whats the best rpm range for ms660 big bore for milling?

[zeroskater58]

so, im getting a tach this week, and would like to get a definitive answer on what the high end rpms i should be shootig for. ive read a bunch of threads, and have come up with a couple different answers. some say tune to 11k-11.5k to keep the saw cool; and others say tune to 12.5k, if its too rich it will run hot and burn up. so which is it? somewhere in between maybe? what are your guys thoughts? thanks for the help!

 

[trains]

if a petrol motor is run lean, it will over heat, running rich helps cool it.

if its a diesel motor, running rich, ie over fueling will cause it to over heat, and low fuel will cause it to run cool, and no power.

11 to 11.5k tune for milling sounds good to me.

 

[zeroskater58]

if a petrol motor is run lean, it will over heat, running rich helps cool it.

if its a diesel motor, running rich, ie over fueling will cause it to over heat, and low fuel will cause it to run cool, and no power.

11 to 11.5k tune for milling sounds good to me.

right on man, thanks for setting that straight looks like i know where im tuning now

 

[BobL]

Rather than specify a specific RPM it's better to first tune the saw to manufacturers spec and then richen up the fuel/air so that the rpms drop off by ~500 rpm.

 

[zeroskater58]

Rather than specify a specific RPM it's better to first tune the saw to manufacturers spec and then richen up the fuel/air so that the rpms drop off by ~500 rpm.

alright, so youre saying around 12500, since the spec is 13000? whats the consequence of going richer to 11-11.5k?

 

[andy]

alright, so youre saying around 12500, since the spec is 13000? whats the consequence of going richer to 11-11.5k?

The consequence?... The saw may bog down and lose power in the cut.
I've had that occur with a 3120... get too low and it starts to bog and lose RPM's when the cutting gets tough.
That said, I run the 3120(MMWS) at 11,000k and it's rich but fully powered up. (no bogging)
I would bet the 660 will be fine there as well.

Open up the muffler to help cool things and free breathing while you've got the tools out.

 

[zeroskater58]

Open up the muffler to help cool things and free breathing while you've got the tools out.

already done

 

[stihl_lyfe]

What big bore kit did you buy? Interested to know how it goes, I need a new cylinder kit for mine and given its 100% milling duty thought I'd go that way - but after reading this forum and others seems to be little love for the BB kits on the 660s...

 

[zeroskater58]

What big bore kit did you buy? Interested to know how it goes, I need a new cylinder kit for mine and given its 100% milling duty thought I'd go that way - but after reading this forum and others seems to be little love for the BB kits on the 660s...

i am along the same line of thinking as you since mine is only for milling too. its a stens bb kit, but not sure about the longevity it will have. after doing a bunch of reading on here too, its made me a little uneasy about it, but it seems to be working fine right now.

 

[stihl_lyfe]

i am along the same line of thinking as you since mine is only for milling too. its a stens bb kit, but not sure about the longevity it will have. after doing a bunch of reading on here too, its made me a little uneasy about it, but it seems to be working fine right now.

So does it have a fatter, more torquey powerband like you'd expect? Most of the negatives I read is that they kinda feel dead and don't rev like a factory cc top end (and they are pigs on gas). If they give a bigger whack of torque in the high mid range where the saw spends most of its time when milling then that'd suit me fine, as saw doesn't need to rev over 10k. If no advantage down low though I'd rather stick to factory cubes and save the gas...

 

[zeroskater58]

So does it have a fatter, more torquey powerband like you'd expect? Most of the negatives I read is that they kinda feel dead and don't rev like a factory cc top end (and they are pigs on gas). If they give a bigger whack of torque in the high mid range where the saw spends most of its time when milling then that'd suit me fine, as saw doesn't need to rev over 10k. If no advantage down low though I'd rather stick to factory cubes and save the gas...

it really is a pig on gas...more than i was expecting, and hestly dont really notice a hell of a lot of differene between stock and bb. sounds a little different, uses a lot more gas, but as far as milling goes, seems a little more torque, but that could be me wanting it to be that way seems to create a little more heat as well. if i were to do it again, id probably just stick with stock and use less gas, but thats just me.

 

[stihl_lyfe]

it really is a pig on gas...more than i was expecting, and hestly dont really notice a hell of a lot of differene between stock and bb. sounds a little different, uses a lot more gas, but as far as milling goes, seems a little more torque, but that could be me wanting it to be that way seems to create a little more heat as well. if i were to do it again, id probably just stick with stock and use less gas, but thats just me.

Right, so reports of generally being underwhelmed sound about right then. Think I'm gonna try the Meteor kit...

 

[tfp]

I agree with BobL. Also, especially when milling logs on the ground, keep a real close eye on your air filter. I usually mill longer slabs (3+ meters) and usually it’s on the ground so I check mine after each cut. It’s saved me a few times on the last few cuts when the whole air filter box was full of sawdust and chips. I paid closer attention when cutting close to the ground after that.