sprocket sizes

[taxidermist]

I have a 2171 Johnsered could you tell me what a nine tooth sprocket would do over a 8 tooth? I know about sprockets on dirt bikes but have never changed a sprocket on a saw.

Thanks,
Rob

 

[zr900]

Increases chain speed, reduces torque. My guess would be that a 9 would not work well on that saw. My 371xp pulls a 20in bar with an 8 pin good, but you cant lean on it hard.

 

[HiOctane]

It will load too much your engine ,and probably your chain will derail often the rim dia being quite large.They come stock with a 7T.Its like installing a 35 teeth sprocket on a bike with a stock 40 Teeth.

 

[SawTroll]

Increases chain speed, reduces torque. My guess would be that a 9 would not work well on that saw. My 371xp pulls a 20in bar with an 8 pin good, but you cant lean on it hard.

:agree2:

 

[J_Ashley]

I've been wondering about this topic myself, sorry to pull this back from the searches, but I suspect it may help others like myself who are also wondering. Ok, I think I understand, but let me post an example/scenario, and see if I'm on the right track...

Let's say a saw comes stock with an 8-pin sprocket. This would mean that during one rotation of the crankshaft the chain would advance 8 drive links...

If one goes to a 9-pin sprocket, it will reduce torque, and increase chain-speed. In this case, one rotation of the crankshaft should advance the chain 9 drive links instead of 8, giving a 9/8 output in chainspeed over original, and cutting torque to 8/9 the original torque level. If the motor has adequate torque availabe, then the increased chain-speed should allow for faster cuts. This should be a good situation for running a shorter bar on a more powerful saw?

Ok, let's take same said saw with 8-pin sprocket, and move now to a 7-pin sprocket. In this case, one rotation of the crankshaft should advance the chain 7 drive links instead of 8, giving a 7/8 output in chainspeed over original, and raising torque to 8/7 the original torque level. This should reduce chainspeed, and increase torque... The result should be a slower cut, but free up some power and let the saw rev-higher (per (less) work done) during the same cut. This should be a good situation for running a longer bar on a saw with less power, possibly using skip chain etc?

Am I right in my thinking here, or am I backwards? At least that's what I would assume anyway... Please please let me know if I'm wrong, I'd love to know if so, so I can correct this, and of course, know for myself!!!

 

[SawTroll]

I've been wondering about this topic myself, sorry to pull this back from the searches, but I suspect it may help others like myself who are also wondering. Ok, I think I understand, but let me post an example/scenario, and see if I'm on the right track...

Let's say a saw comes stock with an 8-pin sprocket. This would mean that during one rotation of the crankshaft the chain would advance 8 drive links...

If one goes to a 9-pin sprocket, it will reduce torque, and increase chain-speed. In this case, one rotation of the crankshaft should advance the chain 9 drive links instead of 8, giving a 9/8 output in chainspeed over original, and cutting torque to 8/9 the original torque level. If the motor has adequate torque availabe, then the increased chain-speed should allow for faster cuts. This should be a good situation for running a shorter bar on a more powerful saw?

Ok, let's take same said saw with 8-pin sprocket, and move now to a 7-pin sprocket. In this case, one rotation of the crankshaft should advance the chain 7 drive links instead of 8, giving a 7/8 output in chainspeed over original, and raising torque to 8/7 the original torque level. This should reduce chainspeed, and increase torque... The result should be a slower cut, but free up some power and let the saw rev-higher (per (less) work done) during the same cut. This should be a good situation for running a longer bar on a saw with less power, possibly using skip chain etc?

Am I right in my thinking here, or am I backwards? At least that's what I would assume anyway... Please please let me know if I'm wrong, I'd love to know if so, so I can correct this, and of course, know for myself!!!

Your thinking is right on, for all practical purpose!!

 

[ciscoguy01]

8's to 9's

I've noticed, for myself, that going from just 7 to 8 I have to keep the chain much tighter than on the 7. I lose a ton of torque also. Specially in bigger wood. I pretty much swear by the 7. Unless your only limbing with the saw, the slower speeds add an amount of torque to the saw that outweighs the reduction in chain speed itself. I can push the saw harder, hence for me, faster cuts. I have a heavy hand though. Since the newer saws run at mostly over 13000 anyways, you have the speed anyhow. That's how I justify using a smaller sprocket and gaining the torque thats lost from older saws that didn't turn the rpms. On 8 tooth I'd throw chains sometimes, with 7 tooth it almost never happens. I can just imagine on a 9 tooth. Specially knowing that huskys/Jreds are lacking in the torque from the getgo, but are truly great limbing saws and whatnot (I'm gonna hear it for saying that). At least everyone I've ever run has. I do have a couple older huskys that I really like, but even they don't pull like the Stihl's. If you want more power, go to the 7 tooth. If your just limbing, keep your chain tight as **** and go with 8 or 9. Least thats what I do...

eh?

 

[timberwolf]

70 to 80 cc saw won't pull a 3/8 9 tooth sprocket and give better results than an 8, not with a 16 inch bar, not with square chain, not with a muffler mod, not with synthetic oil, not stock. Maybe ported with race chain for a gtg in an 8x8. Short of a pipe or alchohol 8 is max for that sized saw. You would think a ported 70 cc saw should be able to do it, a 90cc saw will and the ported 70 cc saw may well be faster than a stock 90cc saw, but at 70 cc in a modern saw there just is not enough torque, and that is the difference between torque and horsepower.

No need to keep chain overly tight, if bar is not worn out and if fit properly just tight enough to keep the chain from sagging, anything more is just friction and increased wear. going past an 8 tooth gear most time means modification to the heal of the bar or cutting down a longer bar. I have run 10 to 13 tooth gears on bigger saws but the bars are cut down from 20 or 25 inch bars to make 16 or 20 inch bars.

Going to long bars over 25 inches the chain does need more tennsion though to keep the sag out.

 

[J_Ashley]

So you don't think my 170 will pull a 20" 9-pin??? opcorn: just kidding.

That is pretty interesting though Timberwolf, something good to remember. Now, Is it safe to assume that most saws come factory with a 7-pin sprocket?

 

[ciscoguy01]

Torque

and that is the difference between torque and horsepower.

No need to keep chain overly tight, if bar is not worn out and if fit properly just tight enough to keep the chain from sagging, anything more is just friction and increased wear. going past an 8 tooth gear most time means modification to the heal of the bar or cutting down a longer bar. I have run 10 to 13 tooth gears on bigger saws but the bars are cut down from 20 or 25 inch bars to make 16 or 20 inch bars.

Going to long bars over 25 inches the chain does need more tennsion though to keep the sag out.

I tell my buddy about torque all the time, he can't grasp it. I tell him to hook onto a 350hp cat tractor trailer or a 50hp tractor and pull that backwards with his V10 and he looks at me funny, hehehehehehe... As far as worn and properly fit chain goes. When your running brand new bar and chain, things loosen a bit after several cuts, THEY JUST DO. You have to consciously look and adjust or you'll booger up your drive links with the speeds of the new saws... Super good info ya got there dude.

eh?

 

[blsnelling]

For GTG fun I'm outfitting my saws with the following:

260 - 7-pin 3/8 or 8-pin .325
361 - 7-pin
460 - 8-pin
066BB - 9-pin
084 - 11-pin

For work I run a 8-pin in the 066BB anda .404 7 or 8-pin on the 084.

 

[Christman]

where do you get 9 pin sprockets from? I must not be looking to hard!!!
I would like to play around with one.

 

[timberwolf]

Dansco or madsens sells racing sprockets.

For gtg/race I run

026 3/8 7
026 piped alky 3/8 8
359 muffler or pipe 3/8 8
stock 272 3/8 8
stock 675 solo 3/8 8
stock 395 3/8 9 or 10 pin
372BB piped alky 3/8 9 pin
066 10 pin
088 12 pin muffler can do 13 on pipe

Work, 90% of the time square chain.

ported 026 3/8 7
ported 359 3/8 8
ported or stock 80 cc saws 3/8 8
ported 066 3/8 9 (it's fun, safe???, cheep???)
ported 088 3/8 10 (it's more fun yet, safe oh ya, cheep who cares)

 

[SawTroll]

I have a 2171 Johnsered could you tell me what a nine tooth sprocket would do over a 8 tooth? I know about sprockets on dirt bikes but have never changed a sprocket on a saw.

Thanks,
Rob

HUH - you must be talking about .325 ones.........

With 3/8" 8-pin will be OK with a 16" bar I guess, maybe with a 20" - but no way a 9-pin will perform well.

 

[albert]

A 9 tooth will make you wish you had a 7 on it

 

[Jacob J.]

Thing to remember also is the 9-tooth and larger sprockets are 'pin-drive' and put more wear and tear on the drive links of the chain and rails of the bar.