Stihl 046 Magnum P&C

[djg james]

As some of you may know, I recently bought a used Stihl 046 Mag of a guy. Not knowing what I was looking at, I am told I paid too much. The piston is badly scoured. So as one of my options, I'm going to try the repair myself. I never took "Internal Combustion Engine 101" so I really don't know what I'm doing. I'm going to have a lot of questions and most will probably be pretty stupid.
I understand I need to do a vacuum/pressure check. How is the pressure check different from a compression test?

Several threads here talk about Aluminum transfer. Is that from the piston? If so how? I thought only the rings were in contact with the cylinder wall?

If the cylinder is scoured too, does it need to be replaced?

More later after I start working on it in a couple of weeks.

 

[Philbert]

Here is a link to my 046 rebuild thread, if that gives you any insight.

https://www.arboristsite.com/community/threads/ms-046-repair-with-public-input.193704/
Philbert

 

[atpchas]

Re: P/V test. Ideally, both pressure and vacuum are tested because a saw can pass one but not the other. Any kind of a leak is bad. That said, I've only encountered one or two saws out of a couple hundred that failed one but not the other. So if saw passes a pressure test, you're probably good to go.

Re: "Several threads here talk about Aluminum transfer. Is that from the piston? If so how? I thought only the rings were in contact with the cylinder wall? If the cylinder is scoured too, does it need to be replaced?"
Yes, the transfer is from the piston to the cylinder wall. Excessive heat buildup (straight gas, bad gas, air leak, dull chain, etc) can melt the piston and transfer to the wall of the cylinder. When that happens, the cylinder must be either cleaned up (if possible - many threads on how to do it) or replaced.

 

[Alphadelta]

As some of you may know, I recently bought a used Stihl 046 Mag of a guy. Not knowing what I was looking at, I am told I paid too much. The piston is badly scoured. So as one of my options, I'm going to try the repair myself. I never took "Internal Combustion Engine 101" so I really don't know what I'm doing. I'm going to have a lot of questions and most will probably be pretty stupid.
I understand I need to do a vacuum/pressure check. How is the pressure check different from a compression test?

Several threads here talk about Aluminum transfer. Is that from the piston? If so how? I thought only the rings were in contact with the cylinder wall?

If the cylinder is scoured too, does it need to be replaced?

More later after I start working on it in a couple of weeks.

If you don’t feel comfortable working the cylinder (sometimes an acid treatment can save the cylinder) you can get a meteor piston and cylinder (this will include clips, wrist pin, and rings) for less then $200 (don’t forget the bearing, my 440 kit didn’t have one)

I’ve bought two meteor pistons both were well made and I was impressed. Several other members on another thread about pistons have echoed the only piston and cylinders they will use besides OEM are meteor.

As for your questions this site, along with Reddit, and the forestry forum are a gold mine. I usually try the search function here first and found copious amounts of good information.

Good luck on your rebuild.


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[djg james]

Reddit? Not familiar with that. And yes, as some here recommended, I'll be buying a meteor piston, but I'll wait until I see how bad the cylinder is. Then I'll buy the whole kit.

 

[svk]

I would try to use the "non acid" cleanup process on the jug and install a new piston.

Pressure and vacuum check find leaks in the motor from around the seals and gaskets. The compression test only checks the cylinder pressure caused by compressing air in the cylinder.

 

[OddSawz]

https://www.arboristsite.com/community/threads/how-to-remove-aluminum-transfer-without-acid.248325/

 

[irhunter]

I'll be buying a meteor piston, but I'll wait until I see how bad the cylinder is. Then I'll buy the whole kit.

Good idea...don't buy anything now.

First, do a pressure/vac test. Then pull the cylinder.

And, BTW, chill about the so-called over payment for the saw. Once you get the saw working, with some care, it will last a really long time. A 100 bucks, or so, paid too-much originally will be meaningless.

Roy

 

[djg james]

...... you can get a meteor piston and cylinder (this will include clips, wrist pin, and rings) for less then $200 (don’t forget the bearing, my 440 kit didn’t have one)

Which bearing are you talking about?

 

[Alphadelta]

Which bearing are you talking about?

The piston needle bearing. My kit from HL didn’t include one.


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[djg james]

I've been watching video trying to educate myself before I start. Looks like special tools may not be necessary. I have this pressure gauge so now all I need is a vacuum gauge for the vacuum test. I have a vacuum pump.

 

[irhunter]

Many people who work on their cars have a vac gauge. Before buying one, you might ask around and see if you have a friend who has one you can borrow.

 

[djg james]

Forgot to mention the main reason for posting. What's the difference between a 046 and a 046 Magnum. Looked up the specs of each and I don';t see a difference.

 

[Mad Professor]

Which bearing are you talking about?

Wrist pin

 

[Yukon Stihl]

Forgot to mention the main reason for posting. What's the difference between a 046 and a 046 Magnum. Looked up the specs of each and I don';t see a difference.

a sticker...

 

[djg james]

a sticker...

But, But it's a MAGNUM!

 

[markbakovic]

bigger AV mounts, bigger dogs, much better chain catcher, full wrap handle option, dual port muffler (only for au and ca though)

and a sticker!

 

[Yukon Stihl]

bigger AV mounts, bigger dogs, much better chain catcher, full wrap handle option, dual port muffler (only for au and ca though)

and a sticker!

Actually your statement isn't true.AV mounts are all the same and all the rest are options that can come on any saw with or without the sticker

 

[markbakovic]

Well mostly I'm going by the ipl, which obviously says nothing about what you can and can't order, just has variant numbers next to some of the parts.

But I assure you mine came with the lower PTO side av mounts listed for the magnum and magnum r, while I could only order the "regular" ones from stihl in aus. They are different. The original ones are fat like the crankcase bore all the way to the fuel tank, while the garden variety taper to ~80% diameter.

In any case, so what if my statement boils down to "it's an option package"? That hardly makes it untrue.

 

[president]

The much coveted D cylinder was discontinued by
the epa for a milder version and the 1309 hot coil
was also deleted.Hence performance suffered
the muffler outlet was restricted on the latter
one also