Oversized rings? Piston play?

[Bill Decker]

All righty then. I finally got a bit of time to spend on the K301 that came along with the 123 we brought home. Everything seems good down low, but, at the top of the stroke, there seems to be quite a bit of play side to side in the piston-cylinder clearances. The motor is bored .030" over already. I am wondering what the options would be on this. I really do not want to throw a boatload of money at this engine, especially in machine work, but I would like to get the tractor up and running to determine the shape the hydro is in, and just to have it mobile as a backup for my own 123. At one time, you could obtain oversize ring sets (Chrome moly?) that would be a temporary fix, we used them on cement mixers and pumps that couldn't be taken out of service very long. Once winter came, they could get a proper going through. How much play is too much? Worth the effort to re-ring it as it sits?

[mgonitzke]

What's keeping it from running as-is? It sounds like the piston is pretty worn, and putting in a set of rings isn't going to be worth it. If you're just trying to see if the hydro works, run it as-is.

[Bill Decker]

I figured since the motor is out, I could throw a set of rings at it that might keep the fog bank down a little and have it a bit more usable until I can come across another motor that I can afford. Pretty much just a band-aid to try and squeek a little more life out of it.

[Klapatta]

How much of a ridge groove can you feel with your finger nail at the top of the bore? Depending on the conditions factory bore wear tolerances do not always have to be adhered to on a scripture basis (IMHO). Personally, I consider out of round a larger issue than taper and that can usually be found about 1 1/2" to 2" down inline at the exhaust valve. I rebored one K series that was still running despite over 1/32" skirt movement. That one took .018 just to clean the bore true. Quality aftermarket piston and ring kits can be had for about the same price as a Kohler replacement ring set. A fresh piston would have to delete some side play. I have had very good results with the Rotary brand piston kits. And I'm still unsure of those overpriced Mahre style pistons, I feel they seem to score at the skirt too easily. Assuming that roughly half the piston slop is from the bore and the other from the worn piston the whole assembly could well tighten up nicely with a new piston installed. If there are no deep scratches on the bore a ball hone may be all there is needed to allow the rings seating in.
Obviously, one can't expect to get the engine life cycle that a fresh rebore would achieve.
But it could make for a cheap long lasting fix.

[Racenitro]

if you do put in a new set of rings, you will need to remove the ridge. If you don't, you will break the top ring, the piston or both. You need to actually remove the ridge before taking te piston out because the rings will catch ont he ridge.

[Bill Decker]

I took some time and mic'd the bore, I think it's not too exotic, I am just going to try to build a fire in it, and make the wheels turn first, then proceed as things develop. Of course, when I got started putting things together from the boxes that were with the tractor, I find I am missing the main engine shroud, which it van live without for a bit, and the fuel tank bracket, which is kinda handy. And of course, while I know darn well there were 3 of each on the shelf (or more), the last time we clkeaned things out and did a scrapyard run, we got a little too cold blooded...now I am working the phones a bit. I had a half dozen K motors laying around at one time, but when things here got crazy, a lot of stuff went down the road...I guess maybe I should build some inventory back up?