Balancing Cruzinimage Pistons

[Drewski]

I've just weighed my new GT750 M cruzinimage pistons kits, weighing the piston, wrist pin, rings and clips......the right piston needs about 4-5 grams taken off. Normally, I'd go for removing weight from the pin bosses but they look a bit thin. Has anyone else had to shave a bit of weight of these pistons? If so, where did you take it from? Any other advice appreciated.

TIA, Drew.

If anyone is interested in the weights, for 0.50 over kits, inc pin, rings & clips, I got

L1...........308.4gms
L2...........307.4gms
R............312.7gms

Pins varied between 64.9g to 65.8g
Rings " " 10.3g to 10.8g

[Coyote]

Don't bother. . You'll never know it unless you are building a 12,000rpm racing motor.. Actually, those are surprisingly close. The .5 over Suzuki pistons I just installed had a variance of almost 9 grams. Runs fine. Those are as close or closer than what came from the factory back in the day. Apart from that, there is no 'safe' place to grind on them.
My plan was to put the heavy one in the middle, but I forgot all about it when building. I have no idea where it wound up. Proceed!

[Drewski]

I probably wouldn't be too bothered normally either but I'm having the crank balanced so it makes sense I guess.
Pics of inside of piston:-

[Coyote]

This is not coming from an expert, but if it were me, I believe I would chamfer the inside of to skirt cutouts.. Go slow, it's not gonna take much.

[yeadon_m]

I agree with Coyote, the weight difference is irrelevantly small. Stock Suzuki pistons for the GT750 I had rebored some years ago differed by 5g low to high and it was a smooth motor.

If you wish to balance it, I would not take meat off the pistons. The density of the alloy is low and you may need to remove a scarily large volume to get rid of 5g.

Instead, search for matching piston pins (16mm OD, 50mm long, I recall) which suit other bikes which has a smaller ID. These are heavier, by about 5g. I bought I think a Malossi 200cc single piston pin and its snug in my GT550 piston, the lightest of which was 16g less than the heaviest (completely difference batches of 550 pistons from Suzuki can differ by this much).

Cheers!
Mike

[Drewski]

What happened was that I left the crank to be rebuilt and balanced at Chris Applebee's. I rang the other day, spoke to Dave there, confirmed I wanted the crank balanced once rebuilt and he asked me to weigh the pistons and get back with the figures. When I rang back, I spoke to Chris this time, told him the weights and he suggested I took some off the heavier piston. Could Dave have originally asked for the weights to help him set the crank when balancing? I wouldn't have thought so as it would all change if the pistons are replaced later on. I'm fairly sure that the way they look at it at CA's is why bother spending time accurately balancing the crank if the pistons are out anyway. I've taken weight of pistons before but they've had much more substantial pin bosses than these.

[Drewski]

One other thing....are folks using the clips that come with the cruzinimage pistons or using OEM ones? And.....same with the rings?

[Drewski]

Anyone know if other pistons are similar in weight to the CI ones ?

[Coyote]

I used cruzinimage circlips with my .5 over Suzuki pistons. . I did this because the clips that came with the pistons would no go in. A nice fellow forum member (bill in okc) had done the opposite and used Suzuki clips with his CI pistons. He sent me the CI clips and I used them. I think Paul Miller sent me the wrong clips. I tried, son tried, son's friend tried, the simply would not go. The CI clips fit fine. There was .002 difference in the wire diameter. The big difference is the CI clips had the extended wire that kicks toward the center. That makes installation a snap.
Here's a pic of the piston and the clip that wouldn't go.

[yeadon_m]

Yes, the Cruisinimage pistons weigh very similarly to Suzuki (heavier stock versions, around 170-174g bare).
Here is the heavier piston pin I mentioned:
http://www.ebay.co.uk/itm/MALOSSI-GUDGE ... true&rt=nc" onclick="window.open(this.href);return false;
Balancing a crank alone is, I believe, done by drilling mass out of the crank webs. I've never done this or had it done, so I'm not sure. I'd always balance crank separately from the top end, for what can be known later, by the next owner, unless this is done and assumed?
Cheers,
Mike