Villiers Lightweight piston ring alignment?
The continuing saga of my Lawnrider restoration! Following my previous thread I got the engine running quite nicely and starting and ticking over ok. All good, however ive now noticed i have a small oil leak from the crankshaft seal on the magneto side. maybe as things have loosened up as i have been running it on the bench. Curses! So ive ordered seals for both ends of the crankshaft so the flywheel has to come off again - at least im getting quite proficient at this now! Im assuming i just carefully drift out the oil seal on the magneto side as it has a metal outer ring, and then the reverse process to get the new one in? The drive side is essentially all rubber so should be easier.
As the crankshaft has to come out i thought i may as well replace the piston rings while it's apart - i wasn't going to originally as i seem to have pretty good compression, though there is some evidence of oil on the top of the piston though that may be as ive been running it mostly when cold before the rings have properly expanded? Could also be the valve stems/guides i guess but im not sure there is much i can do with those.
So my question is really how to orient the piston ring gaps? There are two compression rings and an oil control ring. Ive searched but can't find anything specific to this engine - and ive never played around with piston rings before so not sure if there is a general wisdom i need to apply!
I have the replacement parts manual (i can't find a workshop manual) and the exploded diagram suggests the gaps in the oil control ring and lower compression ring match and the upper compression ring is about 20 degrees off but this could just be for illustrative purposes.
Does anyone have any ideas?
Meanwhile the rest is coming on nicely with various bit of renovating and painting...in between engine fiddling...
You can change both the seals without removing the crank . Different ways of extracting them such as carefully drilling two opposite holes parallel with the crank and inserting two self tapping screws and either alternately hooking onto their heads in turn and pulling upward with a slide hammer or levering with a small pry bar or old screw driver. I’ve got an old Tecumseh special tool with hooks that slide between the crank and the seal and are engaged by a lever that pivots on the crank - semi effective as the hooks tended to break.
Piston rings are always on the move regardless of where they are installed ( other than pegged two strokes) so it doesn't really matter where you put them as if you were to go back and look at them after a period of running they will have moved - known as cyclic rotation. That said I always start off with no gap directly on the thrust side of the piston and the other gaps spaced out around the rest of the circumference of the piston - possibly over fussy , just don’t Line all the gaps up on installation.
All said and done, I’d just deal with the oil leak and settle for it being a vintage engine “with character”. That said, recently I had a 150cc Lightweight that gave me the run around due to main bearing bush wear allowing enough lift of the crank to affect the points gap and timing. Two new bushes sorted the issue ; so check your crank for lift!
Many thanks wristpin - i knew i could count on you! Great idea with the self-tappers, i shall try that.
To be honest with this engine, im quite enjoying learning about it, so being a lot more picky than it probably warrants! Although ive worked on my own cars and bikes quite a bit before ive never really dived into an engine, so this has been a nice way to cut my teeth as it were. Next stop, maybe i'll try to do the head gaskets on my Alfa V6 - or maybe not!
I agree, used to use an old small screwdriver to punch two small holes in old seal 180 degrees apart, either self tappers or sometimes the same screwdriver would be enough to prise them out. With a worn barrel, by the time new rings are bedded into the oval bore they will measure the same virtually as the old ones, Cords used to sell good oil control rings at one time, but I don't hear about them any more now. Oil control ones were in about four pieces as I recall.
All I got was a full page asking if I wanted to start my own website?