Tip & How-To about Garden
Specifically; 2 cycle homelite chain saws; and relevant to other brands also.
Before you can adjust your high & low speed jets ,you must first unscrew the plastic top cover and lift it off. where you have seen the holes to adjust the high & low speed jets,
marked hi & lo in the plastic cover,you will find a rubber or plastic boot that you must pull off to expose the high & low speed needles. after you have removed the boot, you will see plastic needle jet locks that will prevent you from turning the jets more than 1/4 turn,
if even that much.
Now--you need a small pocket screwdriver with a tiny flat blade to release a plastic locking clip that holds the needle jet lock onto the needle.
It is like releasing a plastic tie lock stripe used for holding wires together (as well as many other things).
when you release the plastic tie lock type clip,the needle jet lock circle will split apart into two segments and can be removed allowing you to finally be able to adjust or even remove and spray carb cleaner, in case of the jet seat being clogged with dirt.
This has to be done to both the high and low speed jets before adjustment can begin.
save the plastic needle jet lock parts because you will need to reinstall them when the adjustments are done.
THey will hold the new adjustments from moving as the engine vibrates.
before begining hi & lo speed adj. & before starting the chain saw, make sure that the chain break is off and that the chain tension is properly adjusted.
Test by manually pulling the chain that it turns freely.
CAUTION: be careful not to cut/slice your fingers when manually turning a chain. I adjust a lot of chains,every week & I still cut myself, once or twice a year.
First, before pinching the chain between your thumb & index finger, wipe the saw dust & oil off the chain with a paper towel or shop cloth [shop rag].
NoW, look to see where the chain cutting teeth are and pick a spot as far away from them to pinch the chain between your thumb & index finger at.
REMemBer that if your fingers slip that they can slide into the cutting teeth and bleed,
quite a bit. Usually,this only happens on a chain that is too tight, but can also happen when you dont pay proper attention to what you are doing.
if the chain is too tight it will turn hard and that is a bad thing
because it will wear the clutch and bog down the engine and strech the chain out ,unnecessarily.
after you are sure that the chain moves easily, clean off the air filter some because a clogged air filter is like having the choke on.
reinstall air filter, take out spark plug, put on a soft wire wheel on your electric grinder to clean it ,regap according to spefication and reinstall plug.
NOW , we know that the engine is ready to run if we can only adjust hi & lo speed jets.
Note: you dont have to accually do chain retensioning,the air cleaner & the spark plug if you already know that it is all ok, but you do have to release the hi & lo speed needle locks.
NoW start your saw as you normally do and let it warm up for 3 or 4 minutes.
You will be ready to do adjustments now.
FOR THE NEWBIES-who never did it before. I teach you the difference in engine sound
from too rich towards too lean.
too rich is when you go counterclockwise, turning the low speed jet too far out, unscrewing the needle away from its seat.----This makes the engine loose rpm and
blub,blub,blub. Some call it 4 cycling, but the engine blubs as it looses rpm and my stall.
I teach too rich first, because it wont hurt your engine. and i teach the low speed jet first, because it wont hurt your engine either.
HowEver, the high speed jet being too lean ,for more that 20 or maybe 30 seconds will ,overheat your engine and then seize your piston and maybe burn a hole through your piston.
If you are running too lean, release the throttle , let the engine cool and turn the high speed needle out ,counterclockwise at least 1/4 turn.
when you are too lean, your engine does not get enough oil,runs hot, then overheats, then siezes the piston, throws a rod or burns a hole in the piston.
You already know that turning either the low speed jet or the high speed jet out[counterclockwise] ,unscrew-- makes the engine loose rpm ,then blub and then stall.
Turning the low speed jet in [clockwise] screw down tighter will lean the engine, rpm will increase until it peaks and then drops off rpm. when you get to peak rpm, you are already too lean and starting to overheat and underlubricate. you begin loosing rpm because of not enough oil and the resultant high heat of increased friction.
ReMeMber- a two cycle gets its oil from the gas ,so not enough gas [lean out the engine] means not enough oil. Thats why you cant run lean more that 20 seconds
The LOW speed jet has to do with starting and idling of the engine as well as acceleration from idle to around 1500 rpm where the high speed jet begins to take over.
You unscrew the low speed jet until it starts blubbing and begins loosing rpm and then start screwing it in and listen for rpm increase, when you get to peak rpm , you are already too lean any further screwing in will result in a rpm drop off. so now ,unscrew
until you again hit peak rpm and unscrew 1/4 to 3/8 of a turn richer. You are on the rich side of being just before peak rpm.
This,The above--- is done with the engine idling or with the idle screw set below 1100 rpm. we are finding a good low speed seting where the saw idles at a low speed rpm but not at peak low speed rpm. This is a no load seting and you are not goosing the throttle.
Next is to see if the low speed jet will give good acceration up to 2000 rpm. Start by decreasing the idle speed to just below where the chain tries to start moving. THat is the best setting for the idle speed. You dont want the chain moving when the saw is idling on the ground with no hand on the trigger. However,you may have to set the idle a little
higher with a difficult to adjust carb and put up with a moving chain on the ground ,WHICH YOU CAN WALK INTO AND CUT YOUR FOOT,ANKLE OR LEG .
That is dangerious and not recommended.
If you are having trouble with the low speed jet accelerating,try richening,screw out by
1/4 or 3/8 trun. rich should give the extra gas needed to accelerate. try jazzing the gas to see how it accelerates. you may have to go leaner[screw in] back to peak rpm and then
rich unscrew until the rpm drops just a bit off of peak on the rich side.
now , low speed and high speed interact, because low speed provides the gas to accelerate up to the rpm where high speed jet should be ready to take over.
high speed jet should be adjusted at 1500 to 2000 rpm, but run at those speed only 20 or 25 sec & then idle for 40 sec-to 60 sec to cool off your overheated & under lubricated engine. the low speed jet will restore some lubrication and lower the heat of friction.
I am refering to the high speed jet being set, temporarly & very briefly to the lean side of peak rpm, only for adjustment purposes.
during your 20 sec high speed bursts you should find peak rpm, go past it to hear what too leans sounds like and[ unscrew] [ rich] to where peak rpm just drops off. that should be about 1/4 to 3/8 turn rich [out] unscrew from peak rpm.
Next try a 15-20 sec full throttle test. There should be no blubbing. if you hear blubbing , you need to go a bit leaner.
You are trying to find the sweet spot where the saw runs the best.
You always have to be on the rich[unscrewed] side of peak rpm, but no blubing on high speed and no blubing on low speed.
bulbing = 4 cycling , low rpm = not developing proper power .running too rich.
Tinny wineing--high rpm,ying,ying,ying = too lean, most likely will sieze engine.
It is an art, and takes experience,pacience and the knack, as you are jiggling between low speed & high speed jets to find a smooth and powerful run up of rpms from low to high.
The final test is to put the saw on a log and cut some wood. You may need to richen for power to cut through the wood, but also pull the blade out of the cut and check no load high speed running.
all of this only takes only 15 or 20 minutes and after you have done it several times ,it will probably only take 6 or 8 minutes.
get low speed to run good & then get high speed to run good and then test under load in a log.
stay on the rich side of peak rpm.
NOW---reassemble needle lock,boot & cover in reverse order.!
Note: if you decide to take high & low speed needles compleatly out in order to spray
the high & low speed seats with carb cleaner, know that the needles are specific to their
respective holes and are not interchangable.
That means put all the high speed jet parts in a baggie a paper that says high speed.
you will take off the jet ,a spring,a flat washer or an O ring , or both.
put the low speed jet & parts in a baggie with paper that says low speed.
make sure carb cleaner is all blown away with compressed air and blotted up with facial tissue because carb cleaner burns like gasoline.
The[ rule of thumb] is to screw both the high speed and the low speed jets all the way in
until they seat firmly ,but dont screw them in so hard as to deform the seats or the needles. then unscrew the needles 2 compleate turns and this will be the initial starting point for begining the hi & lo speed adjustments. This is surely on the rich side and you will probably get blubing, but it may be enough to get you running raggedly.
I think I remember something about 1&3/4 turns out, but a cant remember what year that was or what engine that was. There is a reason why I am retired at 65, after all.
the rule of thumb does not work for all saws,many will want a different setting.
ANOTHER WAY is to count the # of turns or 1/4 turns from where the needle jet is before
any unscrewing to where it is fully seated. and that should get you back fairly close to where you started from.
I was told that owner's manuals give the exact number of turns
out from the seat for the initial starting point.
I was also told that some saws give that information on a sticker on the saw.
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