Which model Thwaites is this?

[cobbadog]

In the past I have purchased over sized rings for a completely different type of engine, a 2 stroke mower engine. When I checked the ring gap it was too tight so I very carefully filed the end off the ring until I got the correct gap. It still runs perfectly for long periods of time under load so it did not harm the ring in any way.
I forgot to mention that the ring gap should be taken at the bottom of the bore where technically there is no wear. Thanks for reminding me / us Fowler Man

[FOWLER MAN]

In the past I have purchased over sized rings for a completely different type of engine, a 2 stroke mower engine. When I checked the ring gap it was too tight so I very carefully filed the end off the ring until I got the correct gap. It still runs perfectly for long periods of time under load so it did not harm the ring in any way.
I forgot to mention that the ring gap should be taken at the bottom of the bore where technically there is no wear. Thanks for reminding me / us Fowler Man

Hi,
Thanks Cobbadog, it was always normal practice to gap the rings with a file as you say, but you shouldn't fit oversize rings in a standard bore.

We did fit non standard rings like "Cords Duaflex" and "Hepolite Oilmaster" in worn bores to take up the wear, restore compression and reduce oil consumption. ( Cheaper than a re-bore).
Some of these rings looked standard, some were laminated and some oil control, (scraper),rings were specially developed with expanders behind the rings to keep them in contact with the bore.
These were also supplied in plus sizes for engines that had been re-bored in a former life. (Google up "cords piston rings").
Fred

[cobbadog]

Yes, you are correct about not fitting oversize rings in a standard bore but I was between a rock and a hard place and as it is for Rally purposes only it does do much running but when I start it up I do run it for a while. Obvious issue with this is that the rings are out of shape to the bore but as the bore was somewhat worn to start with and only being run every now and then this was the decision I made. To buy any pistons for this mover is a bit tricky but fortunately under the house are around a dozen extra mowers almost complete so they are my spare parts department. I have done the right thing wit the full restoration of my Model 1 Victa mowers, one in a very rough looking state but still dragged out and used to cut long grass and the other was the whole hog, paint and all even duplicate decals were purchased before they became extinct. So I don't always do a rough repair but sometimes it is just for fun and sometimes I purposely fit a wrong part so that the die hards have something to whinge about, then I tell them I did it just for them, to annoy them endlessly.

[FOWLER MAN]

Hi Cobba,
I can't be a diehard because you certainly haven't annoyed me at all. I'm just glad that your fix worked for you.

While I'm on, I forgot to mention in my previous post that the top ring in those "Cords" and "Hepolite" ring sets was stepped to dodge rhe wear ridge at the top of the worn cylinders.
Fred

[mechman]

I believe those rings were actually called step dodgers.
Norm.

[FOWLER MAN]

I believe those rings were actually called step dodgers.
Norm.

Hi Norm,
They were in deed called step dodgers.
Fred

[cobbadog]

They have many different names around the world, either way they do have a place and a job to do.