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Message started by Dennisgb on 08/23/20 at 11:23:46

Title: Stuck wrist pin
Post by Dennisgb on 08/23/20 at 11:23:46

I am trying to disassemble my S40 engine that was run without oil by the PO.

The wrist pin is “Frozen” in the piston. The bearing contact on the rod and pin move somewhat. Not the normal smooth movement but they move. Both spring clips are out of the piston and it will not move. I’ve soaked with penetrating oil for 2 days. I tried to pound it out. I tried a c-clamp and a socket. No luck. Wondering if anyone has any ideas on what to do.

I’m pretty sure once out the rod will need to be replaced but wanted to inspect before I tear the engine completely down.

Title: Re: Stuck wrist pin
Post by DragBikeMike on 08/23/20 at 11:48:58

Get a long piece of 3/8 threaded rod, two 3/8 flange nuts, and a 1-1/8" deep well socket.

Title: Re: Stuck wrist pin
Post by DragBikeMike on 08/23/20 at 11:54:11

Insert the threaded rod through the wrist pin. Place the 1-1/8 socket over the rod until the socket butts against the side of the piston as shown. Place nut on each end. Tighten the nut on the socket end. Hold the nut on the wrist pin side with a 9/16" socket.

Title: Re: Stuck wrist pin
Post by DragBikeMike on 08/23/20 at 11:59:08

If the wrist pin still doesn't move after applying ample force, start heating up the piston with a propane torch (I assume the piston is trash). Maintain tension on the puller while heating the piston. Periodically check the nuts for tightness and tighten as necessary to keep ample tension on the pulling stud.

Discontinue pounding on the wrist pin. Never pound on a wrist pin. Always use a puller.

Good luck.

Title: Re: Stuck wrist pin
Post by Dennisgb on 08/23/20 at 12:32:14

Brilliant! I will try this as soon as I can get back out there.

Title: Re: Stuck wrist pin
Post by justin_o_guy2 on 08/23/20 at 12:36:30

Discontinue pounding on the wrist pin. Never pound on a wrist pin. Always use a puller.

I have no reason to disagree with
STOP Beatin on it,, But somehow Im thinking you have a real
Why You shouldnt
that you just havent shared..
If so,, would you mind sharing?

FWW, not knowing beatin on it is such a bad idea,, I was gonna suggest a panel cutter, which is just a small jackhammer,,

The only thing that comes to mind is the chance of swelling it from beatin on it..

Ohh,, Elegant puller answer,,

Title: Re: Stuck wrist pin
Post by Dennisgb on 08/23/20 at 13:09:42

Slick as snot...a little heat and once moving the wrist pin came right out. The small end of the rod looks okay. Will measure everything and decide. I’m 50/50 with tearing it down. It got hot enough to score the piston and cylinder, but the engine never stopped. I even tried to get it running when I got it.

Thank you Mike! So helpful to have other eyes and ideas.

Title: Re: Stuck wrist pin
Post by Dennisgb on 08/23/20 at 13:16:10

415E585F42457444744C5E52192B0 wrote:

Not beating on it per say. I had the piston supported. I was just trying to break loose the short distance from the spring clip to the edge of the piston. Assuming the pin would free up at that point. The piston was not free floating. Not the best approach but my original assumption was that the rod would be replaced. This is basically a salvage operation.

Title: Re: Stuck wrist pin
Post by justin_o_guy2 on 08/23/20 at 14:11:45

Something you might do to help decide if a tear down is necessary is pull a side off the crankcase and inspect everything layin on the bottom. How much metal is there? How much of it is ferrous?

Drain the oil into a clean catch pan. This is where plastic is good.. A gallon oil container with one side cut out goes under the bike and holds more than enuff,,
Yes, ya ottsta have the lid on it..
Run a magnet thru..
Dissect the oil filter, dont pollute it with anything gettin into it,
Of course holding the crank at TDC and messing with the rod would tell ya something,,

Might wanna rinse the bottom of the crankcase and get everything out,, this is where I like diesel,,
Ya might even need to go so far as pull both sides off, and set a catch down and rinse everything into that.

What dont stick to a magnet might need filtered thru a paint filtered funnel, or cheesecloth, coffee filter,, piece of old tee shirt,, heck,, ya gotta study whats in there somehow..

Some bits are normal wear.. so,, just seeing signs on extremely fine bits of aluminum or enough ferrous stuff to put a beard on a good magnet isnt necessarily reason for panic.

How much and how big matters,,

Title: Re: Stuck wrist pin
Post by Dennisgb on 08/23/20 at 14:17:53

I think the question has been answered for me. There is a small burr in the bearing surface on the small end. I tried some fine emery and it’s into the rod itself. Looks like it will need a new rod.

Can I split one side to get the crank out? If so which side is best so I can keep the transmission in the engine or is this impossible?

Title: Re: Stuck wrist pin
Post by justin_o_guy2 on 08/23/20 at 15:21:00

Is it too big to carefully clean it up?
A low spot wont hurt anythihg, as long as it doent bleed oil pressure off..
BUT,, surrounding a low spot,, there is a high spot,, Getting a wrist pin to fit with the rod keeping even tolerances along that width is what its about,,
Splitting the case seems Very intimidating to me,, but siezing a wrist pin might not be a load of fun either..

Buddy O mine was working for Rowan drilling in Louisiana,, well,, we both were,, His dad was a big time diesel mechanic in Odessa Texas,, and Paul knew his way around one..
They had a BIG engine that someone tore down and never put back together.. and by big, I mean a catwalk down the length of it,, 6 cylinder thing, about ten feet long and eight feet tall,, best I remember from over 40 years ago..
Anyway,, Paul started hunting parts when he wasnt busy with other things,, and dragged everything up in a pile,, and the crank had a divot in it,, which had some high spots around it.. He used a file on that,, and the bought him gaskets and some minor stuff,, he put it together and it ran,,

Anyway,, point is,, a visible boo boo,, while not desirable,, may not be a problem at all,,
Your skill level and the percentage of the surface it affects may be all that matters.

Title: Re: Stuck wrist pin
Post by Dennisgb on 08/23/20 at 18:42:20

It’s a very tiny standing burr. It would be hard to file it without causing more damage IMO. I can certainly try because even if I make it worse I will still have to tear the engine down. I need to dig for my precision files and diamond stones. Everything was lost in the shop fire. Some salvage is in tubs but hard to find.

Title: Re: Stuck wrist pin
Post by justin_o_guy2 on 08/23/20 at 18:51:21

You can replace the wrist pin easy enuff,,

A carefully built slot in it to engage the burr, rotate the pin?
Gotte decide which way the metal Needs to go,, and work it towards where it came from, Then a diamond bit on a dremel, keep water on it,
SLOW, using whatever ya have to to see it well,, Hobby Lobby has the eyeball cheater hoods with 2 magnifying lenses and a Loupe that rotates down,, More expensive than Harbor Freight, but better, too..

Harbor Freight has outdoor , rain proof work lite,, 250 watt halogen, cheap.

Take yer time,,
that wrist in can possibly be The tool that helps save ya from crackin the engine open,

Title: Re: Stuck wrist pin
Post by DragBikeMike on 08/23/20 at 19:36:03

Justin, regarding your question about why not to beat the wrist pin out, you run the risk of bending the rod or brinelling the needle bearing (large end rod bearing). It's very hard to properly support the piston in a manner that ensures no load will be applied to the rod. Always best to use some sort of jack or puller.

Dennis, can you post a picture of this "standing burr". Is it worse than this?

Title: Re: Stuck wrist pin
Post by DragBikeMike on 08/23/20 at 19:38:19

I was able to clean up that wrist pin bore in the rod shown above. I used a ball hone and as I recall the bore remained within the specs outlined in the manual. Here's what it looked like after honing.

Title: Re: Stuck wrist pin
Post by justin_o_guy2 on 08/23/20 at 21:51:13

Makes perfect sense.
Thanks

Title: Re: Stuck wrist pin
Post by Dennisgb on 08/24/20 at 12:08:02

6E68671B191E1A2A0 wrote:

Much less than that. One very small spot that looks similar.

I can’t post picture right now because not at the location where the engine is.

Where would I find a ball hone that small?

Title: Re: Stuck wrist pin
Post by DragBikeMike on 08/25/20 at 01:01:54

Just do a google search for "7/8" flex hone + brush research". You will find lots of vendors that sell them. Your pin bore is .906". I believe I used a 7/8" flex hone, but I never recorded the exact hone size, it might have been a 15/16". Call Brush Research or send their tech section an eMail. Ask them which size is best for a .906" bore. That way you can be sure you get the correct size hone.

The hones have a size range. For instance, a 7/8" might be good for holes from like .860" thru .950". The 15/16" hone might be good for holes from around .925" thru .990". I don't have the specs but their tech section will be able to give you the straight skinny. I can see from google search that they are available in both 7/8 & 15/16.

I went through my hones and found the one that fits the pin bore just right, but they aren't marked so I have no idea what the exact hone size is.

Good luck.

Title: Re: Stuck wrist pin
Post by Dennisgb on 08/25/20 at 14:34:36

Thanks so much for info. I found one at Grainger and will be here tomorrow [ch128079][ch128512]

Title: Re: Stuck wrist pin
Post by justin_o_guy2 on 08/25/20 at 17:04:02

Good deal,,
are ya gonna try to press the bur into position some first?
Do ya need to protect the inside diameter from the hone everyrywhere but where the boo boo is?
Will it open it up and make the wrist pin loose on that side? Or is it in the middle?

Title: Re: Stuck wrist pin
Post by Dennisgb on 08/25/20 at 19:56:53

5E4147405D5A6B5B6B53414D06340 wrote:

Can’t move the burr it’s burnished hard. It’s not standing very high. Probably less than .001” the hope is that it will clean up without taking much of the bearing diameter. The pin and bearing will still need to be in spec when finished or will not be used. This is a hard surface so you really can’t take much surface with a hone.

Title: Re: Stuck wrist pin
Post by justin_o_guy2 on 08/25/20 at 20:14:03

Thanks for humoring me..
Wish I was there, I'd get in your way

Title: Re: Stuck wrist pin
Post by Dennisgb on 08/26/20 at 07:32:03

5F4046415C5B6A5A6A52404C07350 wrote:

Thanks for humoring me..
Wish I was there, I'd get in your way

That’s funny ;D

I do a pretty good job of getting in my own way sometimes. Getting old is hard. I find myself dropping things more. Then not being able to find them. Screwdrivers are harder to get the tips in the head of the screws. Everything takes longer. Lots of times the logical solutions seem to evade me, like how to get a stuck wrist pin out of a piston. ;)

Title: Re: Stuck wrist pin
Post by justin_o_guy2 on 08/26/20 at 08:13:21

Yeah, I used to fix copiers and cash registers,, Sometimes broke stuff requires a solution that is unique, LIke a developer unit had a leaky seal, trickling its contents into the paper path, onto the copies, and, of course, losing its developer,, which isnt okay,,
Old machine,, finding that seal would likely be impossible, solvie the problem,,

Modern office with a kitchenette,,
Swiped a piece off the sponge mop, Used the ever present Xacto to shape it, Used the always handy superglue to put it in
Bingo,,

Today?
IF I ever clicked on the answer, itd be hours if not days..

Title: Re: Stuck wrist pin
Post by Dennisgb on 08/28/20 at 11:54:46

Slick as heck it cleaned right up with ball hone. Beautiful ;D

Title: Re: Stuck wrist pin
Post by justin_o_guy2 on 08/28/20 at 13:45:13

Excellent! Beats heck outta bustin it down the middle,, dont it?

Title: Re: Stuck wrist pin
Post by Dennisgb on 08/28/20 at 15:18:53

Yes. Awesome.

Now I can’t get the oil rings to compress. New rings, I got them all sized to about .016” gap. Does the retainer need to be sized? Never had to do that before...