rrengineer

My Feedback: (3)

I am trying to replace the bearings in an OS FS-20. I have the cylinder liner out and the valve train is also out. Just the piston and connecting rod, crankshaft and bearings left. I can't figure out how to get the connecting rod off the crank pin. It slides part way and stops. I'm thinking it has something to do with the wrist pin in the piston, but I can't see how to remove it.
Mike

wcmorrison

My Feedback: (2)

It is probably the build up crud on the wrist pin in the piston that is stopping the travel.  Since you are putting in new bearings, why not toss the carcass into a crock pot of Anti Freeze and cook it over night.  That probably will soften up the residue that is keeping the rod from moving freely left and right on the wrist pin.

Anyway, that's my 2 cents worth on the subject.  Good luck.

Chip

earlwb

If a engine has been used a lot and or sat around for a long time, some congealed oil or castor oil can form on the wrist pin on the piston, so it makes it tough to get that extra few thousands of a inch movement off the little end of the rod.

What helps sometimes is to fabricate a hook handle from some piano wire (like 1/8 inch or 3/16" or so) so you can hook behind the rod and try to wiggle and force it a little to slip that extra tiny distance so that the bottom end will come off the crankpin. also you need to work it off with the crankpin at top dead center or close to TDC.

wcmorrison has a good idea on simmering the engine for a few hours in a crockpot too.  But sometimes using a hair dryer and heating up the piston and rod good and liberally spraying some WD-40 or other penetrating oil will do the trick too.

rrengineer

My Feedback: (3)

I worked for several hours last night trying to figure out how to get this pin out. On the OS FS-20 there is a hole in the crankcase that lines up with the wrist pin which I am sure is only for ease of assembly at the factory. I don't think they were concerned with the customer trying to remove it later. I got the teflon button off the end of the pin next to the hole using a dental pick so I could have access to the hole in the pin. It is hollow. I don't have anything to put in such a tiny diameter (easy out?) to grab the thing to draw it out. I managed to get the dental pick around the opposite end between the case and the piston and start to push it out the hole in the case, and it started to move so I know it is not stuck too badly. I just need to figure out what I can use to grab the inner diameter of the pin with. Being hardened steel does not help the situation either.
Mike

traiders

My Feedback: (3)

rrengineer, put liner back in to protect piston, make sure you can see piston pin thru cylinder hole and hit cylinder against piece of wood. This will start pin to move thru cylinder and you will be able to remove pin

rrengineer

My Feedback: (3)

Yes, I got it to back out about 3/32nds of an inch by putting the liner just over the ring and hitting the case on a 2X4. I applied heat first after squirting Corrosion-X on the pin. It is either very stubborn or something is slightly mis-aligned.
Mike

w8ye

My Feedback: (16)

I had a stubborn FS61 that I finally got the pin out by inserting a hardened #6 deck screw. I was able to extract the pin.

rrengineer

My Feedback: (3)

I'm sure the pin on an FS-61 is larger that the pin on an FS-20.
Mike

earlwb

I ran into problems getting the piston pin out of old Fox engines in the past. I heated up the engine good, along with some liberal use of WD-40 on it,  and used a deck screw too. A sheet metal screw might work as well.

I had thought about using a large neodymium magnet and see if it would suck the piston pin out or not.  You know the kind of magnet that you definitely keep any appendages from being between it and metal or you'll regret it.
[X(]

rrengineer

My Feedback: (3)

Oooooooh, Neodymium magnet. That sounds so cool. I wonder if they make one in 1/8th size rod?
Mike

earlwb

Use a big one. I have seen them attract metal from a foot away on the desk. so the less than 1/4 inch gap with the engine to the piston pin would not be a problem.
http://cgi.ebay.com/2-Rare-Earth-Mag...item1c197a1334

if you have a old, bad hard drive you can extract them from it too:
http://cgi.ebay.com/Magnet-out-Hard-...item35b02ef258

I have some big ones myself, but I haven;t had a reason to try out the theory to see if it really works or not. I haven't had to pull the pin out of a old engine yet.
I did put one on my scooter a few years ago. The idea was ti have it help trip the stop lights at those intersections where they still use the wire loop in the road. it worked for some but not other intersections. Now I was pleasantly surprised in that when i looked a few times when I was doing oil changes and I found nails and screws and stuff stuck to the magnet under the scooter. Apparently the front tire would upset a nail or screw and the magnet would grab it before it got to the rear tire.

gkamysz

My Feedback: (19)

I've use a piece of music wire that just fits. Bend it a little so that it now exerts pressure in the hole. This might pull it out. If it doesn't your only option is to take a hardened screw and grind a very shallow taper on it so the point just fits in the wrist pin. You want some threads left. Screw it in to the pin as far as you can and pull it out. Turn while pulling if needed. Of course soaking in your favorite penetrating oil should help, but I find it's either rust or something that was castor at one time (and isn't now) that won't dissolve holding it in. If that doesn't work, cut the rod. I've only cut one rod of many OS four stroke engines I've rebuilt and that wrist pin wasn't coming out by any means. FS-26, and 91 can be disassembled by pulling the rod off the crankpin, but the rest can't. The rod is still available and is the same in the FS-26 and 30.

rrengineer

My Feedback: (3)

I am going to figure out how to get this pin out. I just hate when something mechanical gets the better of me. The pin is moving, it just needs a little more force to get it out. I will try the music wire trick and I have ordered a magnet. One way or another this thing is coming out, but cutting the con rod is the last resort.
Mike

Mr Cox

On a Fox .15 engine I have used a round needle file with tungsten carbide particles on it, insert as far as it will go in the pin and then twist a little sideways and pull back out. Not great but it worked...

rrengineer

My Feedback: (3)

O.K. the bearings are out. The wrist pin was a tough one. What finally transpired was a combination of methods described on this forum plus a twist at the end. The exact method was to remove the cylinder liner then use a dental pick to pull out the teflon button in the end of the wrist pin next to the hole in the crankcase. I then sprayed Corrosion-X on the pin from the bottom of the piston and heated it up with my heat gun. I then used the dental pick to reach in between the empty cylinder between the inner wall and the piston to push on the other teflon button. I got it started moving out of the piston, but I could only push about 3/32nds of an inch. After smacking the crankcase wrist pin hole side down on a 2X4 a few dozen times after heating it up again and more Corrosion-X, it moved about a 1/16th more. I then wedged a piece of plastic on the opposite side of the piston between the piston and the inner cylinder wall and tried to pull it out with a piece of music wire with a bend in it about 3/16ths from the end. I put the music wire in the wrist pin, the pulled on the wire so it would press the bent end against the inner wall of the wrist pin and pulled. I did this several times and got the pin to move a little more. I decide to hook the big end of the con rod and pull it out so it would line up with the piston against the cylinder wall. That's when it happened! the piston/con rod assembly just tilted in the crankcase cylinder inner diameter and it came off the crank pin. Now to replace the bearings and figure out the timing on assembly. Old bearings were absolutely shot. Of couse it is an Ebay purchase. Thanks to everyone on the forum for their help.
Mike