My question is about removing the wrist pins (and then reinstalling them). I have a MC49 that I want to swap piston's. I've looked through the available IPL's and documents here, but I can't find a repair manual that goes into the depths that I need to, or describes the process to remove the wrist pin and install a new one. I've found a tool set on ebay. It says for 2.125 piston's, so figured that would work. Or could I do it like most of my projects/builds, and do the "garage dad" method and use a vise to press it out. I also saw some youtube videos on heating up the Rod. Is there a manual or documentation to describe the process? Is a tool absolutely required? Do I have to use a press? The tool is like $60 and a cheap press from Harbor Freight is about the same price. Like most builds, I try to save a penny everywhere I can. I'd hate to spend $120 on tools that I cant use, and don't know the correct procedure to remove the wrist pin, and then install the new one. Thanks for any help Y'all can provide.
I will try this. It usually fails. I have real trouble attaching files to posts. All credit here to Scott Kneisel. He deserves it!
As I figured, the attachment of Scott's Mac rebuild article failed. If anyone wants the PDF, email me and I will attach the PDF to my return email. Ted
That's the one. I just can't get files to attach anymore. TJ
(05-13-2020, 05:33 PM)Terry Bentley Wrote: [ -> ]See if this gets you there.
Mc8 rebuild
Ted & Terry,
Thanks guys! I feel like a doofus because I have reviewed that document multiple times. I have it on my phone, computer, and printed, lol. I double checked the eBay tool that I think might allow me to do the wrist pin install, and it was for 2.165 piston's, so I guess around the 91's. Do y'all think that the 2.119 (MC49) piston would be okay to use in that tool? Here's a link. If you need it, let me buy it first then resell it to you, lol. Also, the MC8 Rebuild didn't state how to insert the closed needle bearing into the piston. Do y'all know how to do that?
https://www.ebay.com/itm/mcculloch-chain...4361921065
(05-13-2020, 09:09 PM)Ryan Courts Wrote: [ -> ] (05-13-2020, 05:33 PM)Terry Bentley Wrote: [ -> ]See if this gets you there.
Mc8 rebuild
Ted & Terry,
Thanks guys! I feel like a doofus because I have reviewed that document multiple times. I have it on my phone, computer, and printed, lol. I double checked the eBay tool that I think might allow me to do the wrist pin install, and it was for 2.165 piston's, so I guess around the 91's. Do y'all think that the 2.119 (MC49) piston would be okay to use in that tool? Here's a link. If you need it, let me buy it first then resell it to you, lol. Also, the MC8 Rebuild didn't state how to insert the closed needle bearing into the piston. Do y'all know how to do that?
https://www.ebay.com/itm/mcculloch-chain...4361921065
Well, never mind. Back to square one. I post the link here to get advise if it would work. Someone must have read the post then went and bought it. Kind of sucks.
A new piston should already have the needle bearings installed. You dont normally reuse the old one. It just gets pushed out when removing the pin. When installing a new pin, make sure length is correct first. Drop it in piston and see how deep it goes. It should be a little bit below the top of needle bearing. You want to push new pin in a little less than that, just flush, so doesnt bottom against the closed bearing.
When pressing the pin in piston for the first few attempts, always stop and either back off screw or release pressure from arbor press. It is not difficult to get the pin started crooked. I have seen others ruin new parts by not knowing what they were doing. Once you get a feel for it, then dont usually have any trouble.
(05-13-2020, 10:56 PM)Terry Bentley Wrote: [ -> ]A new piston should already have the needle bearings installed. You dont normally reuse the old one. It just gets pushed out when removing the pin. When installing a new pin, make sure length is correct first. Drop it in piston and see how deep it goes. You want to push new pin in a little less than that, just below flush, so doesnt bottom against the closed bearing.
When pressing the pin in piston for the first few attempts, always stop and either back off screw or release pressure from arbor press. It is not difficult to get the pin started crooked. I have seen others ruin new parts by not knowing what they were doing. Once you get a feel for it, then wont usually have any trouble.
The piston was a "Take out" part from another engine. I have two 49m/c blocks that I got from Dwain Parks on Facebook "Vintage Kart Stuff" group. I've already built one of the m/c's by just dropping a 250 rod and piston in it. But since I have these 49m/c Piston's. Plus, I just ordered two wrist pins, and two sealed bearings, I wan't to use them (rather than the saw piston). I'll have to install the closed bearing into these 49m/c Pistons when those arrive some time next week. Just not sure of that process.
You can heat up the piston and just push the closed end bearing in with a press. Or using the pin removal tool with a flat piece against the bearing cup. Put the rod in place so you have a stopping point. Or better to have a steel blank that fits snug instead.
I machined a dummy wrist pin that was slightly undersize to fit thru rod. Used it to help guide the bearing cup in place square. There are other simple ways just using what you have available too. Just dont force anything.
It's funny to what lengths we go today to put the pin into the rod carefully. I remember in '59, Pop took an oak block and cut a hole through it and a concave surface for the piston to sit in. He took an old 1/4" drive socket extension and turned it down to fit nicely inside the wrist pin. He simply shoved the pin in and out with the vise and those crude tools. I was still using that same tool in '78 to install the pin in my open 101 engines, after I modified the radius of the concave surface to fit the bigger piston. It always worked, and I never had a pin failure on my B Limited Macs. I wouldn't think of doing that job today without the "proper" tools. Of course, I don't use a press, simply a GEM piston tool. We "made do" back in the early days. I would not be surprised that if you were to dig through Charlie Craibe's old boxes of stuff that came from Pop, you might find that oak block tucked away in among the old Mac parts. Ted