MS250, need expert advice?

[Okie]

Okie did you use the Nachi bearings?
Kash

I seem to think it was the Nachi.
A member on this forum sent me a Stihl 250 pdf service manual and the part number for the bearings.
I ordered the bearings on-line.
Ask for the part numbers for the bearings and some member will chime in.
I seem to remember they were less than $20

I used a small two jaw bearing puller to remove the old bearings and had to use some grease to space the bearings inside so the race would not pull off sideways, then placed the crank in the freezer and slightly warmed the bearings in a oven for a quick easy install.
I seem to think maybe that I never did removed the piston/rod from the crank.

 

[a. palmer jr.]

I flogged the MS250 late this evening and got the clamshell opened up and found the intermittent erratic snug turning of the crankshaft problem. The plastic roller bearing separator that keeps the roller individual roller bearing separated and in place around the inside of the race on the clutch side bearing was busted up in small pieces and about 1/2 of the bearing were not separated and small pieces were lodging in the bearings race causing some of the bearings to slide and hang on the broken pieces and few plastic pieces were in the bottom of the clam shell. The bearing race had not spun in the housing. The piston/cylinder/rings looked great.

Plastic bearing separators looks like a weak/wimpy design for a high rpm engine? (appears the plastic cage could chip or break at almost any time in the life of this type bearing even a new bearing)

I'm thinking about replacing the following. Both crank bearings, both crank seals, the intake manifold boot, pulse line and maybe fuel line and since the saw had a good strong 140-150 compression just leave the existing rings?

Is their a better bearing design replacement or should I just go back with the OEM plastic cage type bearings?

Anyone have any other recommendations about replacement parts, to install when going back together, etc????

It's been my experience that, since you have the clamshell apart, go ahead and rebuild the whole thing. Doesn't cost that much more to do a complete rebuild. You could also just buy a rebuilt engine and slap in it, not that expensive either..

 

[Okie]

It's been my experience that, since you have the clamshell apart, go ahead and rebuild the whole thing. Doesn't cost that much more to do a complete rebuild. You could also just buy a rebuilt engine and slap in it, not that expensive either..

Very true:

I would have done that to this one but I checked the compression BEFORE I took it apart and it had high compression and the saw looked new. I suspect it had been stored in a very hot enviroment for few years and the plastic separator just hard baked.

Being a clamshell it was easy to work on and they would be easy to rebuild BUT even though I like Stihl saws and have several others models and have some 028's that are years old and some newer ones I'm not a fan of the 250's. (and would not recommend one as a desirable Stihl chainsaw)

They usually crank hard and sound tinny to me when they do run and my 028's and 034 will cut circles around the 250 and the 028 and 034 is just more user friendly.

 

[a. palmer jr.]

One thing I usually don't replace on a rebuild is the main bearings. If I see one is bad I can replace with OEM but I think the regular, used OEM bearings would be better than new chicom stuff. MS250, not my favorite Stihl either..