How to disassemble McCoy 35 cylinder & block

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How to disassemble McCoy 35 cylinder & block

Postby Rayfly26 » Sun Dec 09, 2012 12:03 pm

Have a recent ebay McCoy 35 that needs disassembly of the cylinder and piston. Cylinder seems frozen to block...Any good ideas??
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Postby Frank Klenk » Sun Dec 09, 2012 1:00 pm

If the engine is clean as in no congealed oil consider this. There is the tiniest interference fit between the liner and the block. Warm the block up either in the oven or just wave a torch over it and pull the liner out. Remember the liner is steel and the block is aluminum, so the block will expand with heat quicker.
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Postby chiefss » Sun Dec 09, 2012 6:19 pm

Whoops
Last edited by chiefss on Sun Dec 09, 2012 6:22 pm, edited 1 time in total.
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Postby chiefss » Sun Dec 09, 2012 6:21 pm

The reason the cylinder won't come off the crankcase is there is a fiber gasket between the two and it acts like it was glued in. If you pull the cylinder off you will destroy the gasket. The fit between the cylinder and crankcase is a slip fit and without the gasket they would just slide apart. I have many of those engine in a box. They were cheap engines to start with. $5.95 brand new when a Johnson 36BB was $24.95
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Postby Rayfly26 » Sun Dec 09, 2012 7:06 pm

Thanks for the info. Have it soaking in transmission fluid now and will try the heat... maybe heat gun or propane torch. Will probably have to replace the gasket.
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Postby chiefss » Mon Dec 10, 2012 12:22 am

You don't need heat or ATF. Just twist the cylinder off. It's not a press fit. Easy slip in/out.
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Postby Rayfly26 » Mon Dec 10, 2012 6:05 pm

Got the cylinder off. Basically gunk holding the cylinder in place. Liquid Wrench and a super thin knife did the trick. Now the next problem is the wrist pin frozen to the connecting rod. Been soaking with Liquid Wrench but will not budge.
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Postby ron bennett » Tue Dec 11, 2012 12:41 pm

Stick in the toaster oven set at 300 degrees for about ten minutes (when the wife is out of the house, of course). This will lossen it enough so you can wiggle it around and then push out the pin.

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Postby chiefss » Tue Dec 11, 2012 3:57 pm

There is really no reason to take the wrist pin out. As long as it moves freely there is no point.

The easiest way to get the wrist pin out is to press it out using a drill press.
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Postby Rayfly26 » Wed Dec 12, 2012 5:38 am

Okay .. thanks for the advice...especially using the toaster while the wife it out. I take it the connecting rod should float on the wrist pin. The wrist pin moves freely within the piston but unless the connecting rod is allowed to float the wear will probably be on the piston holes. The piston is so thin I'm sure any pressure or tapping may distort the piston O.D. and cause an ill- fit to the cylinder.
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Postby ron bennett » Wed Dec 12, 2012 11:41 am

You are right in assumng that the wrist pin needs to float on both the rod and the piston. Using force (arbor press/drill press or hammer/drift) is the fastest way to at best distort the piston or crank it in the case of the McCoy's cast piston. The wrist pin and the rod are designed to be slip fit and should be dissambled the same way.
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Postby chiefss » Wed Dec 12, 2012 2:29 pm

In the last 50 years I've disassembled at least 25 old McCoy 35 redheads and NEVER distorted the piston by using a press of some kind to remove the wrist pin from the piston and rod. The only thing holding it in the piston is congealed oil which is easily overcome with a press of some kind. I use a drill press. Have done this on dozens of engine with no problems.

That brings up the question, why remove it in the first place. If it isn't worn as demonstrated by movement there is no reason to take the writ pin out anyway.

I still have 10 or 12 old McCoy red heads in all three sizes.
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Postby Rayfly26 » Wed Dec 12, 2012 7:04 pm

I guess as long as the engine runs well the only issue is the wear factor on the piston wrist pin holes. The connecting rod stuck in one spot on the wrist pin does not let the wrist pin rotate and will wear the piston faster. With the short time the engine actually runs it's not a huge issue but should be fixed if reasonably possilbe. I'm gonna give it at least one try and if I can't free the wrist pin I will run the engine as is.
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Postby Frank Klenk » Thu Dec 13, 2012 4:23 pm

Here is what I have done to free up wrist pins from the rod. Soak it as you have in a good penetrating fluid. Use a torch with a tiny heating tip and point it at the small end of the rod. Get it smoking hot and immediately set the piston on its side on a piece of wood and tap the pin with a small punch. If it does not move allow it to cool down (stick it in the freezer) and try again. The trick is to heat the rod and not the pin. It works for me.
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Postby Rayfly26 » Thu Dec 13, 2012 7:49 pm

Got it free !! made a cradle by .750 drill thick metal bar and then 3/16 hole thru to allow the pin to move out. Used a drill press to gently push the pin thru with an aluminum dowel. No heat, just penetrating oil. Piston moves okay thru the cylinder and the connecting rod floats on wrist pin. Now all I need is new gaskets and I'm back in business. :lol:
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Postby chiefss » Sun Dec 16, 2012 9:34 pm

Yup, it was only held in by old congealed oil.
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