Sheared flywheel key?

I didn't remember them being that thick.

 

Good idea 4Us. +1 on factory gasket thickness and squish out of the factory can be anywhere from 0.030 to 0.050. Nate, removing a base gasket is a cheap easy way to pick up a little performance boost from increased compression. Lets say squish with the factory gasket is 0.035 and your base gasket is 0.015 compressed, removing the base gasket and using 1194 as a base gasket will reduce the squish to 0.020-0.021 optimum safe squish.

 

I've seen guys get away with 0.015 squish on smaller saws <50cc but on the larger saws anything under 0.020 is just asking for trouble! If you have never seen the aftermath of the piston hitting the top of the jug @12.5K, the damage done will amaze you!

 

Not to my knowledge, rule of thumb is no less than 0.020. When you think about it 0.020 is .5mm approximately. That is pretty close! What will throw your measurements off especially on AM jugs is a baad palating job on the jug. You could be at 0.020 in one spot and 0.010 in another. I once tried to figure out a way to measure the complete circumference of the squish by putting a piece of solder completely around the top of the piston but that did not work out too well.

 

20-25 thou on any saw over 70cc is a rule of thumb..
Though I have a 9010 with .019 squish...
I use it on the mill too...
Runs great...

 

Whats been banging around on top of that piston?

 

I looked at the pics and ran downstairs... But those marks wiped right off with my finger, piston top is smooth.

The flywheel puller is slated to arrive this weekend.

I am wondering about the cylinder discoloration as well as that vertical streak exhaust side of piston and cylinder. These have me worried although the saw had no symptoms of an air leak. However, a pressure/ vac test is probably in order.

 

Might be carbon, try a little brown scotch-brite (350 grit) and some muratic acid. Warm the jug a little in the oven first, I find that warming the jug makes the acid work better, don't get the acid in the ports!

 

Arghhhh, it arrived and it's too big! damm it, should have gone with the eBay link with the 2 different threads. Will call them in the morning and see about a refund. If I have to eat shipping I might have someone at work make the other end the 22mm.

 

OMG. Just hit it with a hammer and get it over with. The suspense is killing me!

 

So the $1.80 puller worked like a charm. However, sure looks like the key is good to me.... Help!!?!! Ignition related?

 

The plot thickens. Maybe it's the ignition retarding the timing.

 

I am clearly no saw guru, but is this common with a coil type ignition? I'm about to put this up in the classifieds as an 038 in a box.

 

Don't do that. No it's not common for that to happen. Usually they just quit.

 

darn... late to the party on this one and could have saved you the $ for that puller-
For one: I bought that same puller from weedeaterman and noticed it didn't fit the Stihls I have. I kept it and gave it to my shop in case they needed to pop a larger one. I just ordered the stihl puller for $9.95 (fits all my saws...1125 and 1128 series so far... no need for hammer as the wheel just pops off). He would have taken it as a return so maybe HLSupply will do the same??

For another: I sheared a flywheel key on my first top-end repair.... had the flywheel off for a new seal, ended up not getting the correct torque. Here's what that sounds like--- saw starts and runs good for a bit....turn it off and am proud of my work. Go to re-start and POP... then it backfires, spew mix outta the muffler (if you keep pulling, which of course I did) and won't start. After clearing the flooded saw it still won't start, suspected key right away. Found it sheared flush with the crank and goobered the flywheel a bit (but I had another ready to go). It's good that you checked but since you didn't have it off, it was probably ok.

What were your symptoms again? Hard to pull? (you mentioned high compression earlier) Smoke and bogging? May be a carb issue there...
Piston looks ok, but definitely clean things up as described above. How's your plug look?

 

Symptoms from first post:

In a nutshell, it is harder to pull than normal. I was able to get it to run, but it was rough. The pull cord violently yanked back, as though the timing was off, which brought upon this thread.

Thanks for any help.

My current plan is to put everything back together with a bit of TLC. Given the cylinder showed possible signs of an air leak might be time to buy a Mighty Vac. If I see the same occurrence after the minor rebuild, I guess I will pursue a new coil.