Stihl MS170 crankcase material

[rangerfredbob]

Working on a Stihl MS170 for a coworker that he got used from another coworker because it idled high I found the crankcase was cracked on the bottom...

Is it likely aluminum? I'm just hoping it's not magnesium... What's the chances of that aluminum brazing stuff working? I've used it before with decent success, I know the drill on that stuff with the clean wire brush and so forth, was planning to pull the bottom cover and C clamp it to a heavy chunk of steel in as many places as possible and V out the crack with a Dremel then clean the heck out of it before starting...

Would rather not have to replace the whole jug since the only problem is the bottom cap... it's not a fancy model or anything so not worth putting a whole bunch of money into... it runs like a top just has a high idle from the air leak

 

[mrmikey]

It's magnesium, it's lighter than aluminum. If you want to confirm, shave off a piece on a cooling fin or similar, aluminum will come off in a string usually, magnesium will come off in chips. If you want further confirmation, takes the pieces you just shaved off and hit them with a propane torch, aluminum will melt, magnesium will burn very white and hot............Mike

 

[lman]

I used JB Weld to fix a crack on my stihl. That may work for you.

 

[ericm979]

It's magnesium, it's lighter than aluminum. If you want to confirm, shave off a piece on a cooling fin or similar, aluminum will come off in a string usually, magnesium will come off in chips. If you want further confirmation, takes the pieces you just shaved off and hit them with a propane torch, aluminum will melt, magnesium will burn very white and hot............Mike

I've yet to see a saw (or any two stroke) with a magnesium cylinder. Mag cases are common.

On homeowner saws like the 170 the cylinder and the top half of the crankcase is one piece and is aluminum. The bottom half of the crankcase is a simple curved plate that bolts on. That "pan" is aluminum. The chassis that holds the engine and the other parts is plastic.

Replacement parts are cheap, especially the chinese ones. A whole engine from Farmertec is $23 + shipping. Or you can buy the pan and replace the old one if that's what cracked. The pan is pretty thick though. If the saw took a hit hard enough to crack it, it might be damaged elsewhere. Or the crank seals simply worn out and leaking air.

If you're replacing the pan you should replace the crank bearings and seals... and probably the rings and piston pin bearing and maybe the piston and wrist pin too. Might as well get a new engine.

 

[rangerfredbob]

It's just the "pan" as you say, since it started idling high it apparently has less than an hour on it.

I'll try fixing it for now but will keep a new engine in mind, the current owner is kinda weird at times about cheap parts...

I'm betting it's aluminum but will shave some off for good measure... I'm gonna tinker with it here in a few...

 

[rangerfredbob]

Well, that didn't work...

Will have to look into a new lower case half or something...

It's mostly aluminum but there's definitely some magnesium in the mix... too many angles to get an even heat, ended up with hot spots and burned through, if I got it hot enough the filler fell out of the other places it was, was a mess... rather try and fail than not try, only out half an hour of screwing around...

 

[mrmikey]

.....if I got it hot enough the filler fell out of the other places....

Yup, magnesium. if the arc is a purplish/violet color is another indicator..........Mike

 

[Lnk]

It's just the "pan" as you say, since it started idling high it apparently has less than an hour on it.

I'll try fixing it for now but will keep a new engine in mind, the current owner is kinda weird at times about cheap parts...

View attachment 729225

I'm betting it's aluminum but will shave some off for good measure... I'm gonna tinker with it here in a few...

That is a tough spot to fix. Good try though. Lot of load on that cover when running, reciprocating mass. A new bottom case is definitely in order.

 

[xyz123]

Just buy another cap and reseal it up.

STIHL MS 170 CYLINDER CRANK PAN | eBay

<p dir="ltr" style="margin-top:0; margin-bottom:0;">STIHL MS 170 CYLINDER CRANK PAN. Condition is "Used".</p> <br> <br> <br> <br> <br> <br> <br> <p dir="ltr" style="margin-top:0; margin-bottom:0;">Due to dishonest buyers returning wrong or incomplete parts we will no longer accept returns</p> <p...

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Stihl MS170 part #1130 021 2505 - Stihl Engine pan | eBay

<p dir="ltr" style="margin-top:0; margin-bottom:0;">Stihl MS170 part #1130 021 2505 - Stihl Engine pan. Condition is "Used". Shipped with USPS Priority Mail.</p> <br> <br> <br> <br> <br> <br> <p dir="ltr" style="margin-top:0; margin-bottom:0;">Due to dishonest buyers returning wrong or...

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1130 021 2505 Engine Pan Fits STIHL 017 018 MS170 MS180 Chainsaw | eBay

Replaces Stihl.

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[rangerfredbob]

Perfect! Thanks! That was easy...

 

[dodge man]

I rebuilt a Stihl MS250 a couple years ago, it needed a new cylinder and piston. I was shocked at the number of aftermarket parts available off Amazon. It looked like you could build a saw from scratch. I spent around $100 and could have bought stuff for half that but I went for the high quality junk instead.

 

[nyone]

The ms170 is the cheapest saw they sell. I believe there about $200 new so I wouldnt go spending time much time/money fixing the crack until you figure out why it cracked.

Unless it was free or very very cheap I wouldnt even bother buying a used low grade saw like this.

 

[rangerfredbob]

Yeah, it's a pain to work on... but it runs great now!

Pretty sure it was just a weak spot, knowing the full history of the saw the coworker that had the saw originally (bought new) a tree fell on it not too long before it started idling high which broke the outer handle only (3 rubber isolators), was the first thing the new owner changed, then tried to tackle the high idle issue... started with an Amazon carburetor then an intake boot just for good measure... then of course the crank pan... Apparently the idle got progressively worse over time as the crack progressed I'm sure... probably started from the stress of the crushing spreading the crankcase a bit...

Put it together tonight since the part showed up today, started right up, adjusted the idle screw and it idles down real nice now

 

[209StihlTech]

Yup, magnesium. if the arc is a purplish/violet color is another indicator..........Mike

It's not magnesium it's aluminum. Stihl has never produced a magnesium clamshell style engine nor has any other company from my knowledge. On the left is a clamshell style engine with a plastic crankcase housing and engine made of aluminum, right is a pro style saw with a mag crankcase and aluminum cylinder. Stihl has used a mag piston in the past on the ms400 though.