Johnson K45 piston/cylinder

[Goman]

It looks as though the wrist pin came loose and put grooves on both sides of the cylinder and piston.
Looks like the wrist pin was held in place by some kind of cotter pin that fell out. I know I’ll probably need another piston and cylinder but wanted to check with you all to see if there’s anything else I should be wary of?
Thank You
Glen

[sydinnj]

Yes it was a cotter pin. I have seen this on some of the 1930 era Evinrude Fastwins that I have worked on.

[Mumbles]

That’s a crying shame when that happens. 🙁

I’m not sure if it makes any difference or not but I like to use stainless cotter pins on these applications. Stainless is tough and harder to bend than an ordinary cotter pin so there might be less of a chance of it falling out or breaking.

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[Goman]

Would I need to find another cylinder close to the bore diameter as the other cylinder to make it a decent runner?

[Mumbles]

In a perfect world the pistons and cylinders would be the same size but that doesn’t happen all of the time. I’ve come across several multi cylinder motors with one cylinder bored larger than the others and they seem to run just fine.

[Goman]

Thanks Mumbles that’s good to hear. One of our members wants to try and sleeve it and maybe match a piston to it.
If that works out all I need is a coil, condenser, muffler, several missing and broken pieces a lot of elbow grease and
I’ll be in business. I’m a glutton for punishment LOL..

[pm-t2]

when you put it back together, make some Teflon buttons for the ends of the wrist pin. If the cotter key fails again at any time, the Teflon buttons prevent the wrist pin from walking out of its bore and gouging the walls.

Hope this helps.

Best,
PM T2

[george-emmanuel]

PM T2,

You can’t use buttons on that engine….exhaust ports are on the bottom..

Regarding cotter pins, I have seen too small of a pin used because the holes in the wrist pin and the piston bosses don’t line up perfectly and prevent the correct size from going all the way through, so folks use a smaller pin. I encountered this on a motor recently. So before installation in the motor I put the wrist pin in, aligned the top hole perfectly with the wrist pin hole and then used the correct size aircraft drill and drilled through. Using too small of a cotter pin allows the wrist pin to rock and eventually the cotter pin breaks….ugghh.

[Goman]

I found around 20 different kinds of stainless steel cotter pins online. Could someone recommend a good choice to use in the wrist pin? I make everything complicated.

[garry-in-michigan]

The web between the ports was wide enough to support the wrist pin, it should be fine with a teflon button. . . 😉

[Author]

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