to balance

you probably wont notice much if anything if you take some material off of the pistons unless you are a competitive racer, and making the piston shorter by taking material off of the bottom makes the piston more likey to "rock" in the bore and make it wear out faster and make the cylinder out of round. its a common problem on big bore single cylinder motors when the bore gets too big. they have to keep the piston "short" to keep it from hitting anything. From what I hear, drilling holes in the skirt is the best way to lighten them up as it doesnt shorten them any

wallyworld wrote:

thanks guys,I'll just get them all done to the lightest piston on my paint scale. I just tig welded the 900 crank [didn't add or lose any material, just stirred it around alittle] everything should be in pretty good balance at the bottom. the next thing willbe the valve springs[I've heard it is quite important to have them all close to the same spring rate and pressure] any ideas?

If you want to perfectly balance your pistons, you would need a triple beam scale to weigh them. Straightness/balance of the crank and balance of the clutch basket would probably make a more noticable difference but for a street bike these pistons weight differences won't be enough to warrant the effort required

my electronic paint scale measures to the tenth of a gram [a very small drop of paint].just out of curiosity,how does one balance this crank/rod assembly?I'm assuming it requires a teardown. rods would be mached for weight.then I can't guess what would be next.If anyone knows an easier softer way ,then hook me up.straightness is easy enough with a dial guage and an index rod. balancing the clutch makes good sense as it is a large diameter.anyway, thanks for all your input.

you need a special machine to balance a crank, check out APE or Falicon, you have to be spinning the crank, to balance it, its not just getting the parts to weigh the same, its the centrifugal force of the mass that plays the biggest role.
if you have 2 chunks of material that weigh the same, that are connected to a shaft that is spinning, but one chunk has more material out farther that the other, it wont be balanced even though the parts weight the same. if that's not clear, I'm not too great at describing stuff... say the 2 chunks started out the exact same shape, but you drilled a hole in each one, but not in the same place, they still weigh the same because you removed the same amount of material, just from different spots. the one with the hole closer to the shaft has more mass/material further out than the other one that has its hole farther from the shaft.
its kinda like balancing a tire on a rim, only they don't add weights, they remove material in the proper location
I know a guy that has a set of scales like that, but he doesn't weight paint:P :whistle: :laugh:

More than you ever wanted to know about crank balancing

This page has a couple of photos of a crank in the balancer.

www.aperaceparts.com/crankwork.html