Author Topic: Gudgeon / Wristpin Tool  (Read 417 times)

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Offline Astute Greaser

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Gudgeon / Wristpin Tool
« on: May 19, 2022, 09:54:34 AM »
I had a problem getting a gudgeon/wristpin out of a piston recently. Same when refitting the piston. My thumbs weren’t strong enough to push on a small socket, to get the pin too move. Used a sash clamp, bits of wood, small sockets and lots of care to get around it but with rings fitted it was risky and the other barrel/jug was in place. Not elegant. Sure, others have tapped it out with a hammer but that’s really bad for your big ends.



Walking around Lidl, spotted an Oil Filter Wrench for not a lot. I thought, could I use this hmm and so I bought it.



The clamp works by the nut travelling up the screw, pulling the clamp body and strap, tightly onto the oil filter. So, I unswaged the screw from the clamp, using an old screwdriver and the nut as a jack.



The gudgeon pin is 14mm o/dia & 8mm i/dia. The screw is M14x2p (actually 13.7mm dia) and the stub of the screw is 8 mm. Fortuitous!! Perfect for the 52mm diameter piston on my 200. I’m sure it will fit others.
I hacksawed off the swage and lightly rubbed a file over the stub. Then drilled through the clamp 12mm pilot & tapped M14x2p



Couple of cable ties linked, to get the length for the loop and we have an Extractor. I only used one loop but you could need to use one either side of the gudgeon for extra strength/stability.
Note: Remember to remove the circlip from the far side of the piston. Trick, I found, was to push a large Philips screwdriver through the centre of the gudgeon, twist and lightly push. It catches in the tang of the circlip and pushes the circlip out. True it mullers it but you should replace these anyway. Also, the gudgeon only needs to be pushed out enough to clear the crank rod, to enable the piston to be lifted.



And we now have an Inserter.
The beauty of this tool. Only the cable ties touch the outside of the piston and the stub centralises the screw, so no risk of damage to the piston. Compact, so fits neatly between the head studs.



Put a large washer on the end of the stub and we are back, to our oil filter wrench. You would think 8 mm stub in M14 hole would be loose but when you clamp up tight it works fine. I got tired of the tiny screws in the large nut for the strap and replaced with cap heads, which only need your fingers to fit. It’s great like this for opening jam jar lids.

If you like the idea, make sure your gudgeon diameters work.

Pay me enough, I’ll make you one. You make lots, I want a cut  ;)

Enjoy.
-Mike
« Last Edit: June 19, 2022, 10:08:12 PM by Astute Greaser »

Offline martin1957

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Re: Gudgeon / Wristpin Tool
« Reply #1 on: May 19, 2022, 10:29:18 AM »
Excellent
Retired Electronic Test Engineer (Avionics), Age 64, Owned P50, PC50, SS50z, YAS1, YDS7, RD350B till 1978, then in 2009 a  KH400 A4 - now sold. Have a fully restored YAS1, an AT3, and now a Suzuki T125 Stinger.  A show winner.

Offline 5port

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Re: Gudgeon / Wristpin Tool
« Reply #2 on: May 19, 2022, 01:00:45 PM »
Yes, looks good. :)
  You can also make an extractor with a length of alloy tube and some allthread, nuts and washers.  ;)

Cheers

5port
5port

Offline Astute Greaser

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Re: Gudgeon / Wristpin Tool
« Reply #3 on: May 21, 2022, 07:13:02 PM »
And here it is in action. Two cable tie loops is best.
102643-0