What I’m more interested in is where I have read how running a 2 stroke that is 4 stroking puts high stress on the internals of the engine and long term can cause damage. Thoughts?
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Spark Plug Wisperers?
- Thread starter MAWoodsman
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The other thing that can catch some people out, on occasion not every engine needs to be 4 stroking before it goes under load. This is obvious with engines that are loaded already like a leaf blower. However much less common - I had this with a weed eater the other day, I set it to just 4 stroke out of load. I then put it in the grass and its pig rich & had no power. I leaned the H screw and tried again, continued to do so until it was right under load and I found it wasn’t 4 stroking out of load, though it was still on the rich side of peak. I thought it may be that the diaphragm was a bit hard or a worn metering needle that wasn’t metering fuel supply as accurately. It wasn’t, it was perfect. Some engines, especially the cheaper ones, don’t react according to the “rules”.
Learning to tune one piece of equipment does not mean you can tune. There is so much more involved across different 2 strokes and you really need to use experience and understanding to say you can comfortable tune a 2 stroke. I’d say it took a couple years before I felt fully confident in doing so both consistently, accurately and across a range of engines.
For the op:
Rest assured, you won’t burn an engine up using a tach. It may not be 100% optimal, but it will be damn close when tuning an unmodified engine.
Learning to tune one piece of equipment does not mean you can tune. There is so much more involved across different 2 strokes and you really need to use experience and understanding to say you can comfortable tune a 2 stroke. I’d say it took a couple years before I felt fully confident in doing so both consistently, accurately and across a range of engines.
For the op:
Rest assured, you won’t burn an engine up using a tach. It may not be 100% optimal, but it will be damn close when tuning an unmodified engine.
If you think people can't tune by ear, they are far too cheap to do a plug chop and figure out everything they need to know about that 2 stroke engine from a $4.00 plug. I fight with guys about old plugs telling you nothing on my 1/5 scale rc forum. Can't remember where I got this screen shot. But it's a handy reference.
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I couldn't tell you a thing because all of my plugs are rusty orange because the ethanol free at the pump contains MMT. It has a tendency of turning the plugs orange.
It’s useful info and I have done it a number of times, but again, oil ratios, type and fuel all drastically change the results of even plug chops.
I have tried it with Saber and didn’t get any spot ring at the base of the insulator, repeated the same with dominator and got a good ring. Same tune, back to back. Some oils leave more deposits. By plug chop standards I was way too lean, but in reality, I wasn’t. Nothing is foolproof. Use all the the tools at your disposal.
Yep... this is all true.
I might have done a plug chop or two in my time.
Your not doing the chop right. You need to be consistently and heavily loaded for a prolonged period of time. It appears to me you didn't have enough time or you were in and out of the cut. Honestly plug chopping with a saw is difficult unless you have really big wood.
Oil type, ratio and fuel do not really change the results of a plug chop either. I have done them with all sorts of oils from dirty castor to ultra clean synthetics and everything in between.
You highlighted why tuning by ear is very coarse and why I don't like it at all.
Actually the window is fairly small and if you have tuned a carb that uses jets tightly this is pretty apparent.
Yes, some of us obsess no doubt, but I will say that my stuff will flat out run no matter the conditions and at a high level.
I agree that the tach is the best thing for the inexperienced. Pretty much fool proof.
Na this is correct. A plug chop should only run for about 60 seconds fully loaded, which was exactly what this is. That picture is a perfect high jet tune, but the previous plug chop was clean. Oil is the resulting difference and thus the reason why I don’t like doing them.
That and with a change of temperature, day or other conditions, the engine will need retuning and thus again unless you’re going to mess around with chops every day, it’s pointless in the first place.
Edit: This is another case of “interpretation” on what is good. There are no hard and fast rules for anything tuning. Even using a a lambda, you still need to test it and may need to tweak it too. There are parameters or windows that are safe.
It’s one of a number of “tools” I use.
Hmm, take my stihl ms 260 as you said you have one too. That will happily run between 12k to 14.5k and anywhere in between without problem. No plug fouling and good power throughout.
Sure the 12k is a bit slower but it’s marginal. 12k still cleans up under load no problem.
I’d consider that 2500rpm a huge window in which it will run happily.
At face value I would think that's a bunch of nonsense. For starters excess fuel doesn't cause an increase in pressure. Excess air does and your air present in the cylinder doesn't change much when four stroking. You might gain a little because residual exhaust may be more completely scavenged, but maybe not.
It will run at 12k, but not well. Maybe I should have been more clear... the window for peak performance is pretty small. Not fouling plugs, or misfiring is a pretty low bar.
The 260 is a turd of a saw stock and needs all the help in can get. No need hold it back with poor tuning.
Not sure if your 260’s are different in the USA to the UK, but mines a little ripper 12k or 14k. 12k on mine certainly isn’t holding it back.
I’d not be surprised if they were. The stihl 660’s are hated in the USA, in the Uk (and Australia) they are / were incredible.
Sounds like they dumb them down or limit them for your EPA standards.
You don’t need an any OPE to be anything other than decent and a slightly rich tune is perfectly fine. They’re not race engines that need to work to peak performance too get every extra bit of advantage. I’d say if the engine runs clean under load, doesn’t foul plugs, idles well and starts well, regardless of what the manual says, is certainly running well.
Never seen a plug that looks like yours. They have all looked like the one I posted earlier. Like I said I've done it with many oils. I woukd be interested in what your procedure was when you did it.
With a saw when you plug chop you have to record the max RPM so going forward you have a point to tune to.
There's a knack for reading plugs, but it's the most accurate way to tell everything that's going on inside of a 2 stroke. The tach method is the next best. Really if we cared to be any more specific we'd get wide band o2 sensors and tune that way. I'd argue you didn't run that plug long enough at wot, or it's lean. But your definition of "tuned right" and mine can be vastly different. The oil ran should have minimal effect on plug deposites, it's mostly the crud in the fuel were looking for.
You don't actually have to chop the plug, a small lighted magnifier is sufficient to see the band at the base. And I've never once heard the 60 second is long enough. Actually I've never heard a time other then longer is entertaining at sustained wot with load.
The US models were dumb down for the EPA regs no doubt. I always muffler modded mine, deleted the base gasket, installed a WT194 carb and advanced the timing. Even with that done they were not in the same league as a 346xp snd atpck with the fixed jet carb and choked up muffler they really sucked.
No they are not rave engines, but if your going to take the time to tune them you might as well do it so it nets you the most performance. 12000rpm isn't close to that.
This is correct. And it's important that the throttle and load stay at full open and full load until you chop it.
From memory it was actually a strimmer I was tuning with this plug chop, fs85. Either way - Warmed it up to operating temp doing about 5-10 mins use under load and tuned it to where I thought it was good, swapped the plug out with a new one, started it straight up and got it fully loaded right away for 60 seconds. Killed the engine and cut the plug. Both times using 40:1. First Saber and then this which is dominator.
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This was what I followed, right or wrong. I don’t intend on doing more
