Chainsaw Repair
Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Poulan => Topic started by: redunshee on January 28, 2014, 04:42:43 pm
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Some may have read my issue with a 4000 I just picked up. I wonder if I have a going the wrong route. I've been trying to adjust the Hi speed at around 10,500 using a tach. I know many of you don't use a tach but without wood here to really test the saw this is the next best approach. I'm beginning to think the 4000 may run at higher rpm's than a 3400. Can anyone confirm or debunk my thinking. I always check plug color but again w/o wood to really run the saw under load I doubt I'm getting accurate plug color feedback.
Bob
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Seems low.
My 4000 I never checked with a tach. I just set to 4 stroking and then backed it off till it just barely stopped four stroking. Ran great no idea on rpm's. Least I dont remember if I did check.
Video of it in thread.
http://chainsawrepair.createaforum.com/poulan/poulan-4000/msg29283/#msg29283
Ray Benson = I keep a log on my saws for setting the high speed screw since getting a tach. The poulan 3700 hasn't been run for a couple seasons but it ran best when set it at 11,500. Just follow the owners manual recommendation when setting the carb. Tach isn't really necessary.
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Bob I do not have a 4000 but I have some 3700's and 395's. I always tune them to wood and never checked them with a tach. Tomorrow it is suppose to warm up some and I will do some Checking for you.
Roger
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These older designs work great to tune in the wood by ear.
Some of the newer "Strato" type engines have a very slight two stroke-four stroke break and even a old timer has to really listen to tune a "Strato" by ear particularly if it has a limiting coil.
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I tune most of my saws (including that series) by ear. Don't even own a saw tach right now. I'll have to borrow my bud's tach to see what my 4000 is turning just for a baseline. I set them so they're 4-stroking at WOT unloaded, but clean up when under moderate cutting load. When cutting load's lifted, I like them to go right back to four stroking. That's my "general setting" for most of my saws (including my PP375 and 4000).
If tuning a saw for limbing or 'small wood' cutting I run them a tad leaner than that. I get them to where they just continuously 4-stroke at WOT unloaded, and clean up as soon as there's light-moderate cutting load. That's how I tune my small saws (unless I'm going to be asking them to 'cut above their class'........like doing a bunch of 12"-16" cutting with my S25-CVA). In that case I richen it up just a hair.
If running bigger bars in bigger wood, I go a bit richer, so that the saw doesn't completely run 'clean' until under full load (bar length or greater wood).....................with just a bit of 'off and on' 4-stroking under light-moderate cutting load. That's mostly on my bigger saws wearing 30" and bigger bars.
I need to get a tach for the times that I'm tuning other guy's high-revvin' modern saws. I tend to run my saws a tad richer than some guys do. Better safe than sorry.............and with good synthetic oil at 32/1 I still don't get any carbon buildup. I'm not racing, and long saw life is important to me as I'm on a budget.8)
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+1
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Ok I put the tach on my PP 395 and on my Poulan 3700. Both saws had the bar and chain on them and wide open throttle.
The PP 395 has been MM and the base gasket removed but no other mods. The RPM's were at 10,600.
The Poulan 3700 has been MM and the base gasket removed with another .020" taken from the base and then the intake and exhaust ports were widened. The tops of the transfers were pointed towards the intake side and the plastic intake manifold was smoothed out. The timing was advanced also. The RPM's were 13,000.
Both saws were 4 stroking with no problem.
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Wow, 13,000. Wouldn't dare set mine that high. Really miss having wood around here to tune my saws. All I have is my ear and tach.
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I hear ya. Both of those saws were tuned by ear in wood and is where they happen to end up at.
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What is insane is the fact that the caged needle main bearings used in them are only rated for 6500 RPM in oil,
that's at their full dynamic loads of course. The actual running loads must be lower, as these saws run forever, if
maintained correctly.
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Roger,
If you ever pull the cylinder off that 3700 I sure would like a few pics of the intake and exhaust ports.
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Roger,
If you ever pull the cylinder off that 3700 I sure would like a few pics of the intake and exhaust ports.
Will do Tim. I have another one here that is a 3700 but is a craftsman in red. I am going to do it also. When I do I will take some pictures.
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Roger,
If you ever pull the cylinder off that 3700 I sure would like a few pics of the intake and exhaust ports.
I've got two 3700 cylinders that have different exhaust port sizes. One exhaust port looks exactly like a 3400 i.e. There is a slight ridge on the exterior of the port. The other cylinder has the ridge removed and is open much more. I thought all 3700's were like the latter one as opposed to the 3400 type. Think I'll pull the mufflers off my two 3700 saws and look at the exhaust ports.
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Roger,
If you ever pull the cylinder off that 3700 I sure would like a few pics of the intake and exhaust ports.
Will do Tim. I have another one here that is a 3700 but is a craftsman in red. I am going to do it also. When I do I will take some pictures.
Roger, are the red Craftsman 3.7 , 3800's with plain bore and aluminum piston with thick rings?
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This particular one is the two thin ring chrome bore 3700. The red ones came both ways.
Bob let us know what you find on your other 3700 exhaust ports.
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You'd be surprised what you can crank them up to and they run forever .One of many reasons I'm a proponent of heavier oil mix gas .
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You'd be surprised what you can crank them up to and they run forever .One of many reasons I'm a proponent of heavier oil mix gas .
I agree Al and I changed from 40 to 1 to 32 to 1.
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The needle bearings are the weak link in this series of saws, plus the powder metal crankshaft is weak and heavy. If you run these engines at 13000 plus for any length of time, they will come apart.
The only thing that you accomplish by running 32:1 in these engines is to carbon up the engines, stick the rings, and create smoke. The very slight increase in lubrication over 40:1 or 50:1 will not make any significant improvement in needle bearing life - the needle bearings just can not handle rpm like ball bearings. Virtually any engine made from circa 1980 to present date have engine components that will run better and have equal life with 40:1 or 50:1 when compared to 32:1.
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I don't get any significant carbon buildup, ring sticking, or smoke from running Redline Race Synthetic (or Stihl Ultra or Woodland Pro Synthetic) at 32/1. Been running 32/1 with good synthetic in all my 2-stroke equipment for decades without issues.
Back when I switched from 50/1 to 32/1 I saw an increase of residual oil on internal engine parts, but no increase in carbon. Also, some saws (such as the 365/372 and 385/390 Huskys) have much better bearing life at 32/1 than at 50/1 in logging conditions. Yes I realize those saws have ball bearings vs the needle bearings in the 3400-4000 CounterVibes. I don't wind my CounterVibes up at stratospheric RPM levels............but I'm also not sticking rings in those saws with a 32/1 mix.
Why is it that going from 2% to 3.125% oil will on one hand not give a significant increase of lubrication.......................while at the same time cause a drastic increase in carbon deposits, smoke, and related issues? I think this is another case of agreeing to disagree....
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I will take my chances with my 3700 turning 13000 rpm's. With 40 something saws to use I do not think it will get over used. Besides in the cut it is probably only turning around 9000 rpm's.