Pioneer 620 - Won't rev up clean to full throttle

[cdahl383]

You could after removing the ignition. Check it afterwards I suppose.

You really can’t confirm if the case gasket is leaking as you can’t get in between there.

Once I get it together, before I reassemble anything else, I’ll do another pressure/vacuum test. If it’s good then I’ll put it back together all the way.

 

[cbfarmall]

You really can’t confirm if the case gasket is leaking as you can’t get in between there.

Once I get it together, before I reassemble anything else, I’ll do another pressure/vacuum test. If it’s good then I’ll put it back together all the way.

You can't see it from the bottom and front of the saw? My memory must be fuzzy here.

 

[cdahl383]

You can't see it from the bottom and front of the saw? My memory must be fuzzy here.

Not really. You can kind of see in there but not very good. The seal is hard to see too. You cant see at all on the right side by the gas tank, no way to really see in there.

 

[cdahl383]

Got the crankcase halves back together today. Put some oil on the crankshaft and the recessed area where the bearing fits. Also put some on the bearing itself.

Put some motoseal on the mating surfaces and slid the gasket in place. Fit the case half over the crankshaft and slid the crank seal slowly over the shaft. Got that seated good and then tapped the case half on with a wood block and hammer. Got it seated good and once the studs stuck through the case I put the nuts on and tightened it in a crisscross pattern. Got it tightened down pretty good.

Had to tap the crankshaft a few times to free it up. It spins nice and free now.

Brought the saw inside so the sealant could cure at room temperature. It’ll get down to 20-30 degrees at night out in the garage.

The gasket sealant package said to let it cure for 24 hours. I’ll wait to do a pressure test until tomorrow or Wednesday.

Hope it sealed up!

 

[cdahl383]

Ran another pressure/vacuum test on the saw today. Waited 48 hours for the Motoseal to cure at room temp, figured that would be good enough.

I was able to actually pump the crankcase up to 7-8psi but it did leak down slowly. The flywheel side seems to be fine, no issues there that I could tell. However, the clutch side seal now leaks. I think previously, the flywheel side leak was so bad that all the air just rushed out of that leak and there wasn't enough pressure to push out any bubbles on the clutch side. Either that or from shifting the crankshaft around slightly it tore/ruptured the old seal. Either way, that seal is bad, so I'll have to replace that one before I put the saw back together.

I looked online for a bit and found some different approaches to remove and replace that seal. I'm not a big fan of drilling into the seal and putting a screw in there, though I could see how that could work. I'm just afraid I'll end up going through the seal and into the main bearing.
I found a couple videos online where guys use a little screwdriver looking puller that slides between the crankshaft and seal and pulls up on the inner lip of the seal. Then you tighten the adjustment on the handle of the screwdriver and sort of use it as a fulcrum/lever to lift the deal out without damaging the crankshaft or recessed area the seal sits in. Of course I don't have one of those, so I'll have to buy/order one if I go that route.

I've seen other threads where guys modify a flathead screwdriver to have a little hook on the end and then slide that under the seal lip and use a socket slipped on the screwdriver shaft as a slide hammer to knock it out that way.

Any tips on how to remove this seal and install the new one without damaging the crankshaft or bearings? What method has worked best for you guys? This is my first time doing a seal like this one (the flywheel side one was different than this one).

Here's a quick video of the clutch side seal failing the pressure test...

 

[pioneerguy600]

 

[cdahl383]

View attachment 1239954View attachment 1239959View attachment 1239957View attachment 1239955

Is that just a custom made ground down screwdriver?

 

[cdahl383]

Another question, should I apply some sort of sealant on the outside edge of the new seal once I get to that point? Seems like some air might be able to leak through there if it's not a perfect fit. Maybe a small bead of motoseal?

 

[cbfarmall]

Another question, should I apply some sort of sealant on the outside edge of the new seal once I get to that point? Seems like some air might be able to leak through there if it's not a perfect fit. Maybe a small bead of motoseal?

Won't hurt. Most of it will rub off. Regarding, the seal tool, I've ground a few small screwdrivers down to make them. Also, it helps to knock the seal in slightly to dislodge it. They can get really stuck after 60 years or so.

 

[pioneerguy600]

Is that just a custom made ground down screwdriver?

Yes, it was just a regular flat blade before shaping.

 

[cdahl383]

Won't hurt. Most of it will rub off. Regarding, the seal tool, I've ground a few small screwdrivers down to make them. Also, it helps to knock the seal in slightly to dislodge it. They can get really stuck after 60 years or so.

Cool, I'll try knocking it down just a bit to see if it breaks loose.

I was looking at the surrounding area and it looks like someone might have been using the case for leverage when it was last pulled. There are some imperfections that I might have to grind or sand down in order to get the new seal to drive in straight. I'll have to look at that before I pull the old seal. Just from looking at it, it seems like the new seal is almost too large in diameter to fit inside there. But several guys have told me that is the correct seal to use and they used it in their 600/620 saws.

Was also wondering if I should try to put some sort of film or thin aluminum like a cut up can around the crankshaft to allow the oil seal to slide down on that while tapping it into place? Or if it would be fine just driving it in by itself?

 

[cbfarmall]

Was also wondering if I should try to put some sort of film or thin aluminum like a cut up can around the crankshaft to allow the oil seal to slide down on that while tapping it into place? Or if it would be fine just driving it in by itself?

Exactly. Cut up a beer or soda and wrap a thin shim around the crank steps. I generally curl it up inside the seal. Use some oil as well. Otherwise, you will twist up the seal lip and ruin it.

 

[cdahl383]

Exactly. Cut up a beer or soda and wrap a thin shim around the crank steps. I generally curl it up inside the seal. Use some oil as well. Otherwise, you will twist up the seal lip and ruin it.

Ok cool, makes sense. I’ve read where you can also use an old film negative to go around the crankshaft. That might be even better as there’s no chance of scratching anything with that.

 

[cbfarmall]

Ok cool, makes sense. I’ve read where you can also use an old film negative to go around the crankshaft. That might be even better as there’s no chance of scratching anything with that.

That's true but you're not going to scratch a hardened steel crankshaft with a beer can shim.

 

[cdahl383]

That's true but you're not going to scratch a hardened steel crankshaft with a beer can shim.

Haha that's true! I'm probably overthinking this again haha!