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

[cdahl383]

Ran up to the hardware store this morning and got some stuff for the flywheel puller. I have this bigger puller that's sturdy but the slots/bolts that came with it are too big for the little bolts that thread into the flywheel. Got some spacers and washers and nuts for the three bolts that go into the flywheel. Now they fit into the puller really well.

Got it set up and sprayed some Kroil on everything to help loosen stuff up a bit. Will try wrenching on it later today. Hopefully it will come off without too much trouble. But I doubt it haha! I made sure to put the nut on the end of the crankshaft too. A buddy of mine forgot to do that once on a dirtbike and attempted to pull the flywheel using a puller and he mushroomed the threads on the end of the crank. Not good!

 

[cbfarmall]

That'll work. Tighten the puller and pick the whole mess up by the puller threads and hit it with a hammer. Ought to pop off.

Presumably, you've grabbed all the available threads with your little bolts. I think one time in 15-20 years I had the threads tear out of the flywheel.

 

[cdahl383]

Got it off! Tightened it up really good and gave it some good whacks with the brass drift and dead blow hammer.

Double checked for air leaks again by doing another pressure test. The clutch side is solid, no leaks. Pressurized and sprayed soapy water all over the seal no bubbles. I won’t be replacing that one. It’s possible someone did that one not too long ago.

Checked the base gasket, head gasket, intake, nothing, all good no bubbles. Can hear hissing from around the case half. Has to be that flywheel side seal.

Next step will be removing the coil/points to get them out of the way and then pull that case half off. That should be fun haha!

 

[cbfarmall]

Almost there. Do enough of these and eventually you can strip one of these saws down in an hour.

 

[cdahl383]

Went out to the garage today on my lunch break and started working on removing the crankcase half. First I took some photos of how the points were oriented. I see there is a mark on there that has to line up with the mark on the case half. Looks pretty straightforward, but I took some photos anyway.

Then I started prying on the case half. At first I used some large flat head screwdrivers in three different spots. Eventually the gap got too big for those, so I moved on to using my pry bars. I just kept tapping on them over and over going around the three spots I had inserted them in. I've got the case half up now where I can wiggle it around a little bit and the threads are almost recessed into the holes. The problem is now the gaps are so big it's hard to fit anything in there to continue lifting it up.

I'm thinking of possibly using my big puller to try and pull it the rest of the way off. I could get a couple long bolts/screws and thread them into where the points are mounted, and then push against the crankshaft end (with the nut on of course) and see if that would lift it up the rest of the way. I'm not sure if that will work that well since there's only two bolt holes to utilize unlike the flywheel which had three. I think I'll give that a shot first and if that doesn't seem to be working, I'll just go back to trying to pry it up gently a little bit at a time. It's coming up, it's just a slow process. I'm sure if I whaled on the thing more I could get it off quicker but I didn't want to break anything.

Here's a few pics of my progress so far...

 

[cbfarmall]

Looks like the flywheel key is still in place. You need to remove that. Then, hold the saw in the air by fan housing and tap the crank with a soft hammer. You have it halfway apart.

 

[cbfarmall]

Basically, you are trying to knock the crank out of the bearing which will stay in the case. Sometimes the bearing stays on the crank.

 

[cdahl383]

I got it apart! Crankcase half removed! It just took a little more prying and tapping to get it off. Nothing broke and I didn't even swear at it haha!

The crank bearing stayed on the crankshaft. Not sure if that will be a problem or not when putting the cases back together. I didn't want to mess with it though until I did a little more research. I got the case halves apart, cleaned up my work bench, and called it a night.

The crankcase appears to have some nasty varnished looking fuel residue in the bottom. It looks like it actually leaked out at some point onto the bottom of the crankcase on the outside. Probably why it was leaking and not holding pressure. I'll have to clean that stuff up. I'm thinking maybe leaving some Chem-dip in there for a few hours might help dissolve that stuff, similar to what I used in the fuel tank. I'll have to clean everything up really good too before I think about reassembling.

I'll knock the seal out tomorrow and after I've cleaned everything up, I'll drive the new seal in. I'm assuming you just drive it in until it's flush with the backside of the case?

The crankshaft and rod seem to be okay. The crank bearing seems okay too, it spins freely, no weird noises or hangups, etc. Didn't feel any play that I could tell.

I had to remove both keys like you said to get everything off. The smaller one closer to the crankcase is for the points. The larger key further out on the crank is for the flywheel. Got them out without too much trouble.

I didn't notice a gasket anywhere. I swear in the parts diagram I have it shows a gasket there. I've had several folks tell me there's no gasket though, so I guess I'll just use some sort of fuel resistant sealant/gasket maker and call it a day. Any suggestions on that? Maybe Yamabond or something similar?

I was just glad I got it apart tonight. I knew once I got it further up and I was able to wiggle it around it was just a matter of time before it came off. Thanks for the help and tips!

Here's a few pics...

You can see in the pics where the old fuel/oil must have sat for a VERY long time and turned to varnish.

 

[cdahl383]

I got the crankcases all cleaned up now. They both had some nasty varnish residue from old stale fuel sitting there. I used some Berryman Chem-dip to clean that stuff out. Just let it sit for a few hours, then dumped it out and wiped it up. I made sure I only put enough in there to clean the varnish and not go up against the clutch side crank seal. I don't think that stuff is too good for rubber parts. It looks nice and clean now.

I also noticed that from pulling the other crankcase half off, the crank was pulled out a bit. I couldn't rotate the assembly properly. I put the flywheel nut on the end of the crank and used a wood block to knock it back into place with a hammer. Got it back in most of the way but it wouldn't go much further. I used a brass drift and deadblow hammer and that did the trick. Now the crank is centered properly and the rotating assembly can actually rotate without hitting stuff. I'm sure I could have done that by putting the other crankcase half on, but it seemed like that could turn into a battle. A lot easier doing it this way. Now the other crankcase half should fit on a little easier.

Any tricks to aid in getting that half back on? One guy on FB told me to keep the main case cold and to heat up the other half I'm reinstalling to help with reinstallation. I really don't want to use a torch to heat it up since I have a seal on there along with the ground wire. Maybe a heat gun?

I'm going to use some Permatex Motoseal for the gasket seal. I've read good stuff about that and it's fuel resistant as well. I talked to a few other guys that have taken apart the 600 series Pioneers and they said that stuff always worked well for them. I'm just going to spend some more time cleaning everything up really good first though. Hopefully I can make some more progress later this week.

 

[cbfarmall]

You got new seals, right? Not quite clear in your description.

Far as heat, probably won't hurt any. I bought a harbor freight heat gun years ago and have got plenty of use out of it. It'll be more important to tap the case on evenly. That case cover has to go around the bearing and inside the crankcase so heating it for a looser fit can become a bit of a zero-sum game. Normally the bearing fit is tighter than the case fit but I've seen it the other way.
Don't try to beat the hell out of it.

 

[cdahl383]

You got new seals, right? Not quite clear in your description.

Far as heat, probably won't hurt any. I bought a harbor freight heat gun years ago and have got plenty of use out of it. It'll be more important to tap the case on evenly. That case cover has to go around the bearing and inside the crankcase so heating it for a looser fit can become a bit of a zero-sum game. Normally the bearing fit is tighter than the case fit but I've seen it the other way.
Don't try to beat the hell out of it.

Yes, I just put the new seal in last night.

I watched a video the other day where a guy worked on a pioneer 600 and the case just slid right on. I think he froze the main part and heated the smaller half. I still don’t see how it would have just slid on though. It took me a while to get them separated, so I would assume getting it back together would be equally fun haha!

Yes, I’ll just start tapping on it and slowly work my way around.

Should I try to remove the bearing from the crank and put that back in the other case half first? Or should I just leave it be and just try to tap it back on slowly as is?

I’m going to use that motoseal gasket sealer around the mating surfaces when the time comes.

 

[cdahl383]

Hoping to get the cases back together this weekend. But I’m wondering now, should I try to remove the crank bearing off the crank and get it into the other case half first?

Or should I just leave it and try tapping it back on?

Never done this before, just don’t want to screw anything up. Hoping if I just go slow I can get it back on properly.

I cleaned all the varnish off too. This was the last pic I took a few days ago. You can see the crank bearing sitting on the crank.

 

[89HD]

Put a light coating of grease or oil on the bearing, put the cover on and tap it down until you can get the nuts on the studs then tighten them up alternately a little at a time.
I have a hardwood stick I use for tapping parts like that.

 

[cdahl383]

Put a light coating of grease or oil on the bearing, put the cover on and tap it down until you can get the nuts on the studs then tighten them up alternately a little at a time.
I have a hardwood stick I use for tapping parts like that.

Sounds like a good plan. I read about heating the case up, but I'm not sure that would work that well in this case.

I'll put some oil on the bearing and tap it down gently until the studs come through the other side of the case. Once I get to that point it will be easier to torque it down evenly by alternating each nut, etc.

I have lots of different blocks of wood in the garage, I'm sure I can find one that will work for this.

Sure hope this thing holds pressure/vacuum when I'm all done! I'm going to pressure/vacuum test it once I get everything sealed up good. I might wait a day though just to ensure the motoseal is cured properly. No sense in assembling the rest of the saw if it didn't seal right. I can pop that case half off easily if need be. But hopefully it will work the first time.

I spent some more time last night cleaning the mating surfaces off. There was a little fuel varnish left in one spot and a few spots with just a little bit of gasket sealer left. It's looking pretty good now.

 

[cbfarmall]

To answer your question: that bearing will probably not easily come off the crank while still in the case. Put it together the way it came apart, like the others say. I assume the bearing turns smooth and with no play. Shielded bearings on these saws wasn't a good idea. Canadien did it, Stihl did it.

 

[cdahl383]

To answer your question: that bearing will probably not easily come off the crank while still in the case. Put it together the way it came apart, like the others say. I assume the bearing turns smooth and with no play. Shielded bearings on these saws wasn't a good idea. Canadien did it, Stihl did it.

Ok sounds good. The bearing is in good shape, spins freely and I don’t notice any play.