MS251C gone hard to pull over

[petercb]

Hi,

 

My 251 has developed a problem in that it is extremely hard to pull over - so much so that it's not possible to start it. Has not had a lot of use as it's basically a back up saw to my 450e which I much prefer using. Both saws are run on same mix. Have pulled muffler off and can't see any dramatic signs of any pickup in fact was a bit surprised at machined surface finish on piston - looks like a ploughed field to me! Pulls over a bit better with spark plug out but even then difficult. I seem to remember a comment a bit ago about little ends could give problems on these?

Saw was brand new to me and probably not done much more than 50-100 hours total but does get used every month or so.

Any thoughts would be appreciated. Was skilled fitter back in the day and still maintain all our farm and forestry equipment so happy to get stuck in but just never pulled a chainsaw apart.

[Khriss]

Looks alright exhaust side - nothing jamming the pull start / dogs n cogs? K

[Khriss]

( mix looks ok too on port deposits) 

[petercb]

Thanks Khriss, no it pulls over evenly but slowly with plug out can hear it compressing and exhausting ok. No funny noises.

[Khriss]

Hmmm, might be time to whip cylinder off then, had jamming Husqvarna pulleys before - only thing i can think of  🤔 Bar a collapsed  bearing 🙁 K

[bmp01]

Had a post like this not long ago Stihl 211 or 181 or something like that. No real conclusion but along the way I think Spud mentioned WD40 down the plug hole to dissolve / loosen sticky oil from ring grooves. Worth a try,  quick and easy....

I guess if your concerned about the mechanics flywheel cover off turn it back and forth - see if it's smooth etc.

Presume is not dragging the chain brake,  weak or broken clutch spring....

 

[bmp01]

3 hours ago, Khriss said:

Hmmm, might be time to whip cylinder off then, had jamming Husqvarna pulleys before - only thing i can think of  🤔 Bar a collapsed  bearing 🙁 K

MS250 was a clam shell engine, 251 will be the same ... not 2 mins.

[Paddy1000111]

Have you taken off the pull start mechanism and turned the flywheel by hand to check it's definitely the engine? If there's an issue with the pull start where under load it's seizing up? that could give a similar feel? 

[ChrisNewport]

is chain moving when pulled? ive seen one that was left ticking over with brake on for half an hour and everything around the clutch melted and stuck together.

[Paddy1000111]

10 minutes ago, ChrisNewport said:

is chain moving when pulled? ive seen one that was left ticking over with brake on for half an hour and everything around the clutch melted and stuck together.

didn't think of that, broken clutch spring maybe too, clutch engaging with the chain brake on!