Rpm meter

[Lnewman]

 :new_year: I recently got a meter to try to accurately tune the chainsaw.  But the meter isn't that easy to read it jumps around say from 11,000 to 12,000 what's the correct way to read it the lowest reading the highest reading the average reading or something else?

[Old Greenhorn]

Assuming this is a proximity type meter (hold it near the saw) it is likely it is picking up the spark from the spark plug and the coil and getting confused. Try different areas of the saw so it only gets one signal. it should steady out if your ear tells you the saw is steady.

[Lnewman]

I don't think it's a proximity meter because it has a clip that clips onto the rubber piece directly on top of the spark plug

[John Mc]

a lot of tachs don't have a fast enough response time to accurately tune a chainsaw. Also, many of them aren't able to read a high enough RPM.

Here is what I use, and it has worked well for me:
DTI TECH-TACH TT-20K Tachometer

[Al_Smith]

A tachometer is a nice tool to check things but for all intents isn't really necessary . I know a lot people who run competition saws and they all  tune by ear as do I .
Too many variables,temperature  ,altitude ,condition of the engine .Any modification changes which will determine  where it should run the best .They are all sisters but they are not identical twins . 

[John Mc]

A tachometer is a nice tool to check things but for all intents isn't really necessary . I know a lot people who run competition saws and they all  tune by ear as do I .
Too many variables,temperature  ,altitude ,condition of the engine .Any modification changes which will determine  where it should run the best .They are all sisters but they are not identical twins .

I agree in the long run, but they are nice when you are learning how to tune. I would tune by ear, then check with the tach to see if I ended up in a reasonable place for RPMs. It gave me a bit of confidence that I wasn;t going to burn up my saws in my early attempts at tuning.

[sawguy21]

I learned to tune by ear as well but that was before the days of rev limiters. I now have the Stihl tach, it works well and keeps me from leaning out the saw too  much. I richen it up then lean out until it hits the specified max rpm. I have watched an experienced tech rev out ported saws to well over 15,000 rpm but haven't had the nerve to try it.

[Al_Smith]

You don't dead stick them for long .I've got some that will do it but I don't drop the reins until they blow the piston to kingdom come .They obviously don't do that in the cut .Fact I have no idea what they they do in the cut as far as RPM .BTW I don't own a tach that reads that high it was on someones elses .

[ZeroJunk]

I have been working on 2 cycles for 50 years. Remember West Bend Super Bees.   Obviously, the RPM's have changed a bit.  I don't trust my ear enough to get close to what the specs call for. I use one of those TT-20K's . I usually tune one about 500 RPM below what the max no load RPM is. About 12,500 for most saws. Gives the owner a little room for bad gas or whatever.

[Lnewman]

I have a Stihl 180.  There is only one adjustment screw that is apparently for the low idle. The manual says it supposed to idle at 2800 rpm's. When I check the engine with the steel meter the idol is 3900 to 4000 RPM's. The screw won't let me adjust it any lower and it seems to idle fine is there any problem with this?

[sawguy21]

It should idle just below where the chain starts to move. There should be two screws, one in the carb body to adjust the mixture, it will have a funny head so you can't muck with it, and a larger idle speed screw.

[Lnewman]

I appreciated all the comments they were very very helpful but no one Answered the question of whether to use the high low or other reading when the RPMs are dancing around on the meter

[John Mc]

The answer is to get a better meter: one that is designed to handle chainsaw-type RPMs accurately. If it's bouncing around, either it's too slow a response time or it can't handle the high RPMs, or the chainsaw is not in a "steady state". If you are determined to use that one, I would use the high reading.

[Lnewman]

Thanks for answering my question John I do have a meter that I thought was pretty good it's the Stihl one

[Lnewman]

What is meant by the chainsaw being in a steady state?

[John Mc]

What is meant by the chainsaw being in a steady state?

Sinc eyou set the high speed mix at wide open throttle, that would mean it's at WOT and has stabilized at the RPM you are trying to measure (BTW, it's not good to leave it running at WOT with no load for an extended period).
As others have mentioned, tuning by ear is also a good way to set it. This can be complicated a bit by the rev-limited coils on some saws these days - some people confuse the sound of bumping up against the rev limit with the burble sound that indicates slightly rich.
Here is the Madsen link on adjusting mixture. You will need good speakers or a quality headset to be able to hear the sound file properly (many laptop speakers do a poor job).
Here is a YouTube video with some good tuning tips (and sound track):
How to tune a carburetor on a chainsaw

[John Mc]

Thanks for answering my question John I do have a meter that I thought was pretty good it's the Stihl one

If it's designed for chainsaw use (which I'm assuming it is, if it's a Stihl one), then it should be OK.
My rationale for using the high reading is two-fold:
1) There are several things that could make a meter read low.but not a whole lot that will make it read high. So I'm betting that it's more likely the low reading is the error.
2) You are more likely to do damage by having your RPMs set too high than you are having them set too low, so using the higher reading when setting is probably a safer bet.