Removing wrist pin

[rob 135]

What are some good ways to remove wrist ion without damaging piston skirt . Book says use some heat . Was thinking need some sort of holding fixture

 

[F_R]

Re: Removing wrist pin

You didn't say what motor, but most OMC/BRP motors have wrist pins that are slip fit in one side of the piston, and press fit in the other side. The w/p boss inside the piston will be marked with a "L" or something similar indicating the loose side. Best way to remove it is an arbor press, with tight side down, pressing from the loose side. In other words, press it all the way through the tight side. To do it opposite will distort the piston. To install, pin goes through the loose side, into the supported tight side.

Yes, heat will help.

 

[rob 135]

Re: Removing wrist pin

It's a 1973 135hp. I don't have access to press. I removed one already . I drilled hole in block of wood and drove pin down . Yes from loose end to tight. It didn't damage piston but that was old ones . Was thinking cutting a 3.5 inch notch in block of wood to use as holding fixture . Don't no if just a flat chunk of wood with hole will damage pistons . What have others used ?

 

[175se]

Re: Removing wrist pin

there is a regular plastic ( I think its some material like that) that has different notches for the dif size pistons that don't damage the skirts, but alas my mind cant remember what its called.

 

[boobie]

Re: Removing wrist pin

Cut the 3.5 inch half round notch in a the block of wood and use that. That's what we used years ago.

 

[rob 135]

Re: Removing wrist pin

Ho we'll does heat work? We're do u heat ?

 

[racerone]

Re: Removing wrist pin

Aluminum expands at twice the rate of steel when heated.-----Heating the piston in boiling water and putting the wristpin in the freezer is the way to go.---If you are quick you can usually assemble without a hammer.

 

[rob 135]

Re: Removing wrist pin

I got them all changed over with no damage . I changed first one without heat went very hard. Took others and heated pistons in small oven and wristpin in freezer. They slid together partially then tapped with hammer rest of way . Did go a lot easier . . Now to remove the aluminum from cylinder . Got acid today"

 

[yorab]

Re: Removing wrist pin

I wish I had my books with me. I'd love to find a quote from a Seloc manual that I came across once. It basically said to (paraphrasing) "find a comfy chair to sit in and use your legs as a cradle. Drive the wrist pins out with a hammer and punch. This may take some effort and your legs will become black and blue. But do not worry, the bruises will go away in a few days."

Really.

 

[orbanp]

Re: Removing wrist pin

Hi Rob,

Here is a picture for the set up F_R was talking about.
I guess you can make a tool like that out of a block of wood:


Peter

 

[rob 135]

Re: Removing wrist pin

My thumb is split open from hammer ,couldnt imagine what my legs would look like with a few stray hammer blows.

 

[boobie]

Re: Removing wrist pin

I've done the piston in lap trick but always had a bunch of shop rags around the piston. No damage to myself. Did that before we had piston blocks.