Got me a tach, rev limits and RPMs saws like?

[malk315]

I just got one of these:

Can you guys answer the following:

The 350 has blue coil rev limited and I believe my 2012 372XP X-torq comes w/ factory rev limited coil too.
What will be the rev limit for each? Just wondering so if I try WOT w/ no load I can see if tach shows it rev limit and it sounds like 4 cycle it's probably just hitting the rev limit.

Currently my 262 is on Mastermind's bench getting the works.
That's a 1991 original 262 that I'm guessing is not a rev limited coil (all original saw factory coil).
Randy says the 262 will like 14000 so I'm going to see if I can get it near that erring on the side of rich. If it 4 cycles at WOT at 14000 then great (and cleans up in wood).

Thanks for any info on what the rev limits are for the 350 coil and 372 coil.

 

[SAWMIKAZE]

13800 rings a bell for a 372xt..i might be wrong , i cant remember

 

[KenJax Tree]

Here is my old 372 coil it actually cut out at 13500

They run best at 13800

 

[KenJax Tree]

Not sure if the 350 had the same limit as the 346 but if it does its 14100. I put my limited 14100 coil on my 372 and put an unlimited coil on my 346.

 

[Modifiedmark]

I have the same tach . When the saw hits the limiter you will know it as the tach will go all goofy in its readings.

I found the green coil on my PP475 was actually limited to 10,500. Didn't take long to change that coil out. LOL

 

[malk315]

Oh yeah I remember reading that when researching tachs. Excellent... Will be trying it out with some saws tomorrow.

 

[Whitespider]

I don't know... just assuming a limiting coil does the "limiting" by shutting down ignition...
I don't believe the tach will be able to show what the actual RPM is at the rev "limit", because the coil will be on/off/on/off/on/off...
Depending on the refresh rate of the tach, it could show some pretty wacky numbers.

Or do I need to be educated about something here??
*

 

[blsnelling]

As soon as the tach reaches the limiting RPM, the reading will jump all over the place, rendering the tach useless above that RPM. That's the problem with limited coils. They limit below the tuning RPM of the saw. That not only makes it more difficult to tune the saw, but makes the inexperienced user liable to tune the saw too lean, thinking it's 4-stroking when it's actually bouncing off the limiter. This is why I always replace a limited coil with an unlimited one when possible.

 

[malk315]

That really sucks -- I guess I don't understand then how putting the saw in wood and letting up briefly will allow you to check the tune like I've seen in the tuning videos. When you let up the RPMS will climb up to the limit and then it's unreliable if you are hearing it hit the limit or true 4 cycling... especially if the tune of any saw is always above the coil limit... it's like chasing a unicorn at that point? or am I missing something?

Does the brief picking up of the saw while in wood allow the rpms to climb past the limiter to hear completely clean (no 4 cycling) means too lean or you hear 4 cycling for a moment and the saw is good?

Now I'm going to want all non-limited coils in everything too... gadzooks.

 

[malk315]

I just re-read your tuning thread -- sounds like the key is to let it clean up while cutting -- i.e. start rich so you hear 4 cycling while in the cut and then 1/8 turn lean at a time until it cleans up in the cut. I guess you can let off to hear it climb up a bit in RPMs and hit the limiter to make sure it gets back down to a clean sound while under load. I think I would be fine with a 4 cycle burble while under load once in a while to just not have to worry.

When working last weekend w/ 346OE nmurph just went through (NE piston/cylinder + MM) I found it way easier to hear the tune while someone else was cutting. Could easily hear 4 cycles at WOT (that one is unlimited coil I believe) and nice smooth run while under load in maple. When picking the saw up here and there coming off load you could easily hear 4 cycle at WOT...

I can also hear 4 cycling or limit being hit a lot easier in videos too! When I'm running the saw I find it difficult sometimes to really hear what it's doing. Guess I'll just always need a buddy to really hear the saws live or take video and listen after

Tach could be nice then to see what RPM the saws all hold in a cut. Also to check peak RPM at WOT on unlimited coil saws...

 

[Whitespider]

Now I'm going to want all non-limited coils in everything too... gadzooks.

Limiting coils are like the government (of today)... they're sole purpose is to protect you from yourself... and they only do a half-azz job of it.
*

 

[malk315]

Tried the tach over the weekend.

350 did like 12,500 (didn't record the exact number) -- no craziness from the tach I'm assuming anything under 13K is well below rev limit of the 350. So that saw is probably rich if anything.
372 did 13,368 and it was reading it clearly and not crazy.

I read on here that 372 coil is limited to 13,600 so what I was seeing makes sense.
I might get a 4 cycle sound once in a great while when cutting w/ 372 so it may be a little rich, it was last tuned at the dealer after collapsed fuel line issue was resolved (new line put in).
The saw is very strong I have no complaints so won't mess with it. Carb should have needed limiters on it too since it's bone stock 2012 model.

I don't have any decent test wood handy -- when I do I will see what the RPMs are in the cut.
Since an autotune goes for max RPMs as optimal I'm thinking going for max RPMs in the cut would be a good tune with these limited coils? It's easy to hold the tach or clip it to the handlebar and take advantage of it's max RPM reading. Maybe dial back 100-200 RPMs rich for a little insurance.

When I get the 262 back from Randy (that's a 1991 unlimited coil) I will see what we get. That saw should like to run around 14,000.

If I get to the tree job my brother is doing this weekend I'll check what the Murder 346 is doing for RPMs and the stock 346. This would be a 346OE w/ NE OEM piston/cylinder 50CC new w/ MM by nmurph compared to another OE 346 with OE piston/cylinder 45CC. Those should be good up through 15,000 provided they are not lean right?

Just learning as much as I can here.

 

[joej68]

Hi All,
Can anyone tell me what the rev setting should be for the vintage Poulan Model 25 CVA and the Poulan Pro S25AV (Yellow)? If not, where can I get the rpm specs for these saws?
Thanks

 

[ray benson]

Hi All,
Can anyone tell me what the rev setting should be for the vintage Poulan Model 25 CVA and the Poulan Pro S25AV (Yellow)? If not, where can I get the rpm specs for these saws?
Thanks

Out of a service manual.
Initial setting of idle mixture screw
and high speed mixture screw is one
turn open. Adjust idle speed screw until
engine will idle just below clutch engagement
speed. Adjust idle mixture screw
so engine will accelerate without hesitation.
High speed mixture screw should
be adjusted to obtain optimum performance
with engine under cutting load. Be
sure mixture settings are not too lean as
engine damage will result.

Then tach them and write down the results.

 

[Little Al]

That really sucks -- I guess I don't understand then how putting the saw in wood and letting up briefly will allow you to check the tune like I've seen in the tuning videos. When you let up the RPMS will climb up to the limit and then it's unreliable if you are hearing it hit the limit or true 4 cycling... especially if the tune of any saw is always above the coil limit... it's like chasing a unicorn at that point? or am I missing something?

Does the brief picking up of the saw while in wood allow the rpms to climb past the limiter to hear completely clean (no 4 cycling) means too lean or you hear 4 cycling for a moment and the saw is good?

Now I'm going to want all non-limited coils in everything too... gadzooks.

With a rev limited coil no matter what you do with the saw when the rev limit is reached what ever that is the saw no matter if or not the carb is set correctly the saw will cough/ fart/ misfire.until the revs drop & the sequence starts over again a good example is race cares on the standing start line when the red lights are coming on & drivers rev their vehicles waiting for the lights to go out on the limiters a grid of more rough sounding motors is difficult to imagine