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Alamo 2 H.P. Piston and wrist Pin


Help for new restorer. I have been tutored, but even he has no answer. Does the wrist pin free float within the piston with only the ring holding it in? If so, should there be little to no play, because when we removed the ring it broke and noticed grooves in the ring from where the wrist pin had been rubbing. We don't know how long the ring was on the piston. (original??) Also, how much play is allowed on the piston arm to the wrist pin?

I will be getting new rings and wrist pin.

Thanks in advance for the help.







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Hi Glenn-
Some of these old engines used a piston ring at the pin bore to keep the wrist pin from hitting the cylinder and still allowing it to free float. As long as it does not bind the pin there is no need to do any fitting. :eek: Actually you can save some money and just use one of the old rings out of one of the top 3 grooves at the wrist pin since that one will not hold any compression any way. :brows:
I am not sure about your last question but I will guess that you are asking about the wrist pin to connecting rod clearance. I do not have any spec to offer but my experience has been to see if there is a "clunk" or slop in the wrist pin when moving the connecting rod. If it is not really sloppy let it go. Even if it is worn badly the only problem will be a noise generated when running. It won't hurt anything and you can re bush the wrist pin if the noise bothers you. Or just leave it be referring to it as character earned by hours of running time when showing it to others. Do not use a broken ring to secure the wrist pin as the pin will leave gouges in the cylinder wall causing expensive repairs to be needed.:shrug: But a used ring will hold the wrist pin in place for the next hundred or few hundreds of years to come.
Dave Reed
Otto Gas Engine Works:wave:
2167 Blue Ball Road
Elkton MD 21921-3330 USA
phone 410-398-7340

Greg Mosley

Greetings ggoodearle, Go with Tom's and Dave's advice. A very simplistic way to retain the wrist pin. As far as clearance goes .001-.002 is good. If excessive clearance is in the pin eyelet and piston skirt, take it to an engine machine shop and have a pin hone clean it up and make an oversize pin. Usually not necessary though. Also..., Welcome to the Gas Engine World. Its a Great Pastime and a lot of good people out there to help out. It is Very Addictive. Best of all we have Enginads to bring it all together. Enuf Said.


Thank you for your insight----- again I'm new to this all. And, yes I was referring to the wrist pin to connecting rod.


---------- Post added at 01:30:28 PM ---------- Previous post was at 01:29:19 PM ----------

Thank You also for the Info. Just getting started