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Villiers two cycle engine connecting rod bearing woes


Are there any Villiers experts among us?

I am working on a 1948 Villiers MK25C 147cc two cycle engine with a 55mm bore and 62mm stroke. My particular engine must have had a lot of hours on it because so much carbon built up behind the rings that the ring wore thin enough to jump past the pins which keep the rings in place. It did not cause any major failure, but it scored the cylinder a bit. I am mainly concerned about the big end of the connecting rod bearing. This particular engine uses a three piece crankshaft and a one piece connecting rod with brass and steel needle bearings. You have to press the crankpin out to replace the needle bearings. I chucked the crankshaft in my lathe, locked the spindle and measured 0.003" of slop in the big end of the connecting rod bearing off the top of the connecting rod. I cannot find any literature which says what the running clearance should be. Based on the fact that this engine runs on ~10:1 oil mix, I would imagine the play in the big end of the rod should be 0 to 0.001". The side to side clearance is excessive so i wonder how the thrust faces of the rod look like, if there are any. I would like to know how to proceed with replacing the connecting rod bearings, as the crankpin does not appear to be pinned on either end. It may require a special alignment jig which I do not have for re-assembly. I have already purchased new big end ball bearings for the crankshaft, and some brass stock to make new sealing bushings out of. I simply need to know what to do about the connecting rod, and how to proceed about finding a new oversize piston and ring set for this engine. Villiersparts.co.uk has not been answering any of my requests, which is really frustrating.


Scotty 2

Hello Chris
Post in the Down Under section. There's a few Villiers freaks down this end of the world. Also PM me your email as a have a book with some information on the 25C in it. Sadly it hasn't got the information you need. It's 16:1 mix ratio ;)

They are an interesting engine with spark speed limitations.

Cheers Scott