Merco 61 Posted March 19, 2019 Share Posted March 19, 2019 Hello, I,m in the process of renewing shaft bearings on an old but fairly good OS 120 Surpass .The gudgeon pin is firmly seized in the piston bearings.I stupidly allowed the liner to slide out so piston is no longer supported.Obviously liner cannot be replaced until gudgeon pin is removed.As only access is via hole at rear of crankcase,a rather difficult engineering challenge.I need to revolve the pin back and forth to release the seizure.I wonder if a suitable sized taper tap,sacrificial,could be carefully wound into the pin to give some turning power?The pin seems to rotate OK in the small end bearing.Any suggestions appreciated. Quote Link to comment Share on other sites More sharing options...
Braddock, VC Posted March 19, 2019 Share Posted March 19, 2019 Have you removed the almost invisible wire circlip that retains the gudgeon pin? Quote Link to comment Share on other sites More sharing options...
J D 8 Posted March 19, 2019 Share Posted March 19, 2019 Could you use a taperd " stud extactor " they do come in small sizes. Quote Link to comment Share on other sites More sharing options...
Jon H Posted March 19, 2019 Share Posted March 19, 2019 I have had this problem a bunch of times. It was a somewhat short sighted design in my view. If the hole went straight through at least you could put a punch through from the front and get it out. In the past i have removed the ptfe pad and (after cleaning) glued a wooden stick into the pin and then pulled it out. Its a bit dodgy doing it that way but it worked on one engine i was playing with. Quote Link to comment Share on other sites More sharing options...
flight1 Posted March 19, 2019 Share Posted March 19, 2019 after removing the ptfe bung, find a good quality self tapper that just bites the inner of the gudgeon pin, turn until the pin rotates ( ie screwin with a bit of force) and you will then be able to pull it out. just done a os fs 40 and 60 this way and they were both well gummed in as there was that nasty caster residue due to fuel will caster in it being used for many years. Quote Link to comment Share on other sites More sharing options...
Alistair Taylor Posted March 19, 2019 Share Posted March 19, 2019 A squirt or two of switch cleaner will loosen gummed up castor oil quite well. Available from maplin.....oh. I'm sure it's available from other electronics suppliers. Ali Quote Link to comment Share on other sites More sharing options...
Merco 61 Posted March 19, 2019 Author Share Posted March 19, 2019 Thanks for all tips,much appreciated.Yes,did note the invisible circlip.The self tapper extractor worked a treat and gudgeon pin slid out easily. Whilst in Boots,I noticed a cheap DIY dentistry set,comprising a probe shaped like a shepherds crook ,and a little mirror and scraper.The probe,which is of very tough steel,was ideal for wrinkling out the circlip and cleaning out its groove.No use yet for the mirror.Shaft bearings both out without too much drama so should be plain sailing now.Thanks again Quote Link to comment Share on other sites More sharing options...
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