Plenty on my mind, not sure how it's all going to come out. A partial shear wouldn't change the way the saw runs that much. The way you say it's running it would have to be spun pretty far. Do me a favor and some how mark the wheel and crank so when you pop it you can see the orientation. A wise man on AS don't hit anything with a hammer. If the flywheel isn't coming easy get a puller. As cnice said I just wanted him to look and see of it was obvious plus he's never done it before so I was showing him the basics.
After saying don't hit anything with a hammer don't call me a hypocrit when I show you my homemade whack a mole device. I got a bolt and two nuts that are the same pitch and welded them together. Screw that on and tap it while prying on the flywheel and the flywheel usually pops off.
That's the same idea mweba showed in his vid. I grabbed some aluminum stock from work to act as your bolt, bottomed to the flywheel nut backed off, and used foam to hold and center the stock. Whack, nothing, whack, nothing, whack, nothing.... I might be being too easy on it?
One hit like you mean it is easier on things than many smaller, ineffective whacks. If Stihl didn't want us banging on crankshafts, they wouldn't make flywheel knocker tools.
I think you need a tool. It's too hard to pry and get a good hit with all that stuff loose. Here is a pic from a small engine forum.
+1 with what Rookie1 said! Be VERY CAREFUL with the above set up, VERY easy to break things with the pry bar. Here is the puller for $10, go get one you won't be sorry. http://www.hlsproparts.com/Stihl-chainsaw-flywheel-puller-p/h70070.htm
Well the key to the tool is a hammer ........... but what you do is screw the puller into the flywheel, tighten it up with your fingers until it bottoms out then back it off 1 turn. Then hold it with a box wrench to keep it from moving while you tighten the center pin with another wrench to put tension between the flywheel and crankshaft. When you get it tight then you sharply strike the center puller bolt with a 2 pound hammer, it will either pop right off or it will move a little. e.g. the center puller bolt will loosen up, tighten the bolt up and do it again. Some flywheels that use a seperate key, also have a steel center which can rust to the crank try ATF and Acetone mixed 50:50 to break the rust!
Forgot one thing, after you get the puller on, pick the whole saw up by the flywheel a little off the bench an inch will do, before you hit it. What you are actualliy doing is driving the crank through the flywheel so you need a little room for it to move. If it is one of those that use a steel center, put a little never seize on the crank befor replacing the flywheel. Do it for you not the next guy, who knows, you might be the next one to work on that saw.
I bought the puller, the generic one wasn't setup right for this kind of flywheel. Stay tuned... Neighbor just brought me his backpack blower, garden needs more mulch, going to clean out the chimney finally, and hope to get a couple cords split this weekend to catch up. If time permits I have one last tree to fell that I committed to Bud heavy time.
Ok so I was bored and didn't feel like fighting bugs. Neighbors backpack blower was flooded. No fun there, so he got a good razzing. So, time to check my previous work. I noticed streaking on the piston, but I see no evidence of transfer nor gouging. Rings are good and in place, c-clips still there. I do see a rough edge on one of the transfers. Tell me if you see anything that needs further inspection. This was running a paper bag gasket coated in the copper spray stuff. Gasket looks great.
I'd clean up the cylinder a little. Smooth those rough edges and hit it with a little scotchbrite. Won't hurt it and you will see what's just discoloration and what is a real issue. Kinda curious about the large dark streak under the center of the exhaust port. I'm not a fan of paper bag gaskets even with the spray copper. The spray copper is good stuff but if the gasket is iffy....... Also, you really should check squish clearance since you are this far in and someone has used a thin gasket. Easy to do with the saw torn down this far and no ring on the piston. I like to put four little U's of solder on the piston crown, bolt the jug down leaving the ring off the piston and with or without the gasket (depends on what I'm testing). You need at least .020" to be safe, factory clearance is often more.
Definitely checking squish this time, but I don't have thick enough solder on hand. Why no ring on the piston to check squish? Just easier? The gasket was mine, I did the top end about 2 winter's ago.
No ring is just for easy on/off. Don't need it just to check squish. I'm guessing the squish is pretty tight with that gasket. Might not need very thick solder.
The ring(s) are very important, they hold the piston square in the cylinder. Measuring squish without the rings is an exercise in futility. The saw will not run without the rings so why would you check squish on a saw in a non-running state? An inaccurate squish measurement will contribute to a failure.
How much difference does no base gasket even make? I can't imagine 0.002" or whatever in stroke is making much of anything? I ran some numbers and on a 2" bore 2" stroke it was worth 0.1 cc. As far as pulling the flywheel, I tried using a few 2 and 3 jaw pullers on my 660 and I was worried it was going to tweak the flywheel with the force I was putting. Even with all the tricks. I ended up stopping by my Stihl dealer and using the correct puller. They didn't even want to take any money. That is a big reason I run Stihl. Good luck with that support at the big box store.