McCulloch Chain Saws

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Heli Coil makes a spark plug thread repair kit that is around $30 at most auto parts stores and has several different inserts. The oversize tap prepares the threads and the knurled top on the insert locks it in place with a special swaging tool included in the kit.

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Poge - I went up in the attic tonight and brought down a NOS PM850 cylinder/crankcase and piston.

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This one happens to be an "A" cylinder.

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Locating pins for the rings.

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Good news for Poge - the end gap with a new set of rings in a NOS cylinder 0.075". Best I could guess with my dial caliper is the pin diameter is 1/16" or 0.0625" so the end gap on the rings is 0.012" or so to the pin.

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And there you go...

Mark
 
I have a super pro 60 mcculloch. Could it be equipped with a .354 sprocket? It has a Mcculloch bar and a probably a Mcculloch chain. I tried to put a 3/8 bar and chain on it and it got impossible to turn once I tightened the nuts.


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Very possible it is .354 pitch. The came in both fixed rim and floating rim. It's always good to keep a selection of sprockets on hand to be ready to anything.

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Mark

Thanks! I will check the original chain with the 3/8 chain and compare. If it's .354 I'll get another sprocket and keep the original in case I run into some .354 chains.


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+1 on that Heli-Coil spark plug thread kit. I've used a couple and they worked well in my particular situations. What I found to be a huge plus with those aside from the locking feature is, (when done right), the top of the insert should provide a new mating surface for the plug washers/gaskets to seat/seal instead of relying on the previous seat of the cylinder itself..., which in many cases of stripped threads or previous insert attempts will be a hogged out mess of dings and gouges and not seal properly anyway regardless of brand if only a thread insert is used. Can only vouch for the Heli-Coil plug thread kit which is specifically for plug threads, but have heard the Timeserts, Keenserts and Keyserts are also very good and highly reliable products. They may indeed also have plug thread specific solutions like Heli-Coil. Main difference being they are solid thread inserts where the Heli-Coils are actually coiled steel.

And thanks for all that great intel, Mark. Bit the bullet and ordered a new set of rings. My end gap looks to be about twice as much as what you have pictured.

As for the caps, the only one I have with the plastic post was the one that came on the SP81. I now recall you mentioning some time ago that the Homelite duck bill would require some very careful drilling of the post in order to fit. It does fit perfectly into the nylon insert of the other style caps and may render the spring unnecessary due to the extra thickness of the flange. Will post results after some testing with new gaskets all the way around. BTW, the guy in Ky. has Fel-Pro re-pops of the 69767 gaskets in 20 paks for $22.99 if anyone else with way too many 10 series Macs needs some too.

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Red-Koted the tank yesterday and went through a couple SDC's to kill some time while it was drying and to see what I had to work with carb-wise...

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Now that's a whole lot o' wrong goin' on, isn't it? My first thought was, "a funny place to hide your weed". Then, "so that's what happened to my other contact!" Finally, "Adjustment screws? We don't need no stinkin' adjustment screws!" And this is all just from the carb that came off the SP81. Fortunately the other two from a pair of 10-10 carcasses were in way better shape with only a throttle return spring missing on one. Diaphragms weren't even that bad. A few cycles in the USC and they came out nice and clean.

 
If it comes to it that you have to replace the carburetor, keep in mind that there are (at least two) different sizes, one with a smaller throttle bore and venturi (.750/.625), and a larger one (.812/.750) you definitely want the big one on that saw.

From my count, there were at least 17 different SDC carburetors used on McCulloch saws and I have probably missed as many as I have found.

The original on and SP80 should be the SDC38. The SP81 used an SDC52 with a fixed high speed jet.

Mark
 
The three I cleaned up last night were all different with one having the smaller bore and venturi. The one from the SP81 was an SDC51 and had fixed jets on both hi and lo with the only adjustment being the idle screw. It will definitely be replaced by a fully adjustable version with the larger bore/venturi. Another had no number suffix next to the SDC but had a 37 to the lower right. The third (and the small venturi version) had no SDC or numbers anywhere except a small series in the metering chamber.

Dare I pop the welch plugs for replacement on these or leave well enough alone? I did run across an SDC rebuild video with some pretty nasty crud under the plugs, but not sure if that's the norm or the exception.
 
I do not remove the welch plugs on a routine basis. If I put in gaskets and diaphragms and know the other bits are right and one still doesn't run right I may pop them out for additional attention. It is easy enough to take the carburetor off again if you run into problems that can't be explained otherwise.

I had the Tillotson HS71 on the Super LG6A but gave up on it due to the high speed governor and put on one of the smaller SDC carburetors, I need to put a bigger one on because the 70 cc Super LG6A can't compete with a well worn 2-10G as it is.

Mark
 
The three I cleaned up last night were all different with one having the smaller bore and venturi. The one from the SP81 was an SDC51 and had fixed jets on both hi and lo with the only adjustment being the idle screw. It will definitely be replaced by a fully adjustable version with the larger bore/venturi. Another had no number suffix next to the SDC but had a 37 to the lower right. The third (and the small venturi version) had no SDC or numbers anywhere except a small series in the metering chamber.

Dare I pop the welch plugs for replacement on these or leave well enough alone? I did run across an SDC rebuild video with some pretty nasty crud under the plugs, but not sure if that's the norm or the exception.

I have several mcculloch SDC carburetors. If you are looking for a core. Give me the carb number that you want and I can see if I have one. Mine are all from 10 series macs, except for one pro Mac 700 carburetor that I swapped out the throttle shaft on.


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I was wrong about the SDC-51 not having any H/L adjustments. What I thought was an idle screw appears to be an adjustment ..., presumably for the lo since Mark referred to the H being fixed. The other two had the diagonal idle screws for the throttle plate and I assumed that's what the one on the 51 was too since both the hi and lo screw locations were plugged. Duh.

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Idle screw for this comes from the side of the fuel tank assy ?
The shown one is the L screw

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Yes..., a tank mounted idle adjustment screw on this saw for the SDC-51 carb. The screw in the previous pic is definitely a jet adjust needle screw, not one of the blunt ones that engages the throttle plate for idle adjust as I originally thought it did on this particular SDC version. It's in a completely different position than the diagonal throttle plate adjustment screw at the top center of the body (where the indentation is in my previous pic). Would seem to be a distinctly different body to accommodate the fixed H jet and the adjustable L, unless it's the other way around. In either case, the screw seems to diagonally pass through what would normally be the H jet adjustment screw threads to reach an L seat or perhaps an H seat with a fixed L? Ends up in that bulb in the venturi which is below where the small welch plug would normally be. Clearly has to be internal differences also for the circuit.

Typical SDC.​

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The weird fixed jet model 51 (or what's left of it).

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Gentlemen, I am sad to report that I just got a message through eBay that the Seller has refunded my money since USPS has returned my purchase to the Seller as it was damaged in transit. I have send a message to the Seller asking the extent of the damage.

Ron

I spoke with the Seller. Not only did USPS manage to bend both handles they broke the casting. Seller said it is completely trashed. He wasn't sure if the anvils made the return trip.

Ron
 
I spoke with the Seller. Not only did USPS manage to bend both handles they broke the casting. Seller said it is completely trashed. He wasn't sure if the anvils made the return trip.

Ron
Wow...
Must have been packaged poorly?
 
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