Rpm tunning

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Eric howes

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I have a 266se and just got a new tach and wanted to dial in the saw. Problem is there is 2 different spec that I found. One that is for a 266se with is 12500 free and 8300 on a load. The other spec I found is 12500 free and 9300 on a load. My 266 says SE and xp on it so I'm not sure why the load difference . Does anyone have any insite on this?
Also, how exactly is the load rpm done? I can see there being alot of variations in load rpm running. Should I set the free rev rpm and call it good?
 
Ok, I also have a partner 5000. Specs say 14000 free. Saw seem to run pretty good with good power but once I put the tach on it, it won't even free rev 14000.
 
I bought a $150.00 Tac when I first started working on saws and have not used it in ten years. There is a thread on tuning by ear that bsnelling posted several years back, sorry I do not have a link, but someone should be able to send it to you. Tom
 
You can't tune to a specific RPM under load. There are WAY too many variables that affect that RPM.
That's what I was thinking as well.

I can tune by ear, but I like to get the spec rpms and the dial it in from there. I set the 266 to 12550 but to me still seems in the rich side
 
Yes, I suppose. But familiar saws tune can also be felt. Not so much with unfamiliar saws.

I hope I can continue without a tach, although it might be an interesting exercise just to see where a saw really is.
 
Ive never used a tac. Not really sure what theyre good for but they seem to be veey popular here.
Guys want me to put my cummins on the dyno. Im like why i dont really care if the number is 250 or 500hp its gets the job done i need it to do
 
I don't think they ever intended for you to try and tune it under load with a tach, just a spec as to where it has optimal performance. Probably no way to do that other than a dynamometer.

Yes, the "under load" number is the rpm where they expect the max power to be - it is just for information, not for tuning.

12,500 rpm is a fairly conservative "max WOT" rpm number, so I wouldn't be afraid to go a bit higher if the saw still "four-cycles" out of wood.
 

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