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Adjusting a Stihl Carburator

Started by mtnman, December 02, 2012, 06:50:55 AM

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mtnman

I have been using stihl chainsaws for 20 years and dont remember doing any carburator work on any of them.  I have had to work on some weedeater carbs.  I read on another thread in here that you needed to learn how to adjust your own saw carburator for better performance. 

I am not sure on a Stihl but here is what it says in my weedeater manual:

Inital adjustment
1-Turn HI and LO Adjustment screws clockwise until they seat lightly in the carburator body.
2-Turn LO adjustment screw counter-clockwise one turn.
3-Start engine and allow to run at high idle until warm 2-3 minutes

Low Speed adjustment
1-Slowly turn LO adjustment screw clockwise and note the posistion when engine speed drops.
2-Turn LO adjustment screw counterclockwise and note the posistion when engine speed drops.
3-Set the screw midway between these points.

High Speed Adjustment
1-Turn HI adjustment screw counterclockwise 1-1/4 turns.
2-While engine is running at full throttle, turn HI adjustment screw clockwise until engine runs smoothly.
3-Turn HI adjustment screw counterclockwise 1/8 turn to obtain optimum fuel mixture for full power under load conditions.

Will this weedeater proceedure work for my Stihl Carbs?
How do you adjust yours or what would you recommend?
mtnman

T Welsh

 mtnman, Your pretty much spot on for carb adjusting! I start with 1 turn out on high and low and go from there. The fuel we have been getting with ethanol in it has been a nightmare to small engines in the last 5 years. Check your fuel lines and impulse lines for cracks first. If it doesn't help and carb rebuild kit will usually fix the problem if its a carb related issue. Tim

Randy88

Can anyone tell me what the large adjustment screw under the high idle and low idle screws are for on a ms660 saw, how to adjust it and also how to adjust the carbs on stihl saws so they start easier, do you just do the initial adjustments again, or simply adjust either the low speed or high speed adjustments slightly, I was told years ago how to do this, but over time this has been forgotten. 

SwampDonkey

If it's on a spring it's an idle screw. If at idle the saw chain spins it needs idling down.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

JohnG28

Is it flooding as you try to start it? If not try opening the L screw 1/4 turn.
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

Randy88

I'm having all sorts of problems with this saw, and not sure why or what exactly is wrong, I just had my local saw shop guy, who's really good, put a carb kit in it on friday, and he started it right up for my wife when she had it into him, she got it home and we fueled it up and tried to start it, after about fourty pulls and about to give up it started and ran good for about ten minutes.   When we shut it off we've had nothing but problems, sometimes it starts on the first few pulls other times not at all, I figured it was plug problem and this morning we put a new one in, started on the first pull, never started again today with any attempt.  Sometimes it smokes, like its flooded, other times nothing, sometimes the plug is wet when we take it out to look, other times not.  I'm thinking we have multiple problems, fuel and also ignition.   

We had trouble a few years back with the same thing, every time I'd take it to have looked it, it would start on the first pull every time, when we'd get it home, same old thing, nothing, back to the shop only to have it start good again, after about four trips to town, it's worked fine ever since till now, my guy didn't do anything to it but adjust the carb before, this time he rebuilt the carb, same symptoms as before, sometimes it starts right up, the next time not at all, any idea's and if so how do I test them while its at home, every time we take it in, there's nothing wrong to test.   Bad ignition switch? electronic ignition going bad, some carb problem?   I'm out of ideas, we just set it aside today and ran my other two saws instead.

SwampDonkey

Just a little yarn here. I worked with a fella, actually he worked for me, and he was always messing with the jets and idle screw. Me, I have a brush saw I've used for 6 years and cut hundreds of acres and I bet I never touched those adjustments but 3 or 4 times. I let this guy borrow my saw once and here he was messing with the jets and said it was about to blow up he thought.  :o ::) It's been a Dang long time and it's not blown up yet. I guess he never had a good run'n saw of his own because he was always mess'n with his. :D  ;)
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

JohnG28

How old is it? You the original owner? My uncle has a 660 and it can be a pita to start too. Similar issues I had with my Stihl leaf blower turned out to be a bad crank bearing. Flooded at first then no fuel after carb rebuild. May be an issue. :-\
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

AdkStihl

Please explain your starting procedures  :snowball:
J.Miller Photography

Randy88

I bought this one new a ms660 along with a new 361 about seven years ago now, we go through anywhere between 100-300 feet of chain per year, two years ago we also bought a new 460 to go with the above two saws.   The carb on this 660 has been rebuilt at least twice now, along with several oil pumps and the usual maintenance items.   

Starting procedures are as follows, full choke, switch all the way down, same thing as full choke, decompress the button, pull a few times till it fires, then switch up to partial choke, depress button again, few more pulls and or less and its running..............normally.    This go around, it either never fires even once, or does once and not again, sometimes there's smoke, most times not, let sit for minutes or hours, try again, similar results as before, otherwise, it starts just like it should, its totally unpredictable, has been for the last few months, till this weekend, nothing.   We usually let it sit in my unheated shop when not in use, we've tried leaving it in someplace warm, no difference.   

In the past we've had problems with the carb adjustment screws vibrating out of adjustment, my shop guy told me this every time we have taken it in, usually about every couple years to be readjusted due to poor starting, he's changed the springs in the adjustments screw, I'm guessing the idle screw, at the time I didn't worry about the details of where or how.    All my stihl saws are started about the same way, usually a few pulls and they're running, no matter what the temps or conditions.

We use stihl oil mix, nonethanol gas and mix the 2.5 gallon mix to a two gallon container, its the jug I like to use, has been since the saws were new.   This week we've used up about 12.5 gallons of gas/mix, so its pumped fresh, not old gas.

SwampDonkey

My old Stihl brush saw. I just take it out every spring from the storage room, which is not heated, put in new gas. Put the switch to start, with the trigger locked on. Push in decompression valve. Turn the choke, prime 4 or 5 times, pull 3 or 4 times and we're off to the races. I usually whack the red dogwoods all down around the back yard every spring to clean the cob webs out.  ;D A saw is no good if you have to crank your guts out. We had a brand new Sacs Demor (spelling) and once that got heated up a little and shut off it was no good the rest of the day or for a long time until it got cold. Worked that way straight from the shelf at the shop. Junk.

:new_year:
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

Randy88

Before buying my latest saw, the 460, my stihl shop guy, loaned me a dolmar saw, about the same size as the 460, that was the nicest starting, best balanced, great power to weight ratio, and the auto oiler put out enough oil to do an excellent job of oiling.  My entire crew fell in love with it, the only problem I had with it, was if I bought it, no bars or parts were inter changeable with my existing saws, the sole reason I bought another stihl saw.    With three the same, all bars, drivers, my extra bars, bar cover nuts,, even the self adjusting screws were all inter changeable with each other, so it didn't matter which saw i took, I have the bars anywhere from 16-36 inch's long can fit any of them.   

If I'd ever bought a new saw that didn't perform, someone who sold it would be doing whatever it took to make it work right, and start each time, that to me sounds like a dealer support problem, or company support problem, you'd expect that with an older saw, not one new out of the box, with a warranty.   

SwampDonkey

I can't remember where it was bought. I have no idea about the warrantee then either. All I know is it was no good to us. We had to cut wood, and no time to run around with junk saws. If your not producing, you don't get paid squat.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

s grinder

Randy88,I also have a MS660,two years old,use the same starting procedures you do,never had any problems,thats no saw you want to pull 30 or 40 times to start,hope someone will steer you in the right direction

Randy88

Tomorrow its bound for my stihl fix it guy, we'll see what he comes up with after he has it a few days.   

Sgrinder, I can agree with you totally on that issue, I always figured if I had to pull it much over a half dozen times, someone was going to do something about it, with a 36 inch bar on it, I have enough of work out just running it, I don't need one starting it too.

cuterz

Yes take it in, being new you should not have to adj. it unless they didn't. When you pick it back up have them go through the way they checked cold and warm starting.

deerslayer

Try this: On the MS660, do not pull the rope more than 3 times in the choke position. If it doesn't "pop", move the lever up a notch anyway and then see if it doesn't make a difference. The 660 is the only Stihl saw I start this way and it seems to work for me. I think with the compression release the pop may be so soft it doesn't get noticed and then the saw floods.
Too many chainsaws, not enough wood.
Stihl, Husky, Craftsman, Mac, Homelite, Poulan. Some live here, some just passing through.

Randy88

Took it back to my fix it guy, both saws actually, and he put another new jet in the carb of the 660 and a fuel filter in the 361 or screen or whatever he called it, now they are both back up and running right, start like they should, he said no amount of adjusting would cure its problems this time around, put a new pull rope in the 660 and also a new diaphram in the carb of the 361, something I didn't catch about the explaination it kinda went over my head.  I told him we have the perfect relationship, I break it, wear it out and he fixes it for me to do all over again.   

On a more hilarious note, discussing idiotic problems, on my cement saw, I had nothing but problems with it, it was always flooded, I'd take it in and he'd get it to start and run just fine, I'd bring it home and run maybe a few minutes   or a half hour then choke off and die, this went on for a dozen or more trips to the shop, every time the same thing, when flooded it wouldn't start again.   Someone would have to hold my hose for me when I ran the saw to keep the dust down, as it ran, it doesn't have a water valve on it, so anyhow there was always two people around when we ran the saw, one holding the hose, one running it.   Finally out of desperation I tossed the saw aside and said, go buy a new one and as I literally tossed it away from me as it was flooding out, I realized my shirt tails were sucked to the intake of the saw, as I tossed the saw, it came back to life and ran idling on the ground, all that while, all those trips, nobody had noticed my shirt tails would suck up the air intake and flood it out, the fix it guy was right handed and held the saw from the other side, I was left handed and as I'd stand up, the intake holes would sometimes brush up against my pants and choke off.   After all those trips to town, we just drilled holes in the other side of the intake cover and now it runs perfectly fine no matter what handed you are, left or right or how it brushes up against your pants as you run the saw.   I told my fix it guy this and we both stood there laughing till our sides hurt, neither of us had ever realized there were air intake holes in one side of the cover and it would do that, most are right handed just like he is and never have any problems with it, he told me after all those years, he'd never thought about which hand someone picks up anything with before or how they hold it while using it.   None of my crew ever noticed this while I was running it either, they are concentrating on the blade and nothing else, doing their job of keeping water going to where it needs to be.  Just something over time to make look back on and laugh about, thought some here might enjoy a chuckle over that one.     

thecfarm

Like I use to say at work,do not over think the problem. Something so simple can be so hard.  :D  I would always say you have 100 problems,90 of the solutions will be right in front of you,7 you may have to look a little harder,the other 3 you will really have to think and dig hard to solve.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

BARPINCHER

Randy you said you were mixing 2.5 gallon mix into a 2 gallon container....  I would start there before turning more screws.
Serving hunters and the hunted with science based; non-traditional resouce management methods

deerslayer

Quote from: BARPINCHER on January 08, 2013, 11:06:19 AM
Randy you said you were mixing 2.5 gallon mix into a 2 gallon container....  I would start there before turning more screws.

Not sure the mix ratio could account for the type of troubles he was having. People successfully use a lot of different mix ratios on a daily basis and putting a 2.5 gal mix in 2 gal of gas would be a ratio that many use.
Too many chainsaws, not enough wood.
Stihl, Husky, Craftsman, Mac, Homelite, Poulan. Some live here, some just passing through.

Randy88

Barpincher, we've always used the 2.5 gallon mix in a two gallon can, since new.  That has never been an issue before, that way we don't need to worry about under lubing the engine, that and I don't want to mess with one gallon mixes, and put two of them in instead of just one 2.5 gallon mix, sometimes we even mix up five gallons at a time and do it that way, but not very often.

But while on the subject of oil's, my dolmar cement saw calls for a synthetic oil mix, whereas my stihl saws don't, just how critical is it to use synthetic oil mix, and is it better than conventional mix, for use in my stihl saws? 

thecfarm

I use the husky 5 gallon mix to 4 gallons. I burnt up one saw mixing it to 5 gallons.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

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