084av not a happy camper

[Mike Bergen]

So in the process of kitting up for log gathering and chainsaw milling I seem to have killed my 084av.  Hope someone can point me in the right direction for what to do to fix it.

Rebuilt the carb. Cleaned the whole thing. new plug. new air filter. new fuel filter. new gas (93 octane ethanol free and mixed with stihl oil at correct ratio).  drilled three 3/8" holes in carb and pulled out spark arrestor. no bar or chain mounted on it.

Turned the screws all the way in then backed them out one turn.  Fired up on third pull.  Did not want to idle.  Backed low speed screw out half turn and she idled just fine.  Let it warm up then backed out idle speed screw until she idled at a reasonable speed around 2500 (using tachometer).  popped throttle open and she stuttered a little bit.  Started fiddling with high speed screw.  (Probable where I went wrong as I wasn't paying close enough attention to where my high speed screw was at)  Ran saw wide open for 20 seconds or so.  Tach read around 11000 rpm.  fiddled with high speed screw.  Chainsaw backfired and immediately died.  puff of smoke came out of muffler.

I checked to see where the high speed screw was set and I was only a half turn out.  cussed.  Turned screw back out to full turn.  pulled cord and... no resistance.  Just the flywheel or whatever spinning around but no compression, no starting... more cussing.  Put the saw back in garage and here I am.

Obviously I don't know what I'm doing.   :-\ Anyone got any ideas of what I messed up on the saw?

I would appreciate any feedback-

Mike

[Texas-Jim]

check flywheel to make sure its  key way didnt slip or shear. only way it can backfire is timing and that key will do it.

[ZeroJunk]

Wouldn't cause no resistance pulling the rope would it ?

[celliott]

Wouldn't cause no resistance pulling the rope would it ?

If the key sheared then yes, there would be no resistance pulling the rope. The starter pawls would engage the flywheel, spin the flywheel, and the flywheel would free spin on the crank due to no key.

[starmac]

Pull the muffler and have a look at the piston.

[Mike Bergen]

Alright guys- appreciate the feedback. I'll check those ideas out and let you know what I find

[isawlogs]

 I also think you are turning flywheel only. Pull the starter it will be very easy to check.

[Mike Bergen]

Looking at the schematics and having a bit of a hard time figuring out which part is the "key" that would engage flywheel to crank.  If anyone feels up to having a look and letting me know which part I should be checking here's the link to the schematic: http://www.declicmotoculture.com/fs/eclates/6h3k2-084.pdf

Might be one of those things that is easy to find once I start pulling the actual saw apart but the saw is over in my shop and I'm on the couch at the house.  I'll grab it tomorrow but trying to get as good of a head start as possible.   ;D

[isawlogs]

 illustration A Part number 24

It holds Illustration G  part  1 in place

[weimedog]

If that key is sheared and the flywheel is loose enough to pull over with the pull cord...shouldn't take much to get things apart enough to see.. probably don't even need a pull!

[Mike Bergen]

Thanks Marcel! I finally located that little guy just after I asked for help.  I'll let y'all know what happens when I pull it apart tomorrow. Thanks again-

Mike

[starmac]

If you pull the muffler, you will be able to see whether the piston is moving up and down anyway. It shoule be relatively to feel if the piston is not moving versus just no compression. I can't imagine the flywheel beeing loose enough to not turn the crank even with a busted key.

[isawlogs]

 To me it is the backfire that was the givin' idea that the key is broke, not much else can make a saw backfire and die.....

[starmac]

I hear you, a lean condition can sometimes make one backfire, but usually a lean condition bad enough, would score the piston, killing the compression, but the drag makes it still fell like it has compression. Iirc he was revving it with out the bar and chain, it could have broke the key and let the flywheel freespool, but I would think the flywheel almost had to be a little loose to have done this in the first place.

[isawlogs]

 I am guessing we will all know in a while  ;)

[ZeroJunk]

Yeah, I can't see the flywheel free spooling unless the nut came off somehow, or worse, the crankshaft broke.

[old2stroke]

Easy to check if flywheel is spinning on the crank, just take the bar mount cover off and see if the center of the clutch is turning when you pull the cord.

[Mike Bergen]

OK guys- got home from work after grabbing saw and a beer and checked it out.  First thing I did was pull the muffler so I could check out the piston.  It was moving intermittently (like something would occasionally catch and turn the engine over) when I pulled the starting cord.  Looked ok though.  So I pulled the starting coil cover.  The nut that holds on the flywheel was loose.  I tightened it then pulled the cord while observing the piston.  Started moving much more regularly.  yaaayyy- fixed!  Well, maybe not.  I pulled the nut off then the flywheel and this is what I found:





Got some metal bits and who knows what else here.  The seal on the crankshaft was quite crooked.  I put a socket over the end of the shaft and tapped it down.

Questions I now have are:

1. How far should I tap this seal down?
2. Should there be something that secures the flywheel to the crankshaft other then the compression from the nut (the one that was loose)  i.e. am I missing something?
3. What else have I damaged?

Hmmmm.... pesky mechanical devices!  heheh

Thanks!

Mike

[Mike Bergen]

to clarify the second question- I'm not seeing any evidence of a "key" or keyway that would secure the flywheel to the crankshaft.

maybe I should clean it up a bit and check again? lol

[isawlogs]

 There is a key and keyway there... Keep lookin', key is gone for sure. there is a slot for it on the crankshaft and also on the flywheel.  ;)

[Mike Bergen]

Ah hell, looks like I'm in trouble then.  Found evidence of slots in crankshaft and the flywheel.  Currently they are filled in solidly, smoothly, and it appears... irrevocably.  Looks like the key sheared and got ground up and filled in the slots nice and evenly.

Who reckons I can fix it with a dremel to make some new slots and a piece of a beer can for a new key?   ;D

Seriously though... time for a new saw?  Or is it fixable?  Fixable without buying a parts saw for a crankshaft, key, and flywheel???

[ZeroJunk]

If the threads are good on the shaft and the flywheel and shaft are in good shape you don't need the keyway for anything other than establishing the correct timing. Think of it like the way a chuck fits on a drill press. If it is tightened down properly the taper will hold it just fine. Now, I don't know if yours is damaged too much to make that proper fit or not.

[isawlogs]

 That key is removable from the slot and fly wheel, not the first to have one shear off. If you don't feel comfotable taking on the task, bring the saw to a reputable small engin repair shop and have them do it.

[Mike Bergen]

Ok- anything else I should check before the next time I fire it up?

Thanks again for the help guys

[ZeroJunk]

I think I would pop that seal out and replace it while you have the flywheel off. Good time to check the bearings as well. Something made it get out of position.