Gidday All,
Im cuttin timber in New Zealand using a range of Stihl saws from 880 down. I have previously considered modifying my favourite saw 660 Magnum (just for fun- not due to performance complaints) after reading a number of views on the matter but its hard to sort the good advice from the bad. A previous discussion on here from 2010 (Stihl 660 vs 880) discussed dual ported mufflers and boosting rpm for torque. I have afew ideas myself but would be interested in what others suggest in terms of possible mods. Not many engines produce max. torque at full rpm - check out torque curves for proof. It has been suggested that I can run the 660 up to 14000rpm. Sounds too high? I have read that 660's are not factory tuned for best performance but Im not sure about this. To increase the rpm will not increase torque. The only time this would help is if you were to run high rpm on a very short bar say 15" using racing fuel as they do in chainsaw racing. In a working saw it would last about 5 minutes as racing saws only run for about 40 seconds at any one time. I believe that the Optimum rpm to run my MS660magnum for my application (large diameter hard wood) is 12850 rpm to 13000 rpm. If its too big and dont cut fast enough I crack out the 880. Keen to hear others ideas on this as I prefer using my 660 over the 880 (alot of vibration on the 880!) where possible and would always like more performance if its available. Or Maybe its not worth doing anything to change a good thing?
That's a very intereasting post. Find the hardest of hard woods in your area lay the bar down in it and adjust carb to where it cut's the best and engine sound's like it will cut 1000 more just like it then it's tuned keep your chain sharp and oil in its tank the gas is not so important cause it will let ya know when ya need more 8)
You're right, raising your out of the cut RPM will do nothing for overall performance in the wood.....unless your in the cut RPM's also increase.
What you basically want to do is to widen your powerband/increase torque in order to keep your rpm's as high as possible while in the cut. A ported muffler and re-tune -may- help a little, but a full woods port will make the biggest difference.
What chain are you pulling ?
Full Chisel on the 22" bar (tungsten carbide for some applications) and I use semi chisel on the long bar (36") skip tooth. Stihl Chains have served me well but interested to know what you guys all prefer.
Im not the oldest bloke in the woods and Im the first to point out that nothing beats time on the tools in terms of experience so I take all advice from senior loggers seriously. Ya never stop learning and I appreciate all knowledge shared.
After doing some reading the woods porting sounds like a good move. My local Stihl shop is somewhat against doing the work (they reckon its not worth muckin with it but I cant see a downside?) so Im getting busy finding the right man to do that job for me.
I think the biggest gain modifying the muffler on the 880 is made in redirecting the exhaust so it doesn't melt the handlebar. Other wise that one is good. I had vibration issues with one 'til we switched to skip chain. And stay away from .404.
This is what i did, i grew up with a saw in my hands, i never played by the rules. Like with a 044 Mag or 034 Super, first thing take the screen out of the muffler, then i leaned-em out on till they started to dump, then turned it back till she screamed. I ran 16" bar [22 is fine] with f-chisel chain, 3/8, 50 gauge, rakers 30 to 40 thou., 35 degree angle with a little pitch, using a 5/32 file. I always filed freehand, used this method about 8 yrs, couldn't find a another way to get my saw to cut faster.
When cutting big wood you don't stick your saw in wood and hold full throttle on till its cut off. I always worked the saw up over and back down working the throttle never holding full throttle any length of time.
I ran Stihl like this about 8 yrs, never scored a piston. When i was running Huskys i had to be care full, they scored easy, just my experience with them.
I'm not recommending anybody to set their carb like i did.