Can't start my 92cc saw

[Bedford T]

With the plug out, just put a pencil in the spark plug hole, eraser end on the center of the piston, or something similar. I realize on an ms660 it's at an angle.
Then take the starter off.
Then rotate the flywheel counterclockwise until you are at the top, then look at the central point between the flywheel magnets in relation to the center of the two coil legs. It should be about an inch difference about (26 degrees) ahead of the coil.
Usually if it has slid on the keyway it will backfire once in a while out of the muffler, but not always.

it is exactly where it should be, the top magnet exactly lines up with coil, the top dimple on the flywheel is @tdc

The spray to look for is with plug pulled out and starter yanked on a few times with the throttle wide open, and the choke open. The spray I'm talking about is out of the spark plug hole. A Ziptie on the throttle makes it easier, but don't try starting it like that though.
Pull slower at first, because if there's a bunch in there, you might belch it out on you or something flammable nearby.
If it does spray out, then tilt the saw back slowly with the piston at top dead center, the fuel in the crankcase will run out of the carb throat.
If the crankcase is full of fuel, it can also cause partial hydraulic lock, depending on the amount in there. That might explain the excess compression you are experiencing.
If this is what has happened, then you have a leak in the carburetor.

no spray out the spark plug hole. after i put plug back in put it on run and pulled on it 3-4 times i saw a puff of something come out of the front of the carb. happened one brief time.

I've seen new Bosch spark plugs be bad right out of the box. It's very rare, but still.

put another new plug on and tried to crank it after checking everything.

i had some drool out the muffler went i tilted it down putting it away. so there is fuel in the case. i will tilt it like you mentioned and drain it

 

[blsnelling]

Unless I missed it, I don't see where you've pulled the flywheel to check the key.

 

[Bedford T]

Are you saying the check I just did is no good. The flywheel has to be removed. I checked the position. It had not moved.

 

[alexcagle]

I cant really see the two magnets in the pic. Just to be clear; it should lead the coil when the piston is at TDC.
Is that one of those aftermarket flywheels to replace a poly flywheel?
The coil is aftermarket right?

 

[grizz55chev]

Keep it simple, pull the flywheel, check the key. Blow out the cylinder with compressed air, do not prime for starting, report back with yore findings.

 

[TBS]

I cant really see the two magnets in the pic. Just to be clear; it should lead the coil when the piston is at TDC.
Is that one of those aftermarket flywheels to replace a poly flywheel?
The coil is aftermarket right?

The magnets are right in line with the coil legs.

 

[Mad Professor]

Check the decomp valve.........yet?

 

[Bedford T]

i pulled the flywheel and the key was whole and not deformed. the oil seal is dry. the decomp valve is working. the cylinder is not flooded. after removing the flywheel i checked the install and the magnets lineup exactly with the coil and i used the pencil trick to check cylinder position. the coil is firing

please see the photo

 

[grizz55chev]

The magnets are right in line with the coil legs.

Also looks like a large gap, that can cause some timming issues.

 

[blsnelling]

A guy on FB just went through the same thing with 660. He had a bad flywheel. The magnets can go bad.

 

[Bedford T]

here is a close up of the magnets and i moved it slightly so you could see them. the magnets line up perfectly between the top and bottom dimple. are you saying thats wrong? i don't undrrtstand. because that is exactly where they have always been when it cut wood. the red lines meet @ tdc

 

[Bedford T]

is there a way to test the flywheel.

i am following along here but why would the plug fire if the flywheel is bad? i understand we are looking for a cause. but i have said the plug fires, the coil would cause that. the coil light tool indicates the coil is working.

it is what it is i just wonder if everyone is getting what i am writing

 

[Bedford T]

i used a piece of metal and put it on the magnets and it they both had good holding power. not like a thump when it grabbed it but it did not want to release it when i pulled it away

 

[Bedford T]

Also looks like a large gap, that can cause some timming issues.

what do you mean? where is there a large gap?

 

[blsnelling]

...so much compression I have to use the decomp to pull starter...

If that is indeed the case then there is something wrong with the saw. A 660 can be pulled over even with >200 PSI compression.

 

[blsnelling]

Remove the spark plug. Does it turn over nearly effortlessly, with only a slight "bump" as the magnets go past the coil?

 

[Bedford T]

If that is indeed the case then there is something wrong with the saw. A 660 can be pulled over even with >200 PSI compression.

I had that checked early on and it's me a stihl tech was the one that first started the saw. He said that was a good sign. That's when I knew it was me. Holding and impact wrench can bring tears to my eyes. I have arthritis. In both my thumbs. I quit shaking another man's hand cause it hurts. There is nothing wrong other than it has very good compression

 

[blsnelling]

I had that checked early on and it's me a stihl tech was the one that first started the saw. He said that was a good sign. That's when I knew it was me. Holding and impact wrench can bring tears to my eyes. I have arthritis. In both my thumbs. I quit shaking another man's hand cause it hurts. There is nothing wrong other than it has very good compression

I'm sorry to hear that, but that's good to hear for the saw.

 

[Bedford T]

Thanks. I am no expect but I pay very close attention. That was my job. Details. Troubleshooting. Everything appears ok. For example When you asked if I had removed the flywheel we had checked the integrity of the key, but removing it did allow for visual inspection and of the seal. So each item involved in the straight forward process fire, fuel, air has been tested mostly twice and I don't see light at end of tunnel yet.

I am really hung up on why given the facts I don't get a burble when introducing something straight into the cylinder bypassing the carb. If the test light glows on pull when placed properly, if the plug fires when grounded outside the cylinder but these things don't end in at least a burble it's got to be a one off. Like the coil not firing under load, it fires outside the cylinder I am on 3rd plug. So plug is not an issue

Yes it turns effortlessly and the bump is more audible when the piston pushed to the top

 

[blsnelling]

1. Remove the spark plug. Does it turn over nearly effortlessly, with only a slight "bump" as the magnets go past the coil?
   
2. How does the piston and back cylinder wall look with the muffler cover removed?
3. How does the cylinder wall look through the spark plug hole?
4. Turn the saw upside down with the spark plug removed and pull over quickly. Does any fuel spray out?
5. Is the plug wet or dry when attempting to start WITHOUT choke?
6. Is the plug wet when attempting to start after several pulls when it IS choked?
7. Are you getting a nice blue spark?
8. Is the flywheel key sheared? Answered no.