Bernie’s MS250 Upgrade

[Loony661]

A "quiet cough" is right.
They will crank it over until they have gas running out of the muffler or it hydrolocks, then bring it back saying it's junk.
I would take the saw out back, clear it out then instruct the new owner (again) on the correct starting procedure.

Yep, I know the feeling! I usually showed them how to start it once flooded so I (hopefully) didn’t have to deal with it again.

 

[Woodslasher]

I remember hearing all the MS250 horror stories online before I was gifted my MS250, and then none of them ever happened. I never flood it, it always starts, and even after a ~3-month hospital stay left me barely able to carry it 200 feet I could still start it with almost no trouble. Hell, I sold a 346 in favor of keeping my little 250.

 

[sawmikaze]

This. Then they blame the saw for not being adjusted correctly or being junk… In reality, one of the toughest “homeowner” saws made IMO.

"Homeowner" is one of my favorite words internet chainsawers use .

"variables" was up there with it

 

[Paul Fithian]

Started to work on this saw, all looks good. Ran it a bit before disassembly. Starts, idles, revs great. Starting pull effort is much harder than the 024/026 saws I have.

Plug and cylinder/rings look good



Carb has Hi/Lo adjusting screws with limiters, what’s the best way to pop these off?

 

[GMB74]

Carb screw limiters:
Remove the carburetor for better access.
Take a small screwdriver and pry them off at the base.
Reinstall carburetor.

Pulling effort is a little harder on these saws compared to similar pro-level saws.
It's not excessive, but noticeable.
That's just the nature of the beast on these.

 

[sundance]

Pulling effort is a little harder on these saws compared to similar pro-level saws.
It's not excessive, but noticeable.
That's just the nature of the beast on these.

"A little harder". Mine's border line impossible. Saw is rarely used as it's such a beast to pull.

 

[lehman live edge slab]

I took an 021 and put an 025 crank in it.
4mm difference in stroke but 20 thousandths off piston and 40 off squish left

 

[lehman live edge slab]

I took an 021 and put an 025 crank in it.
4mm difference in stroke but 20 thousandths off piston and 40 off squish left

 

[lehman live edge slab]

Here’s rhe compression after machine work, still nor where it needs to be hit will continue working on ir

 

[Hulpio]

What is your target?

 

[sawmikaze]

Started to work on this saw, all looks good. Ran it a bit before disassembly. Starts, idles, revs great. Starting pull effort is much harder than the 024/026 saws I have.

Plug and cylinder/rings look good
View attachment 395481
View attachment 395482

Carb has Hi/Lo adjusting screws with limiters, what’s the best way to pop these off?
View attachment 395483

I crack those limiters with a utility knife and they basically fall off.

 

[lehman live edge slab]

What is your target?

I mean power wise, I did some port work and it seems down on torque but maybe it’s just me since it is basically a higher compression 023 so 40cc. Also advanced the timing some for the longer stroke and may go more after I run it some.

 

[drf256]

Had a buddy over who asked me to get more out of his MS250 yesterday. Saw started right up before I touched it. Already had a mufkin mod.

I advanced timing only and saw wouldn’t run afterwards. Interestingly enough, saw needed a fatter L and more on the LA for it to idle after the advance. Did run better with the TA for sure.

 

[Paul Fithian]

Removed the flywheel, cleaned up real nice. Looks like a Brazil cylinder


Shaved the key with a triangular file, advanced ~ 1/2 fin rotation, or 11 degrees

Muffler mod done, I was able to get a drill/grinder inside and open it up

 

[jed1124]

Randy did mine in I think 11 or 12. I'm not sure what he did, but it was a different saw when I got it back. I do commercial tree work and every guy that has run it has been surprised. It's been on the harness of a lot of guys hanging off a crane.
It still runs great. Got ran over by a chip truck and I replaced the tank and handle. Retired to firewood now.
Still love that little plastic saw.

 

[Paul Fithian]

Installed the double starter pawls:


Put everything back together, no start. Checked over everything again, all good. Loosened coil and set gap to 0.010, still nothing.

Won't even fire with starter fluid. Time for a new coil? I never touched the coil on this saw.

 

[drf256]

Ground strap Paul?

 

[Paul Fithian]

Intact, shown in one of the pics above.

 

[redline4]

Didn't accidently hit the recoil on the coil ground tab and bend it into the coil, grounding it?

 

[Paul Fithian]

Failed coil?

Reads 2.7 ohms when coil is connected in circuit between clamshell and stop switch in run position:



Reads open circuit when disconnected from coil: