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