Husky 35 / Pioneer P12 / Frontier saw question - Oil tank vent into crankcase?

[FrontierSaw]

Hi all, long time reader, first time poster.

I have a small Frontier (sold under about a hundred different names, Husq. 35, Pioneer P12, etc) that I use for pruning and limbing. It's Canadian, and so am I, so I like having it around. It runs OK but it will intermittently smoke like a tire fire, seemingly burning bar oil.

I took it apart to investigate, thinking I had a bad tank gasket, and I am now even more confused. There's a port from the crankcase that vents into the bar oil tank. it's up top, but when you tilt the saw back, or use it on it's side with the bar oil tank full, bar oil can leak into the crankcase, causing all kinds of smoke (it will literally cloud out the sun). The oil tank vent has a vent in it already, so I don't understand what it's for.

I've looked at the parts diagrams for the Husq. 35 (same saw, only diagram I can find for this saw), and you can see the same boss on the crankcase. I can't see any threads in there, and it's straight through. Any ideas what this does? I suspect there was something plugging this hole originally that's now gone. Unless you guys have any ideas I'll probably drill and tap it, and put a set screw in there.

Thanks for any insight you might provide...

 

[rupedoggy]

I think that saw pressurizes the oil tank from the crankcase to force oil to the bar. That saved them having an oil pump. The line needs a one way valve or duck bill so pressure can build but oil can not go the other way. Mike

 

[FrontierSaw]

Yeah I think you're right. I don't see any provision for a check valve but there might have been a rubber valve in there that disintegrated over time. I think it might have been sucking in air as well (the seal from the tank to the crankcase was no good).

 

[rupedoggy]

I had a Homelite that was like that. I found the valve inside the oil tank, once I drained it. Mike

 

[ray benson]

Should be some type of check valve that allows crankcase to pressurize the oil tank and not let bar oil to enter the crankcase.

 

[FrontierSaw]

I looked at the parts diagrams again. They do list a piece in the crankcase that might be the check valve in question, 507433868, called a "stop". Not sure if it’s the right piece. I am also looking at diagrams for a later Husqvarna 35 with a regular gear driven oiler, so it might not have the crankcase pressure oiler. On these other saws, do they use crankcase pressure in addition to an oiler, or just crankcase pressure?

 

[FrontierSaw]

Update, Ray Benson sent me some parts diagram PDFs (THANKS!). There are a few different versions of this saw. The Jonsereds One has the duck bill valve, Jonsereds 100237, crosses to Poulan and others, available on Ebay, $3.99. Looks like this might live to see another day (with the oiler running).

Thanks all. Will see if I can scrounge some new crank seals too.