Just a quick question for the engine builders. When fitting the pistons into the cylinders, do you: a) compress rings on pistons, fit piston to the cylinder off the engine then fit the pin and clip to the rod with the piston hanging out of the bottom of the cylinder. Or b) fit piston to the rod, then compress rings, then push cylinder over the top of the piston that way? I guess bonus points for anyone dodgy who uses method b above but without a spring compressor using a flat screwdriver or finger nails to compress each ring as you push on the cylinder. I've always thought method a was the only option but saw a video of option b and thought it looked easier. It's a pain in the butt putting the second clip on the piston without dropping it in the engine. Thanks
Always done piston in cylinder, then fit to motor. Small pistons, 2 stroke stuff, yeah, it’s doable but big pistons, oil control rings etc. you’re asking for trouble imo.
I've always used a piece of grey plastic drainpipe tube... it's a really good solution in place of a piston ring compressor... a plastic PVC drainpipe cut down, with a large ziptie (that you then release with a very small screwdriver)...the fact that it is flexible means it's super easy to remove once the pistons are in the cylinder. (Barrel offered up just after photo - option B).
Piston in cylinder then fit it to the rod. I found the lead in to the cylinder on ducatis isn't big enough to get the rings in easily when the piston is already on the rod
Piston onto the rod, to make sure the clips are on properly (hard to see when cylinder over the piston), then using a narrow strip of shim steel and a jubilee clip as a ring compressor. Tighten until the rings are fully in then back off a little & plenty of oil so it will slide and just tap the cylinder over the piston with the palm of your hand, once the cylinder's over the piston just undo the clip. Done it loads of times - easy as.
Fit conrod to piston, fit rings to piston, ring compressor, slide assembly in from top of block, rod passes through cylinder *edit to add: always been car engines, never done a bike engine yet
I'm always looking at learning new ways of doing things. On these engines you have put the piston and rod in from the top as mentioned by @Robert Colliver earlier then tightened the bottom ends up?
You can only remove conrods by splitting the crankcases. Unlike a car engine (or a Moto Guzzi*) where you can remove the sump to get at the rods and have to do that to remove/refit the pistons. M900 engine before fitting front cylinder: *Following a piston to valve incident on my Guzzi, I fitted new pistons but removed the rods to change the shells and check for straightness. It can be done from under the engine as the bottom end is car-like (tractor?) with a removable sump, though I still fitted the pistons to the (fitted) rods before dropping the cylinders over them as with the Ducatis.
I've only ever done this on a bevel and I found it was hard enough to insert the gudgeon pin spring clip without restricting the access even more by pre-inserting the piston. The lead in on the barrel was pretty good and allowed the rings to be compressed relatively easily by faffing about with fingers/screwdriver/plastic etc. This was a lot easier to do on the front cylinder as the barrel is supported by the studs but the rear cylinder was a lot trickier as I had to hold the barrel up at the same time as trying to compress the rings. I seem to remember supporting the barrel with a wooden block and applying a lot more faff. So time and some top quality faffing was my secret
Done it both ways but if putting piston into cylinder first, make sure you put a rag around the crank and cases to prevent the circlip falling into the crankcases.
My preference: On bikes with full length cylinder studs -a. Piston in cylinder first. On bikes with separate studs holding cylinder to crankcase and head to cylinder, -b. Piston on conrod first.
Thanks for the interesting conversation. I'm no wiser but will probably use the way I'm used to and pop the pistons in first and cover the hole in case i lose the clip. THere's kind of a way that you put your little finger through the clip so if it pops out it rests on the finger rather than falling into the engine or running under the bench in the garage. On a related topic I've noticed the clips can't bend much before they yield and are then no use. Even brand new ones Cheers
When i do pistons I always buy a few extra circlips in case they make a dive for the corner of the workshop or I bend them
I'm actually doing a BSA bantam barrel at the moment and it's got a lovely lead in for a small piston. This one is will put the piston on the rod then put the barrel on
