Stihl Contra - On the Bench - Refresh/Rebuild

[bulletpruf]

All -

I have several Contra's; figured it's time to go through one. And since I'm documenting it anyway for my own records, figured y'all may as well come along, too.

And here she is, sitting on my workbench -





I bought the saw through a popular auction site in early January 2017. Given the condition, it appeared to be a low-hour saw, so I pulled the trigger. It came with the 21" Stihl Duromatic hard nose bar, but it was missing the dogs and chain. Original bars are out there, but not real easy to find. You can still find NOS dogs, however.

The serial number is 176143; this doesn't tell you the date, but there are a few ways to figure it out. If it had the original bar (it doesn't), these are usually date coded. I have also seen date codes on mufflers, too, but I'm not seeing one on this muffler. However, you can still get an idea of when it was produced just by going from the serial number. We know that the sand cast crankcase model production ceased on 24 June 1959 with serial number 84832. And the manual oiler (which this saw has) started with serial number 112000 which appeared sometime in 1960. And then I've seen a couple of posts from folks with saws that apparently have their original date coded bars (188587 with a February 1962 bar and 208362 has a bar dated November 1962). We also know from Stihl literature that serial number 275000 was produced in December 1963. So with a bit of redneck math, my best guess is late 1961.

Anyway, when the saw arrived, I did a quick once-over. Compression was good - right at 140. And when I pulled the muffler to take a look at the cylinder, I realized it had a broken muffler stud -- it's about 1/4" deep; too deep to weld a nut to it and just unscrew it. I fired it up and it ran fine, but I only ran it for a minute because of the exhaust leak.

So, it's time for a rebuild/refresh. The original paint is in pretty good shape, so I don't see a need to do a media blast the current paint and re-paint it. A good cleaning and replacement of gaskets and wear items should do the trick.

Scott

 

[bulletpruf]

This is the 106 cc Contra, by the way. The 137 cc Contra's are much rarer and significantly more expensive.

The original tag will denote what the saw was originally - as you can see, this one is an 1106. A 137 cc saw will be listed on the tag as an 1106 S.


As you can see from one of the pictures above, it has the correct starter housing; the 137 cc saws came with a different housing that had more ribs and they're spaced closely together. Here's another one of my saws, this one with the 137 cc type starter housing.



You can also tell the difference between a 106 cc and 137 cc saw by the shape and configuration of the cylinder cover (137 cc covers also have a piece of asbestos or something similar attached). This is the correct 106 cc cover (although it's missing the two rubber spacers from the top); it's fairly thin sheetmetal. There is at least one other version of the 106 cc cover that's cast. A 106 cc cylinder cover will not fit a 137 cc cylinder; the cylinder is too large.

 

[bulletpruf]

The bonnet or top cover is cracked, of course. And some of the rivets have been replaced with screws. There are high quality reproductions on the market; this saw will get one of these unless I can find a very nice OEM one.



There are at least two different styles of rear handles; the other one has black plastic on the grip. I'll have to post a picture of it.



Everything looks pretty good under the clutch cover. Still a lot of original paint.

 

[bulletpruf]

This saw has the clutch cover with the hole in it, presumably to help clear out sawdust. It's also cracked, but I may have a good one in my stash somewhere. I will have to look for a part number on it; I'm not sure if these carry a different part number than the ones without the hole. I am also assuming that this is the correct cover for an earlier saw, but the later ones did not have the hole.

 

[bulletpruf]

I need to edit the post above, but can't. Are you unable to edit after a certain amount of time has passed?

The post I'm referring to has a picture of the starter/recoil cover. Specifically, that's a picture of the later 106 cc starter/recoil cover. It has more ribs, but the ribs are still concave. The 137 cc starter/recoil cover looks similar, with more ribs than the earlier 106 cc saws, but the ribs are concave. I'll post some pics when I can find some good ones of the 137 cc cover.

 

[bulletpruf]

Here's the muffler - 1106 145 0310 - when I Google it, it comes up as a Contra muffler. However, it has a boss in the bottom that's been tapped, just like my 07 mufflers -- on the 07, a bracket attaches the muffler to the saw case, using this hole for the bracket. Of course, none of the Contra's that I checked have any such bracket, so I guess I need to check 'em all, and take a closer look at my 07 mufflers. Does anyone have a Contra or 07 IPL? If so, can you look it up? Would love a copy, too. I'm using an 090 IPL.



And here's the tapped boss on the bottom -



To clarify my earlier post -- see below for a picture of the starter/fan cover used on 137 cc (090 and Contra S) - it's easily distinguished from the early Morse Fairbanks starter because of the number of ribs (the early M-F has less ribs, more spacing between) and it's distinguished from the later 106 cc starter because of the concave ribs on the 137 cc starter/fan cover, instead of the convex ones.



And here's the early Morse-Fairbanks, with concave ribs.



Scott

 

[madhatte]

This ought to help you get that broken stud out.

 

[bulletpruf]

This ought to help you get that broken stud out.

That's a new one for me!

 

[madhatte]

Chemistry is almost magic.

 

[bulletpruf]

Ok, more progress...

I tried to drill the stud out using left-hand drill bits, heat, and Kroil, but no luck. However, I was able to drill right through the middle of the broken stud, so I just need to finish drilling it out and then hell-coil or TimeSert it.



Got the saw completely disassembled - it's all in the box. Bagged and tagged.



Had a few surprises along the way, including some oil problems. I'm not sure what was in the oil tank, but it was the consistency of Permatex gasket maker - sticky, thick, and gooey. It must have had some water content, too, because the oil pump was frozen; when I took it apart, the guts had a fair amount of rust. You can buy an inexpensive reproduction pump on eBay, but I'll see if I can source an OEM or NOS one.



The oil line was kinked, too, so I need to source a new one of these, too.

The sprocket was chewed up, but that's no surprise. I'll get a new Stihl replacement. The clutch had obviously been replaced or at least opened up at some point. The rivets holding the cover (top right in the picture) on had been ground down, so they were no longer holding the cover down. Not quite sure how to attack this; either buy a new assembly, try to rivet it back together, or put it back together without riveting the cover to the clutch shoes. Any thoughts? The bearing looked ok, but I'll replace it, of course.



And the clutch shoes themselves are rusty. I'm assuming I should go ahead and replace these, right? I guess I could also send 'em down a bit and re-use, but I'm going to lose some material when I do this.



The case halves are pretty much cleaned up - LOTS of time spent scrubbing, brushing, going after the tougher deposits with a pick, liberal does of Brake Cleaner and Simple Green, etc. Now I'm thinking I should go ahead and blast 'em and paint while I've got it all apart. I have some of the correct color Stihl paint, and it shouldn't take that long to blast, prep, and paint.





I'll also replace the seals, of course. And I'm thinking I should replace the crank bearings and piston pin bearing while I'm at it. I also need to rebuild the carburetor.

Scott

 

[bulletpruf]

Here's the muffler - 1106 145 0310 - when I Google it, it comes up as a Contra muffler. However, it has a boss in the bottom that's been tapped, just like my 07 mufflers -- on the 07, a bracket attaches the muffler to the saw case, using this hole for the bracket. Of course, none of the Contra's that I checked have any such bracket, so I guess I need to check 'em all, and take a closer look at my 07 mufflers.



And here's the tapped boss on the bottom -



Scott

Did some comparing with my 07 mufflers and I think I've figured it out. Sort of.

The 1106/Contra mufflers have the clip on the top to hold the top cover on and the 07 does not. The muffler above has this so it's a Contra muffler, not an 07 muffler. I'm still not sure what the threaded boss is for on the bottom.

Also, when you compare an 07 muffler with an 1106/Contra muffler, they have the same spacing on the exhaust bolts, but the port opening is larger on the Contra muffler, which makes sense.

But the 07 muffler is actually physically larger than the Contra muffler. And I believe it has the same overall area for the exhaust to exit. Wondering if you can really wake up a Contra by adding another port to the muffler? Wouldn't be as easy as modding a stamped steel muffler, but I don't think it would be very difficult.

Need to consult the IPL to back up my hypothesis.

Scott

 

[NewToStihl]

I can't explain what was going on during that transition period, but the threaded boss on the bottom is where the muffler you'll see later on the 070/090 saws attaches to the case for stability. There is a threaded hole on the lower front of the flywheel side of the case and a small bracket bent at a 90-degree angle with two holes connects the 'dots'. I've not seen a Contra with the case hole or bracket, but I have seen mufflers like yours before (has the threaded hole along with the bonnet clip). I suppose they probably made the change to the muffler before making the change to the case?

I'll get some pics later if I get a chance.

 

[NewToStihl]

 

[bulletpruf]

I can't explain what was going on during that transition period, but the threaded boss on the bottom is where the muffler you'll see later on the 070/090 saws attaches to the case for stability. There is a threaded hole on the lower front of the flywheel side of the case and a small bracket bent at a 90-degree angle with two holes connects the 'dots'. I've not seen a Contra with the case hole or bracket, but I have seen mufflers like yours before (has the threaded hole along with the bonnet clip). I suppose they probably made the change to the muffler before making the change to the case?

I'll get some pics later if I get a chance.

NTS - thanks for the details and the pics. Your explanation makes sense to me.

Scott

 

[bulletpruf]

Lots of work done; need to post some updated pics.

I was able to get the broken exhaust stud drilled out on the cylinder and got a TimeSert installed. First time using TimeSerts - nice piece of gear, but not cheap!

Looks like I'll have 3 Contra's going back together at the same time. I'm thinking I'll do two stock-ish, and then hotrod one a bit. At least one will be repainted in olive drab (West Germany military style).

Not real impressed with the Stihl spray bomb gray paint; doesn't lay down very well. Putting it on top of some self-etching Seymour primer.

Anyone know where I can find a 137 cc jug and piston for a Contra? All of my Contra's are 106 cc. Have $ or stuff to trade.

More to follow!

Scott

 

[bulletpruf]

Here's the expensive ($70!) TimeSert kit that I used on the boogered threads on the cylinder -


And the finished product is below. Several steps in the process. First you drill the hole (correct bit provided), then you tap it (tap provided), then you counterbore the hole a tad bit because the insert has a lip (counterbore bit provided), then install the insert using their tool. Easy peasy.

 

[bulletpruf]

So far, I painted the bottom panel (gas tank), the clutch cover, and the oil tank. Started off by gently blasting all with some aluminum oxide, then Seymour self etching primer, then Stihl gray paint from a spray can.

This isn't a concours restoration, so I didn't fill in the scratches and gouges. However, it was in pretty good shape to start with. Anyway, I'm not a huge fan of the Stihl paint -- I'm getting some runs, so have had to hit the parts with some 320 and then spray again. Paint can is nice and warm and I'm shaking it up plenty, so not sure what the issue is. Having to put on a few coats to get decent coverage, too. Maybe it's just a bad can.

I'll have to attach some pics of the finished product once I get something that's presentable.

 

[Adam08ski]

Here's the expensive ($70!) TimeSert kit that I used on the boogered threads on the cylinder -


And the finished product is below. Several steps in the process. First you drill the hole (correct bit provided), then you tap it (tap provided), then you counterbore the hole a tad bit because the insert has a lip (counterbore bit provided), then install the insert using their tool. Easy peasy.

Used to use these at work a lot in the past. They are life savers in a wide amount of material, even used them in hardwood jigs and fixtures

 

[bulletpruf]

Ok, so I've got questions about bearings. The crank rides in the case on four needle bearings encased in a bearing race on each side. I have some OEM replacements for these, as well as some aftermarket ones. I don't think the races will be real easy to remove and reinstall (will use temperature differential for the reinstall), but I can't see skipping this step.

As for the piston pin bearings, they seem to be in pretty good shape, but I'm not seeing any replacements out there - aftermarket or otherwise. Any thoughts here on sources of replacements and whether or not to replace?

And then on the big end of the connecting rod there's another needle bearing. This will take some work to break the rod bolts free without tweaking the rod or crank, but I think I can put the rod in a rod vise (something I use for automotive rods) and remove the rod cap and bearing. Again, I'm not finding any sources of rod bearings, except for one NOS one that I grabbed on eBay. Any tips on where to find these? And should I change them?

Thanks!

Scott

 

[bulletpruf]

I can't explain what was going on during that transition period, but the threaded boss on the bottom is where the muffler you'll see later on the 070/090 saws attaches to the case for stability. There is a threaded hole on the lower front of the flywheel side of the case and a small bracket bent at a 90-degree angle with two holes connects the 'dots'. I've not seen a Contra with the case hole or bracket, but I have seen mufflers like yours before (has the threaded hole along with the bonnet clip). I suppose they probably made the change to the muffler before making the change to the case?

I'll get some pics later if I get a chance.

Was going through some files this weekend and found an old service bulletin that explains what happened. Will post it when I get home.

Scott