why chain length is different for same size bar on diff saws?

[toddol1971]

Is it just the crank to bar stud spacing? For example my ps5100s 18" takes 64 dl instead of 68. My 372xp 20" is 72 dl but if I put it on the partner s65 theres to many dl's. So my only guess is space between crank and bar studs. Although 2nd guess would be small vs large bar mount? I've never looked into it before cause I usually buy bars for the saw and thats what it runs. Now I thought the s65 was a large mount. The 20" cannon bar with 72 dl's will fit but will just barely tighten up. Whats the correct answer?

 

[a. palmer jr.]

Yeah, there's a difference in the spacing between a Stihl saw and say a McCulloch. The Stihl takes 2 more links for a 20". Some bars are a bit wider also but it's mostly the spacing between the crank and the bar mounts.

 

[jl4c]

Is it just the crank to bar stud spacing? For example my ps5100s 18" takes 64 dl instead of 68. My 372xp 20" is 72 dl but if I put it on the partner s65 theres to many dl's. So my only guess is space between crank and bar studs. Although 2nd guess would be small vs large bar mount? I've never looked into it before cause I usually buy bars for the saw and thats what it runs. Now I thought the s65 was a large mount. The 20" cannon bar with 72 dl's will fit but will just barely tighten up. Whats the correct answer?

Bar profile. Sometimes two different bars of the same length have a difference circumference--a wide, fat bar vs a "skinny" bar when viewed from the side. You can lose/gain a couple of drive links due to this alone.

 

[Wood Doctor]

You don't even have to have a different MFG and look what I discovered. I can run a 68-link loop of .325 chain on a Stihl 025 with an 18" bar, and the same chain will fit until it stretches to high heaven on an Stihl 026 Pro with a 16" bar.

So, I cut the same length chain for both saws because the 68 links yields the same number of right and left cutters.

 

[toddol1971]

I never thought about it before, cause like i said I just used what was on there. I was gonna put the 5100s b/c on the s65 but it wont fit over the bar studs. Thats when I tried the 372's bar and no go. Well it would go but just barely. Thanks for the replies.

 

[toddol1971]

If i only had a bar shrinker the s65 wooda bin throwin chips.

 

[Philbert]

Bar style, length, height/profile, nose diameter; number of drive sprocket teeth; etc., etc., etc.

STIHL MS250 uses 62dl of .325, .063 gauge chain on 'small mount bar'; MS260 uses 67 DL of the same chain on a 'large mount bar' .

Philbert

 

[Wood Doctor]

Bar style, length, height/profile, nose diameter; number of drive sprocket teeth; etc., etc., etc. STIHL MS250 uses 62dl of .325, .063 gauge chain on 'small mount bar'; MS260 uses 67 DL of the same chain on a 'large mount bar' .

Philbert

This always makes me wonder what the actual length of a 16" bar really is. As I mentioned above, I can run a 68-tooth .325 chain loop on both a 16" Stihl 026 and then again on an 18" Stihl 025.

 

[toddol1971]

This always makes me wonder what the actual length of a 16" bar really is.

Yea I know. Now for the punchline you knew was coming............ 16" Just ask me, I'll concur

 

[ChoppyChoppy]

Oregon has a book for chain lengths, sprocket part #, etc. It's about 4" thick. We Use it often.

 

[SawTroll]

Is it just the crank to bar stud spacing? For example my ps5100s 18" takes 64 dl instead of 68. .... ?

In that case it simply is about a shorter bar, that also is called 18" for some odd reason (it is an old tradition for some brands, so not something that Dolmar "invented). The 64dl ones really are 17" bars, and the 68dl ones actually a little longer than 18".

The stud spacing isn't a factor as such - but the distanse between the centre of the crank on the front of the case sometimes is regarding true bar length, but not regarding dl count.

The limitations of the chain adjuster may be a (slight) factor regarding dl count though, as may the size of the drive sprocket. The length of the slot in the bar sometimes becomes a factor - but mostly when mount adaptors are used.

 

[SawTroll]

Bar profile. Sometimes two different bars of the same length have a difference circumference--a wide, fat bar vs a "skinny" bar when viewed from the side. You can lose/gain a couple of drive links due to this alone.

Usually that is compensated for by making the "fatter" bars a little shorter, for the same dl count - mostly not by increasing the dl count. Oddities do exist though, as with "fat belly" racing bars.

 

[Franny K]

Is it just the crank to bar stud spacing? My 372xp 20" is 72 dl but if I put it on the partner s65 theres to many dl's. Whats the correct answer?

My idea of the correct answer is to hang the bar chain and sprocket off the saw and decide how I like the looks of the chain coming off the top of the drive sprocket and going onto the bar. I fail to see how, unless the drive sprocket is different changing the saw would make a difference. Like stated somewhere above might go a bit less than ideal to get away from two cutters pointing the same way and a skip.

 

[Wood Doctor]

My idea of the correct answer is to hang the bar chain and sprocket off the saw and decide how I like the looks of the chain coming off the top of the drive sprocket and going onto the bar. I fail to see how, unless the drive sprocket is different changing the saw would make a difference. Like stated somewhere above might go a bit less than ideal to get away from two cutters pointing the same way and a skip.

Agreed. There are times when I move up an extra drive link if (1) it yields a number that is divisible by 4 , and (2) the adjuster can still supply tension with some room to spare for eventual stretch. Seldom do I reduce the DL count from an odd number to that magic "divisible by 4" because usually that means the chain loop is too short to mount.

 

[toddol1971]

In that case it simply is about a shorter bar, that also is called 18" for some odd reason. The 64dl ones really really are 17" bars, and the 68dl ones actually a little longer than 18".
.

Thanks, now I have to tell my wife my bar is an 1" shorter than I thought it was. Talk about a bad day

 

[nenicu]

My experiment with a 16"[?] Oregon for a chinese Redmax clone: A divisible by 4 number of links the chain is too short, add another drive link and when the chain stretches i reach the adjuster limit and that link must be taken off. So i cut the end off the bar[ Stihl style] and now i can mount the chain without that extra link . The adjuster is moved back to the max and when the chain is stretched it still has some room to work.

 

[Wood Doctor]

My experiment with a 16"[?] Oregon for a chinese Redmax clone: A divisible by 4 number of links the chain is too short, add another drive link and when the chain stretches i reach the adjuster limit and that link must be taken off. So i cut the end off the bar[ Stihl style] and now i can mount the chain without that extra link . The adjuster is moved back to the max and when the chain is stretched it still has some room to work.

Seems hard to believe that adding one drive link causes the "too long" problem after a stretch. I suppose it is possible, but I would check to be sure that one less DL does, in fact, produce a loop that is too short. If so, then you are not getting near enough chain adjustment with that hardware.

 

[SawTroll]

Bar style, length, height/profile, nose diameter; number of drive sprocket teeth; etc., etc., etc.

STIHL MS250 uses 62dl of .325, .063 gauge chain on 'small mount bar'; MS260 uses 67 DL of the same chain on a 'large mount bar' .

Philbert

Yes, and in that case it is the true length that is the main factor - the 62dl bar is less than 15", the 67dl pretty close to a true 16".