OS FP wrist pin

[Donald Main]

What is the proper method to remove a wrist pin from an OS FP motor? Thanks for your help

[Dan McEntee]

    Since you are asking the question, I'm going to assume yours is stuck and can't just push it out, because if everything is normal, that's all you have to do. What you are encountering is some dried castor oil jamming the wrist pin in either the rod, or the piston, or booth. It's been a while since I have done an FP of any size, but I think they have teflon pads and no retainer rings? Take a sharp pin and carefully dig out the teflon pads and then heat up the piston assembly with a monokote heat gun. This will melt down the dried and caked up castor. It helps to have some PB-Blaster or transmission fluid on hand and apply a little to the pin where you can see it. As you heat the assembly that it will work in and help dissolve the castor crud. It may take a few tries until it breaks loose, so just be careful with any pressure you put on the pin with any tools and such. Go back and forth with the pressure and once you feel it give a bit ne way, keep working it back and forth and it will come out. There are special tools for doing this on small motorcycle and go-kart engines and I have always wanted to make myself  something like that for model engines. It is basically a tear drop shaped band that wraps around the piston with a hole for the pin to pass through, and on one end is a nut with a threaded rod. You tur the rod in until it touches the pin and as you crank on it it will push the pin out through the hole in the other side. Everything is supported, but even with a special tool it still requires some heat to loosen up burnt and caked up oil, and then some penetrating oil to clean things out and help it along.
  Type at you later,
    Dan McEntee

[Air Ministry .]

As an aside , the NYLON wrist pin caps ARE BRITTLE .

If you try and flick them off / out , with a knife blade ,

THE ENDS COME OFF . If you insist , get them warm
and pliable . Theyre Hi Temp , so you can get them
rather warm . Like 90 / 100 Deg . Then there malable
and dont snap .

A woden dowle with a concave end , for a drift .
A wooden concave saddle , with a 1/4 in. hole
If youre going to get physical with it .

Heat / CRC/ Dryed Castor is usually the culprit .



You can see how thin , use hardened plastic / brittle , they can be . Cack it over or apply force & THE END DISC  parts company .
HEAT seems to make it all soft & gooey . or flexable & pop uotable , at least . IF theres a 1/2 mm hole in one , you push a 1/2 mm
wire ( cut pin ) through , One Off and the others a cinch - drill bit shank / wire etc - Diameter of the wrist pin bore . 

[Donald Main]

Thanks guys. I somehow bent a connecting rod today. Its fixed now.

[Dan McEntee]

Thanks guys. I somehow bent a connecting rod today. Its fixed now.

     Do you use a starter a lot? If you get an engine flooded and try using a starter that has a nice, hot battery you can get a hydraulic lock and bend the rod. Don't see it too often but is possible.

   Type at you later,
    Dan McEntee