290 chain. .325 or 3/8? sorry........

[2000ssm6]

im going to be running a 3/8 chain on my 026 as well with a 16 inch b&c

Go for it, that is what I run on mine, pulls great also.

 

[windthrown]

So then why do they put .325 chains and smaller sprockets on smaller displacement saws? I meant no offense to you or the types of wood out there. But I've ran several 029 supers with 18" bars and .325 chains. IMO, increasing the sprocket size and or widening the kerf would slow the saw too much.

That is a good question. I dunno why they only offer .325 on the 270, but they offer .325 or 3/8 on the 260 which has less power. The kerf issue is funny. Comparing .325 std. kerf to 3/8 std. kerf cuts, they are about the same width. If you cut the same width out of a log, it will require the same amount of power. So I do not see all the raving about .325. More drivers per inch would equate to more torque delivered to the cutters with the same size and pin count rim. But they have higher pin count rims with about the same size rim diameter so that the difference cancel out. Doing the math, here is the rough comparison:

Large format .325 vs 3/8 (.325) chains and rims:

Drive links per 100 feet of .325 = 1840
Drive links per 100 feet of .375 = 1640

Rim diameter of 8 tooth .325 sprocket = 1.45 inches
Rim diameter of 7 tooth .375 sprocket = 1.40 inches

Comparing the 8 tooth .325 sprocket to the 7 tooth .375 sprocket:

1840 - 1640 = 200 and 200 / 1640 = 12.2% more cutters per length for .325 chain

8 - 7 = 1 and 1 / 7 = 14.3% more spin delivered to the .325 chain per rev

Comparing these and the roughly 2% difference in radius in the rims, it seems like they pretty much all cancel out, and you have about the same torque and chain speed delivered to both types of chain. If the kerf is about the same, then I do not see the case for .325 being any better than 3/8 chain. Actually, with more cutters per inch, it seems like the .325 chains would be more prone to bog down than 3/8.

Now in the IPL for the 290, they list a 7 pin rim for the .325 size. So that may be the only real reason that I could see for using .325 chain on that saw or the 270; adding the option for more torque at the expense of chain speed.

 

[windthrown]

Are those usually sold with 20" bars? The reason I ask is that I'm considering switching the drum & spur on my 290 to a 3/8" rim sprocket to simplify my bar and chain types among my saws. I like running a 20" bar (more reach. less bending over).

The 290 I ran had a 20 inch Farm Boss logo Stihl bar specifically made and marketed for the 290, in 3/8". Ran great. Also I could swap them out to and from my other larger saws. One reason I wanna flip to using a 260 from the 250... then I can have all the same type of B&Cs on all my saws, and have one file size for sharpening. Then I will also get a roll of 3/8 chain and be done with buying loops. I suppose I could get a rim drive for a 270 and do the same thing though? :monkey:

 

[TreePointer]

The 290 I ran had a 20 inch Farm Boss logo Stihl bar specifically made and marketed for the 290, in 3/8". Ran great. Also I could swap them out to and from my other larger saws. One reason I wanna flip to using a 260 from the 250... then I can have all the same type of B&Cs on all my saws, and have one file size for sharpening. Then I will also get a roll of 3/8 chain and be done with buying loops. I suppose I could get a rim drive for a 270 and do the same thing though? :monkey:

Thanks for the info! That's where I'm headed. I got the standard 290 for my area (spur sprocket, 20" FarmBoss logo bar in .325 .063). The problem is that the $$ I put into a 290 conversion to 3/8" could be put toward a 260. Darn CAD!

 

[Evan]

i switched my 026 to 3/8 bar and chain and was in just shy of 100 bucks. i guess it was worth it so that all my saws have 3/8 chains

 

[windthrown]

Thanks for the info! That's where I'm headed. I got the standard 290 for my area (spur sprocket, 20" FarmBoss logo bar in .325 .063). The problem is that the $$ I put into a 290 conversion to 3/8" could be put toward a 260. Darn CAD!

Sell the .325 stuff in CL or Ebay and make up some of the cost. I flipped all my smaller format Stihls to 3/8 picco and sold the .325 bars and chains and sprockers to pay for most of it. You want to upgrade to a rim style sprocket anyway. Spur sprockets suck in comparison (and cost more to run over the long term).

 

[outdoortype]

That is a good question. I dunno why they only offer .325 on the 270, but they offer .325 or 3/8 on the 260 which has less power. The kerf issue is funny. Comparing .325 std. kerf to 3/8 std. kerf cuts, they are about the same width. If you cut the same width out of a log, it will require the same amount of power. So I do not see all the raving about .325. More drivers per inch would equate to more torque delivered to the cutters with the same size and pin count rim. But they have higher pin count rims with about the same size rim diameter so that the difference cancel out. Doing the math, here is the rough comparison:

Large format .325 vs 3/8 (.325) chains and rims:

Drive links per 100 feet of .325 = 1840
Drive links per 100 feet of .375 = 1640

Rim diameter of 8 tooth .325 sprocket = 1.45 inches
Rim diameter of 7 tooth .375 sprocket = 1.40 inches

Comparing the 8 tooth .325 sprocket to the 7 tooth .375 sprocket:

1840 - 1640 = 200 and 200 / 1640 = 12.2% more cutters per length for .325 chain

8 - 7 = 1 and 1 / 7 = 14.3% more spin delivered to the .325 chain per rev

Comparing these and the roughly 2% difference in radius in the rims, it seems like they pretty much all cancel out, and you have about the same torque and chain speed delivered to both types of chain. If the kerf is about the same, then I do not see the case for .325 being any better than 3/8 chain. Actually, with more cutters per inch, it seems like the .325 chains would be more prone to bog down than 3/8.

Now in the IPL for the 290, they list a 7 pin rim for the .325 size. So that may be the only real reason that I could see for using .325 chain on that saw or the 270; adding the option for more torque at the expense of chain speed.

Oregon's website shows actual sizes of their rim sprockets and this would explain it better. When you see the pics, .325 x 7 looks a heckuva lot smaller than .325 x 8 and 3/8 x 7. Changing drive sprocket sizes makes a huge difference on smaller saws.

 

[BarkBuster20]

the 026 i got is set up for 3/8 right now it has a sprocket sleeve? it has the original sprocket on it but it has a deal for a 3/8 chain over the sprocket, i know you guys are prolly gonna laugh at me for not knowing what it is but im not what you might call a whiz when it comes to saws. anyway just curious what its actually called and wondering if it would be better to just get a sprocket set up for 3/8. somone said it was about 100$?

 

[Justsaws]

the 026 i got is set up for 3/8 right now it has a sprocket sleeve? it has the original sprocket on it but it has a deal for a 3/8 chain over the sprocket, i know you guys are prolly gonna laugh at me for not knowing what it is but im not what you might call a whiz when it comes to saws. anyway just curious what its actually called and wondering if it would be better to just get a sprocket set up for 3/8. somone said it was about 100$?

Rim. Drive rim. The rims are usually around $5-10.00 each. Pull off the E-clip and washer and pull the old rim off and replace with a rim of the same pitch. If you change pitch it becomes more expensive.

 

[BarkBuster20]

Rim. Drive rim. The rims are usually around $5-10.00 each. Pull off the E-clip and washer and pull the old rim off and replace with a rim of the same pitch. If you change pitch it becomes more expensive.

yeah..i want to run 3/8 i just dont think its a good setup on it. and i guess anything thats 5-10 dollars to convert your saw to 3/8 prolly isnt the best bet. ill spend the extra money.

 

[Justsaws]

yeah..i want to run 3/8 i just dont think its a good setup on it. and i guess anything thats 5-10 dollars to convert your saw to 3/8 prolly isnt the best bet. ill spend the extra money.

I might be misunderstanding what you are referring to but I will try again.

There are generally two types of drive systems.

Spur Sprocket=Clutch drum and drive sprocket are one piece. When the drive sprocket wears out you have to replace the entire piece. Typically around $20-30.00.

Rim and spline clutch drum=Two separate pieces. When the drive rim wears out you only have to replace that. Rim=$5-10.00. Drum=$20-30.00

If your saw is already setup as 3/8 then you just need to buy another rim. You could convert it to a spur but it is not better for any typical user..

 

[BarkBuster20]

hm what would be the advantages to converting it to spur?

 

[yodayoda]

Wow I can't read any more of this thread, my head really hurts,now

 

[windthrown]

hm what would be the advantages to converting it to spur?

:monkey:

I cannot think of any!

 

[Justsaws]

In very crappy conditions they do not bind with crap. I have had to disassemble the rim setup to clear "noodles" and "pulp" from behind/around the rim itself. Rarely and only when slabbing/parting large pieces. The spur does not do that. The spur also handles dirt/sand/wood/water better.

The few people that I have met that use carbide chain correctly recommend the spur as well for paper rolls and the like. I have not cut large paper rolls myself so I took their word on it. In my limited use of carbide the rim was worn very quickly and plugged with crap constantly. The spur still wore fast but it did not bind.

Again, splitting hairs but the spur is better for some very specific purposes.

It is more expensive to run the spur but in these instances I would pay extra to avoid the aggravation that the rims caused.

You can run anything you want on your saw for any reason you want.

However, for a 026 use the rim. No good reason for a spur on general purpose 50cc saw.