I have bought some new pistons for my Ruby. They are old stock and hence could be more than one decade old. The gudgeon pins are so tight in the pistons that they can't be pushed out by hand. They can be shifted a little using hammer and brass drift.
Is that normal for new pistons?
I guess that I can get the pins out easily after heating the pistons. But as the pins will be so tight after reinstalling, how can they be lubricated ready for starting the engine?
To remove, drop them in a pan of boiling water and let soak for a minute or two, then they should tap out easily enough.
You may find minor corrosion, in which case - depending on severity - replace the pins or give them a polish with very fine emery.
Some pins are a bit tight in their pistons from new. If the piston won't articulate freely at room temperature, as you surmise, trouble is in store. The usual way to deal with this is to warm the piston and lubricate with paraffin, and spin the gudgeon pin in its hole until it frees up a bit. You can hold it in a hand brace or an electric drill, just don't go crazy. Machining will take too much off.
You may do best to start off whizzing with a worn pin which will be less aggressive - it doesn't take much.
Hi Chris,
Thanks for that advice. it all worked out in the way that you suggested. The boiling water allowed the pins to slip out easily. As the pistons cooled I twisted the pins coated with kerosene and they freed up to the extent that I could still revolve them with my fingers when at room temperature. I think that there must have been a tiny amount of corrosion causing the interference with the pins.
Regards
Graham.
I’ve just been dealing with a similar problem today. I have an engine that was rebuilt about 30 years ago and left under a bench. The gudgeon pins were very tight and it was difficult to move the pistons on the rods. I drove out the pins and used a flexible ball type honing tool in an electric drill to clean out the pistons and allow the pins to rotate freely again.
