stihl 051av eating chain oil

[phpreto]

I've got an older stihl 051Av that I use to run a 30" alaska mill. Problem is, it has a gasket leak from the chain oil to the crankcase, fills up crankcase with oil when sitting and burns a little blue when running. How hard is it to crack the case and replace the gasket? I've considered gas tank sealer or something similar as a fix. When I pour gas in the oil tank the idle slows and saw tends to flood out, so its not a pinhole..
I'm a decent mechanic, just don't have a manual for it and not sure if I need special tools to crack the case.

 

[TimberPig]

You do need a couple special tools to tear it down, mostly a flywheel puller, clutch tool, and probably a couple others as well.

Your idea of doing a temporary patch job is not a good plan though, as the change in idle that you noticed, says there is a rather large air leak occurring there, when it's not sucking oil in. This can and will kill the saw sooner rather than later. It would be a very good plan to get it torn down and sealed up properly, before running it any further. With a little caution, this isn't too bad of a job, as saws are pretty simple to rebuild.

 

[cbfarmall]

Are you sure it's the case gasket? This series of saws has an rubber sleeve/collar around the oil pump that seals the crankcase. If this sleeve failed, you would be dumping oil into the engine. It's easy to check. You'll have to remove the inner spike and the little plastic plug covering the oil pump at the front of the engine. Oil pump pulls straight out the front by threading a screw into it and prying.

One word of caution: when you pull the pump you'll leak alot of oil into the engine initially. Makes it a bear to turn over.

If it is a case gasket, don't monkey with it. Fix it straight away. Parts are readily available for this engine.

Chris B.

 

[phpreto]

thanks, I pulled the oil pump and the seal was slightly torn, it then tore completely by itself ( saw is 30?+ years old)tears, and I was having trouble with the bar oiler. Ordered a new seal from a local shop and hope it fixes it!
Don't really want to crack the case...Seems like a low hours saw (paint in very good shape)
I've seen posts on muffler mods, will removing a baffle give me more power?

 

[Lakeside53]

It's almost aways the rubber seal on the pump!

 

[TimberPig]

I've seen posts on muffler mods, will removing a baffle give me more power?

There probably isn't much in there to begin with on a saw of that age. It might give a slight boost, but nothing compared to the much more choked up saws produced these days. Another advantage on newer saws is to get rid of heat from the engine, which again isn't likely an issue as that old saw won't have a very restrictive muffler.

 

[phpreto]

put in a new seal, filled er up with chain oil and gas and it runs great+ oiler works! seems obvious now...
seems to have fixed the problem,
should be a lot better next time I am milling
Thanks for the expert advice - saved me from cracking the case!