Stihl chain sprockets

[KGNC]

I month or so ago I came across a deal on a very used looking Stihl 066. Didn't really need it but couldn't pass it up. I put in a new plug, bar and chain and did a like carb adjusting. This saw is amazing strong, and loud.  ;) The muffler seems to have been modified.
My question; I ended up with two chain sprockets, a 7 tooth and a 8 tooth. I'm using the 7 tooth because it was in better shape of the two but I'm wondering which is the best choice. Would the extra speed with the 8 tooth make much difference in cutting? I'm using a 25" bar with 3/8" chain.
What does stihl offer as a standard? Does it depend on the bar length? What would be recommended if I were to move up to a 32" bar?
thanks

[Climber]

Hi,
I have a new version MS660. Almost the same. Tried to use 7 and 8 sprockets.
The bottom line is if your chain resistance is smaller - use faster 7 teef and if your chain is grabbing too much - use 8 teef.
Chain resistance?!
Well it few variances:
Full chisel is more grabbing then scip, so resistance is more;
Longer bar is more resistance;
Angle of sharpening - more angle is more resistance
Wood - hard wood is more resistance.

If you running 24" bar on 066 put 7. If you put 30" bar, consider for scip chain or put 8 teef sprocket. Then I put full chisel on 30" bar and 7 teef - the saw was labobing.

As I remember, the sprockets are not much expencive, under $10.00. Always keep some spare. 066 have alots of power on bracke them.

Good luck with new toy.

P.S. tip: after ajasting chain tention tight bar nuts and then loos tentioner. It will prevent damadge of tentioner if you hit wood with tip of the bar.

[joe_indi]

If you run a 18 or 20" bar or, if the cutting load is not much, use the 8 teeth sprocket.It will give you a better cutting speed, but at the loss of some power.
But if your cutting load is higher or if the bar sizes are bigger than 20", use the 7 teeth sprocket.
If you have a 20" .404" bar available try a 7 teeth 404" sprocket. You will  need a .404" saw chain then.

Joe

[Zundapp]

A 066 has enough power, your not going to gain any advantage with a 7 tooth rim. The extra chain speed you pick up with a 8 tooth rim will utilize that extra power more. On a smaller saw, a 044 for exsample, changing rims can be benifical. A 7 tooth rim for dogging into larger diameter wood, an 8 tooth rim for higher chain speed for limbing or cutting small stems. Over the years I've worn out over 20 chainsaws & nearly half of them were 066's. I always ran a 30" bar & never saw the need to run anything other than an 8 tooth rim. I will say that a 066 has plenty of snuff to handle a 32" bar, I've even seen some run a 36" bar just fine.

[Captain]

8 spline rim on my 066 - bar lengths from 20 to 32 full comp chain - unless cutting something like standing dead oak that is next to petrified...then I'll back off to the 7 spline.

Captain

[SawTroll]

The chain speed gain with 8 vs 7-pin is about 14%, with a corresponding loss of effective torque.

Just try both for yor applications, they are cheap, and easy to swap back and forth..... ;)

[KGNC]

Thanks guys:
I'll get a new 8 tooth and see how it goes.
My son was watching me buck a 24" white pine and was very impressed. He told me I need to be on the "timbersports" contest he was watching on ESPN.

[Climber]

On ESPN they use same 066 (or 660 now) in some competitions.
Imagine how 880 go through....

[Al_Smith]

An 066 will handle a 36" bar with no problems what so ever ,in hardwoods,bar buried,chips flying.

I would imagine the reason they chose the 066/ms 660 for the timbersports series is the fact that the saw is pretty much a standard that most saws are compared with.The saws used are basically the same,tuned by one person to factory specs with a chain sharpened by one person.This portion of the competition is testing the sawyer and not the saw.In the world of modified saws they are not praticularly fast.

In the sized stuff they are cutting,Ohio white pine by the way,I doubt an an 088/ms 880 would cut any faster.Most large saws such as an 088 don't really shine until the wood gets big and tough.

[Climber]

066/ms660 is the best power to wight ratio:
Model   Displ.   Weight   Power   Ratio
   cc   lb   Hp   (Hp/lb)
880   121.60   22.20   8.50   0.38
660   91.60   16.30   7.00   0.43
650   84.90   16.30   6.40   0.39
460   76.50   14.40   6.03   0.42
441   70.70   14.80   5.50   0.37
440   70.70   13.50   5.30   0.39
361   59.00   12.30   4.40   0.36
361CQ   59.00   12.60   4.40   0.35
260   50.20   10.40   3.20   0.31
250   45.40   10.30   3.00   0.29

[Al_Smith]

Years back the 048 held the honors of the HP to weight ratio.As you can see by the chart,the 460 is real close to the 660 in that department now.

[ComputerUser]

Years back the 048 held the honors of the HP to weight ratio.As you can see by the chart,the 460 is real close to the 660 in that department now.

True, but when you fix the EPA muffler and put the factory dual-port muffler cover back on, the ratios change and I think that the gain on the 660 is greater - getting it back up to 7.8hp or so, and you can easily feel the increase.  A DP cover+muffler hole opened back up on a 460 still lags behind a stock Dolmar 7900 (6.3hp), which is why I think that the 460 isn't picking up as much power as the 660 does.

As for the original question, I think that 8t is good on the 660 up to 32" with full-comp chain, or 28" if you are running an EPA'd, choked-down saw.  Anything larger calls for 7t or skip chain, or both.