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Author Topic: Dam wrist pin!!  (Read 4018 times)

Offline Bootlegger

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Dam wrist pin!!
« on: July 16, 2014, 02:46:31 PM »

 Trying to break down an engine, got the sleeve  out, now the rod will not slide down the wrist pin to pull the piston.

Tried penetrating oil for 24 hrs, nuttin, tried regular after run oil for about 8 hrs, still nuttin.
 The rod will move, but not enough to pull the piston.

  I've never had this much trouble removing a piston, what am I doing wrong??
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Gil Causey
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Offline De Hill

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Re: Dam wrist pin!!
« Reply #1 on: July 16, 2014, 02:55:54 PM »
This might help.

Heat up the wrist pin with a heat gun or soldering gun. Then take a hook (or a loop of wire) and pull the top of the rod by the wrist pin towards the back of the piston.
If you can get the rod to move to the back of the piston, you might be able to get the rod off of the crankpin.
De Hill

Offline Gerald Arana

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Re: Dam wrist pin!!
« Reply #2 on: July 16, 2014, 07:37:26 PM »
Put the sleeve back in about 1/2 way or enough to cover the wrist pin, heat in oven (could take up to 4-500 deg.) to 300 degrees and using an oven mitt place an allen wrench under the rod and gently pry it to the side. You should be able to disassemble it then.

Good luck. Jerry

Offline Bootlegger

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Re: Dam wrist pin!!
« Reply #3 on: July 17, 2014, 03:23:10 AM »

  Guy's I sure do thank y'all for the help/advice, the pin will slide some, but not enough to clear the crank pin.
 I have it soaking over nite in some Acetone in hope that this will help.

 It is a R Smith aero tiger 36 and I wanted to check the brngs even though I have kept it oiled with after run oil.
 I sure didn't think that it wiuld be such a "bear" to did dis assemble !!
  Ty, no this is not a "throw away" engine fur shure...
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Gil Causey
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Offline Randy Cuberly

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Re: Dam wrist pin!!
« Reply #4 on: July 17, 2014, 11:12:56 AM »
Do what De Hill said above!  The rod is aluminum and the bearing is bronze and they will expand more with heat than the steel wrist pin.  The problem usually is that the wrist pin develops a tiny ridge of wear right at the outside edge of the rod bearing and if the rod is cocked to the side at all it hangs up on this little ridge.
The force to make it slide must be input at the top of the rod ...use the wire to pull the rod to the backside
(I actually use a pick that I made from 3/32 music wire).  Hold your mouth just right and it will work...
I've had this problem several times when disassembling A. Tigers.

Randy Cuberly
Randy Cuberly
Tucson, AZ

Offline Bootlegger

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Re: Dam wrist pin!!
« Reply #5 on: July 17, 2014, 12:27:37 PM »

 De and Randy, I have tried heating the con rod using a 140watt soldering gun, and it still will not slide over enough to remove the piston.

 I am about at my wit's end on this thing, but I want to say THANKS for the help.

  If y'all come up with other suggestions please let me know.
Agai thanks a lot...
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Gil Causey
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Offline Dane Martin

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Re: Dam wrist pin!!
« Reply #6 on: July 17, 2014, 01:49:43 PM »
i posted this in four stroke discussion about an os40fs. procedure and tool is the same....i hope...lol


as you can see, this poor engine is in bad shape. the wrist pin is locked up. i just bake the engine at 300 for ten minutes. use a #1 extractor and it should pull out by hand. if not, bake the engine until the old nitro and gunk start to sweat on the wrist pin hole of the piston. this engine was really locked up and this method worked no problem. you can't get the piston out without pulling the pin. sorry four the bad pics. the engine was a little warm to work with and hold a camera!

Offline Bootlegger

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Re: Dam wrist pin!!
« Reply #7 on: July 17, 2014, 01:57:59 PM »

 Dane There is no opening like that, Ive seen those on some two strokes, Tiger 60 & 46's, but this one is set up to remove the cylinder liner, then slide the con rod back off the crank pin, then remove the piston.
 
   But thanks for the suggestion...
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Gil Causey
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Offline De Hill

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Re: Dam wrist pin!!
« Reply #8 on: July 18, 2014, 07:02:56 AM »
Gil,

Send your wife out shopping. Turn your kitchen oven on to 350, and bake the engine for 20 minutes. Remove the engine from the oven and take it to your workbench. Hold the engine down with a potholder, and then try to pull the rod towards the back of the engine. This might work.

When your wife returns from shopping, deny that there is a funny smell in the kitchen.   ;D
De Hill

Offline Lauri Malila

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Re: Dam wrist pin!!
« Reply #9 on: July 18, 2014, 07:39:39 AM »
Don't deny, rather ask if she knows where the funny smell comes from.

Offline john e. holliday

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Re: Dam wrist pin!!
« Reply #10 on: July 18, 2014, 10:00:18 AM »
She would never know if he burns a frozen pizza after the engine is done. LL~ LL~
John E. "DOC" Holliday
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Shawnee, KANSAS  66203
AMA 23530  Have fun as I have and I am still breaking a record.

Offline bob whitney

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Re: Dam wrist pin!!
« Reply #11 on: July 19, 2014, 06:04:53 PM »
as  a last resort u could drill a hole in the back of the case like the 4 stroke  prob wouldnt hurt anything
rad racer

Offline Motorman

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Re: Dam wrist pin!!
« Reply #12 on: July 19, 2014, 09:31:37 PM »
Are you sure the rear bearing is seated? Does the rod run in a groove? Maybe the crankpin needs to be at 12 o'clock.

Sometimes the piston gets tilted and the rod actually gets locked on the crank pin. make sure the piston is straight up and down and against the back wall, pull the crankshaft forward, grab the rod in the middle with a pair of needle nose pliers, pull it back with a twist. Don't force it too much. You'll mar the conrod slightly but it can be dressed out later.

Some engines are assembled with a hard push and you need X amount of conrod bushing wear before you can get them apart. Can you get a tiny mirror in there with a strong light to see what's going on?

MM

Offline Douglas Ames

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Re: Dam wrist pin!!
« Reply #13 on: July 19, 2014, 09:36:18 PM »
She would never know if he burns a frozen pizza after the engine is done. LL~ LL~

Lol, they smell they same. Tastes like cardboard too.
AMA 656546

If you do a little bit every day it will get done, or you can do it tomorrow.

Offline Steve Helmick

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Re: Dam wrist pin!!
« Reply #14 on: July 19, 2014, 10:29:46 PM »
Doc, I had no idea that you were such a devious person. I'm mighty proud of you!  LL~ Steve
"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline John Stiles

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Re: Dam wrist pin!!
« Reply #15 on: July 20, 2014, 04:46:02 AM »
Doc, I had no idea that you were such a devious person. I'm mighty proud of you!  LL~ Steve
Doc ain't devious.......he fell asleep! LL~ LL~ LL~ LL~ ;D
John Stiles             Tulip, Ar.

Offline Bob Reeves

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Re: Dam wrist pin!!
« Reply #16 on: July 20, 2014, 05:31:34 AM »
De and Randy, I have tried heating the con rod using a 140watt soldering gun, and it still will not slide over enough to remove the piston.

 I am about at my wit's end on this thing, but I want to say THANKS for the help.

  If y'all come up with other suggestions please let me know.
Agai thanks a lot...

My bet is you didn't get it hot enough, follow De Hill's instructions and either use the oven or try your Monokote heat gun and it will come apart. I use a commercial heat gun and an Ove-Glove.

Offline Motorman

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Re: Dam wrist pin!!
« Reply #17 on: July 20, 2014, 06:41:14 PM »
If all else fails you can mail it to me and I'll fix it for you since we're both AF veterans.


MM

Offline RandySmith

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Re: Dam wrist pin!!
« Reply #18 on: July 22, 2014, 06:56:20 PM »
They are  NOT that hard to get apart, send it to me and I will take it apart for you

Randy

Offline Joseph Patterson

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Re: Dam wrist pin!!
« Reply #19 on: July 24, 2014, 06:29:18 PM »
  Put'er back to gedder!

Offline Gerald Arana

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Re: Dam wrist pin!!
« Reply #20 on: July 25, 2014, 09:21:45 AM »
So, did you get "The damn wrist pin" out or not?  #^ You're putting her back "togger" doesn't mean that you were successful in removing the wrist pin or does it? n1

Curious minds want to know............. y1

Jerry

Offline EddyR

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Re: Dam wrist pin!!
« Reply #21 on: July 25, 2014, 02:43:02 PM »
A frozen wrist pin is one of the most common problems in our model motors I worked on ST motors for years and I a lot of the motors that were sent me had frozen wrist pins. Most of the time the pin is frozen to the piston. When the pin is frozen it will pull down the power a big amount. I have seen 25 year old  new in the box ST motors with frozen pins. I am sure Randy will tell you the same thing.
Ed
Locust NC 40 miles from the Huntersville field

Offline Norm Furutani

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Re: Dam wrist pin!!
« Reply #22 on: July 25, 2014, 05:55:46 PM »
Had the same problem on an OS 46. I made a tool from some K&S brass strip 1/16 X 1/4 x 6+. Bent about a 1/4" of one end into a sharp 90 deg. Was going to use it as a lifter but what I found out was the 1/4" width allowed me to lever the con rod from center to the back of the piston. This was using the raised boss inside the piston.

Norm

Offline Bootlegger

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Re: Dam wrist pin!!
« Reply #23 on: July 26, 2014, 03:46:52 PM »

 Got some more info today, will report back when I get a chance to try it.
 Thanks a lot for all the suggestions.. H^^
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Offline Bootlegger

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Re: Dam wrist pin!!
« Reply #24 on: July 28, 2014, 05:43:23 AM »

  I got it!!  Thanks to all y'all for the suggestions/advice this A M I got the "bugger" alose I had put some after run oil on it last week and this mornin it came off.

  So  again thanks for the help.
8th Air Force Veteran
Gil Causey
AMA# 6964


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