RPMs 2 questions

Treeaddict

Treeaddict

Treehouser
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My 334T idles at 4200 rpm. I did this to make starting easier. Most of my saws idle at an RPM just before the clutch engages. Manual says idle is 2800 rpm. Is it ok to be elevated?

Manual says 9600 rpm when revved and I’m reading 12,200. Seems to make no difference warm or cold. I never touched the hi and lo jets and can’t believe the previous homeowner did when he used the saw for an hour, once. Any harm in the 12,200? Most saws run that range anyway, correct?

Using FastTach.
 

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I'd be questioning the tach. Seems to read high in both cases. Saws aren't precision instruments, but I'd expect it to be closer to spec than what you're getting. I'd check the tach against a known good gauge, maybe from a shop? You may have to buy a little shop time, but then you'll know for sure. IMO, it's better to tune by ear and feel. It isn't something I'm good at, but that's the goal. Since a saw isn't a precision instrument, an ear tuned saw will be tailored to that specific tool, even though it'll vary from spec.

edit:
You could put a tach on all your saws, write down the results, then take them to a shop, and have them test the saws. Compare the results. If they're different, see if there's a pattern. Best case(aside from your tach being correct) is your tach reads the same amount off every time. That's just a simple correction. If it isn't that easy, it might be better to buy a different tach. I'd still work on ear tuning though.
 
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I could definitely see the idle rpm being that high as I raised it from stock. Never touched the carb jets though. But you’re correct, I cannot prove that the tach is correct. It is a reputable $90 instrument though and not Chinga brand.
 
Your full throttle reading concerns me most. Could be lean, and giving you high results. If you can't hear 4stroking when it's out of wood, crank the high jet up; maybe a full turn. See if you can hear then. If not, turn it up some more. Still can't hear it? You may not know what to listen for, or have a bigger problem.
 
No offence @lxskllr, I used to do the same a lot just trying to be helpful like you, but you jumped the gun yet again being first to reply when more than a few here know better.

9600rpm is the peak power rating. Run at 9600 to get the most power, but it may be advantageous in some cases to run at a lower rpm for peak torque. Some manuals tell you the peak torque rpm.

Any modern saw will rev higher than the peak power rpm. It is both natural to how engines work, and there is useful power to cut small stuff faster at that high rpm. 12,200 could be where the rev limiter is set.

An elevated idle shouldn't be a problem as long as the chain doesn't spin. It could start to spin if the clutch barely engages and the chain loosens over time, and if changing orientation or temperature causes it to idle even faster. Just a safety issue if anything. Of course the clutch could burn up if the brake is left on with too fast of an idle.
 
:shrugs: Where's the other replies? I do what I can based on the experience I have. All I can say is all my saws work, and I don't use gauges.
 
I suspect the idle is a bit high but if the chain isn’t creeping along at idle I wouldn’t be concerned. And 12,000 plus rpm at WOT is about right.
 
lxskllr said:
:shrugs: Where's the other replies? I do what I can based on the experience I have. All I can say is all my saws work, and I don't use gauges.
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They hadn't seen the thread yet. It's ok, I get it.

I had a Chinese ms250 have the clutch engage at 5500rpm, which is really fast. I filed the springs to get it down to 4800, which is still a bit fast. Some manuals tell you the clutch engagement rpm. I want to say it was around 4400 or less.
 
As already mentioned, the 9600 is where the saw produced peak power, pretty common in most saws around the 9000, 9500 mark.

Your saw is up around the 12500 13500 max rpm at wot (Wide Open Throttle) no load with correctly tensioned chain, so at 12200 its ok, and where I would set it or close too, its within 500rpm.

Most clutches engage at 3600 ish.

if you brought up the idle, I would just add a bit of richness to the L side again, if its not that easy to start cold, or is not crisp on accelleration, its a bit lean on the L.

Adjusting the LA, or butterfly position often requires another adjustment on the L or mixture screw, just enough to bring down the idle speed a bit, if it was not idling well to begin with, was it idling ok, then slowly start to load up and stumble, and you needed a blip of the throttle to clear it ? if so, its a bit rich.
if it was hard to start, lag on accelleration, then you were most likely lean to start with, and adding more idle speed to help it with the LA will only make it leaner, add more L to bring the idle speed back to 2800 and see how it performs now.

Ok, just to clarify, your currently at 4200 with idle, re adjust it to 3200 with the LA or butterfly screw, then use your L to richen it and bring the idle speed down to 2800, and report back, if that is still troublesome at idle, add a bit more LA, ie 200 rpm, then bring back down with the L, it sounds like it was lean to start with, so you need to get the adjustment back in the window where it should be.

let us know how that goes.
and we can fine tune from there.
 
Nutball said:
They hadn't seen the thread yet. It's ok, I get it.

I had a Chinese ms250 have the clutch engage at 5500rpm, which is really fast. I filed the springs to get it down to 4800, which is still a bit fast. Some manuals tell you the clutch engagement rpm. I want to say it was around 4400 or less.
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get some genuine clutch springs, the chinga ones are not correctly set, genuine ones are really cheap anyway. 3 bucks a piece over this side of the pond, and cheaper over your side.
 
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  • #11
Trains said:
As already mentioned, the 9600 is where the saw produced peak power, pretty common in most saws around the 9000, 9500 mark.

Your saw is up around the 12500 13500 max rpm at wot (Wide Open Throttle) no load with correctly tensioned chain, so at 12200 its ok, and where I would set it or close too, its within 500rpm.

Most clutches engage at 3600 ish.

if you brought up the idle, I would just add a bit of richness to the L side again, if its not that easy to start cold, or is not crisp on accelleration, its a bit lean on the L.

Adjusting the LA, or butterfly position often requires another adjustment on the L or mixture screw, just enough to bring down the idle speed a bit, if it was not idling well to begin with, was it idling ok, then slowly start to load up and stumble, and you needed a blip of the throttle to clear it ? if so, its a bit rich.
if it was hard to start, lag on accelleration, then you were most likely lean to start with, and adding more idle speed to help it with the LA will only make it leaner, add more L to bring the idle speed back to 2800 and see how it performs now.

Ok, just to clarify, your currently at 4200 with idle, re adjust it to 3200 with the LA or butterfly screw, then use your L to richen it and bring the idle speed down to 2800, and report back, if that is still troublesome at idle, add a bit more LA, ie 200 rpm, then bring back down with the L, it sounds like it was lean to start with, so you need to get the adjustment back in the window where it should be.

let us know how that goes.
and we can fine tune from there.
Click to expand...


At the risk of sounding like a fool: The saw started and idled fine to begin with but I didn’t tach it to see where it was. I increased the idle to just below clutch engagement believing it would start easier as this was the case on my 450T. I had a time starting the 450T until I brought the idle up (didn’t tach, just put it below clutch engagement). I asked on here about low idle and starting difficulty. Burnham informed me that they were related more or less. After I increased idle, starting became easier. Then, I increased idle on a couple other saws thinking it may lead to one or two less pulls when firing. I can take idle on the 334T back down to the 2800Rpm and see how she does. Currently, the 4200 is just below clutch engagement. Hopefully I’m not too foolish to have increased idle.
 
Not foolish, just need to know why its doing what its doing, and apply the correct fix to it. If incorrect fix is applied, you add problem on problem, and make diagnosis, and eventual fix more difficult.

did it start poorly when cold, idle not steady ? often a lean L side symptom.

Trust your tach for now, and do as I mentioned above, make it richer on the L, and report back exactly what you did, and what its doing after that, and does it make it start easier ?
was it cold start or hot start that was more difficult, and exactly what do you mean when it was difficult to start, lots of pulls before it would fire, would it start, then stall, would it start fine, then slowly stumble and not idle/ stall, spell it out, as diagnosis like this is not easy at the best of times, and I want to give you the right advice.

once that is sorted, lets look at your 450T and sort that.
 
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