STIHL hedgetrimmer HS82 T and R : carburator "H" screw setting???

[StarTech]

Have you tried adjusting the throttle cable to keep from over revving.

 

[Flatsix]

Have you tried adjusting the throttle cable to keep from over revving.

I think this is not done. I have several stihl motors with rev.limutation in them and they all start to produce that strange sound when it kicks in to prevent the motor to climb in higher rpm. It is supposed to work that way i think and not by adjusting the throttle cable of course then comes the question : how to adjust the H screw ...

 

[StarTech]

What I am suggesting is running the engine at about 3/4 full throttle and try tuning this way as you are running off the main jet [and idle jet] and not just the idle jet. This should allow to tune the H mixture screw.

 

[TobyU]

Okay you do need the Tach as going by ear just don't cut it.

Both the T and R are adjusted the same; unless, you have a Brazil setup which is slightly different on the R.
View attachment 66914
And I assuming the throttle cable has not been removed and reinstalled or otherwise messed with.

I respectfully disagree. I guess it depends on the person or the ear who is listening.
The average homeowner or newbie doesn't stand a chance either way so they need to get someone to show them how to do it a few times and then they can figure it out.
But you know me, compression testers and tachometers don't have much of a place in these repairs as far as I go.
I do use a digital attack on all the push mowers to set the RPMs but that's just because it's easier.

 

[StarTech]

IF your ear is that good then you should be read CW at 20+ words per minute. Here I was only get about 15 words to pass my General Class license test.Even they wanted to see written copy which I could keep up with the conversion.

 

[TobyU]

Hello,

I bought last year 2 hedgetrimmers STIHL HS82 - the "T" and the "R" version. They do good, only I see and hear that 1 of them, the "R" is running too rich because fumes , sound and more oil coming out of the exhaust.
I went to 2 Stihl-dealers here, but both don't seem to be able to adjust the machine as I wish.
I checked how many turns the "H"-sscrew was screwed out on both machines. The "R" had 2.5 turns out and the "T" had 2.1/8" turns out.
I have set the H also at 2.1/8" on my "R"-type and thought that then they would be the same, but I see that the "R" is still running too rich.
Then I asked STIHL-Belgium what the factory settings are for the hedgetrimmer HS82, they replied: turn H and L-screw both 1.1/2 turn out. Then turn the rpm on the L-screw as low as possible and the H-screw as high rpm as possible.
I know that the HS82 has a speed-limiter (9300 rpm) - so when I turn the H-screw it is difficult to hear because of that speedlimiter. I have also a tachometer.
Can somebody explain to me HOW I CAN SET THE H-screw CORRECTLY ON MY 2 HEDGETRIMMERS HS82. Both machines are the same when you only compare the motor. I can use my tachometer eventually.

HOW TO DO IT ??

Thanks for your technical advise.

Okay, here's the deal. I'm not even going to bother to read that owner's manual or service manual instructions because there's too many variations the way they send the equipment out.
You're lucky if you have a low speed and a high speed fuel mixture which obviously you do.
Many of the Zama carburetors have a mixture but it's hidden under a plastic plug which have to use a very tiny screw to screw into it and then pull it out and then use one of those smaller like Jewelers screwdrivers to adjust it which is the dumbest thing I've ever seen!

Then a lot of the newer cheaper carburetors don't have any mixture adjustments at all so there's nothing you can do as far as adjusting goes.

So here's the basic rule for these carburetors that have a low and a high speed. If they have limited caps take them off and throw them away..
Lol
Next, get you an adjustment tool that fits because it makes it far easier than trying to mess around with bullet connectors and the wrong style tool etc.
You're also not going to be able to have an exact number of turns to set these by because even manufacturers who give a specification, it's not exact it's just a basic starting point and it doesn't always work.

I keep hearing people tell me that humans don't like ambiguity but I'm sorry people are just going to have to learn to get over these things and understand that you don't always have a step-by-step to tell procedure to do everything in this world despite how much people try to make it so.
This is EXACTLY how people get into a situation where they say repeatedly they have done something and they think they've done it correctly but in reality they have it because their instructions are flawed.


Regardless, one and a half to two turns out from lightly seeded in will typically be enough to get the machine running if it's going to run and it doesn't have other problems which unfortunately is often the case.

So put them between one and a half and two turns out from lightly seated position and try to get it running possibly using the choke or the original lever etc.

Turn the total idle stop speed screw up a bit so we'll help it stay running if you do get it to start and can let it idle down.

If you can get it running try to adjust your high speed first..
To do this you have to have the throttle at wide open. If leans out and bogs and dies when you give it throttle try opening your screw a little bit more..

Once you get it to run at wide open throttle you adjust that one in and you'll see it speed up and then as you keep going you'll see it start to slow down a little bit because it leans out and then if you keep going it will die so don't go that far.
There's a slight difference doing a string trimmer or a blower versus doing a chainsaw but for the most part you really don't want to set it as close to lean as most people do especially when they try to tune by highest RPM but then some tell you to back it off slightly from the highest RPM which is kind of a convoluted method.

Go back and forth a few times to get a feel for what it does as you hold the throttle wide open and as you go in toward the lean side it starts to slow down then back it up to where it's nice and smooth and fast and then as you continue to open it up some more you'll hear it start to burble. That's the word I use for it - burble.
That's when it's getting too rich and you don't want to go that far so you just turn a little bit clockwise to lean it out and just a nudge more and I'm talking probably not even an eighth of a turn but definitely not a quarter.

You just don't want it to be too close so it gets into the rich verbal zone but you do want to be closer to that than closer to the lean side which is clockwise which makes it slow down.

Reason being, your engine will run cooler and the piston will be lubricated and run cooler and you'll get longer life this way that if you're running the edge of lean.

Then you let the throttle down and hopefully it stays running if not you'll have to adjust the low speed screw between a quarter and a half turn each direction until you can get it to run with the throttle in the minimum position.

Now you might have to slow down your total screw some because if you have it too far turned it keeps your throttle too far open and you're no longer actually in the idle circuit only of the carb.

But you do the high side and get it running well and then you do the low speed and then you will see that as you tighten the screw and lean it out it will speed up but don't go too far because that kills your response and it's too lean overall.
Back it out a little bit and usually somewhere between the two extremes is where you want it. You don't want it too close to the burble rich side because that tends to make them stall out and not sit there and idle nicely.

Once you get the low side adjusted nicely it should have nice instant response when you squeeze the trigger.
Sometimes a quarter turn one way or the other makes the world a difference on the revving up so adjust for best performance.

Then, I always go back and check the high side one more time because they do tend to have an effect on each other to a degree.

Do the same thing you did before with the throttle wide open and go to the lean side where it speeds up and then starts to lean out and then back it back down until it burbles and then tighten it clockwise a little bit so you're not at risk of burbling....
Then you should be done..

I know it's hard to explain and it sounds more complicated than the factory procedure or whatever but it only takes about 2 to 4 minutes to do one of these.

 

[TobyU]

IF your ear is that good then you should be read CW at 20+ words per minute. Here I was only get about 15 words to pass my General Class license test.Even they wanted to see written copy which I could keep up with the conversion.

Different type of ear! LOL

There's definitely a feel for it just like people who work with a lot of small engines can put a typical push more engine right at the proper RPMs they set them at without a tack whereas the average homeowner has no idea whether they're running it 2,200 RPMs or 4700 RPMs.

 

[RevB]

He must have some mighty good hearing if he can tell the difference between 11,000 rpms and 10,900 rpms. For me that takes a tach to done that. Even the idle settings should be done using a tach when tuning by the factory service manuals.

Here is an example where the max rpm are drop by 20 rpm though a mx rpm is allow it is still better to enrich a tad.
View attachment 66943
And this one of the simple tune ups on the Echo line.

You said AND using a tachometer....which wasn't debated nor omitted. Yes...my hearing is pretty damn good.

 

[TobyU]

He must have some mighty good hearing if he can tell the difference between 11,000 rpms and 10,900 rpms. For me that takes a tach to done that. Even the idle settings should be done using a tach when tuning by the factory service manuals.

Here is an example where the max rpm are drop by 20 rpm though a mx rpm is allow it is still better to enrich a tad.
View attachment 66943
And this one of the simple tune ups on the Echo line.

But the whole premise of that is completely irrelevant.
I don't care what any of them say or any tech manual says.
800 RPM difference in a high revving two-stroke is pretty irrelevant anyways and as your adjusting them you're going to have a lot bigger RPM drop on the lean side and even on the rich side than that and it will be quite obvious.

In real world situation, you could have 6 people set up with 10 different machines and you could have a couple of them do it solely by here and experience, and the other ones do it by whatever method they want with whatever attack they choose.

When it's all said and done they would be no difference in the operation of the equipment OTHER than the all too common irregularities in the small carburetors that don't like to hold their tune and settings from minute to minute and from heat cycle to heat cycle and even from being cold to being hot but that has nothing to do with the actual tuning.

Let's assume we take 10 pieces of equipment that are very nice and forgiving and respond perfectly to the mixture screw adjustments and then intentionally make them out of adjustment then let our six people go at the adjusting.

I will never believe anyone needs a tach to set a two-stroke machine fuel mixtures.
Now wide open throttle RPMs is completely different story as I often use one of those for push mowers and riders but for setting the mixture is simply not necessary.

I guess the people to follow this mindset are the same ones who use an RPM gauge for a vacuum gauge when they set the carburetor on the old cars in the 70s and before.
I know the tech manuals told you to do that but it was still unnecessary and I always got those cars running better doing it by ear two or three times back and forth than doing what they said and turning the screw a certain way until a certain RPM reduction it was exhibited.

Of course within just a few years the way they told you to do things was not for the best running or best performance of the machine at all but rather being interfered with by emissions etc.

Regardless, experience and listening with your ear and knowing how to do it from again.. experience is how you get these things running the best not by some method in a shop manual.
I will go out there and say that the method in the shop manual is a bare minimum base place to start but it is NOT the best.

 

[rhkraft]

Thanks Fish for the pages you showed. I do not have limiter caps on the machines - the airfilter is clean and as new and nice as a brandnew machine.
The STANDARDSETTING of the "H"-screw is 1.1/2 turn OPENED; this is the same as the people of STIHL-Belgium wrote.

But from 1.1/2 turns out to the optimal setting to have the right mix air/fuel : that is my question. HOW TO DO THIS TO OBTAIN THE RIGHT MIX AIR/FUEL by adjusting the H-screw.

At present both machines their "H" screw have I set to 2.1/8 turns out. I did so because my T-version was set on 2.1/8 out. The other was set at 2,5 turns out and I changed it to 2.1/8 - but for me still to rich....

HOW TO ??