Goofy Chainsaw question! - Smokes when pressing oiler

[volvo09]

Hey guys, been poking around for years, but finally figured I'd toss this Q past some more experienced 2 stroke / chainsaw folks. This is goofy, and I havn't been able to find ANY info on a situation like this, my experience is limited to 4 stroke engines.

I was given a Mculloch Eager Beaver 14" saw a few years ago (no idea of the model number... no markings). When I got it you could not pull the cord because the cylinder was hydrolocked. I pulled the plug and it looked like bar oil, very thick and clear. Cleaned it out, put in fresh fuel and it started and smoked like hell. It would eventually clear out, I'd use it, and I would put the saw away for a while. Every time I go to start this saw, it would SMOKE like a dragster doing a burnout... REALLY thick blueish / white smoke, and oil blowing out the muffler.

The bar oiler never worked too well (it has a manual press, but I think it's supposed to be an auto oiler also). So the last few times I used the saw, I would just lube the chain with a thick spray grease, no smoke from the saw at all. If I fill the oil tank and press the oiler, it starts smoking like a banshee again and misfiring from so much oil in the cylinder till it finaly clears out.... cycle repeats when pressing the oiler again.

I finally got boggled by this one and took the saw apart completely. I found the oil tank hooked up to a chamber, with what appears to be a vacuum operated piston inside of it on the connecting rod end of the engine, this chamber was full of oil, and has a 3/16 or so sized opening directly into the crankcase. My theory is that every time I press the oiler, oil passes by this piston, and directly into the crankcase... causing all the smoke. I took everything apart, found a ball valve inside this that was blocked and stuck... cleared everything out, and while the bar oiler works now with manual presses, I still get the crazy smoke situation, and when running the saw with no bar, I can't see any auto oil action... not a seep out the hole... but works great when pressing the manual plunger.

My question is...
1. Has anyone seen anything like this? Any experience with this type of oiler? seems most saws use a small gear pump.
2. I would like to just remove it and make it a full on manual oiler like my older saw... Is this engine reliant on some bar oil for lubrication? My understanding of 2 strokes is that they get all of their oil from the fuel, unless it takes straight gasoline and uses oil injection to inject 2 stroke oil... the tank on this saw says premix. It's a good little saw, so I don't want to ruin the engine converting to manual oil.

Thanks!!! Sorry for the long winded post!

For the "too long didn't read" types... My saw burns bar oil when I press the oiler plunger. I want to convert it to manual, but when taking it apart I found a vacuum operated piston pump open to the crankcase... This hole is how oil is getting in, but is this helping to lubricate the engine also? Never seen a setup like this... This is a solid little saw and it has seen very little use over it's life, I don't want to un intentionally oil starve the engine and kill it.

 

[machinisttx]

Sounds like something is wrong with the auto oil pump. Could be that an o ring is broken/torn and allowing the vacuum pulse from the engine to pull bar oil through the pump and into the cylinder/crankcase. Or there could be a failed gasket.

 

[GPX433Todd]

I would put nitromethane in bar oil tank and cut wood like a boss.

 

[SEAM]

Cleaning the oil pump (with integrated manual pump plunger) should help...

 

[milkman]

Does it have one of those duckbill things that is our of quack, I mean whack?

 

[Mac 6-10]

That saw uses crankcase pressure to move a piston to pump the oil. The round plastic thing that hangs off the end of the crankcase is the an to oil pump. I believe it is held in place with a spring clip. There should be an oring that seals the pump to the crankcase. If that is damaged or missing that will cause the engine to fill with bar oil. Also the pump can leak inside itself and get bar oil in there too. Find another auto oil pump on ebay. They are everyware for those things.

You cannot omit the auto oiler as the manual oil pump flows through the auto pump before it reaches the bar

 

[OPE FIXER]

There is a duck bill valve under the oil cap inside the tank, kinda off to the side, at the top. It is about a $2.00 part.

 

[heimannm]

Duck bill valve in the cap is not a likely problem to the smoking issue. Check the piston (fiber disc and o-ring) and replace the gaskets and diaphragm between the oil pump and the body of the saw. You have a path open from the oil ports to the crank case.

Mark

 

[volvo09]

Thank you very much for the replies! I did spot quite a few of the oiler assemblies for sale on the internet, so I will pick up another. I took this one completely off and that's how I came across the stuck ball and spring inside of it. I was pushing a tiny drill bit in a zillion times cleaning it with air and spray till it started moving and I said Woah! I must have fixed it! but no such luck. The gaskets looked ok, no oil was leaking outside of it, but the "piston" itself was a flat fiberglass type disk attached to a rod with a rubber seal / oring. That was kind of loose.. I will order another.

Mac - Do you know how these work so I can tell when it's fixed? Do they pump oil the whole time the engine is running? Only under load? or high revs? Know of other saws that use them so I can do some research?

I had this saw 100% apart (I even split the crankcase and pulled the piston), and did not spot a duckbill valve or any sort of check valve except for what I assume was a non serviceable one inside the pump. All hoses were straight through and I cleaned them all, the pump plunger had nothing special on it when I removed it, and the tank was sealed (well it should have been, but I had to fill a crack which was the source of all the gunk that got inside my oiler). The fuel cap and oil cap were also just plain seal less caps, although they don't leak I've always wondered if seals were missing... but by design the tank is open to air where the oiler plunger passes through from the top.... it just passes through unsealed.

Thanks again everyone!

 

[Mac 6-10]

All McCullochs had this style auto oiler. with the exceptions of some gear driven pumps on some. they pump anytime the engine is running. is there a spring pushing up on the plunger? (the rod with the fiberglass disk) if that is missing the pump plunger wont return to "pump" any oil. there should be two ports on the oiler. on is in and the other is out. I am not too familiar with the mini mac style oiler so I cant tell you exactly which one is what but if you squirt some light oil like gun oil or the like in a port and pump the plunger a few times the oil should come out of the other hole.

 

[volvo09]

Yes there was a spring. When putting it back on the order went like this, outer casing, inner "spring cup" with the indexing mark on the side, spring, and then piston and finally a brass sleeve... adjusting screw on the back.

When I had it apart I actually did that pump test you described and could not get anything to pump through, it just sucked the oil in and out of the same hole with each press, and the other hole did nothing... I assumed it must have been because I didn't know how it worked and that it must need to move faster... Thanks to your description I am pretty confident this one is broken... I have put all I can into freeing up this thing.

MUCH appreciated!

 

[Mac 6-10]

The check valves in the pump are not sealing. the pump is bad.