Gudgeon Pin Fit

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Re: Gudgeon Pin Fit

Postby jack clegg » Sat Aug 03, 2019 11:54 am

A modern forged piston should not require heating to fit the pin. Cast pistons, such as the Indian type fitted to Royal Enfields do require heating to fit the pin. Low expansion alloy saves a lot of burnt fingers.
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Re: Gudgeon Pin Fit

Postby 56G80S » Mon Aug 05, 2019 8:00 pm

At the risk of being derided, if the piston is slack on the gudgeon pin is it possible that the gudgeon pin then operates on the piston and the pin remains semi stationary in the little end?

With adverse consequences?

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Re: Gudgeon Pin Fit

Postby jack clegg » Wed Aug 07, 2019 11:16 am

Yes. However all pins move in the piston. It's just that the older/cheaper types have to warm up first. Note the oiling holes in the piston bosses above or below the pin. I had a little end which was tight & the only movement was that in the piston bosses. Not good but it still functioned.
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Re: Gudgeon Pin Fit

Postby bodgert » Wed Aug 07, 2019 11:49 am

A lot of modern car engines have the pin captive in the conrod and all movement is in the piston

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Re: Gudgeon Pin Fit

Postby Andy51 » Thu Aug 08, 2019 5:59 am

Not just modern cars. My old '61 Austin A55 had the gudgeon pin clamped in the small end by a pinch bolt. Andy

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