what method do you use to tune your saw?

Arborist Forum

Help Support Arborist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

how do you tune your carb?


  • Total voters
    25
images
I tune by ear.
 
There is only one way to tune a two stroke engine and its my way. Not completely true. To explain to some one that has not been tuning engines their entire life kinda hard to do. About a year ago My former helper kicked over my jug of two stroke oil and never mentioned it. We get to a job site and I had to mix back up oil. Immediately the saws ran weird. I had to retune and adjust how I was mixing oil. Then checking the plug more than once to see if I was on track. I am one who has more than fifty years of experience. For some one who does not do this every day could be a problem. For the beginner they need to eliminate as many variables as possible and go through the process carefully taking each step with thought. Yes there are many upon many threads how to get ones saw four stroking. Thanks
 
I set the carb to get the saw running without dying. Roughly adjust low screw to get good throttle response and so saw is not running too rich. I have found that if the low end is set too rich, the saw will load up with fuel if you leave it sitting idling. If too lean, it will stumble when you hit the throttle. Adjust idle screw. Apply full throttle and richen H screw until saw is four stroking or hitting the limiter (often the two sound a lot alike). Put screwdriver in back pocket and start cutting some wood. Saw should four stroke (burbling sound) at full throttle out of the wood and then "clean up" or smooth out during the cut and be more of a scream while cutting. I like to have mine set where when I am cutting, I can lift the saw out of the cut a little and hear it four stroke and then go back to screaming in the cut. If it is screaming all the time, adjust H richer. If four stroking while in the cut, adjust H leaner. Once H is set just right and saw is cutting right, I'll look at the idle characteristics again and see if I need to fiddle with them anymore as the H screw does affect idle to some degree as well. If I have to do much fiddling with L, then I'll reevaluate H. By this point only tiny adjustments are being made and saw is done.

Whole process only takes a couple minutes.

Make sure to let saw warm up completely before finalizing adjustments.
 
I go strictly by sound (mild four stroking @WOT no load using the high speed screw, idle and transient using the low speed mixture screw, and then idle speed with the stop screw), I could care less how many turns in or out the screws are......
I also don't understand using OP's method of using low speed mixture screw at WOT conditions.....
 
I set the carb to get the saw running without dying. Roughly adjust low screw to get good throttle response and so saw is not running too rich. I have found that if the low end is set too rich, the saw will load up with fuel if you leave it sitting idling. If too lean, it will stumble when you hit the throttle. Adjust idle screw. Apply full throttle and richen H screw until saw is four stroking or hitting the limiter (often the two sound a lot alike). Put screwdriver in back pocket and start cutting some wood. Saw should four stroke (burbling sound) at full throttle out of the wood and then "clean up" or smooth out during the cut and be more of a scream while cutting. I like to have mine set where when I am cutting, I can lift the saw out of the cut a little and hear it four stroke and then go back to screaming in the cut. If it is screaming all the time, adjust H richer. If four stroking while in the cut, adjust H leaner. Once H is set just right and saw is cutting right, I'll look at the idle characteristics again and see if I need to fiddle with them anymore as the H screw does affect idle to some degree as well. If I have to do much fiddling with L, then I'll reevaluate H. By this point only tiny adjustments are being made and saw is done.

Whole process only takes a couple minutes.

Make sure to let saw warm up completely before finalizing adjustments.
Great explanation sir.

Sent from my moto g(7) power using Tapatalk
 
I got the method of adjusting L screw for highest rpm at WOT from here. About 4 minutes 9 seconds into the video is where it starts.

 
I use a tach to set max at 500 rpms under max rating and on the low side set for best trigger response and once that is accomplished set the idel screw for around 2800-3000 idles speed. Been doing it for years and hads lots of feedback how impressed the saws ran and longevity of them. YOu want a mix of chain speed vs. torque... Fast chain speed is worthless if you don't have torque and also an over lean saw is no good in the junk pile ready for a rebuild.



I had always adjusted my 2-stroke engines "by ear" and only just recently purchased a tach, specifically for my 4 chainsaws.

They were all pretty close to their max rpm's but just slightly above it. Ended up re-adjusting all 4 of them by slightly "richening up" the H jet so that they now max out at around 500 rpm below the manufacturer's max limit.

My lesson was:
Should've bought a tach years ago!

IMG_4129.JPG
 
I got the method of adjusting L screw for highest rpm at WOT from here. About 4 minutes 9 seconds into the video is where it starts.


This guy is just one of the many idiots that knows little about chainsaws but seems compelled to post his lack of understanding on U-tube.
 
funny thing is... the only saw ive ever adjusted, that would not get out of 4 stroke at high rpm is the 015L i just rebuilt
no mattert how carefully i adjusted the H needle..i could not get it to cleanly rev out..
so i leaned the L needle and ill be damned if it didnt cleanly revout of the 4 strokin
i was confused..so i reset it the way i always have with the H needle for the high rpm..because i didnt know how to react to that.

the problem is that when i set it the video way the low side is definitely a bit lean cuz i get that little sag once in a while when i hit the throttle
i cant get it outta my head that the actuator lever is set a bit to high...

this one has me confused, because ive never touched the low speed needle for high rpm..period
 
funny thing is... the only saw ive ever adjusted, that would not get out of 4 stroke at high rpm is the 015L i just rebuilt
no mattert how carefully i adjusted the H needle..i could not get it to cleanly rev out..
so i leaned the L needle and ill be damned if it didnt cleanly revout of the 4 strokin
i was confused..so i reset it the way i always have with the H needle for the high rpm..because i didnt know how to react to that.

the problem is that when i set it the video way the low side is definitely a bit lean cuz i get that little sag once in a while when i hit the throttle
i cant get it outta my head that the actuator lever is set a bit to high...

this one has me confused, because ive never touched the low speed needle for high rpm..period
How far out are the H and L from the stock setting?
 
Low factory is 1/2t open it is a 1/2t open

high factory is 3/4t open it is 1/2t open

This is what led me to believe the actuator lever was set pretty close to where it should be.. But maybe a bit high

The only thing that changed drastically after the rebuild is the compression.. Which went from 124psi to 187psi... Allota compression for this little saw.. But I guess thats not a bad thing

Before the rebuild the carb low needle did not have the described effect
 
Low factory is 1/2t open it is a 1/2t open

high factory is 3/4t open it is 1/2t open

This is what led me to believe the actuator lever was set pretty close to where it should be.. But maybe a bit low

The only thing that changed drastically after the rebuild is the compression.. Which went from 124psi to 187psi... Allota compression for this little saw.. But I guess thats not a bad thing

Before the rebuild the carb low needle did not have the described effect
do you have a tach?
 
I ordered one and waiting for it... cuz I decided that doing it by ear with 30 percent hearing loss just makes me a dumbass
 
I know the bottom is too lean with the leaning the low needle for high rpm.. Is also if hang the saw with the bar straight down it will stall unless I slightly fatten up the low speed
 
I know the bottom is too lean with the leaning the low needle for high rpm.. Is also if hang the saw with the bar straight down it will stall unless I slightly fatten up the low speed
Then turn it up till it holds idle then when you get the tach set the H rpm and if that dont work you didnt do it right or the carb is bad.
 
im leaning towards i didnt get the lever set quite right., but when i get the tach in, ill take your advice and fiddle with it some more.
as far as i know the two needles are the same shape too.
 
im leaning towards i didnt get the lever set quite right., but when i get the tach in, ill take your advice and fiddle with it some more.
as far as i know the two needles are the same shape too.
Did you look up that particular carb for the right needle lever setting? If you cant find it try tweaking it a tiny bit.
 

Latest posts

Back
Top