Mighty lite 26ss starts fine, but needs half choke for a long time. Runs for 10-15 mins. and seems to starve out. Acts like an air leak at carb or downstream. Any ideas?
I fixed one of these with the same problem yesterday. Theonly thing I've found wrong with this little saw is the carbs are terriblyadjusted from the factory and the mixture screws have a 'proprietary' head.they're a flat-topped cylinder with a notch in the side.
fortunately, there is a way to turn them. The insulation on a blue solderlesselectrical terminal will grip the outside of the mixture screws enough to movethem. you use the big end of the insulation you stick the wire into. doesn'tmatter what kind of terminal it is. splices work the best because theinsulation is long enough that you can grab on to it, but I just pulled theinsulation off a spade terminal and used pliers to turn it, as I didn't haveany splices.
I pulled both mixture screws out and cut a slot across the top with a smallfile so I can turn them with a flat head screwdriver. if you do this, only pullout one at a time, they need to go back in the respective seat they came fromor they won't seat properly.
I also took a file and cut an access notch in the air cleaner housing so Icould adjust the high mix while the trimmer was running. takes 10 seconds witha coarse round file, but a chainsaw file takes forever.
To set your mixtures, screw both mixture screws all the way in until theylightly seat. DON'T tighten them way down, just lightly seated.
now, look at where the notch is pointed and turn them out 1 1/4 turns. turningthem out (counterclockwise) makes the mixture richer. turning them in(clockwise) makes the mixture leaner.
now, screw the idle in a full turn so it idles very high (you'll turn this backout later, but this takes some of the frustration out of tuning the carb). You maywant to take the string head off, as it will 'run' at idle now.prime the trimmer (10 pushes if you haven't tried to startit earlier, 2-3 if you did. you can't over-prime, though, you're just removingair bubbles from the fuel pump)
put it on full choke, grab the throttle with your left hand and pull the recoiluntil it tries to start. if this takes 10+ pulls, turn the low speed jetout(richer, counterclockwise) 1/16 to 1/8 turn. you want to work in smallincrements, or you'll waste a bunch of time overshooting where you want to be.
once you get it to bump over full choke, back the choke off a bit. if you'requick you can usually do this while thetrimmer is trying to run fully choked. most likely you're still going to belean on the high mixture, so having the throttle pulled may kill the saw. if itseems like it's dying when the throttle is pulled, but not at idle, then you needto turn out the high speed mixture screw.Concentrate on getting the low speed jet set so it will idlewith the choke off and the throttle off first. Once you get it so it will idle unattended, you can startbacking the idle speed down. From there, you can adjust the low speed jet whilethe saw is idling. Start by turning it leaner in small 1/16 turn incrementsuntil the speed picks up. If this kills the saw before the idle picks up, youhad it a bit too lean to start. if you get the idle to pick up, richen up themixture 1/16 turn. You want to be just richer than where the speed picks up. Ifthe saw died before it picked up, richen it up 1/2 a turn and start it again. Leanit out as before until the speed picks up, then richen it up a bit. This may sound time consuming, but you can stick ascrewdriver on the idle screw and gently turn it in continuously, so itactually goes pretty quickly once you get the saw to idle.Now that you have it idling nicely, you can adjust the highspeed jet. Start by 'blipping' the throttle. If the trimmer bogs down, richenthe high mixture. Now, if you're WAY rich, it will behave similarly, but with thistrimmer, that's pretty unlikely if you're starting at 1 1/4 turns. One way youcan tell if you're way lean or way rich is with the choke. If it will run fullthrottle with the choke part way on or if it picks up faster with the choke partway on, you know it's too lean. The choke richens the mixture up to compensatefor the gas condensating in the throttle bore when the saw is cold. If thechoke kills it, you're too rich.if it will run, then you can adjust the high speed similarlyto the idle. A leaner mixture will have more power and spin a higher RPM to apoint, but it will also run MUCH hotter and an excessively lean mixture willseize the piston. So, you're going to want to err on the rich side. You'lldefinitely be able to hear the rpm change, a way rich mixture will be almost 1/2the speed of the proper mixture, and a too lean mixture will sound like thetrimmer is going to fly apart at the seams. Once you get the high mixture to the point that you can grabthe throttle and the saw will pick up to max speed in less than a second, thenyou're ready to cut something. You may need to adjust the mixture leaner for abit more power if it bogs down in normal grass trimming, or if it is running througheverything including big weeds without changing speed, you should probablyrichen it up. This is NOT a big trimmer, it SHOULD bog down a bit if you loadit up.A final note about this trimmer, I never could get it to acceleratesmoothly from idle to high speed. It lags for about 1/4 second just above idlethen it picks up as it should. It runs fine once it gets past that hesitation,you can vary the throttle to be delicate around things, ect, but if you let itidle, it does hesitate when you pull the throttle again.I was pretty surprised how well it ran once I tuned itthough, this one is my boss's and he's got a 3-blade cutting head on it that'sa lot heavier than the string head and it will spin it just fine. It will cutdown saplings to maybe 5/8".Good luck!
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