Is there a specific position to place the joint of each piston ring ?

It is frequently recommended that they are fitted with the gaps at 120 degree intervals to ensure a better gas seal...

Personally I never do that, I just put them at a slight offset to each other..It keeps things simple with the ends of the ring compressor...

In the past I have just fitted them in line and it doesn't seem to make much difference...

It is interesting that 2 strokes have the rings 'pegged' to stop them getting caught in the ports...This could be taken to infer the rings move radially when the engine is running...

If that is the case then positioning the rings gaps during fitting would be a pretty academic exercise...Ian

email (option): ian@wright52.plus.com

It is interesting that 2 strokes have the rings 'pegged' to stop them getting caught in the ports...This could be taken to infer the rings move radially when the engine is running...

If that is the case then positioning the rings gaps during fitting would be a pretty academic exercise...Ian [/quote]

It doesn't necessarily mean that the rings turn in the piston, but makes sure you put the ring ends in the correct place to miss the ports on a 2 stroke. I once fitted new rings in my son's 125 2 stroke, the piston had to be fitted into the barrel first and then fitted to the conrod. All the rings were pegged, but I didn't put the piston at exactly the right angle in the barrel and snapped a ring as I slid it up Very annoyed and another new set of rings, I didn't make the same mistake twice.

email (option): horror@blueyonder.co.uk

('It doesn't necessarily mean that the rings turn in the piston, but makes sure you put the ring ends in the correct place to miss the ports on a 2 stroke..)

That's may well be the case..I suggested it only as a possibility...

Despite the fact I've lost track of how many engines I have rebuilt I have always forgotten to look and see whether the rings have moved when I next stripped one of them down... ...

Consequently I haven't really determined whether the rings move or not...Ian

email (option): ian@wright52.plus.com

I'm sure that they do move.

This article argues the case :-

http://www.diagnosticengineers.org/journal_%20articles/Ring%20Gaps%20vs%20Knowledge%20Gaps.php

I'd always had the idea that it was simply done as good practice to avoid immediate blow-by on first start up. It certainly can't hurt and is probably a good idea on three-piece oil control rings, where spring pressure is likely to keep them relative to each other.

Piston rings rotate in their groove @ 1/2 engine speed - well documented but no one knows why - first recorded by Sir H Ricardo.

I don't both where the gap are - BUT, you need to get them right way up and in the right order - particularly modern (50's onward) rings.

Two stroke are a different matter - they are pegged to stop the ring rotating and snagging a port - though there are some early strokers and some much later outboard motors which have un-pegged rings as the ports are so small.

It is frequently recommended that they are fitted with the gaps at 120 degree intervals to ensure a better gas seal...

Personally I never do that, I just put them at a slight offset to each other..It keeps things simple with the ends of the ring compressor...Ian [/quote]

I cannot use a ring compressor, I find it too fiddly and easy to break rings. I use the 120 degree method and fit by hand very slowly and carefully.

(' I cannot use a ring compressor, I find it too fiddly and easy to break rings. I use the 120 degree method and fit by hand very slowly and carefully.')

Risky on an M20 unless you have three or four hands...The weight of the barrel alone is enough to break piston rings...

I use a Snap On 'ratchet' ring compressor I've had for years...It's pretty easy to use with the piston supported on a pair of parallels resting on the crankcases...Ian

email (option): ian@wright52.plus.com

parallels !! or resting on the handles of a pair of pliers or in my case metal-shears.

tried many different ring compressors over the years, but still use fingers - but then again I mainly work on strokers.

Fitting piston into barrel on the bench is one option, usually easier to fit a wrist-pin, than struggle with a heavy cylinder and rings.

Always stuff something in crankcase mouth for when the rings do break...

I've found I can't move an M20 barrel with any degree of accuracy using one hand..or even support its weight for very long...Especially so if I try to fit the rings or the gudgeon pin with the other hand......

I guess I need to spend more time in the gym... ...Ian

email (option): ian@wright52.plus.com

I would always fit the piston on the rod first, then slide the barrel on. For some reason, (I can't remmember what it was) I couldn't do it that way on this short stroke 2 stroke. So I asked my local bike shop how they do it and was told to put the piston in the barrel first, which was the only way to do it on this bike. I hate 2 strokes

On a 4 stroke I try to get the ring gap at opposite sides but making sure the ends of the rings aren't in the cutaways in the barrel. On my ES2 and 16H, the tapper on the barrel edge was enough to get the rings nicely in the barrel without ring compressors. I was only lowering the barrel into the right position and it just slide straight on.

email (option): horror@blueyonder.co.uk

Yes a nice taper at the bottom of a barrel is nice, unfortunately for various reasons I tend to be involved in bigger/oversize engines and these tend to lose the internal chamfer.

Many piston ring clamps are for automotive applications where the piston is fitted from the head end of the cylinder - damn near impossible without a ring compressor.

I do seem to be taking the piston in cylinder then fit the lot to the con-rod option more and more - I have a shoulder injury, so currently lack strength in my right hand, so have to get a bit creative using above technic + things across the crankcase mouth to support the weight.
Thinking about the problem overnight also helps.

Many ways of doing it - I have found best way of ensuring you don't break the rings - is to have a spare set handy!!

My ring compressor is the automotive type. It suits fitting from the top. If I have to fit from the bottom, I use shimstock and cable ties.

email (option): pvlietstra@gmail.com

This simple tool keeps both hands free for mess around with the rings:

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Cheers, Michiel

email (option): m.wijbenga@hotmail.com

Well after chipping no less than three oil control rings whilst fitting my new piston to one of my Enfield's (never happened to me before).
I decided to fit the piston differently (never done it this way before on a bike).

The bottom edge of the barrel/liner is very thin and sharp. So I used a Dremmel to make a small chamfer, and with a new set of rings, installed the piston into the barrel. I cut some tube legs to support the barrel whilst I fitted the gudgeon pin.

I've still got to fit the exhaust and petrol tank before a test ride. Ron
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email (option): ronpier@talk21.com