Gudgeon pin help

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Gudgeon pin help

Postby ajsm18 » Fri Jan 10, 2020 11:18 am

Hello,

I'm rather embarrassed :oops: to ask this question but here goes...

Inspired by the tales of building a bike from a pile of different bits, I've decided to try and finish stripping down a G80 bottom end I acquired 20+ years ago, specifically, to remove the wire wound piston before getting the crankcases apart and seeing how good or bad what is inside is.

The gudgeon pin is part of the way out, although I can't remember if I started removing it and got stuck or if it was like that when I got the engine.

Over the Christmas holiday I thought I would try and press it out using a long bolt and various sleeves and spacers plus a blow torch. I got it to be about 3/4 inch out one side of the piston but no further. In a spirit of "trying" to do things properly, I bought a gudgeon pin extractor tool from ebay and set to again with plenty of heat. Unfortunately, it was still stuck so I thought I'd apply some leverage to the tommy bar on the extractor. Here's the embarrassing bit :oops: , I snapped the end off of the extractor tool and the pin still won't move any further!

I may be able to find someone to turn the end of the tool down so it can be used again but, meanwhile, does anyone have any ideas on how to get the pin out, please? I really don't want to destroy any of the parts but am not sure what else to try.

Many thanks

Mark

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Re: Gudgeon pin help

Postby SPRIDDLER » Fri Jan 10, 2020 3:04 pm

ajsm18 wrote:Thanks for the suggestions, Spriddler. I wasn't clear in my initial post but the piston is still on the rod.

Ah, understood Mark. The misunderstanding in my original post is now corrected to read.............

That's a bind, especially if the wire-wound is still serviceable.
Since the conrod is still there and as Mick mentioned I think my next speculative step might be to try to push it back into the piston (not too hard though) with the piston heated and examine/clean up the circlip grooves.
Last edited by SPRIDDLER on Fri Jan 10, 2020 5:23 pm, edited 6 times in total.
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Re: Gudgeon pin help

Postby ajsm18 » Fri Jan 10, 2020 3:31 pm

Thanks for the suggestions, Spriddler. I wasn't clear in my initial post but the piston is still on the rod i.e. the pin is only part of the way out of the small end bush and moves freely on it.

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Re: Gudgeon pin help

Postby Mick D » Fri Jan 10, 2020 4:51 pm

Hi

Thoroughly clean the exposed area of the pin and piston bore, lube with acetone / ATF mix and press the pin back into the piston. Examine the circlip grooves for burs etc. and remove any found then applying copious amounts of acetone / ATF to the inside of the piston and heat to the crown with a non igniting source, (a clothes iron or similar), press the pin from side to side repeatedly, it will come out, be patient and gentle.

Regards Mick

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Re: Gudgeon pin help

Postby ajsm18 » Fri Jan 10, 2020 6:28 pm

Thanks Mick, I'll give that method a go. Is ATF/Acetone a good substitute for Plus-Gas?

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