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Tool Talk Discussion Forum

Hydraulic lock in a chain saw?

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Rod in Smiths F

04-27-2007 15:31:58




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I'd left my old McCullough Pro-Mac 850 chainsaw back in the woodlot for a couple of weeks. When I found it again it was sitting with the bar pointed upward on a 45 degree angle. When I tried to start it, it kept painfully snapping the cord out of my hands after a quarter-turn. And that's with the decompressor engaged. Oil was leaking out through the decompressor and the muffler. I turned the saw on its side and a lot of oil ran out through the exhaust, red oil like the bar lube. Pulled the spark plug and pumped more oil out of the cylinder with the starter cord. Cleaned the plug. Now it turned over fine with the decompressor engaged. Choked it and the thing started and ran normally. The oiler pumped, the engine revved, and the trees came down.

So how did all of that oil get into the cylinder, and how could an engine survive that and run normally?

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jeffcat

05-02-2007 18:32:30




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 Re: Hydraulic lock in a chain saw? in reply to Rod in Smiths Falls, ON, , 04-27-2007 15:31:58  
Well let us see. All of the"PRO" MacCulloch saws I have do have auto oilers. IF it has the DPS valve it is a Pro saw. The very thin gasket under the pump body can tear or warp. It is exposed to direct pressure and vacuum from the crank case as the saw runs. There is no other way unless you have a small crack somewhere. Now Homelite saws will suck oil through the system cause they use the crankcase to presurize the oil tank. Therre is always something out there ready to bust and make your day! Jeffcat

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mjbrown

04-28-2007 12:46:37




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 Re: Hydraulic lock in a chain saw? in reply to Rod in Smiths Falls, ON, , 04-27-2007 15:31:58  
The oil cetainly won't hurt it and as far as hydro-locking, I doubt you can pull hard enough to bend the crank unlike hydro-locking a running engine.



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Charles (in GA)

04-28-2007 05:57:12




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 Re: Hydraulic lock in a chain saw? in reply to Rod in Smiths Falls, ON, , 04-27-2007 15:31:58  
Store the saw, hanging vertically, blade down, hanging from the handle, will prevent this. I think the oiler uses exhaust gases or exhaust gas pressure to blow the oil on the chain, and the bar oil works itself back into the cylinder thru the exhaust port.

Charles



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Davis In SC

04-27-2007 19:55:08




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 Re: Hydraulic lock in a chain saw? in reply to Rod in Smiths Falls, ON, , 04-27-2007 15:31:58  
I have that same saw, and had the same thing to happen last year, when I got it out after the ice storm. Pulled the plug, cranked it over to blow the oil/gas out, replaced plug and it ran fine...I think heating/cooling might siphon fuel through the carb, letting it fill the cylinder. That is a great saw, now that McC is defunct, I hope I do not need any major parts for repairs..



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Jim K

04-27-2007 16:30:39




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 Re: Hydraulic lock in a chain saw? in reply to Rod in Smiths Falls, ON, , 04-27-2007 15:31:58  
I believe that the bar oiler tank is part of the engine housing, bar oil fueltank crankcase is all contained in one casting, either the gasket is blown out or the case half screws came loose.
Do a tighten up.



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Rod in Smiths Falls, ON,

04-28-2007 15:19:58




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 Re: Hydraulic lock in a chain saw? in reply to Jim K, 04-27-2007 16:30:39  
The local repairman had the oil reservoir apart in order to repair one of the bar-holding studs. I wondered if he had broken something in the process, but to my astonishment the engine ran normally once I got the oil cleared out.

This saw has a manual oiler, so I don't see why exhaust gases would be ported to the oil tank.



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