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Re: Carburetor adjustment on McCulloch Mini-Mac 30
Turning Hi & Lo mixture screws in leans the mixture,out rich-ens it.turn the T screw in to increase idle speed the chain should slowly come to a stop at idle [chain brake off] adjust Low needle first until it accelerates smoothly then Hi needle for best 'revs'.then Lo again if necessary if you don't know where they were set before,start w/ screws 3/4 to 1 turn out from a lightly seated position
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Re: Carburetor adjustment on McCulloch Mini-Mac 30
You got it almost right. The screws go in to lean and out to richen. Idle will be in to increase and out to lower.
Always adjust the high speed needle first. Slowly lean till you hit top rpm then back off 1/8th turn.
Low speed needle, slowly lean till the engine stops burbling on exceleration. If you go too far the engine will stop quickly when the throttle is advanced. Back it off a little and try it again.
Back to the high speed needle, adjust again.
NOW adjust the idle screw.
Time to adjust the needles again.
This procedure may need to be repeated as the engine breaks in. Most small industrial engines need a minimum of 5 gals through the engine to break in.
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Hi williamsc32... Before you remove or try to adjust your low and high speed jets you should always count the number of turns it takes to lightly seat the idle mixture screw and high speed needle adjusting screws. Be sure to write the number of turns down on a piece of paper so you will know how many turns from the seated position to open the jets when you go to reinstall them, or if you remove them for cleaning or replacement. If you have aready tried to adjust them then the adjustments below should get it running for you for final adjustment when warm. Normally you will adjust your idle jet to 1/2-3/4 turn open from the bottom seated position. Then you will re-adjust the low speed of the engine when the engine is warm by turning the idle screw in or out till the engine runs smoothly at idle speed, around 1200 RPM. The high speed jet is adjusted to 1 1/2- 1 3/4 open from the bottom seated position, after the engine is warm. Then re-adjusted by turning the High Speed jet adjustment screw in or out till the motor runs smoothly at high speed. Alway use the "lightly seated" method if you have not changed the screw settings. Please take time to rate me Bud
The idle adjustment screw will probably have a spring on that screw and
will push directly on the throttle linkage. You just adjust this screw
until the engine idles like you want it to. I believe on saws, they have
to idle to where the clutch will not engauge when the engine is at
idle. As for the mixture screws the low speed screw (L) you adjust when
the engine is at idle, the high speed screw (H) you adjust while the
engine is running with a good bit of throttle. Once you get the idle
speed where you like it, then all you have to worry about is the mixture
screws. When adjusting the screws, just listen to the engine, to much
one way and the engine will run rough and sputter, to much the other way
the engine will run rough and maybe start hunting (reving up and down).
One thing to check on these small 2-strokes is that the air filter and
the muffler are not clogged cause if they are, then you would be having
to adjust the carburetor to make up for the air restrictions that these
two problems can cause which would mean that the carburetor isn't
actually adjusted perfectly.
Hi tracey4t, I will try to give you a few suggestions. You might have to adjust the idle speed screw that is located top on the carburetor where the throttle cable is hooked. There you will see a screw with a spring that if you turn it clockwise you increase the idle speed, and if turned counterclockwise will decrease the idle speed. It could also be a carb adjustment of the low or idle speed mixture needle, if there is one on your carb. In the past few years, most carburetor makers have eliminated 1 or 2 of the adjust needles. These ports are now inside the carb and are fixed, not adjustable. If you have a low speed needle or the 2 needle adjustments, they are positioned about the center of the carb. They have springs on them. They are marked by L or H on the carb body, and the low one is usually the one closest to the engine. Turn it out or counterclockwise to add more fuel to the mixture. Do this 1/8 of a turn at a time while the engine is running. The engine should turn faster if that is what is needed, keep doing this until max. RPM. If that does not increase the idle speed, try turning it the other way. If that does not work, then it could be a number of things, but I think this will work. Hope this is helpful to you. All the best and good luck. Denis.
Make sure the air cleaner is clean. Turn both jet needles CW to stops (lightly), then back each out CCW 1-1/2 turns. The engine should start and run--allow to warm up, then pull the throttle full on. Turn the H needle CW until the engine starts to speed up, but still 4-stroking. Final adjustment is when the engine 4-strokes no load, but immediately 2-strokes when cutting. Release the throttle and adjust L needle CW until the engine idles fairly well, but will allow the engine to follow the throttle. Adjust the idle speed screw so that the chain doesn't turn and the engine continues to run. Hope this helps!
Which idle screw are you adjusting, the idle jet (L) or the idle speed screw which sets the throttle stop position. Adjust the idle speed screw while watching the throttle stop position so that it is pushed away somewhat. Adjust the L jet needle CW to stop (lightly), then back out 1-1/2 turns CCW. This should allow the engine to idle after warm up. Turn the needle CW while running for better idle, yet it should allow the engine to 'follow the throttle'. If this doesn't work as described, then check the fuel filter, air filter, and muffler for plugging. Check the fuel lines for decay or other damage. You may need to remove the carburetor and clean it inside and out with spray carburetor cleaner. For further insight, go to: http://www.drystacked.com for a 12 page article on Walbro brand carburetor theory and troubleshooting. This material applies in general to other brands of carburetor as well. Hope this helps!
Check the fuel filter, air cleaner, and muffler for plugging. Check the fuel line for decay or other damage. Make sure you have fresh fuel mix in the tank (40:1) using a modern synthetic oil made for saws. If the above doesn't help, you will need to remove the carburetor, clean it inside and out with spray carburetor cleaner and check the lower chamber diaphragm for flexibility--no holes or cracks. If the two jet needles have been disturbed, turn both screws CW to stops (lightly), then back out CCW 1-1/2 turns each. This is a basic setting which should allow the engine to start and run. Start the engine and allow to warm up, then pull the throttle full on and adjust the H needle CW until the engine starts to speed up, but 4-strokes. Correct adjustment is when the engine 4-strokes unloaded, but immediately 2-strokes when cutting. Release the throttle and adjust L needle CW for better idle, yet allows the engine to 'follow the throttle'. Adjust idle speed screw so that the chain stops turning, but the engine continues to run. Hope this helps!
Try turning the L needle CW to stop (lightly), then back out CCW 1-3/4 turns. Turn the idle speed screw CW about 1 turn. Start the engine and let warm up. Set the idle speed screw so that the engine keeps running but doesn't pull the chain. Turn the L needle CW until the engine runs fairly smoothly, yet allows the engine to 'follow the throttle'. Make sure the H needle is adjusted at full speed for 4-stroking, but immediately 2-strokes when starting to cut wood. If the above idle mix (L) adjustment doesn't help, you will likely need to clean the idle jets within the carburetor. Hope this helps!
The standard setting on needles is to screw them in all the way and then back them out 1 and a half turns.
You need to set the mixtures for the carburetor. You will find a Low and High adjustment screw. turn the low adjustment screw out. You will notice that the rpms should start increasing. keep turning it out until the rpms start to drop then turn it back in a quarter of a turn. You may need to readjust the idle speed so the chain doesn't turn during idle. Do the same for the high adjustment screw.
The H is for high rpm (Main mixture) and the L is for Low rpm (Idle Mixture). First turn in both screws all the way in and then turn them both out 1 and a half turns. Pump the primer bulb if the equipment has one. Start the engine, once it is idling, turn the L (Idle Mixture) screw out (counterclockwise) from the preliminary setting until the engine speed decreases (rich). Note the position of the needle. Now turn the adjusting needle in (clockwise). The engine speed may increase, then it will decrease as the needle is turned in (lean). Note the position of the needle. Set the adjusting needle midway between the rich and lean settings as in the picture below. Don't touch the throttle during this procedure. Once you have found the best idle speed for the engine then you need to adjust the high rpm. This process is the same as with the idle rpm process but you need the to hold the throttle wide open while you are adjusting the H (Main Mixture) needle on the carburetor.
Before you start check the status of your choke. One that is stuck on will cause a high idle. If the choke checks out, proceed to the following:
You should have what's called a 2 needle carburetor. A larger screw adjustment for idle, and a smaller for high speed.
Start by adjusting your low speed (idle) needle until you reach the desired idle. I prefer about 850rpms. Do this with the engine running and adequately warmed so that your adjustments are not thrown off by the automatic choke.
Next slowly open up the high speed needle. As you open it your idle speed will gradually increase. Adust it in 1/8 turn increments, pausing after each adjustment to allow the changes to take affect. Keep opening it until you stop increasing your rpms, then take it back 1/8 of a turn.
Next readjust your idle mixture screw so that your idle is back down to 850rpms.