Chainsaw Repair

Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Stihl => Topic started by: farmboy on March 28, 2013, 07:55:26 pm

Title: MS440 Cylinder Screws
Post by: farmboy on March 28, 2013, 07:55:26 pm
Firewood guy brought me an MS440 to fix.  Long story short I wound up buying 3 MS440's inc the one he brought me.  2 complete, 1 torn down w/broken handle in a box.  #1 rebuilt carb, replaced crank seals wouldn't stay running.  Did pressure test couldn't pump fast enough to get it over 2 #.  Muffler was off was able to see the right front clutch side cyl. screw missing.  2 were loose 1 tight.  #2 complete saw had 2cyl screws broken off in the crankcase and the whole right front corner was broken off the cyl.  Some DA he carried it to before me did the damage and lied to him said the cyl rocked and broke the screws.  Yeh right.  Shorten some more, all 3 saws the cylinder screws were loose the right front loosest on all.  Have ya'll ever seen this?
Shep
Title: Re: MS440 Cylinder Screws
Post by: Al Smith on March 28, 2013, 08:35:45 pm
Well it's peculiar at best because if the bolts were taken to yield they theoretically would never loosen .

I can't tell you the torque and yield angle off the top of my head but they are M5 bolts .
Title: Re: MS440 Cylinder Screws
Post by: chainsaw-57 on March 29, 2013, 08:26:25 am
  Good Morning all,

  Loose, missing, cylinder screws are not at all uncommon.  Usually starts with right front.  Have seen this many times.

  Sometimes the threads are destroyed, sometimes not.  The PTO rear and flywheel front screws may be broken or damaged.   Check the crankcase screws also.

  Had a "Red Eye" come to me, "worn out, no impulse."  Two screws missing on PTO side, right front cylinder mount broken off, flywheel side screws backed part way out.  No impulse because cylinder was flopping around on crankcase.

  Not a bad idea to check these screws when doing maintenance.

  Take care, Larry.  HOS.
Title: Re: MS440 Cylinder Screws
Post by: farmboy on March 29, 2013, 02:01:33 pm
  Good Morning all,

  Loose, missing, cylinder screws are not at all uncommon.  Usually starts with right front.  Have seen this many times.

  Sometimes the threads are destroyed, sometimes not.  The PTO rear and flywheel front screws may be broken or damaged.   Check the crankcase screws also.

  Had a "Red Eye" come to me, "worn out, no impulse."  Two screws missing on PTO side, right front cylinder mount broken off, flywheel side screws backed part way out.  No impulse because cylinder was flopping around on crankcase.

  Not a bad idea to check these screws when doing maintenance.

  Take care, Larry.  HOS.

I don't understand why they get loose.  Is it because of the steel shim cyl gasket?  I've never seen a Husky get loose but I'm a relative newbie only about 10 yrs.  I will make it standard practice to check the screws from now on.  Thanks.
Shep
Title: Re: MS440 Cylinder Screws
Post by: Al Smith on March 29, 2013, 08:41:43 pm
A portion of how I make my living is work involved in the tightening of screwed fasteners used on automotive engines .Every fastener from the factory assembley is robotically/electronically  tightened ,none by hand .

I had a mechanical engineer explain  how a screw works which is exactly like a spring under tension .It can stretch or give a very slight amount but if properly torqued it will snap back .More failures are experianced with under torqued fasteners than slightly overtorqued .

The auto industry uses a formula of initial torque than a certain degree of rotation afterwards .Of course this varies as to the bolt size .

For my little life actually the cylinder bolts on a saw engine are the only ones I get anal about and I use a torque wrench on every one of them .
Title: Re: MS440 Cylinder Screws
Post by: farmboy on March 30, 2013, 08:42:20 am
Myautomotive mentor taught me 2 main things: 1- clean, clean, clean (initial exp I cleaned a 265 Chevy block til I was sick of seeing it) 2- torque mains, rods, cyl. bolts everything else use common sense.  I have read on another site guys say just tighten cyl screws it's just a saw.  NOT it's a piece of highly reving piece of highly engineered machinery.  I ALWAYS torque my cyl. screws.
Shep
Title: Re: MS440 Cylinder Screws
Post by: Cut4fun . on October 14, 2013, 06:29:37 pm
farmboy was the 440 cylinders looking like this 460 cylinder a friend is fixing for his logger neighbor?