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pitting in cylinder

Posted: Sat Jan 02, 2010 11:32 am
by gregvasale
How much pitting can be tolerated in the cylinder of an old hit and miss engine? If needed, can they be bored and fitted with a new piston? any idea on cost?

Posted: Sat Jan 02, 2010 4:16 pm
by Harold_V
I believe I'd be more concerned with the amount of overall wear than pitting. The very fact that there is pitting likely indicates that the cylinder is no longer round or straight, generally because pitting isn't uniform, plus the engine may have considerable mileage to its credit, resulting in uneven wear.

If you find the pitting to be uniform and the cylinder round and straight, assuming the pits are small, there's no reason why you can't simply use it as is.

I think I'd explore boring for a sleeve before I'd consider making a new piston. That, of course, depends on the condition of the piston. If it, too, is trash, you most likely would be better off to bore the cylinder and fit a new piston. More information would be required to make a respectable decision.


Posted: Sat Jan 02, 2010 5:53 pm
by Richard_W
Most of the time you can't buy an oversize piston for the old engines. So you have to bore and sleeve to fit your existing piston.

Minor pitting shouldn't be a problem as the rings will just slide over the pits.

Here is a list of old engine parts.

Richard W.

Posted: Sat Jan 02, 2010 6:15 pm
by gregvasale
The pitting is the result of neglect. I salvaged this from someones back yard where'it was exposed to the elements. The piston was stuck, sort of. Penetrating oil and some evaporust and some hammerblows with a brass drift removed it. The piston looks good, with only a little scoring. Rings came off without too much effort. I'm guessing the piston is tin plated too.

Aside from needing a magneto of some type, the only other problems are a stuck exhaust valve and the need for new freeze plugs as they have rusted away, then a determination of whether there is any un noticed cylinder damage. Whatever else I discover will be in the future.

This is a Monarch / Royal model U 2hp.

Posted: Sat Jan 02, 2010 8:51 pm
by dly31
You might be surprised how much wear and pitting those old engines will tolerate and still run good. If you get it where the piston and rings will slide freely, that's about all you need. Even when the piston is so loose as to clank on each stroke, they will chug away.

I personally would get it all cleaned up and the valves sealing and fire it up. If you want to restore it to new condition, that is good too.

Don Young

Posted: Sat Jan 02, 2010 10:11 pm
by gregvasale
any other suggestions on what kind of ignition and fuel system this might have had would be appreciated. Also, there was some kind of resilient spacer between the rod / cap. Any idea of what the material is, or what to replace it with?

Posted: Sun Jan 03, 2010 1:14 am
by J Tiers
Watch out on the boring idea.... needs material to accomplish it, material left after boring. I've seen teh results of one boring job where the cylinder broke off when running because the thin remaining iron wasn't up to the stress. And there was a reasonable-looking amount left.

Posted: Sun Jan 03, 2010 8:48 am
by steamin10
Yep, agree the old putters can run really well with more pitting than you would think to allow. They are a good low speed machine and as such are not all that choosy. Do the minimum amount of messing with the piston and bore, and reassemble.

A larger carb from a Briggs v-twin can work. They can be had relatively cheap if you dont have an original. They are volumetric, and can be tuned roughly to the rate the chugger needs. A slug of aluminum plate can be tapered into an adapter to mount it.

I have a small witte that needs a head (frozen) and other parts. It was a rusty barn thing, just cleaned it up and it is rolling nice. Lots of Emery work on the journals for exposed rust.

Posted: Sun Jan 03, 2010 9:32 pm
by dly31
For ignition, assuming it has a spark plug (there are other ignition methods), you have two basic choices. You can arrange a battery, a set of points, condenser, and coil like older cars had. Or you can use a battery and vibrator coil like the old Model T Fords used. You can adapt a regular set of ignition points or just make something. The points and condenser system fired the ignition with basically a single spark when the points opened. The vibrator coil provides a continious spark as long as the energizing contacts are closed and thus make it easier to start the engine. Be sure your sparks do not occur until just past top dead center, exact timing is not critical and can be worked on after you get it running.

These engines generally had only a very basic carburetor and when they are missing they can be made fairly easily. Of course, you could also adapt an available carburetor.

Don Young