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Some carbs used a semi fixed hi jet. I have a homelite super XL 925 that has one. It is a Tillotson HS series carb. It runs best with the H needle all the way in. They did this so guys couldnt lean them out too much and burn them up. This saw runs a bit on the rich side and I'd like to lean it out but I would need to find the right high speed nozzle. Like this
 
My manuals show the P41 using both Tillotson and Walbro carbs, the Tillys used were HS 147D and 214A, they did not have governors but the Walbro SDC 79A did and it was part #84-530. You must check your carb model and make sure what you have and need before ordering any parts you may not need or want.
 

Model numbers will be on the side of the carb, must have model number designations to get proper part numbers as many different model carbs can and have been swapped onto old saws. Likely have to remove the carb unless you can squeeze an inspection mirror down the side of the carb to read the stamped in model designation.
 
0722191311_resized.jpg While you're researching carbs today, Jerry, this SDC 53D from the P62 is getting rebuilt later after a few heated USC cycles in some fairly mild solution.
I gather the plug is the governor on one of these? Should I leave it alone and just let the USC do its thing, or disassemble for a better result? And what do I need to know about the governor in general on this carb? I'm pretty sure my running issues were the floating welch plug along with the metering diaphragm nub not being inserted into the metering lever fork..., but I hear the governor can also be problematic on occasion. Just not sure how, how to know, or how to remedy such a condition.

And do the new welch plugs on these just need to be pressed into place with an appropriate punch/drift to simply act as a cover, or do they actually need to be sealed as part of the circuits? I've it read both ways.

TIA as usual for any enlightenment.

 
A little work done on the 600 restoration. My daughter did the lettering for me. Will add a couple layers of clear coat.
2610fb858756e09208173488a0ca63ed.jpg
 
View attachment 748706 While you're researching carbs today, Jerry, this SDC 53D from the P62 is getting rebuilt later after a few heated USC cycles in some fairly mild solution.
I gather the plug is the governor on one of these? Should I leave it alone and just let the USC do its thing, or disassemble for a better result? And what do I need to know about the governor in general on this carb? I'm pretty sure my running issues were the floating welch plug along with the metering diaphragm nub not being inserted into the metering lever fork..., but I hear the governor can also be problematic on occasion. Just not sure how, how to know, or how to remedy such a condition.

And do the new welch plugs on these just need to be pressed into place with an appropriate punch/drift to simply act as a cover, or do they actually need to be sealed as part of the circuits? I've it read both ways.

TIA as usual for any enlightenment.

The governor can usually just be left alone until they fail, when they fail they will cause the engine to run so rich the saw will not reach WOT. To disable them one can punch out a small disc from a pop can, place it in the bore and then reinstall the brass plug. The Welch plugs need to be flattened into place, I have done so with a close to fitting diameter punch if I had one or look through my bolt selection to select one that almost matches the diameter of the plug, tap the domed disc down flat. The Welch plugs were originally sealed around the perimeter from the factory but since the gas is now laced with ethanol, a type of alcohol , it will cause the sealer to let go and float around until it plugs a jet or other orifice, not the best of scenario`s. I have sealed them with Indian Head shellac and its still there 20 years or more later.
 
Hi I realize this is an old post, however glad to have found it. I recently picked up a 3071 and considering the same ignition system modification. Question though... does this setup bypass the secondary condenser located in the plastic shell located above the muffler? Although the ignition system on my saw is currently working, I'm looking at sourcing replacement parts for when the inevitable happens. The secondary condenser is Pioneer part #429681 and I haven't had much luck sourcing an original or slightly more modern part number to replace with.

--------- Pioneer 3071 repair of the ignition system ---------
Hi All. I picked up this pioneer 3071 a while back. and it was running well. THEN, one day it wouldn't start and had no spark.
The 3071 was pioneers first electronic ignition model. and uses a wico-prestolite system. and parts for it seem to be scarce.
After trying a new plug. I tested the output coil. The primary metered at 0.5 ohms and the secondary was just over 1K.
when I dabbed 12v across the primary I could get a small spark from it. Next to test was the pickup-unit near the flywheel.
Putting a meter on the output of this gave me pulses, but they wearn't enough to drive the output coil. I took a dremel to
the thing and found that although the coils and diodes were intact. The transistor buried inside the unit was dead.
Rather than replace it and re-seal it all in resin, I thought it would be a better plan to just replace the whole thing.

After spending a week looking for some original Wico ignition parts, I took the advice of some folks here and converted
the 3071 to use a more modern, and obtainable ingnition system. a search of an online-auction site found a similar shaped
unit, that was advertised as a non-original ignition coil to fit the following.....

<Snip...>

The whole repair took me a couple of hours. and the saw runs well... Although I think it now could do with a fuel-filter / carb-rebuild, and a new chain.
 
So the P62 SDC is in the USC this afternoon but the large welch plug wasn't going anywhere without a fight. Left it in place and crossed my fingers that nothing bad is underneath it. Sure as hell didn't want to gouge the carb body trying to get it out if it wasn't absolutely necessary.

So on to inspecting the reed block. Found quite a mess. And the pic is after I cleaned up all the funk and silicone that was spread everywhere in an apparent attempt to seal around a gasket that should have just been replaced anyhow. Was rather surprised to find sludge on the inside of the reed chamber. Is it common for it to accumulate there?

0723191520b_resized.jpg
Found some minor cracks in the block right at the threaded inserts that don't appear to be problematic and don't travel far. I would assume they're common and not to be overly concerned about em?

0723191523a_resized.jpg

0723191523_resized.jpg
I'm guessing there shouldn't be any light between the reed itself and the block? So am I looking at just replacing the reed, or an entire block assembly due to the cracks?

0723191521_resized.jpg
But the good news is, the saw does have the later cylinder with the top fin relief for the additional cooling. Was very happy to see that.
 
So the P62 SDC is in the USC this afternoon but the large welch plug wasn't going anywhere without a fight. Left it in place and crossed my fingers that nothing bad is underneath it. Sure as hell didn't want to gouge the carb body trying to get it out if it wasn't absolutely necessary.

So on to inspecting the reed block. Found quite a mess. And the pic is after I cleaned up all the funk and silicone that was spread everywhere in an apparent attempt to seal around a gasket that should have just been replaced anyhow. Was rather surprised to find sludge on the inside of the reed chamber. Is it common for it to accumulate there?

Found some minor cracks in the block right at the threaded inserts that don't appear to be problematic and don't travel far. I would assume they're common and not to be overly concerned about em?

I'm guessing there shouldn't be any light between the reed itself and the block? So am I looking at just replacing the reed, or an entire block assembly due to the cracks?

But the good news is, the saw does have the later cylinder with the top fin relief for the additional cooling. Was very happy to see that.

Replace the reed block reed and all if you can find one, it would still be usable if the cracks do not go through to the outside, if they do they can be fixed but new is best.
 
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