replacing bearing in a os FS 61???
 

Can anybody please tell me or show me how to replace the front and rear bearings on a OS FS 61 please? Can you do it with out tearing down the whole engine or do you have take the whole thing apart? Any help or tricks to doing it would be very helpful. Thanks for your time.

I'm sorry to say that you have to tear it down, including the cam gears, and there is a hard part to it...getting the wrist pin out of the hole in the back. You might get lucky and find that it's not stuck too badly. If it's really stuck, then there are whole threads on this, and clever ideas. Great feeling when you finally get it done, but I don't think there is a quick and easy way. Jim

Thanks I found a lot of good stuff on it. But you are right I am going to half to teat it down all the way. So I will be able to lap in the valves and check the whole thing out inside and out. Thanks for the time.

You will also most likely find the bearing hard to get out so the easiest way to get them out is to heat the crank case up in your oven at about 250 for about ten minutes or so and then use a wood dowel as a punch to get then out and then the same when installing new ones ok .
I did this with a saito 100 engine and it works just great .
cheers.

Hi!
A much easier way is to use a propane torch!
If the bearings don't fall out as you slam the crank against a wooden plank...just cool the crank in water and then reheat it again. Repeat this process until the bearings fall out.
This process is the same whether it is two or four-stroke Engines.
This is very easy to do!

There are some good tutorials on Youtube on this process.

Unfortunately that's not the hard part for the OS FSs. The hard part is getting the wrist pin out of the back hole. It's a terrible design because you have to pull it out, but if it is stuck it is very difficult to get enough grip via the tiny hole in the pin. Only AFTER that is done do you get to pull the piston and crank and knock out the main bearing.

would a good strong magnet do the trick

I used a thin wood screw that would engage the pin (pin is much harder so no damage to it) and rotated as I pulled out gently on it. Use WD 40 or similar penetrating solvent to loosen deposits on the pin. This is not a easy engine to take apart
but it can be done. Jaka has very good advice, just remember to spread the heat around to prevent warping or a melted case..........good luck!

Bruce

Hi!
Yeah!
It's vital that you heat the crank evenly with propane torch.

M4 tap
 

Hi, my OS FS-61 was SEVERELY seized due to old and gummed up castor oil residue. Had to put it in the oven several times to loosen it up. The cam followers were stuck TIGHT, the rockers did NOT rock, everything was frozen solid.
My objective is always to disassemble projects without leaving ugly toolmarks or gouges.
The piston wrist pin was removed by inserting an M4 thread tap into the hole, after having removed the Teflon cap by inserting a small screw and pulling it out.
With the tap (and a small torch to heat the piston from below) I was able to exert enough rotational force to break the gummy residue that was holding it in the piston. It could then be pulled out, still stuck to the M4 tap.
Next project is the wax method to remove the cam bearings..;)