046 magnum problems

[gsx60trim]

Quick background on myself. I live in Arizona, originally from Texas. I have a somewhat extensive background in rebuilding engines, race engines and drag racing (hobby). I've since fallen out of the hobby due to raising a family. I recently rekindled my passion for rebuilding engines, albeit 2 cycle. Still fairly new to 2 cycle engines, but not anything I can't tackle and enjoy. I've since purchased a few Chainsaws ranging from McCullochs, Husqvarnas and now STIHL varying in different conditions. Mainly, needing to be rebuilt which I have enjoyed doing and all run like champs. EXCEPT....

For my recent purchase this morning when I acquired a STIHL 046 Magnum. From the research I did prior to the purchase, I surmised that this is an excellent saw. Purchased it for $200, previous owner is a firefighter that used it on the job, front line saw. Previous owner claimed the saw ran, 3 days ago. Error on my part for not being adamant on being sure that the saw truly ran when I purchased it. Bought it with an empty tank, so I couldn't test it out before the purchase. Simply took his word. Saw was originally run at an elevation of 7000ft and now sits at 1000ft elevation. Carb may need to be adjusted?

Brought it home, filled the tank up a little more than half full 50:1. Set it full choke, decompression valve pushed in, pulled the recoil string a few times. Not even a sputter. Did this many more times, nothing. Tried, half choke (warm start) nothing either not a noise other than compression. Pulled the plug, noticed a dry plug. Figure I would try putting fuel in the carb, did this on full choke, valve in, the saw sputtered. Set it to half choke (warm start), valve in, gave it a tug and the saw came to life. Hit the throttle and it immediately died. Tried this a few more times, got it running for a quick 3 seconds, 14,000 rpms, then bogged and died.

I pulled the plug once more, dry as Phoenix, AZ. So I came to the conclusion of no fuel. Pulled the muffler off, and noticed scoring on the piston and ring. From what I learned on a Husky I rebuilt, this is one of my issues. Second, issue is locating what caused the scored piston. Sounds like it ran lean, elevation change that caused this? Operator error? Crankcase leak? I'll have to find out how to test for a leak on a saw.

I have thoroughly enjoyed the site and hope to gain some well needed wisdom.

 

[old-cat]

I'd say you need to completely disassemble the saw and automatically put in new crank seals and check and clean every part. When you put it all back together with new piston etc. it WILL run.

 

[gsx60trim]

Those were my initial thoughts as well. I also forgot to add that I checked for spark. I didn't check it properly with a spark plug tester but it did have a nice blue spark to it.

 

[1Alpha1]

I'm with old-cat and what he said. You can fix this and that, and maybe it'll run close to the way it should.

Or, you could make a project out of it, break it all down, and go thru it from one end to the other.

That's a nice saw, and running as intended, it will serve you very well for years to come.

 

[Rookie1]

opcorn:I would do a compression test. Vacuum test. And pull carburetor apart. Also check impulse and fuel line for cracking.

 

[gsx60trim]

I'm with old-cat and what he said. You can fix this and that, and maybe it'll run close to the way it should.

Or, you could make a project out of it, break it all down, and go thru it from one end to the other.

That's a nice saw, and running as intended, it will serve you very well for years to come.

That's what I find myself doing as of lately. Any specific rebuild brands to go with on STIHL saws. This will be the first STIHL I rebuild. Meteor? OEM?

opcorn:I would do a compression test. Vacuum test. And pull carburetor apart. Also check impulse and fuel line for cracking.

I plan on doing this. I'll have to search the site in order to learn to do a vacuum test on a chainsaw.

 

[old-cat]

OEM cylinder, Meteor piston, Caber rings
Set the squish @ .020" or a little more
De-baffle the muffler

 

[gsx60trim]

Can you hone 2 stroke cylinders? If so that would great on this saw. I've got a few husky's that I can salvage too if it's something that can be done.

 

[old-cat]

Can you hone 2 stroke cylinders? If so that would great on this saw. I've got a few husky's that I can salvage too if it's something that can be done.

WHY??? There's threads in here about fixing toasted cylinders. Or you can get used OEM from a guy on ebay

 

[Adirondackstihl]

If the saw was tuned properly @ 7000ft, it will be pretty lean @ 1000ft.
Have you tried fattening up the "L" low circuit a bit?

Your description sounds like a very lean tuned carburetor.

Pull the muffler and have a look before doing anything. If youre unsure what to look for, just post pics. Honing a saw cylinder is a touchy subject depending on who you talk to.
I see youre a new kid on the block......be careful who you let influence you, before you know it you'll be
be pulling the saw down to rebuild for no reason other than perhaps a fuel delivery issue !!

 

[cgraham1]

Pulled the muffler off, and noticed scoring on the piston and ring.

Second, issue is locating what caused the scored piston. Sounds like it ran lean, elevation change that caused this? Operator error? Crankcase leak? I'll have to find out how to test for a leak on a saw.

I have thoroughly enjoyed the site and hope to gain some well needed wisdom.

If the saw was tuned properly @ 7000ft, it will be pretty lean @ 1000ft.
Have you tried fattening up the "L" low circuit a bit?

Your description sounds like a very lean tuned carburetor.

Pull the muffler and have a look before doing anything. If youre unsure what to look for, just post pics. Honing a saw cylinder is a touchy subject depending on who you talk to.
I see youre a new kid on the block......be careful who you let influence you, before you know it you'll be
be pulling the saw down to rebuild for no reason other than perhaps a fuel delivery issue !!

 

[gsx60trim]

I definitely thank you all for the help. Yes , I'm a 2 stroke newb. Maybe I'm over thinking. I'll start with the basics, check compression. Scored piston says it all to me. Check for leaks. Would a few hours of trying to get the saw started in 6k ft less elevation damage a piston and cylinder that quickly?

 

[old-cat]

You have to have some pretty high rpms to cause enough heat to score the piston. You need to rip that thing totally apart and find the source of the air leak or straight gas .
Maybe just fuel starvation.

 

[Adirondackstihl]

I missed the post about the scored piston.