Hi; I need to replace the piston-ring in one of my engines. I have never done this before, are there any special tools you need or any special procedures to follow? Also with a new ring what is the proper ring gap supposed to be? And is the procedure for a standard ring the same for a dyke's ring? Thanks for any help.
Veco

Work one end of the ring out and very gradually and carefully push it back and up very slightly as you work your way around until it comes off. Reverse the procedure to install. Same deal with the Dykes. Bear in mind that the ring land is an important part of the seal and if ideally the piston should be replace along with the ring. Less than ideally you might be OK without it if the land is in good condition. I think the end gap should run around .001" Pretty hard to measure it in place.

I usually break to old ring in two & use the broken edge to clean the piston lands, clean the carbon out at the bottom of the land. Check the ring end gap by putting the new ring in the sleeve & align with bottom of the piston , check gap ,1 to 2 thousands. Most Dykes rings are pinned so they don't rotate & catch the ring end in a port , don't put the pin anywhere but at gap or you will break the ring when you put piston in sleeve. I clean the sleeve & piston with the finest Scotch -Brite . Wash the whole works with hot soapy water & spray with carb cleaner. I have always used medical castor oil when I assemble an engine . MAX H.

Yeah Max, I don't recall any two stroke not being pinned even with a plain ring but that would just be the ones I had apart of course. Even the plain end could hook a port. No sweat like that with the four strokes.

John

Most ringed Schneurle engines have pinned rings because the ports are so large although I just had a look at my OS 40SR which uses an unpinned Dykes ring but the exhaust port has a bridge in the centre. All the earlier cross flow engines had bridged ports so they didn't need pins either. In some ways this is a better system because then the ring can rotate and wear perfectly round.

Rings should always be removed and fitted in a spiral because this gives the least amount of flex and strain (especially important with a Dykes ring). Lift one end out just far enough so it can rest on the piston crown then very slowly work it around out of the groove. As it comes out the free end will slowly move across the crown. Installation is the reverse by twisting the new ring slightly until one end will just fit in the groove then work the rest in carefully.

If I remember correctly the proper end gap is about .0015" to .002" per inch of bore diameter.

And while we're on the subject, does anyone have Frank Bowman's details? I lost them in a recent hard disc crash

I have this:

Frank bowman
1211 N. allen
Farmington, New Mexico 87401-3568
(505) 327-0696

Also:

http://www.dol.net/~dave.reed/otto.html

OK guys, I pulled the head off of my Webra .50 the other day to make certain it had a dykes ring because some were talking about it in another thread. The ring gap is in the center of the back intake port, should I move it?

Assuming the piston hasn't been removed, leave it alone. I haven't had my 50 apart but the Speed 40 and 61 are pinned so the gap runs on a solid part of the liner. toward the rear IIRC. You can tell if it's a Dykes without taking the head off by looking in the exhaust port. A plain ring will be down a little from the top so you can see a bit of piston above it while a dykes is at the top. If you have had the piston out make sure the gap is at the pin when you replace it. If you compress the ring with your fingers and rotate it you will be able to feel it when the pin falls into the gap. If it ain't broke............

It is at the very top of the piston, I have never removed it, the engine runs well so I'll just leave it be. I might call Paul at Paul's model supply and run it by him though.

Hi Dave. With a case brain drift I forgot the whole point was that you wanted to replace the ring. Anyway if you decide you need to you have the info. Did anyone mention to make sure the rod is put back in facing the same way? There is generally a chamfer in the front of the big hole to accommodate a radius on the pin. Is the power down on your engine?

Sorry John my .50 is brand new, I just broke it in, when I saw the discussion I decided to see if I had an ABN or a Dykes ring equipped engine. It was then that I noticed the ring ends were in the center of the rear intake port. The engine runs great. As my old Italian neighbor that I grew up beside would say, I mak-a you veddy confuse, so sorry. I learned a lot about oil well pump engines when I was quite young from those old guys.

Oh, right. Veco didn't come back. Things just haven't been the same since my lobotomy! I have a Webra 50 on a Northstar. Equipped with a mousse can "pipe" it goes like heck, turning an APC 10 x 7 at 15k on 15%. I had to add head shims to keep from blowing plugs on those long steep dives in full labotomy. These are terrific engines.http://members.accesswave.ca/~parkla....html#Pictures