Page 1 of 2

S4 Cylinders

Posted: Sun Dec 21, 2025 12:50 am
by BrianReynolds
Hello all, I am assembling a 57 Square 4, just about finished the bottom end and starting to think about installing the cylinders. I have a lifetimes experience rebuilding British bikes but this is the first S4.Trying to figure out the best way to replace the cylinders, several ideas but I thought I would ask the experts. The 2 methods under consideration are to secure the pistons on wooden supports, fit clamps and lower the cylinders. The other idea is to partially insert the pistons in the cylinders so the pins are exposed then support the cylinders on suitable wooden strips at the correct height then insert the pins when rods are aligned. I am interested in learning how others do this, any responses appreciated. Thanks

Re: S4 Cylinders

Posted: Sun Dec 21, 2025 2:25 am
by Simon.Gardiner
Is this Mike Loehr's method?
viewtopic.php?f=21&t=12933&p=90473#p90472
(Also condensed into a pdf in the website Members Area 'HowTos')

SG

Re: S4 Cylinders

Posted: Sun Dec 21, 2025 10:12 am
by Chris Sealy
When I built my 52 Mk1, I lay the bottom end on its side, on rags, timing side down. I then pushed the barrels sideways onto the pistons.
No worries about anything slipping and breaking.

Re: S4 Cylinders

Posted: Sun Dec 21, 2025 11:56 am
by chris.shearwood
I'm no expert but I had success with the "pistons inserted in the cylinders" method:
viewtopic.php?p=90276&hilit=ceiling#p90276

Re: S4 Cylinders

Posted: Fri Dec 26, 2025 1:06 pm
by paul.jameson
For many years my favoured approach was to hang the cylinder from the top frame rail with bungees, of appropriate number and strength such that the cylinder was weightless. You can then fit the pistons into the cylinder one at a time by appropriate tilting of the cylinder.

That method fails with flying colours when you have to fit the cylinder to an engine whose bottom end is not in the frame. So for such cases I use the ring clamps and rods under the pistons method. I find that some combination of the various different diameters of rods I keep to make studs from, and/or lengths of hex bar will always support the pistons as necessary.

Re: S4 Cylinders

Posted: Fri Dec 26, 2025 11:12 pm
by nevhunter
IF you warm the Pistons a bit the Pins should slide in easilier. DON'T DROP any circlips. Don't forget the thrust side changes from front to Back. Nev

Re: S4 Cylinders

Posted: Sat Dec 27, 2025 5:38 am
by david.anderson
Before I fitted new liners to my 4, I turned a taper to the bottom edge of the liners, same as was on our singles originally. That means I do not have to worry with ring clamps. So I fit all 4 pistons to the conrods, then I place wooden blocks to support 2 diagonal pistons a bit higher than the other 2 and then lower the cylinder onto them with just finger pressure to help the rings through the taper into the bore. Then lower the cylinder and engage the other 2 pistons into the bore. I generally do have a person assist with the lowering but it can be done on my own. It is much faster than having to worry with ring clamps. So if you are going to fit new liners, make sure that the bottom edge is tapered before fitting the liners.
David

Re: S4 Cylinders

Posted: Fri Jan 02, 2026 11:37 am
by markus.nikot
I mount the pistons on the conrods and then hang the cylinder on a stand with an arm. I can easily lower the stand, which makes it easy to insert the pistons. The water canisters serve as counterweights. The pistons are missing in this picture; it was just an assembly test.
4Gcy.jpg

Re: S4 Cylinders

Posted: Fri Jan 02, 2026 6:18 pm
by klaus gerhard
Many roads will take you to Rome. Here is a contribution that was developed by Herman Noord from NL. I have tried it but I went back to the traditional way!

Re: S4 Cylinders

Posted: Sun Jan 25, 2026 8:21 pm
by bill.bowers
We slung the block on a cord threaded between the cylinders and then over the frame above. It was then very easy to lower the block in a controlled manner over the pistons.