Whats the cause? Broken 039 engine pan

[stevieb]

Just got down to the very last bit of a strip down of my MS039 and I think I may of spotted a problem!

What would of caused this? I did buy the saw second hand very cheaply had been abused but it ran ok for about 6 months so nothing lost.

Before I replace it do I need to be looking at anything else to stop it happening again?

 

[stevieb]

Also having problems getting the bar mounting stud off to release the broken corner bit. Tried the hair dryer as reccomended but no luck

 

[Lakeside53]

I bet the pan screws were loose on one side and the vibration busted the botttom off. Check your crank for runout.. Use a torque wrench when you put the pan screws back in.

If it tries to rotate, just clamp the broken part in vice grimps and put a stud puller (socket with cams) and a big wrench (or a pipe wrench) on the other side. It will be tight...

 

[stevieb]

When I undid the bottom engine screws they did break open with a crack! Do you reckon im ok to just re-fit another one. Also before I start the whole assembley as I have never done it before what do I need to check for and what bits and pcs do I need to buy that will need to be replaced? Thanks for your help lakeside

 

[Lakeside53]

Hmmm.. screws were probably o.k. then. Are your main bearings are in good shape? If a cage colapsed, it could have broken the case with vibration.

You'll need some Dirko sealer... You might need new seals.

If the saw was running fine before it quit suddenly (assumption)... it might be o.k. to just replace the pan. You shouldn't have a problem finding one used.

How does the piston, cylinder, crank-rod bearing etc look?

 

[stevieb]

The piston looks ok to me. Bearing in mind the first time I have ever seen on in my hands. Have the Stihl fault analysis book and nothing jumps out at me. I will take some pics and post them up tonight.

 

[stevieb]

Here's pics of the piston. Hope there good enough. As I said earlier dont really know what im looking at with the bearings. Little bit of play in them as you would expect. Look clean and rotate around smooth.

http://www.arboristsite.com/attachment.php?attachmentid=53555&stc=1&d=1183227445
http://www.arboristsite.com/attachment.php?attachmentid=53556&stc=1&d=1183227539
http://www.arboristsite.com/attachment.php?attachmentid=53557&stc=1&d=1183227539
http://www.arboristsite.com/attachment.php?attachmentid=53558&stc=1&d=1183227539
http://www.arboristsite.com/attachment.php?attachmentid=53559&stc=1&d=1183227539

 

[stevieb]

The second pic of the piston it looks like a scrape. Just a trick of the camera

 

[Lakeside53]

What are the marks on top of the piston?

 

[stevieb]

The top of the piston has carbon on it which im assuming is normal. The spots you see are where the carbon has flaked or not fixed to. There is no dents.

 

[Lou]

Going off topic a little.
Torque Wrenches - Avionics Instrument types calibrate them; every 90 days.

Break away type - Jo-line, Utica, Snap-on were all good wrenches (remember to exercise the wrench 3 times before use) Consolidated Devices Incorporated (CDI) when several hundred bundled together made fabulous boat anchors. Consider them low end Poulan. With a break-away you get what you pay for with or without rachet.

Dial type (torque reads out on analog display) - CDI probably the best.

Beam - Shaft bends, pointer shows displacement as torque. Almost NEVER go out of calibration. All manufacturers good devices.

My 2¢, now back to your regularly scheduled thread.

 

[stevieb]

Dude what the hell you on about?

 

[Lou]

Lake talking about torqueing pan screws. Triggered thoughts of torque wrenches.

 

[Lakeside53]

Well... as you bought it up. Using a torque wrench to set a specified setting requires continuous motion up to the torque value. If you stop just short, you need to back off and redo it again... Why??? "Break-away torque" is much higher...


The there's torque-to-a-value, and angle of rotation beyond. I have one of those, but it's of little use in a chain saw as nothing is spec'ed that way.

I like dial types for small torque as I can see how close I'm getting to the required value...

 

[andrethegiant70]

Hi, Lou.. thanks the for lesson on torque wrenches, its relevant in my case.... by "break away" do you mean the "clicker" type ones? I'll admit to cinching most of my bolts down by feel, but I'm about to put together a 288 case that I don't want to screw up (hey, is that a pun?) and I figure a bit more care is called for. By "beam" type I assume you mean the ones where the little metal pointer swings along a graduated scale?

Again, thanks.. I'm weak in this area. Ok, I'm weak in a lot of areas.

 

[Sprig]

Just got down to the very last bit of a strip down of my MS039 and I think I may of spotted a problem!

What would of caused this? I did buy the saw second hand very cheaply had been abused but it ran ok for about 6 months so nothing lost.

Before I replace it do I need to be looking at anything else to stop it happening again?

Here is my totally uneducated guess, thinkin' outside the box type thingy. Barring a really bad day under a tractor, how about this; the bearing has been going and heating up the surrounding area for a few hours, it is a cold winters day, and tired after some serious cutting the user plops the saw on the snow covered ground, contranction of metal structures takes place fracturing the casing leading to furthur catastrophic failures. I am thinking magnesium casing crystalisation/weakening with repeating this procedure.
Dunno. Like I said, unedumacated. :monkey:
My drunken opine fer the evening.



Serge

 

[PES+]

In the first pic it looks like there is a small section of the crank broken out.

This may just be an illusion but can you more close ups of the crank?

 

[Lou]

Hi, Lou.. thanks the for lesson on torque wrenches, its relevant in my case.... by "break away" do you mean the "clicker" type ones? I'll admit to cinching most of my bolts down by feel, but I'm about to put together a 288 case that I don't want to screw up (hey, is that a pun?) and I figure a bit more care is called for. By "beam" type I assume you mean the ones where the little metal pointer swings along a graduated scale?

Again, thanks.. I'm weak in this area. Ok, I'm weak in a lot of areas.

Exactly right Andre.

Break aways - click or have a small dead zone once the set torque value has been met. Always exercise a break away 3 - 5 times before using it to set a torque value (need not be at set value, set it at zero break it with your thumb). Jo-Line and Utica were the manufacturers that most consistently maintained calibration. I recommend you not use a CDI in a break away configuration. Always set a break away to its lowest value when not in use.

Beam types - are the least expensive and least trouble with maintaining calibration. They have two parallel shafts one is connected to the torque head and handle, the second shaft connected to the head only with a pointer floating above a torque indicator.

Glad to be of help.

 

[stevieb]

You are correct it was the middle of winter when this saw went down. I don't remember any snow but it must of been cold. The one thing I have noticed in my orginal postings I said what looked like a scrape was the trick of the camera. But after I examined closely the spot and it was indeed a very faint scrap but not enough to really feel with your fingers. Looking at the pics again the camera, I presume the flash the way it bounced the light has picked up every little imperfection. Good thing to know

 

[Lakeside53]

o.k.... Let's define "cold".. In MT (USA), cold is -45F... In Wolverhamption U.K.), cold is +35F...:hmm3grin2orange:

In any case, the engine pan is isolated from the ground by the nylon tank/engine cradle assembly).