GT550 nikasil pistons from cruisinimage

[yeadon_m]

Folks,

Please see this link. I'm sharing in case anyone else is data hungry and also because I'm interested in views on piston pin tightness of fit.

http://www.kettleclinic.co.uk/kcforum/v ... =16&t=7408" onclick="window.open(this.href);return false;

Cheers!
Mike

[Vintageman]

I had same problem fell right through with gravity only. Maybe not as loose and throwing a Hot Dog down a hallway but, you can rock it a little when in piston. I did not use. Think about it. If the piston and pin move about each other here, it's not the intent and will only get worse with time. I thought about knurling the inside but how would I do that? Found OEMs

Too bad he won't take feedback well. No big deal $. what's important is he make a tweak, revise the design, and get it like it should be. It is so nice he does this but too bad he won't fix stuff, I am sure he could.

Wish I knew who in China he is working with

[yeadon_m]

Vintageman,

That was my worry too, so I did a bit of googling, as you do, and found this:

By and large, problems with piston, connecting rod bearings, crankshaft and seals can be avoided simply by following the recommendations made in the manufacturer’s shop manual. The single exception to this is in the fit between piston and wristpin, for the very high temperatures in a modified engine tend to cause a breakdown in the lubrication between pin and piston. Trouble can be avoided in the racing engine if the wristpin is a light, sliding fit through the piston; it should slip through of its own weight, without forcing, for if it is tight enough so that you have to tap it through with a mallet, you eventually may have to remove it with a hydraulic press. Too-tight fits may be corrected by using an old wristpin as a lap, and a dash of some fine, non-imbedding lapping compound to polish out the piston’s pin-bore to size.
http://www.datafan.com/Horsepower_Blog/ ... -handbook/" onclick="window.open(this.href);return false;

In other finds, I learned that pin to piston clearance should be 1-2 thou. Thats as big as a piston in a cylinder and even that big bore where clearance is a small % of diameter allows the piston to fall right down the bore. So a forced fit, even a gentle one, may be on the lower limit. Obviously, a pin can be too great a clearance but I don't know what the upper limit is. On the crusinimage pistons, the pins slid through under gravity but they didn't fall down clunk, but slid. A fellow in UK has fitted 3 sets to 550s from this seller, with no issues as yet.

Cheers,
Mike

[Coyote]

1-2 thou. seems like way too much. Logic tells me the pin should be snug. You want the pin to ride around the bearing - not revolve in the piston pin hole. The bearing, pin and rod small hole take the wear. The pin to piston fit should never change. My 3 cents (price has gone up )

[Vintageman]

Mine fell out with a clunk to the floor even when I applied light oil to surfaces (video I should post).

I have never ever seen that in my short life until I had the "cruzinimage" experience

Way too loose IMO... did not measure... have no inside tool that small. I foresee the gap being hammered egg shaped very soon.

I agree no press fit. They do move side to side... just forget to put a circlip in properly and we learn that real quick. I thought no press was for difference in rate of expansions could cause stress on piston, but I was guessing.

Check this out page 18 and page 25 I see fit as
-0.002mm to + 0.006mm
or
-0.0000787" to +0.000236"

http://www.oldjapanesebikes.com/mraxl_G ... /index.php" onclick="window.open(this.href);return false;

What I did just learn is knurling is not the way to fix too loose a fit. So junk piston

fun stuff

[yeadon_m]

I can't disagree with your analysis of what Suzuki appears to spec here. I'd definitely prefer a light push fit for the reasons you state!
Cheers,
Mike