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Engine basics => Engine set up tips => Topic started by: Gordon Tarbell on September 28, 2009, 10:08:06 PM
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What is the proper way to remove the wrist pin on the ST 46 once the liner is removed? I need to remove crank to send to a freind in need.
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Gordon - I've removed quite a few that were very stubborn.
Heat up some oil in a Pyrex measuring cup. Get it really hot.
Holding the engine upside down, carefully pour the oil into the piston.
Insert a small drill bit into the end of the wrist pin.
Cock the bit slightly so it binds in the wrist pin and carefully draw it out.
You may have to repeat it a few time but I've never had this system fail.
Bob Z.
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Thanks Bob , I will give it a go.
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I've got the same issue with an ST60 right now. I had given up and just bagged the engine up for later efforts. Thanks Bob, I'll also give this a try.
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I seem to recall using two different "removers" for such a problem. Once used an "EZ-0ut" (the round-ish spiral type), and another time used a tapered piece of spruce to jam into the wristpin and push/rotate and then pull the pin out as heat was applied. Both worked.
One of the more stubborn removal chores was a rear bearing in a Taipan 2.5cc rear exhaust (Rossi .15 clone). Nothing worked, until I turned a plug of soft aluminum to fit, sawed it + with a hacksaw to form an internal expanding mandrel (with a sheet metal screw to expand it in the slot intersection). A bit of heat and some tapping on the head of the sheet metal screw worked very nicely. :! Steve
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I've got the same issue with an ST60 right now. I had given up and just bagged the engine up for later efforts. Thanks Bob, I'll also give this a try.
It is very very common to have a ridge of wear or castor on the wrist pin that keeps the pin from sliding out no matter how hard you pull, I have ran into this many dozens of times
I soak the engine in Carb Cleaner (Berryman's) in a gallon dip can, this will make the ridge soft enough to pull it thru
Or you could try it upside down with the head and backplate off in a crockpot with antifreeze
Regards
Randy
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One thing that helps a lot also is to not pull the liner all the way out. Lift it just enough to clear the pin.I have used a crock pot and a very small tapered file and turn the file into the pin and then pull. I also made a tool that goes through the pin and a small hook on the end grabs the pin and pulls it out. As Randy said if you do not soften the old crud it will never come out. Many ST/46's that do not run well have frozen wrist pins.It is very common.
Ed