Bernie’s MS250 Upgrade

[Paul Fithian]

My good friend Bernie has a nice MS 250 that he’d like me to improve. Usage is for dead tree cleanup on his property and firewood cutting. Runs great, he takes care of his stuff.


After reading a bit more about this model, looks like a muffler mod is in order, but not much else. I hesitate to open it up and adjust intake and exhaust port widths.

Any suggestions on the muffler mod recommended for one of these?

 

[PA Dan]

I woke up a very early one with a muffler mod and timing advance.

 

[drf256]

Muff mod and the WT215 carb, which is H adjustable. Maybe a mesh AM air filter. Probably a TA Like Dan said.

Not much else to do there. The muff mod is mandatory.

The early 025 were dual transfers. The 250’s are quads. Both open designs. I wouldn’t open the clam, BTDT.

 

[Paul Fithian]

I wouldn’t open the clam, BTDT.

Agreed on the clam. What’s BTDT Doc?

 

[Loony661]

Agreed on the clam. What’s BTDT Doc?

I’m assuming he means “Been There, Done That”.

 

[Hulpio]

YAJLYA. You Americans Just Love Your Acronyms

 

[GMB74]

Muffler mod is pretty straight forward. Open up the outlet as shown, then pry open the louvers a bit. Easy peasy.

 

[Paul Fithian]

Thanks @GMB74 !

How much should the key be shaved for timing advance?

 

[Hulpio]

If your flywheel diameter is 4" and you move magnets 3/8" you changed a little bit over 10deg. (circumference 320mm. 320/360=0.89mm. x 10 = approx 3/8")

 

[sawmikaze]

I always put the oil pump with a higher output in them, they barely oil the 68 driver bar sone people run on them, either way more oil isn't a bad thing.

1123 640 3201

 

[GMB74]

I've done the MM and WT215 carb on mine.
Now thinking about the timing advance.
The key is cast into the flywheel on this model.
How much should you file off the key for a proper timing advance?
I'm looking for a width measurement so I don't go too far.

 

[sawmikaze]

I've done the MM and WT215 carb on mine.
Now thinking about the timing advance.
The key is cast into the flywheel on this model.
How much should you file off the key for a proper timing advance?
I'm looking for a width measurement so I don't go too far.

I took a 1/3 and it ripped.

 

[PA Dan]

I took a 1/3 and it ripped.

Same!

 

[GMB74]

Yowza!
That's a lot of advance.
How did it start, especially cold?

 

[GMB74]

Elastostart handle is a good addition/upgrade
0000-190-3402

 

[sawmikaze]

Elastostart handle is a good addition/upgrade
0000-190-3402

This too.

 

[sawmikaze]

Yowza!
That's a lot of advance.
How did it start, especially cold?

Actually better..for whatever reason.

 

[Paul Fithian]

For the timing advance, file the key as shown below, right?

 

[Hulpio]

You will then move flywheel forward and coil "sees" magnets earlier so I would say yes.

 

[farminkarman]

For the timing advance, file the key as shown below, right?
View attachment 394397

Yep.