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Cylinder O ring

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Does anyone know the correct thickness of the original cylinder O rings?

I have a box of assorted O rings but the larger diameter ones seem to be too thick and the cylinder won't screw down far enough to allow the starter cover to fit.

 

David

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Thanks for measuring an original, the ones I have are about .105".

It's for the early engine from the Petro pump, the part no (33-2) used is the same from 1962 to 1972, maybe my home-made exhaust gaskets are slightly too thick, or perhaps the modern O rings don't crush enough. O rings are available in lots of different thickness on ebay, should I try some slightly smaller?

 

David

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Seems like it must be a combination of things but I believe that cylinder needs to screw all the way in. If not, the piston can't reach the top for the best compression.

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The cylinder was all the way in before I started the repair of this engine, as can be seen in this picture.

post-325-0-67092500-1422720084_thumb.jpg

 

This is as far as I can get the cylinder with the .105" O-ring, the gaskets were made from Klingersil C-4324 1/32" that I bought at a local engine show last year.

post-325-0-13248200-1422720105_thumb.jpg

 

I bought some O-rings the next size down at .079" (2mm) earlier this week, I managed to get the cylinder all the way down, but the cylinder tool T-bar got bent in the process.

post-325-0-21639200-1422720390_thumb.jpg

 

The engine will have to be stripped down again though, as it has lost spark. This is due to me fitting a later aluminium flywheel key when I replaced the flywheel with a later one. The flywheel must have turned when tightened. The key slot is deeper than the later crankshaft & the damaged key is now stuck. :banghead:

 

David

 

 

 

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These little suckers can be very frustrating to work on. I can attest to banging my head on the wall a few times, and I bet Wallfish would say the same!

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I had to remove the crankshaft to remove the damaged key, These early engines aren't as bad to strip down as the later ones though, the bearings don't escape as easily. I will need to made to a custom flywheel key for this engine, as it needs one smaller than the original but bigger than the later one.

 

David

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As I once read from an old dude that used to work at a shop that serviced O&Rs- "Anytime an O&R came in to the shop for repair, everybody would disappear!"

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