Pioneer 620 - bringing it back to life

[cdahl383]

Recently picked up an old Pioneer 620 chainsaw. The seller said it was his father-in-law's (the seller looked to be in his late 60's to early 70's). He wasn't sure if his father-in-law bought it new or not, but said he had it for a very long time. It looked like it sat in the corner of the garage for decades. Very dusty/dirty, but appeared to be complete. I brought some tools and my compression gauge with me when I checked it out. It had good compression and looked complete, so I bought it.

I brought it home and spent some time just cleaning it up. Not a fan of working on dirty stuff. Got it cleaned up pretty good and then did some basic diagnostics on it. Checked the compression (showed 150psi on my gauge), verified that it had spark, and took the muffler off to check out the piston/cylinder through the exhaust port (looked really good). Everything seemed to look pretty good. I opened the fuel tank and it was all varnished up in there and stunk terrible. I pulled the sediment bowl/fuel line out and filled the tank with Berryman Chem-Dip carb cleaner. Four hours later the tank was spotless!

I ordered a carb rebuild kit for the old Tillotson HL22A carb, cleaned the existing air filter, and continued cleaning the saw up as much as I could. Now I'm just waiting for the carb rebuild kit and a few other small things. Hoping after rebuilding the carb I can get it fired up and running again! No plans to put it into serious use, but would like to use it occasionally around the house to cut up a little firewood just for fun.

Here's a few photos / videos I've taken along the way so far:

 

[cdahl383]

Here's some photos after I cleaned it up a little bit and a couple before/after photos of the fuel tank...

 

[cdahl383]

Cleaned and rebuilt the carb last weekend. Got it to fire up and run, but it didn't run very well. Smoked a lot and wouldn't rev up or idle. Appeared to be running very rich.

I suspected an issue with the carb, particularly the needle/metering lever as the kit I bought had significantly differently looking metering lever and needle. I took the carb back off and swapped the original needle and metering lever back in. I also noticed the metering lever was not flush with the chamber floor, so I adjusted that as well. Hoping that does the trick.

I haven't had a chance to fire it back up since it was snowing out and we got busy around Thanksgiving. Hoping it runs good now, we'll see.

Also replaced the fuel line and filter as it had the original line and filter on it when I pulled the sediment bowl out. It had a little small felt filter in the sediment bowl. Not sure where to get one of those, so I just cleaned that one really good using dirtbike air filter cleaner and Chem dip. It came out pretty good and seems to be fine as the saw is pulling fuel from the tank through the bowl, etc.

I also tested out the oiler. I dumped some bar oil into the bar oil tank and pushed the lever about a dozen times or so. It finally picked up some oil and started squirting it out of the oil port by the bar mount. Excellent! At least I know that works now.

 

[cbfarmall]

That looks like the original style needle and lever, without a fork. Any modern kit will have a forked lever needle, make sure they are engaged. Make sure the lever pivots freely in the carb body, some aftermarket kits give issues here. A little filing to the side of the lever will fix this. Replace the oring on the high speed needle, should take a 007. This can cause an slight air leak. Doesn't look like your low speed has any spring or seal there. In an extreme case, the welch plug in the fuel chamber can leak fuel causing a rich condition.

Hopefully those carb parts pictured are the old ones and not what you are trying to use.

Finally, make sure the choke is open. I had trouble once tuning a saw, turns out the choke was closed. Operator error.

 

[cdahl383]

That looks like the original style needle and lever, without a fork. Any modern kit will have a forked lever needle, make sure they are engaged. Make sure the lever pivots freely in the carb body, some aftermarket kits give issues here. A little filing to the side of the lever will fix this. Replace the oring on the high speed needle, should take a 007. This can cause an slight air leak. Doesn't look like your low speed has any spring or seal there. In an extreme case, the welch plug in the fuel chamber can leak fuel causing a rich condition.

Hopefully those carb parts pictured are the old ones and not what you are trying to use.

Finally, make sure the choke is open. I had trouble once tuning a saw, turns out the choke was closed. Operator error.

The kit came with o rings. I’ll have to replace them. Wasn’t sure what those were for at first.

I didn’t replace the Welch plug. Maybe something is dirty below that? I don’t fully understand what the function of the Welch plug even is honestly. Still learning.

Yes, those are the old parts. I just laid them out so I would remember the order of everything.

I made sure the choke was open. It sort of springs back when you open it. That’s how I remembered if it was open or closed since there is no indicator anywhere.

If it’s still running goofy I’ll pull it off again and look at the Welch plug. I can replace the o rings on the needles with the carb on the saw.

 

[cbfarmall]

The welch plug covers metering ports into the throat. Without it, fuel would run straight into the motor without being adjusted by the needle. Don't try to run aggressive tools through the ports if they are dirty. Carb cleaner has always been the only thing necessary. I'm sure there are videos on YouTube if you decide to remove the plug. Be careful here. If the chamber was clean when you pulled the diaphragm odds are it's clean under the plug.

FYI, raising the lever relative to the floor would tend to make it rich, lowering it leaner.

A Mityvac is a useful tool for checking leaking needles and seats.

 

[WoodmanSr]

The kit came with o rings. I’ll have to replace them. Wasn’t sure what those were for at first.

I didn’t replace the Welch plug. Maybe something is dirty below that? I don’t fully understand what the function of the Welch plug even is honestly. Still learning.

Yes, those are the old parts. I just laid them out so I would remember the order of everything.

I made sure the choke was open. It sort of springs back when you open it. That’s how I remembered if it was open or closed since there is no indicator anywhere.

If it’s still running goofy I’ll pull it off again and look at the Welch plug. I can replace the o rings on the needles with the carb on the saw.

Acquired a 600 under similar means & condition. Sat 45 years or longer in dad's basement.
Those are interesting fuel pickup. Pic of my rebuild.

Do you have a Tach. Remember those old girls only turn 5500 rpm WOT. Mine sounds horribly rich there. Not more than 10 minutes in wood. It will wear you out & wanting for a modern saw. Just have as nostalgia (would sell probably).

Shown with another oldie, Sears 758G (David Bradley).

 

[cdahl383]

The welch plug covers metering ports into the throat. Without it, fuel would run straight into the motor without being adjusted by the needle. Don't try to run aggressive tools through the ports if they are dirty. Carb cleaner has always been the only thing necessary. I'm sure there are videos on YouTube if you decide to remove the plug. Be careful here. If the chamber was clean when you pulled the diaphragm odds are it's clean under the plug.

FYI, raising the lever relative to the floor would tend to make it rich, lowering it leaner.

A Mityvac is a useful tool for checking leaking needles and seats.

Ok cool. The insides of the carb were pretty clean when I pulled it apart. I think I’ll leave that alone for now.

I soaked the metal carb body in chem dip for a couple hours then cleaned and sprayed all passages with carb cleaner. Appeared to be very clean afterwards.

Yes I think the lever was too high before. That may have been causing the rich condition. I’ll have to test it out again and see how it runs.

I just recently got a mityvac. If I end up taking the carb off again I’ll test it. I did see some YouTube videos out there about how to do that, as well as test the crank seals for air leaks.

 

[cbfarmall]

You can test needle and seat thru the fuel line without removing the carb. Should hold pressure up around 12-15 pounds I think and release. You'll at least learn if the needle wants to leak or not.

 

[cdahl383]

You can test needle and seat thru the fuel line without removing the carb. Should hold pressure up around 12-15 pounds I think and release. You'll at least learn if the needle wants to leak or not.

I may try that next time I have the carb off. The way the fuel line is situated on this saw it really sucks to get it off. I have to loosen the sediment bowl too as the fuel line is literally only an inch or so long from the sediment bowl to carb.

 

[cbfarmall]

I see. It's been while since I've had one apart.

 

[cdahl383]

I see. It's been while since I've had one apart.

I did buy one of those Mity-Vac kits though that comes with the vacuum pump and a bunch of attachments/fittings. Maybe I can use that to test it out. I've never done a pressure/vacuum test before, so it would be good to learn.

 

[cdahl383]

Forgot to update this thread as I sort of started a different thread about this saw.

Rebuilt carb, cleaned air filter, new plug, fresh fuel, new fuel lines and filter, 150psi compression, spark, fired up and ran, but would only idle and not rev up properly. Determined it must have an air leak.

Hooked up Mityvac to saw, performed pressure/vacuum test, it failed miserably. Could actually hear the air hissing out of the leak under pressure. Would not even build up to 5psi on the gauge. Decided it likely needed crank seals. Ordered both flywheel and clutch side seals.

Split crankcase, needed large puller for flywheel removal, small puller for clutch removal, liberal use of Kroil on old parts. Found nasty fuel varnish residue inside crankcase. Was a real chore removing the crankcase half, required use of pry bars, large screwdrivers, and lots of patience. Soaked that with Berryman Chem Dip to clean and remove the residue. Came out clean like the tank.

Drove out old seal on flywheel side, cleaned mating surfaces up really good, made my own gasket for the crankcase halves, applied thin bead of Permatex Motoseal to both mating surfaces and put gasket on main crankcase half over studs. Sandwiched the two parts together and used a wood block and hammer to tap the crankcase back together. Once over the studs, used nuts to tighten down in crisscross pattern. Brought saw inside to cure Motoseal at room temperature for a couple days.

Performed another pressure/vacuum test. It was better, but still not good. Pumped up to 7-8psi but leaked down fairly quickly. Sprayed soapy water on clutch side seal and it bubbled up like crazy.

Drilled small pilot hole into metal surface of seal on opposing sides, inserted two small screws into seal and lifted it out evenly using a wood block/rag to protect saw surface and 90 degree needlenose pliers to pull the seal up. Removed seal, cleaned up crank, inserted new seal with oil/grease applied everywhere, tapped into place, seal snagged on step on crankshaft, seal trashed. Got another seal, this time inserted a piece of film negative strip inside the seal over the crankshaft step. Tapped into place, seal slipped on perfectly, removed negative strip, seal installed correctly.

Ran another pressure/vacuum test. This time it passed. Pumped up to 7psi and it held with no drop. Applied vacuum up to 14" and only saw about at 1.5" drop over 30 seconds. Appeared to be good.

Ready to reassemble the saw now. Hoping to start on that this weekend and get it running again by Sunday.

 

[Bob Hedgecutter]

Have a very similar journey to follow with a new to me Danarm 110- basically a 620 carbon copy.
Have found this and your other thread most interesting.

 

[cdahl383]

Have a very similar journey to follow with a new to me Danarm 110- basically a 620 carbon copy.
Have found this and your other thread most interesting.

Oh ok cool! I'll have to look that saw up, not familiar with that one.

I'm glad someone is finding some of my ramblings useful haha! There's a few guys on my Youtube channel that are following my progress on the 620 as well as they have similar saws. Pretty limited audience with these old saws haha!