Compressing piston rings?

Need to get my pistons up into the jugs on my KZ750-four. In the past I have tried popcycle sticks and lubed hose clamps. I've got a good beveled edge on the bottom of all the cylinders, but getting the rings in is still hard. The popcycle sticks were almost useless and the clamps, while they worked to a degree, kept trying to go inside with the pistons. In fact, I broke a new ring trying the clamps.

So I got to thinking about it. I'm going to try cutting some straps out of a thin aluminum soda can, just wide enough to cover all the rings. I will include a few tabs at the top, bent out to act as stops against the bottom of the cylinder bores, and then use the hose clamps to hold the straps against the rings (with just enough tension to hold the rings closed, yet be able to slip down as I lower the block.

Anyone see a problem with this?

give it a go no harm in trying

polkat wrote:

Need to get my pistons up into the jugs on my KZ750-four. In the past I have tried popcycle sticks and lubed hose clamps. I've got a good beveled edge on the bottom of all the cylinders, but getting the rings in is still hard. The popcycle sticks were almost useless and the clamps, while they worked to a degree, kept trying to go inside with the pistons. In fact, I broke a new ring trying the clamps.

So I got to thinking about it. I'm going to try cutting some straps out of a thin aluminum soda can, just wide enough to cover all the rings. I will include a few tabs at the top, bent out to act as stops against the bottom of the cylinder bores, and then use the hose clamps to hold the straps against the rings (with just enough tension to hold the rings closed, yet be able to slip down as I lower the block. Pop sticks suck, get some bendable metal little thicker than soda can stuff. you can bend it as needed to clear the studs on each cylinder. Bend out each end for grip during the squeeze. works fine. I used a cheap chineese filter wrench that was plyable, worked real well. The metal only has to bend a little to get it between the studs. And you hear that everone? popsickle sticks suck. Don't bring knives to gunfights. Even us porr folks can survive this one.

Anyone see a problem with this?

Well, I had thought of that, but I want to do two cylinders at a time, and don't have anyone local to slip the block down as I would hold each metal strip tight. That's why I thought of gripping them with the clamps.

I think a part of the problem was that I might have had the clamps too tight. I understand that they have to be loose enough to slid down the piston as the block comes down, but they seem to be too tight on the piston when tightened even lightly.

I'll give my idea a try and report on what happens. Thanks for the replys!

ne of the reasons they tighten up as you go down the piston is that it actually gets bigger toward the bottom of the skirt. motorcycle pistons are what is called cam ground they are done this way because of heat expansion.

I've gone the hose-clamp route and it didn't work for me because the tightening screw on the clamp is at the same level as the tightening bands...so the skirt hits the screw as you drop the jugs onto the pistons. However, the same principle works with the new generation ring clamps except the clamp tightener is offset lower from the tightening band...which is why they work. I have returned to using the extra set of hands (my wife) and wooden sticks to hold the rings in the pistons while I wiggle the jugs down.-

Yep, that's why I was thinking of making little straps (perhaps from a Coke can). If made wide enough. then the clamps could be placed near the bottom, and little notches could be bent outward at the top. That would keep the straps from entering the bore and keep the clamps low enough not to interfer. Basically it would be a miniture version of the old type car ring compressor. Should work if the clamps are tightened only enough to keep the straps around the rings, but not tight enough to cause much friction.

OK guys, not trying to be hardass here but I just don't get this whole ring compression issues.... Sure is it somewhat time consuming, well yeah but difficult to to the point of chop sticks, popsicle sticks, coke cans etc...

I just don't get why this is so difficult... Maybe the 750's are harder...

First off, insure ring orientations are correct for all pistons and clips are 9n place correctly. Spread a little oil around the rings/piston walls. Rub a a little oil on the inside of the cylinder walls...

Insure Cylinder Base Gasket is in place.

* Raise pistons 1/4 up to TDC (17mm ignition nut)...

* Gently place the cylinder onto and over the domes of 1/4 pistons.

* One at a time, with your fingers compress and rings in slowly & gently lowering the cylinder over the rings in a back and forth process until all rings for both 1/4 pistons are in the sleeve.

* Then rotate the crank til 2/3 piston domes are in place in the sleeve and slowly do the same for these 2 pistons and raising the pistons (17mm ignition nut) until all 4 piston/ring sets are in place.

I've done this several times on my KZ build and worked out with no problems every time... Need patience sure but it truly wasn't that difficult.

OMR

Have you tried nylon tie straps?

Only on Mr Happy... Oops... :blush: :woohoo:

I used popsicle sticks only because my finger nails are too short. It was a piece of cake. Clamps and ring compressors are only going to get you into the bevel of the cylinder. It's not like on a car engine where you transfer from the ring compressor into the cylinder. I just let the weight of the cylinder rock down on the rings rocking the piston and cylinder one side and then the other side (1 & 4) the (2 & 3). Not difficult at all because the bevel acts like a funnel and the pisons go right in.

I never use clamps, just moly lube the sleeves chamfers. prepare to wood spacers to keep the block in the air, rotate crank till the two inner pistons rings just get in the chamfer. work around with sticks or screw driver, going around.

another tip, if piston gets cocked a bit going in, tap it from above with a wooden stick to straighten it.