HELP! Sprocket Change?

[toolmaker]

My son want to change his MS250 over to 3/8 pitch.
I already have a bar and chains for him.

What does he need to change from .325" to .375" pitch?

 

[singinwoodwackr]

My son want to change his MS250 over to 3/8 pitch.
I already have a bar and chains for him.

What does he need to change from .325" to .375" pitch?

Don’t. The 250s should stick with .325.

 

[hacskaroly]

My son want to change his MS250 over to 3/8 pitch.
I already have a bar and chains for him.

Of the newer Stihls, the MS 261 (4 hp) is really the tipping point between .325 and 3/8 and is fine using either. The MS 271 is a 3.5 hp saw and I would not put 3/8" on it and the 250 is a whole horsepower lower than the 261 at 3 hp. Unless you are modding the 250 I don't think it will have the power to pull a 3/8" chain, and if it did, not very effectively.

Edit: To answer your question, on any saw that you are going to change chain size, you will need to change three things, chain, bar and sprocket (spur or rim) to the new size you are wanting to use. I am not sure if the 261/271/291 clutch drum is the same size as the 250/251. If not, then that will be your biggest challenge is finding a clutch drum for that saw that will handle 3/8" chain.

 

[singinwoodwackr]

Of the newer Stihls, the MS 261 (4 hp) is really the tipping point between .325 and 3/8 and is fine using either. The MS 271 is a 3.5 hp saw and I would not put 3/8" on it and the 250 is a whole horsepower lower than the 261 at 3 hp. Unless you are modding the 250 I don't think it will have the power to pull a 3/8" chain, and if it did, not very effectively.

Edit: To answer your question, on any saw that you are going to change chain size, you will need to change three things, chain, bar and sprocket (spur or rim) to the new size you are wanting to use. I am not sure if the 261/271/291 clutch drum is the same size as the 250/251. If not, then that will be your biggest challenge is finding a clutch drum for that saw that will handle 3/8" chain.

I’m not sure there even is a 3/8 rim/sprocket or sprocket for the 250 anyway.
There is a 3/8 lo pro, however.

 

[hacskaroly]

I’m not sure there even is a 3/8 rim/sprocket or sprocket for the 250 anyway.
There is a 3/8 lo pro, however.

Yeah, Oregon makes one, you just have to make sure you get the small spline rim (what the 261 runs), the larger ones are too big to mount on this.

 

[singinwoodwackr]

Yeah, Oregon makes one, you just have to make sure you get the small spline rim (what the 261 runs), the larger ones are too big to mount on this.

View attachment 487672

Awesome. Now I can throw a 42 on my 170
O wait…sm sp…crap…

I’m Stihl looking for a standard/large sp version of a .325 8t for my 361. I have a 7 and a 9 but want to experiment with an 8.
The saw pulls a 20” with the 9 just fine, even in black locust, but…

 

[hacskaroly]

O wait…sm sp…crap…

Sadly, that will not work, however this one will, no modifications needed to use on a MS 170, I have verified it and even made a custom 33 driver 3/8 LP .043 full skip chain to go with it:





*Disclaimer: Not responsible for missing fingers due to this chain!

 

[singinwoodwackr]

Sadly, that will not work, however this one will, no modifications needed to use on a MS 170, I have verified it and even made a custom 33 driver 3/8 LP .043 full skip chain to go with it:

View attachment 487678
View attachment 487680
View attachment 487682

*Disclaimer: Not responsible for missing fingers due to this chain!

Might as well go to 1/4”.
I have a carver friend with some tiny, dime tip Japanese bars in .043/ 1/4”. Hard to sharpen, they are so small.

But, heck…Kodiak Kid has a pic of his 170 with a 60, so…

 

[Bill G]

Might as well go to 1/4”.
I have a carver friend with some tiny, dime tip Japanese bars in .043/ 1/4”. Hard to sharpen, they are so small.

But, heck…Kodiak Kid has a pic of his 170 with a 60, so…

Would that be the ole barefoot Tarzan Zip Line Plitz *s-wordz eh

 

[Al Smith]

I'm not going to pass judgement about a 250 but it is sub 3 cuber .As such in reality is going to over load it going to 3/8" chain .Most 3 cubers run 7 tooth .325.Exception might be the Partner 5000 plus that came from the factory with an 8 tooth .325 on a 16" bar .Not all 3 cubers have the mustard for that .Keep in mind the little 3 cubers are not redwood slayers but some act like Jack Russel terriors which the 250 is not .

 

[larasea]

Bad idea.

 

[Sloughfoot]

If you just gotta do it (and I agree with those saying stay .325), 3/8 LP/picco super is the way to go. I've got 3/8 picco super on both my little saws and wish they were .325. Definitely pulls better than regular 3/8 though.
Btw those 250s are badazz little saws. The 180, 210, 250........ clamshell engines are fantastic simple designs.

 

[Bill G]

Bad idea.

A bad idea is better than no idea.....

 

[hacskaroly]

The 180, 210, 250.

My preference between the 170, 171, 180, 181 if I had to buy one would be the 171. It has the side tensioner, adjustable carb and larger tanks than the other three. Although, the 182 might be something to look at too.

 

[Al Smith]

There comes a time in life that a 3 cuber is more prefered depending on what it's used for .For two foot diameter hard wood it will cut it just not as fast as an 80 or larger cc model .A good bit of what I cut for fire wood is downed dead ash etc. around 6 inch stuff .In that case I have several 3's that work nicely plus the stuff doesn't need split .On the other end I have some of the most powerfull chainsaws ever made that seldom get any run time . That vintage Homelite in my avatar is an old school redwood slayer that was rated for a 60 inch bar hasn't cut anything for 5 or 6 years .114 cc power house ,heavy as lead .

 

[larasea]

A bad idea is better than no idea.....

View attachment 487894

Really! OK

 

[toolmaker]

Not gonna do it. Thanks for the info!