Stihl 066 Rebuild questions or comments

[asdf4240]

So here's the deal: I purchased a broken Stihl 066 Magnum (later model) from my local dealer. The dealer said it had a scored piston and cylinder. I've removed the muffler and verified the piston and rings are gone. However, I'm not sure about the cylinder. I haven't completely dissembled it yet. Overall condition of the saw is very good and appears to have very low usage. It was owned by the local fire company and looks like it was used as a rescue saw. Lot's of black saw dust.

My needs for the saw are as follows: It's for my personal use albeit not very often. But when I do need it, I need it to run reliably. I don't want to deal with any field repairs. Normally, I'm too far away from home and have a limited amount of time to cut. Finally, if I decide to start milling logs, then this chainsaw would be used for that as well.

So here's the questions:

1) What to do with the piston and cylinder? New Stihl? Big Bore Kit (I've read about the issues)? Or if the cylinder is okay, then new piston? What brand of piston, OEM or aftermarket?

2) This saw looks to be a very late model 066 and it already has the following options(?) - dual port muffler and HD air cleaner? Where these factory installed or added later? Or is this just the Magnum option?

3) I'm thinking of replacing the following, fuel line, fuel filter, impulse line, air filter, spark plug, carb kit, and rim sprocket. Probably crank case seals too. Am I missing anything else?

4) Can crank case seals be done with out splitting the case?

5) Porting the saw, opinions? I'm thinking of a mild port especially if I'm considering milling.

6) Finally, the major question is putting the least amount of money into the saw just to get it running or spending more money and have a rock solid saw whenever I need it. So far I only have $159 into it.

To answer the question of how the piston was scored, it looks like the saw was overheated. The cylinder fins are full of thick saw dust and the filter base plate is completely clogged. This is my initial guess as to the cause.

Also, I've rebuilt all kinds of engines, even several smaller chainsaws. So I'm very comfortable working on chainsaws, however, I've never rebuilt this specific model.

Thanks in advance.

 

[mdavlee]

If the cylinder will clean up re use it. Meteor makes nice pistons for about 1/3 of oem. I don'lt know of any one that's had problems with them. I put one in a 660 a few years ago and haven't heard back from them so I guess it has done fine. Seals can be done without splitting the case.

 

[Bounty Hunter]

Hey asdf4240,

I rebuilt an early model 066 last year, and like yours, the cylinder cleaned up with some work and emery cloth. I went with a Meteor Piston, and put new bearings and seals in it.
The rear handle was completly broken, so i bought a new one (for a 660) and that led to a bunch of compatability problems with the airbox and trigger controls. I basically had to update to all 660 parts.

The flywheel has plastic fins, and they are somewhat fragile. If one puts a too-long screw in one of the holes for the engine cover, the screw will tear off ALL the fins when you attenpt to start the saw (please don't ask how i know this...)

I put and extended clutch cover with chip flap, a 3/4 wrap handle, roller chain catcher, big dawgs, and modded the stock single-port muffler A LOT.

This saw is now my FAVORITE felling and bucking saw, and has been super-reliable.

Good luck with yer rebuild, keep us posted...and send pics

(ArboristSite Rules: No pics, it didn't happen :biggrin

 

[ZeroJunk]

I have rebulit them with OEM top ends and aftermarket and had no problems with either. If the saw is in really nice shape I would go OEM. If it's rough I would go aftermarket. Or, if you really think you are going to mill with it I would go OEM. If you are not planning on trying to make a living with it I would go aftermarket.

As far as the piston only, Meteor is fine.

 

[srcarr52]

1) I just did a 066 with a Meteor piston. Meteor or Espian are the best aftermarket pistons, either one and you'll be in good shape. If you can't get the cylinder to clean up I hear good things about the newer BB kits from Baileys.

2) You could get the dual port muffler and HD filter from the factory. Still the factory dual port is stuffy. You can modify the right side output to flow more but the face outlet I wouldn't hog out too much to keep it from lighting wood on fire. The one I just did I put a Husky 288 deflector on the left side of the muffler and opened up the right side factory outlet.

3) Don't forget to check the bearings. Better to get them now then have to go back in later.

4) Crank seals can be done without splitting the crankcase. Be careful when prying them out not to gouge anything.

5) Most 066 have pretty aggressive porting from the factory but the standard porting rules apply. Get your squish set, widen the ports to the max. Really they can use more transfer timing which takes special tools to do but just doing the standard plus a muffler mod will make a impressive saw.

6) Aftermarket piston, fuel lines, fuel filter, seals, air filter, and spark plug should run you $80. You'll have more in a good bar and chain for it.