Advice Needed On a Stihl MS 290

[sefh3]

The top end is done that is for sure. Most of the "stuff" were pieces of piston ring and piston embedded in the top, as well as pits from that being mashed against the top of the cylinder.




I plan on taking that apart tomorrow. My son took off with the tools I needed to do that to help his Grandpa with something while I was tearing down the rest of it. Danged kids!

The bearings spun freely and no balls were missing that I could see, but I'll know for sure tomorrow.


It pulled straight out - I didn't have to unscrew it. Is that normal?





Thanks for the offer. I live about 45 minutes north of Ann Arbor, so I don't get as close as you are to enemy territory very often, but if I can't get it going, I may take you up on it.

I work in Ann Arbor so if you need help I can met you after work one night.

What does your spark plug look like? Did your electrode fall off of it?

 

[redunshee]

The kit that Baileys has sounds like a really good deal now. The crank and bearings are included in those kits.

Yea and for $99.00(unassembled) I jumped on it.
Bob

 

[Fish]

Looking at the damage, makes it look like someone used an object in the exhaust port as a piston stop before it's last run. And the damage
built up from there.

 

[Saw Dr.]

Looking at the damage, makes it look like someone used an object in the exhaust port as a piston stop before it's last run. And the damage
built up from there.

That is what it looks like to me also. Good call Fish.

 

[Fish]

That is what it looks like to me also. Good call Fish.

Hard to say for sure, as auctions tell no tales...

 

[dw8468]

You may have a point there, fish. I hadn't thought of that. I think I'll run down a parts list to see if everything is OEM, just to satisfy my curiosity.

The spark plug and bearings are intact, as another post suggested, so that or the broken ring idea seem the most plausible.

How do you suggest holding everything still while tightening the flywheel and clutch down? I read somewhere on this site to put rope in the cylinder, but it seems like that could cause the same type of damage. When you compress anything it will become very hard at some point.

 

[sefh3]

I use a rope down the cylinder. BUT if your not careful and you don't have the rope above the exhaust port, you will be in the same boat. I'm wondering if that happened to this saw. Also, post a picture of your cylinder, exhaust port. Usually if an object is used to hold the piston still, it will leave a mark on the top of the exhaust port.

 

[nstueve]

When re-assembling the saw start with strapping the cylinder down to the crank case. After that you can use rope or a piston stop to remove/install the flywheel and clutch.

 

[Stihlofadeal64]

You may have a point there, fish. I hadn't thought of that. I think I'll run down a parts list to see if everything is OEM, just to satisfy my curiosity.

The spark plug and bearings are intact, as another post suggested, so that or the broken ring idea seem the most plausible.

How do you suggest holding everything still while tightening the flywheel and clutch down? I read somewhere on this site to put rope in the cylinder, but it seems like that could cause the same type of damage. When you compress anything it will become very hard at some point.

Buy the Stihl "piston stop" it's only a few bucks or so. Put it in the spark plug hole (cylinder) and rotate the piston till it engages the stop. Then you may install your clutch and flywheel. (Since I bought the piston stop I no longer use nylon rope as a piston stop). Has worked flawlessly on hundreds of saws. opcorn:

 

[jus2fat]

There is a certain method for using the Stihl piston stop..!!

You must put it in pointing opposite the exhaust and intake..

As in the same direction as the piston pin..this way the piston can't try to "swivel"..!!

J2F

 

[dw8468]

Thanks, Stihl and J2F. I'll look for one of those.

This is my first rebuild where I don't have a good way to do it externally, so I appreciate that tip!

 

[sefh3]

There is a certain method for using the Stihl piston stop..!!

You must put it in pointing opposite the exhaust and intake..

As in the same direction as the piston pin..this way the piston can't try to "swivel"..!!

J2F

Great advise. That is one of the easiest ways to bend a rod.

 

[Stihlofadeal64]

There is a certain method for using the Stihl piston stop..!!

You must put it in pointing opposite the exhaust and intake..

As in the same direction as the piston pin..this way the piston can't try to "swivel"..!!

J2F

*in the voice of ole frog-horn Leghorn*
" I say...I say...I say...muh boy - I believe you might be on to somethin!"

 

[dw8468]

Ok, another question.

I'm putting this puppy back together now, and I'm wondering how much to torque the clutch.

I found the repair manual, and it doesn't specifically list the clutch in the torque value table. The only thing I see that seems to be the right part is the "Carrier/Crankshaft" which is listed at 50Nm. This seems like an awfully high value.

Does any one know if this is correct, or should I be using the same value as the flywheel (28Nm)? Maybe I'm looking at the wrong part description?