I have just began to fool around with using a tach to tune my saws. I have made a observation. When setting the HS screw tach surges to a certain rpm and then continues to build rpm. For instance- the tach pegs 13,900 and then will continue to build rpm till the throttle is chopped. This happens no matter where the screw is set. So the question is how are you guys setting the HS with a tach? Do you shoot for the the ideal rpm before it starts to climb?
Tach readings
- Thread starter bwalker
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formersawrep
ArboristSite Operative
I am always confused when I hear the phrase "setting saws witha tach". The numbers listed by the manufacturers are MAXIMUM no-load numbers. You adjust the saw (this has been covered repeatedly here) by ear and then CHECK that the maximum no-load rpms have not been exceeded.
Crofter
Addicted to ArboristSite
If you have adjusted your carb to give the correct audible signs and these conditions result in a full throttle no load rpm exceeding the manufacturers reccommendation, does this mean that the mixture is too lean or that centrifugal and inertia forces etc are becoming harmful in themselves?. "Power in the cut" setting, on some saws will require different mixture than either, rec max rpm., or slight 4 stroking.
Is there any problem in other words with a mixture that would result in excessive rpm providing you dont hold open throttle under no load. I think this is something that a lot of users both casual and oldtimers can find elusive.
Frank
Is there any problem in other words with a mixture that would result in excessive rpm providing you dont hold open throttle under no load. I think this is something that a lot of users both casual and oldtimers can find elusive.
Frank
HUSKYMAN
Addicted to ArboristSite
This is the method I would use. It would be curious to see how accurate your ear really is. And remember the no load rpms are not the most important, its the rpms while the saw is in the cut. Since there is no easy way for the OEM manufacturers measure this (everyone cuts differently) they go by no-load rpms.
If your saw keeps accelerating I would saw its lean, or the tach is off, because all my saws level off (going by ear). Or maybe they are all just pig rich
I believe I found my problem. I failed to fully tighten the airfilter after I cleaned it prior to testing. This was causeing the climbing rpm. Now the rpms are rock solid. Doing some timed cuts today I found the fastest time for my 026 was about 13,800. Max no load rpm is 14000 so I should be relitivly safe.Now that my 026 has a adjustable carb and a walker's muffler it really sings. Its also really nice tro be able to fine tune the mixture screws.
BTW When I tuned it by usinf the audible method my cut times where slower and my no load rpm was 12,500.
BTW When I tuned it by usinf the audible method my cut times where slower and my no load rpm was 12,500.
So what were your times? 12 seconds in a 40" hickory?
ha ha ha
Seriously, it would be interesting to hear what bar and chain you were using, and whether they fit each other snugly or loosely. Also, if you were to, say, put a 24" bar/chain on it and tune it for 13.8k (if it will), what would it run with a 16" or 18" bar/chain combo (or vice versa) without other adjustment? Maybe next time you're testing you could check a range like that?
It's good to hear that your manual adjustments are safely conservative, in the event anyone might be interested in one of your used saws.
Glen
ha ha ha
Seriously, it would be interesting to hear what bar and chain you were using, and whether they fit each other snugly or loosely. Also, if you were to, say, put a 24" bar/chain on it and tune it for 13.8k (if it will), what would it run with a 16" or 18" bar/chain combo (or vice versa) without other adjustment? Maybe next time you're testing you could check a range like that?
It's good to hear that your manual adjustments are safely conservative, in the event anyone might be interested in one of your used saws.
Glen
NevadaWalrus
ArboristSite Operative
Ben I'm happy you got the tach and have started to experiment with it. I seem to recall you were not in very high opinion of using them in the past. What you found with the old set by ear method listening for that 4 cycle blurble is many saws today rev beyond that blurble and the tach is needed to stay within safe rpms.
When setting a high rpm saw to 4 cycle, you lost power in the cut. We have a convert.
When setting a high rpm saw to 4 cycle, you lost power in the cut. We have a convert.
formersawrep
ArboristSite Operative
What it seems you have done is adjust the saw to the point where it still barely 4-cycles (which you state was 12,500) and then leaned it out considerably to get to max. no-load rpm of 13,800? I think you want to be very careful. The 026 is a very forgiving saw, but none of them will run lean forever.
Glens, I was using a new 18" Stihl rsn bar with new 3/8, 0.050 Stihl RS chain tickled once with a hand file and a husky roller guide. The wood was 14" unseasoned rock elm. I didnt actually time the cuts with a stop watch. I instead used by trusty digital dyno AKA the cut and feel method. Its not very scientific, but it does work better than I thought it would. Its actually very easy to notice the slightest turn of the HS screw. I might also add that I had the tac velcroed to the saw so i could observe the rpm when loaded. I was very supprised to see that the saw at the lowest(heavy load) pulls around 8K and cuts the fastest around 9500. Mounting the tach this way could be a advantage to novice racers as it would help you keep the saw in the power band at all times.
formersawrep, Since the max no load rpm for the 260 is 14k I should be safe at 13.8k. If you read my post you will notice that I said it cut fastest at this rpm. A two cycle will not make peak power when it is too lean despite reving higher so I believe I have it tuned to perfection. Now that i have a baseline to shoot for I can simply tach the saw before I use it and adjust accordingly to assure the machine is opperating at peak performance at all times and to avoid seizures from being too lean and crappy power/carbon deposits form being too rich.
So you had a pretty fair no-load load with the new bar and chain, right?
I picked up a 3/8 roller guide as well a 3/8 depth gauge from a Husky dealer a week or two ago. The depth gauge reads virtually the same on 33RS as does the Oregon center-drop .025 gauge I'd been using at the middle of the bar, on a chain very near the witness marks. Not enough difference to write home about. The Husky gauge does rise above the depth gauge on a brand new 33RS by what must be no more than a couple thousandths, so it's probably better to use anyway, not to mention having better individual tuning. The Oregon gauge would take about that same amount off a new depth gauge when used in the middle of the bar on a new 33RS.
The reason I'm posting is to tell you that the roller gauge is phenomenal in my opinion, but that when used on the RS chain it needs to have a plastic zip tie wrapped in each rear opening to raise it almost 1/16". The top plate relief angle is (evidently) shallower on the 33RS than on the Oregon 72LP, 73LP, or 73LP-VL the guide is tagged for. I also had to file the front notches a very minute amount, and it then works perfectly with 33RS from brand new to used up with a 13/64" file.
Whew.
It's a little bit of a pain to set initially, but the dam<i></i>ned thing works so well it's worth it. You can almost file with your eyes closed with the roller guide and it really holds the tooth quite nicely in relation to the file, even though the whole assembly can wiggle around in use.
Works exactly the same on 33RM (at least at the start of the tooth, I don't have one used up yet, but it looks like the top plate angles are the same on both chains).
Glen
[editing performed: corrected file size from 11/64" to 13/64"]
I picked up a 3/8 roller guide as well a 3/8 depth gauge from a Husky dealer a week or two ago. The depth gauge reads virtually the same on 33RS as does the Oregon center-drop .025 gauge I'd been using at the middle of the bar, on a chain very near the witness marks. Not enough difference to write home about. The Husky gauge does rise above the depth gauge on a brand new 33RS by what must be no more than a couple thousandths, so it's probably better to use anyway, not to mention having better individual tuning. The Oregon gauge would take about that same amount off a new depth gauge when used in the middle of the bar on a new 33RS.
The reason I'm posting is to tell you that the roller gauge is phenomenal in my opinion, but that when used on the RS chain it needs to have a plastic zip tie wrapped in each rear opening to raise it almost 1/16". The top plate relief angle is (evidently) shallower on the 33RS than on the Oregon 72LP, 73LP, or 73LP-VL the guide is tagged for. I also had to file the front notches a very minute amount, and it then works perfectly with 33RS from brand new to used up with a 13/64" file.
Whew.
It's a little bit of a pain to set initially, but the dam<i></i>ned thing works so well it's worth it. You can almost file with your eyes closed with the roller guide and it really holds the tooth quite nicely in relation to the file, even though the whole assembly can wiggle around in use.
Works exactly the same on 33RM (at least at the start of the tooth, I don't have one used up yet, but it looks like the top plate angles are the same on both chains).
Glen
[editing performed: corrected file size from 11/64" to 13/64"]
Last edited by a moderator:
I agree. I have never had chains as sharp as I do when using the rollerguide. I have modified the roller at all but I may trie it to see how it works. BTW what I would really like to do is incorperate the husky sharpforce file system with the roller guides. That would be slick.
The first thing I did was file a smidgen off the middle of the rear top corner on the inside of the front notch, to provide a little clearance for the top of the drive link. It was a little too tight and was causing the chain to bunch up just a bit, enticing the either the front or the rear of the cutter to pop up, likely causing inconsistent results. This was on the almost-used-up chain. Then I went ahead and used a 13/64" file on the chain (on one tooth) and it cut way too deeply, producing grossly excessive hook. That's when I went to the truck and fetched a couple different sizes of cable ties, settling on the (approx.) 3/16" wide ones. They're a little less than 1/16" thick, but it's near that measurement according to the architectural scale I've got here in my desk drawer. They were slightly curled when cinched up in place, requiring the outer edges to be trimmed with the utility knife to flatten the profile in the top of the notch. I'm sure they'll change with use and wear, but we're not talking kitchen cabinets (or race chains) here...
As you said, it produces very sharp results; better than sharp enough for a woods chain.
The top plate angle is slightly less than the 30° witness mark, but it's not worth fighting it. If you just let go, the file rights itself and wants to run 90° to the rollers. I've found the best results so far by simply rolling the file slightly forward on the rollers and leaving it on them for the rearward stroke, then rolling it back into the tooth again before the forward stroke. It's quite speedy and sure.
Glen
[editing performed: corrected file size from 11/64" to 13/64"]
As you said, it produces very sharp results; better than sharp enough for a woods chain.
The top plate angle is slightly less than the 30° witness mark, but it's not worth fighting it. If you just let go, the file rights itself and wants to run 90° to the rollers. I've found the best results so far by simply rolling the file slightly forward on the rollers and leaving it on them for the rearward stroke, then rolling it back into the tooth again before the forward stroke. It's quite speedy and sure.
Glen
[editing performed: corrected file size from 11/64" to 13/64"]
Last edited by a moderator:
I have had the problems you mentioneed with the front slot fitting the chain. The angle produced are good as well, but I am useing Stihl's reccomended 13/64 files. I always used 7/32 on RS, but my dealer claims 13/64 is the file to use. Learn somehitng everyday I guess. BTW have you noticed that Stihl or Pferd files last much longer than Oregon files?
I meant 13/64, sorry. I make that mistake all the time, I think it's the question I got wrong on the math part of the SAT. I'm such a retard sometimes.
The Oregon files I've seen lately are the same as the Stihl files near as I can tell by looking - both are double-cut Swiss-made - though I haven't used one (Oregon) yet.
Glen
The Oregon files I've seen lately are the same as the Stihl files near as I can tell by looking - both are double-cut Swiss-made - though I haven't used one (Oregon) yet.
Glen
formersawrep
ArboristSite Operative
So then what happens when your master control lever (on your 260) or your little metal throttle link (on many huskies) is not allowing the butterfly in the carb to not open all the way? (possibly as a result of worn a/v mounts) Of course, using the tach adjusting method, you would lean it out a little to get it back to 13,800, right? Not trying to say you are "wrong", I am just trying to point out the problem with using the tach to adjust. The tach should be used to check, not adjust.
Crofter
Addicted to ArboristSite
Bw; There was question about what bar length you were using to establish your baseline and what actual difference in mixture would be requilred to get the same rpm with a chain, bar combination of considerably different length. I'm thinking that the tach would lead you into selecting a leaner mixture fir the longer bar. I'm not trying to stir the pot, but have had conflicting results when trying the different tuning methods. My two saws, the 260 and Husky 365 are certainly examples of high and low revving saws. Just my observations, but I feel reliance on a tach figure would get more people into trouble than out of it!
Enjoyed the discussion on the filing guide; dang, now I,m going to have to try that out so I can see what you and Glen are talking about.
Frank
Enjoyed the discussion on the filing guide; dang, now I,m going to have to try that out so I can see what you and Glen are talking about.
Frank
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