Bar oil leaking into combustion chamber - Mac Super Pro 81

[Wallypedal]

I'm new to this forum, and I've got this problem and have done the forum searches - have found some excellent threads and information. Have learned this was a common problem on Mac 10 series and some of SP's. My question, and the embarrassing part: When I pulled the oil tank front screw and cover off I was pretty careful. It had a single screw holding the automatic oil pump on, so loosened it up and the pump came right out. I got to cleaning and inspecting parts of it, then happened to look back in the oil tank. There was a black disk about 5/8" diameter, maybe 3/32" thick, with a small hole in the middle and a little pin protruding from the flat surface. I need to get a picture. I've got no idea and can't figure out where this goes, what it does, or anything!! I fix up vintage sewing machines, and this has me stumped. Anyone able to tell me what it is and where it goes?? Thanks. I think I've got a handle on what to do about the leak, based on the great info here.
Wallypedal

 

[SEAM]

That is probably the oil pump piston which sits in the pump housing to pump by reciprocating via the impulse from the crank case... Without the piston installed the pump will leak oil into the crank case.

 

[rwoods]

Oiler piston. Goes in the oiler. Oil in the crankcase is an indication of a leak between the pump and the case/tank. MAC used a spring clip in later years to put pressure on the backside of pump to tighten things up.

Mark Heimann has a thread somewhere on here with almost everything you need to know about the ten series oiler.

Ron

 

[Wallypedal]

I thought it might be the actual piston, but the piston is all there. I've read and memorized all Mark Heimann's threads, I think. The piece I have doesn't look like it logically fits or stays put, I've been studying the pictures and schematics especially looking for the pin or protrusion and where it goes. I'll take a picture this afternoon. My pump and all it's parts are complete. This stray oddball thing might be part of the manual oiler, someone else's leftover junk or better idea for a wedge or something.

 

[PogoInTheWoods]

If you don't already have this it may shed some light...

 

[Wallypedal]

Pogo, thanks for the file, I found it earlier. Here's the rest of the story. I haven't owned either this SP81 or the PM 10 10 very long. Not long enough to tinker until now, like I did for years on my Huskies and Jonsereds. After opening up the SP81 and removing the auto pump, I found this stray part. Turns out it is the inner baffle from the oil tank cap!! I was thinking it was part of the pumps or something. Got that figured out. This is a one-screw pump without clips or wedges, and has a thick made-in-Japan gasket. It also has two brass pins with heads which go to the rear as alignment pegs for the gasket. EXCEPT on this one, there were holes recessed for the brass pin heads, but the heads were too large. This meant the sticking out heads were interfering with the gasket getting squashed properly. Trimmed them to fit in the recesses, will test tomorrow.

 

[PogoInTheWoods]

Good catch on that cap insert. Didn't think about that! You would benefit from one of the spring wedges to help seat that pump body against the gasket to eliminate the oil seeping into the case. I have them in a couple of my 10 series saws but most don't have them and are one screw pump bodies. They all leak into the case a little, but it usually burns off in short order and isn't a major problem -- more of a minor annoyance than anything.

There is a fellow who made a bunch of the spring clips for Mark Heimann and you may be able to get a couple from him if you're interested in trying them. They're a little tricky to install but they do the job once you get them wedged into place.

 

[Wallypedal]

Pogo, thanks again. I saw those clips and wondered if he still had any. I will try to PM him. Here's a pic of the mystery piece.

 

[PogoInTheWoods]

That exact piece was a 'spare part' for another fellow who had a few extras from a recent Mac rebuild. Had a few of us scratching our heads on that one, too. LOL

Enjoy your saws!

 

[rwoods]

Walleypedal, look at the next to last page of the file Poge reference. The hollow brass “pins” go in and through the pump body then into the gasket thus they float so they should not need trimming. I believe the recesses you are referring to are actually the sealing surfaces to seal around the pins. Ron

 

[PogoInTheWoods]

They're actually receptacles for the tabs of the spring plate if I'm not mistaken..., which would presumably mean that the spring plate would have been installed in that saw at one time or another. Not sure how those inserts (eyelets) would have even stayed in place unless they were installed upside down with the flange end against the gasket..., if that's what was meant by 'brass pin heads' earlier -- unless those were something entirely different and maybe/possibly foreign to the assembly and simply added by someone as alignment pieces in what would otherwise be the 2nd and 3rd screw positions for the 3 screw model tank. Or..., maybe I'm missing something in the illustrations?

 

[rwoods]

I believe you are correct. The brass pins are part of the spring clip setup. Seems Wallypedal is missing the clip.


Ron

 

[Wallypedal]

rwoods, your response is spot on. I took pictures when I took this out, and those pins were in the wrong way, and the gasket upside down to boot. All of which helps explain the leak. I hope. I'll fashion my own spring if I have to, and will report back to this thread.

 

[rwoods]

Good. There are usually a spring clip kit or two on eBay but I didn't see any just now. Ron

 

[PogoInTheWoods]

As mentioned, @heimannm may be able to hook you up with one of the spring plates.

 

[PogoInTheWoods]

Here's a drawing if you want to fashion your own. I believe it was courtesy of @fossil back when I began looking for one for my SP81 project (and before Mark mentioned having some nice knock-offs that were made by yet another member).

​

 

[Wallypedal]

Yep, I got connected with @heimannm and we'll follow up on the spring plate. Busy for the next week or so, will report on this when back.
Wallypedal

 

[PogoInTheWoods]

Not sure if you saw the drawing I just posted also. Seems our last posts were nearly simultaneous.

Regardless, good luck with the projects. And drop in over at the McCulloch sticky when you're finished just to say "Hi" and to show off a little!