CARBURETOR TUNING: Single Adjuster Screw Setting EXPLAINED!

* VISUALLY EXPLAINED
Carburetors with a single adjuster for high RPM (often called the high-speed or H adjustment) and a hidden low-speed adjustment screw at the top are typically designed for simplicity and ease of use. These carburetors are often found in small engines, such as those on lawnmowers, chainsaws, or other outdoor power equipment. Here's how they work:
High-Speed Adjustment:
The single adjuster, often a screw or a small knob, is used to set the air-fuel mixture for high engine speeds, typically wide-open throttle (WOT) or full power. This adjustment controls the amount of fuel and air mixture when the engine is running at high RPM.
Hidden Low-Speed Adjustment:
The hidden low-speed adjustment screw is typically located on the top of the carburetor, underneath a cap or plug. It's hidden to discourage users from tampering with it, as it can affect the engine's idle and low-speed performance.
High-Speed Operation:
To adjust the high-speed setting, you typically run the engine at full throttle and then adjust the single visible screw to achieve the desired RPM. Turning the screw clockwise generally leans the mixture (more air, less fuel), while turning it counterclockwise enriches the mixture (more fuel, less air).
Low-Speed Adjustment:
The low-speed adjustment screw, when accessed, can be used to fine-tune the engine's idle and low-speed performance. You might need to remove the cap or plug to access it. Adjusting this screw can help with smooth idling and acceleration when the engine is running at lower RPM or transitioning from idle.
Caution and Considerations:
It's essential to make small adjustments and monitor the engine's performance closely. Adjusting these screws improperly can affect the engine's operation and potentially lead to issues like poor idle, stalling, or running too lean or rich.
Regulations and Emissions:
Keep in mind that tampering with the carburetor settings, especially in regions with emissions regulations, can lead to non-compliance and legal issues. Manufacturers often set these carburetors to meet emission standards, and altering the settings may violate those standards.
If you find that you need to adjust the low-speed screw, it's a good idea to consult the owner's manual for your specific equipment, as it may provide guidance on how to access and adjust the hidden screw. Additionally, pay attention to local regulations and emissions standards when making adjustments to small engine carburetors, as non-compliance can lead to penalties.
For some FREE Printable Download help Leaflets: www.therepairspecialistonline...
TIMELINE:
01:16 - How to Adjust a Carburetor Single Adjuster Screw
02:00 - Adjusting the Carburetor Fuel Screw -Explained
02:24 - Turning the Adjustment Screw Clockwise - Effects on Engine
02:57 - When a 2-Stroke Carburetor is too Lean
03:38 - Turning Adjustment Screw Anti-clockwise too far - What happens!
03:50 - When a 2-Stroke Carburetor is too Rich
04:22 - What is engine Flooding? - Explained!
04:50 - When the Fuel Adjuster Screws are set correctly
I really hope you find it useful.
Many thanks indeed
Craig Kirkman (Owner and Creator of the 'The Repair Specialist' Channel) carburetor adjustment.
The images in this video are Copyrighted!
Please check out my amazon shop. I have recommended some useful items from Amazon below. I guarantee you that these items are the sorts of things I use on a daily basis so I know they are good. I have to be careful in recommending products because I have my name and credibility at stake. So I will only recommend good products. www.amazon.co.uk/shop/therepa...
#CarburetorAdjustment
#SmallEngines
#HighSpeedAdjustment
#LowSpeedScrew
#EngineTuning
#OutdoorPowerEquipment
#CarburetorSettings
#MowerMaintenance
#ChainsawTuning
#HiddenScrew
#LawnEquipment
#EnginePerformance
#DIYMechanics
#SmallEngineRepair
#CarburetorTips
#MechanicalAdjustments
#EngineIdle
#CarburetorSynchronization
#OutdoorPowerTools
#SmallEngineMaintenance

[@gbt722]

3:29 for the most accurate human made noise of an engine bogging down ever.

[@qxrpze4725]

Haha too good

[@gumbilitous2804]

It really is

[@seanclancy3972]

20 years working on small engine's,this is by far the best explanation for even the novice.

[@TheRepairSpecialist]

Thank you so much for your nice feedback. It's comments like yours that motivate me to continue making these videos. Craig 😀👍

[@henrymensink8761]

My son bought a new Jiffy ice auger a few years back and it never did run right. Thanks to your video on how the bulb type carburetor works I was able to determine that the intake gasket was blocking the the little vacuum hole going into the crankcase. Thanks for the awesome explanation. 👍👍👍

[@billysherling6106]

everybody, i mean everyone, took the time to search this video again just to post Thank you, thats how appreciative we are....!!!! so take a bow.... well done

[@billysherling6106]

o my god, finally, this was THE absolute best instruction video !!!!! THANK YOU.

[@battheman777]

THANK YOU! I finally understand the internal workings of my carburetor. I have a few more ideas for my repair attempts now.

[@bidders77]

another top notch explanation. very helpful. thanks

[@luked1xon]

Fantastic Vid, Thank you for taking the time to make it.

[@neonboy22]

don't forget the idle mix is set by removing the plastic plug on "tip" of the barrel. There is a tiny flat blade screw inside which sets the orange vertical height in your diagram. Brilliant diagram and explanation thanks.

[@xx3868]

Hi, how do you set both screws as the main one will effect the idle one two. So do you run full throttle and find the mid point between too rich and lean for the main screw, THEN idle and adjust the idle jet slightly? Of course if you rich this a little , there will be a touch more fuel at wide open throttle too? Tricky?

[@JasonDainter]

I just loved every bit about this video. Thanks

[@RCTanksTrucks247]

Excellent video mate. Thankyou

[@SuperAsjc]

Great instructional video, Exceptional presentation, thanks.

[@yugorc9386]

Thanks for the great video's I learned a lot from your videos

[@joedap1699]

after days of looking for videos thank you soo much i appreciate you 6years later its still does well

[@robbiecouch9897]

Thanks for the clear explanation.

[@jmdds]

Excellent video explanation.Well done.You deserve a street corner named after you.

[@Bigeye291]

Thank you very much for the knowledge, perfect explanation

[@callmemxmba7857]

Thanks this helped me with my 2 stroke scooter

[@rsdevarapalli]

Thanks for sharing. Nice explanation.

[@alanlake5220]

Thanks a very good video from you as always, and easy to understand excellent diagrams

[@rudorc]

👍👍 very clear and smooth explanation.

[@johnvitz310]

Thanks,,,,my screw was way too loose,,,,I turned it in 3 turns,,now only use half the fuel I did before and it runs great. I wish I knew how to produce these brilliant imagines. Worth a thousands of words.

[@jovicastojanovic177]

Odlicno objasnjenje

[@ColdWarVet607]

Fantastic ! Thank you, You the Man!!!!! Im going to watch the full version and many more even if I dont have the equipment because I love this stuff. Just got my Earthquake auger started after a zillion tries but it has near no power and I have to hold the throttle down or it will stall. Im guessing from watching your video the needle needs to come out just a bit. I put a new carb on it, new plug, new lines, so hopefully this tweak makes it dig like it Badger.

[@RogerHalsham]

Many thanks for this, I've just got my leaf blower going like the clappers now. I just wish I hadn't got rid of my old colour tuner plug.

[@Jim-ie6uf]

Excellent explanation.

[@bdog8858]

Thank you for the tips, i needed them to get a two stroke i have running better

[@bimalnandana9679]

Highly appreciate your service .Thank you very much for knowledge sharing .It's very helpful to understand .❤👍

[@s1914]

Really a top quality vid 👍

[@rayrenzi4860]

Excellent explanation

[@Boymandudeguy]

Thank you for this incredible slice of information in human history.

[@TheRepairSpecialist]

Thank you so much for your nice feedback. It's comments like yours that motivate me to continue making these videos. Craig 😀👍

[@toddbarton2014]

You explain so well that even I can follow 😂. Thank you.

[@hectornagano1819]

Very educational.

[@philipoakley5498]

Excellent. Actually solved my problem with a strimmer that wouldn't start properly, and even when it did it wouldn't idle. knowing which way to turn the idle screw, and which end of it's range we'd expect it to be was essential info to solving the issue (lots of pull starts to get to the optimum point). Many thanks.

[@TheRepairSpecialist]

Thank you for your kind feedback. 👍

[@coles591]

Excellent video

[@caryfoster3379]

Very clear explanation and the diagrams helped a great deal, thanks for all the time and effort with production!

[@TheRepairSpecialist]

Thank you for your kind feedback. I really appreciate it. Craig

[@Lovejhand1]

This video is very helpful

[@parkerbarbietinker9655]

Superb tutorials in every way.

[@TheRepairSpecialist]

Thank you for your positive feedback. I really appreciate it. Thanks again. Craig

[@fa046192]

Very GOOD , thanks , best explanation.

[@elclonado]

Working like new my low mower. Thank you.

[@Psykologisss]

Excelent video. Thanks!

[@TheRepairSpecialist]

Thank you so much for the nice feedback. I really appreciate it. Craig

[@alphaomega8998]

Just found your video channel with this vid. Just wanted to say thank you for finally answering questions about these mechanisms. So many videos out there that drag with misinformation.

[@Diohernandez]

Another incredibly well explained video!

[@TheRepairSpecialist]

Thank you so much for your nice feedback. It's comments like yours that motivate me to continue making these videos. Craig 😀👍

[@emmams5]

@@TheRepairSpecialist, when you screw the mixture screw all the way in till it's lightly seated, how many turns out would you recommend to get it running without any fine tuning.

[@alanzanotti]

Hi Friend Craig Kirkman ...Great explanation.. I subscribed to your channel 😊Grande abraço...

[@stevewilliams1197]

Excellent, graphics were done very well.

[@TheRepairSpecialist]

Thank you kindly! Craig

[@b8a33021]

GOOD EXPLANATION

[@paulmagee8171]

Great vid

[@willvandermeer4733]

Thanks man!

[@JuanPerez-rr2fp]

Cuantas vueltas a la izquierda se le dan al tornillo? Gracias por su respuesta. Esta muy bueno el video felicitaciones.

[@rspeed5008]

THANK YOU!

[@Ptomify]

Watched ur video solved my engine bog prob. So helpful

[@TheRepairSpecialist]

Thank you so much for the nice feedback. I really appreciate it. Craig

[@thewordfulloffun8598]

I have followed you for some time. The videos were really helpful to adjust the carburetor all by myself. When you adjust the idle crew what is the position of the mixture should be.

[@tonyd6821]

Thank you for your professional explanation how the carburetor works ....I have a Bolen Wipe Sniper single screw adjusting I have cleaned the carburetor put back and not knowing how many turns the screw as to come out it does tempt to start on 1/half turn out but then stops ....Could you please give an idea where the problem is ?

[@GlenB1963]

Thanks excellent video and explanation 👍

[@TheRepairSpecialist]

You are welcome! Thank you for your kind feedback. Craig 👍👍👍

[@Mr109off]

The most complete explanation I have found.Thank you. How about Initial setting of the carburetor when cleaned, all screws were being taken out then reassembled? I know that the bottom screw is 1.5 to 2 turns , but the other, upper one, that from the throttle adjustment? And how to set the best idle ? Thanks.

[@ColdWarVet607]

Came back again to say thank you once more. I got my auger dialed in to real power, and wouldnt have got it even running if not for you. Problems was wouldn't start and when it finally did after shooting starting fluid in it and holding down the throttle, it didnt have much power. If I let go of the throttle it would stall. So I tweaked the adjust screw CCW first and eased off the throttle, still stalls. Then tweaked more CCW and found as I did I had to hold throttle open more. So I went to the CW dir and after 1/2 turn I could start to let go of the throttle although it had not real power. As I started making another 1/2 turn CW I could hear the idle rpms picking up and it sounded great. I was able to drill a big hole in the ground. Thanks again!

[@rattlin9194]

Fantastic vid, from this I'm going to see if finding and turning my screw in a quarter will stop my Honda spitting fuel out into the air filter 🤔👍 thanks

[@bryanmicklewright8600]

Thanks hellped alot

[@jorgemenjivar6526]

thank you for your videos..really educative.. but I have a question..my weed eater only stays on for a couple seconds and shut off.. could that be a wrong adjustment on carburetor? it sound like it round out of fuel.

[@tombendstrup6516]

Thanks for your perfekt videos, but i got and issue with my hedge trimmer. I've just change the carbureator with a new original one, but now its die right after powered up. How shall the single screw adjustes? Shall I fully close it clockwise, and then turn anti clockwise once before starting the engine? And what about the idle screw? Best regards

[@antonio_alfa]

Very helpful. Thanks a lot ! It is a Husqvarna 143II. After a complete carb cleaning, as preventive maintenance, I couldn't restart. It barely maintained idle with 100% choke. Every time I opened the choke, the engine died (too little fuel). I tried mix and idle screws in all positions...nothing happened. At the end I had to adjust the position of the needle in the venturi, by one complete turn counterclock wise (upwards) and it is working fine now. Is it normal ?. Do adjustment shims exist for this screw? in order to adjust this needle?

[@daza2838]

This video explained a problem I had with a new carby that just happened to be the bigger brother of the carby I needed. That meant the hole for the pump mech wasn't lineing up, a simple fix with a spacer made for the offset, thanks so much !!

[@hunterh1033]

I was having idle issues the other day, I got the engine running and in real time was messing with the mixture screw. I got it to the point right after it was about to die out and would now idle and left it. Took it for a test drive for about 20 minutes and it ran great. The next day, I gave her one pull with choke and she started and I immediately pushed the choke back in, it died. Never could get it to start again and it was badly flooded, it made no sense to me. Is it possible I have the mixture screw too loose and that flooded it? Perhaps having it so loose is masking some other idle issue? Thanks for the great video!

[@deviprasadb1829]

Thanks a lot 🤩🙏🏻

[@TheRepairSpecialist]

Thank you so much for the nice feedback. I really appreciate it. Craig

[@ronsbeerreviewstools4361]

Very good educational video .

[@BANKPLAY212]

I bought a Bladez 60cc Street Competition standup scooter from a guy 5 months ago, and the scooter was completely apart it took me 3 months total to put the scooter back together. I rode it to work a few times, but today, i had an issue. The scooter acts like it wants to go so bad, but it hesitates when i give it full throttle, I noticed that my tomb screw keeps getting loose after a few minutes of me riding but in this carburetor that i have install, it do not have the spring on the screw so can that be the issue. 2003 60cc Bladez Moby XL Comp Stand up Scooter

[@joevee72]

Craig, can I put a shutoff valve in the fuel supply line of a 2 cycle motor with two fuel lines, one supply and the other is return. The fuel tak is mounted below the carburetor. I have a southland, 43cc walk behind weed wacker. I'm concerned because the fuel line is under vacuum to "suck" the fuel up into the carburetor and I don't want to stress the thin gasket material inside the card.. Thaks, Joe V

[@mantrapjicker]

Hi, can you disassemble the throttle body to replace the seal

[@federicosaez6022]

Hi Craig, thanks for such a good channel. Really helpful and in depth explanations. I was having a problem with a trimmer with this exact same type of carburetor. It will start and idle but it bogs down when pressing on the throttle. But pressing gradually on the throttle and at the same time opening the adjustment screw will rev up and run perfectly for as long as you want. So I assumed there was a problem with the fuel not being sucked out properly and increasingly as the air flow increased. I put everything apart but didn't find anything wrong with the needle o anything else, so I clean everything and put it together and back on the trimmer. And it run perfectly after tuning the adjustment screw. So I fix it, but don't know exactly how.

[@TheRepairSpecialist]

Brilliant. I'm pleased you fixed in the end. Thank you for the nice feedback. Craig

[@federicosaez6022]

Actually, I was wondering if you could tell me what do you think the problem was?

[@madyottoyotto3055]

@@federicosaez6022 I can't say to what the problem was so much info needed for that However This is not a single mixture screw carb The hi flow mixture screw is hidden extremely well so please don't look down on the content creator It took me years to find this guy If you look at the top where the throttle wire connects to the throttle barrel there is a brass collar/screw in the top of the throttle barrel It has a rubber tube hiding underneath it is the hi flow mixture screw Also this video demonstrated that the so called air/fuel mixture screw has NO POSSIBLE WAY to adjust the air flow meaning its the lo flow mixture screw not a air/fuel mixture screw So Lo flow mixture screw Where he shows the fuel/air mixture screw is Hi flow mixture screw In the top of the throttle barrel opposite side of carb to the prime bulb Look for the brass collar/screw in the centre of the throttle barrel behind the rubber tube in the centre of the brass collar/screw Air mixture screw Is the idle screw valve after the initial setting the air flow is naturally limited Hope this helps

[@timothywooding4424]

How many turns out should the mixture screw be as I can't get my 2 stroke running right? It runs for about 30 seconds or dies instantly if I give it throttle?

[@nimotaranger8252]

hi buddy !! my bike had a bogging problem until i shut off the air screw completely and it ran without a problem...is it safe for me to keep riding or it could damage the engine ?

[@MrFuselier08]

How many counterclockwise i turn to get it just right?

[@russgordon9327]

Which of the two scenarios would cause back firing?

[@henrybrown6023]

I have a brass switch on mine and not sure what it does. any tips?

[@fernrjf]

I have a 2cycle generator from Harbor freight with 800 to 900W. Would you have information on setting the timing of the generator I have had a problem on mine, which I believe is the timing. It jerks the starter cable out of my hand when starting. It may be trying to fire be it is supposed to. Thanks! Regards, Robert Fern

[@acostin4004]

Why would a strimmer carburettor need adjusting its set to factory settings so why or how would it need adjusting the screws cant move on there own im attempting to adjust mine as its hard to start.

[@Mistatech-yt8cg]

Hi grate explanation simple and easy to understand well done. Please may explain why these engines are very hard to start even with new cuburator or spark?

[@TheRepairSpecialist]

Hello, Thank you so much for your kind words and feedback! I'm glad to hear that you found the explanation helpful and easy to understand. Now, regarding the challenge of starting small 2-stroke trimmer engines with primer bulbs, even with a new carburetor and a good spark, there are a few common reasons why this can happen. I appreciate that you might already know some of these reasons but i have listed a few reasons to be sure: Primer Bulb Issues: While the primer bulb is meant to help with easier starting by delivering a burst of fuel into the carburetor, it can sometimes be a source of trouble. If the primer bulb is damaged, cracked, or not functioning correctly, it may not be delivering the fuel effectively, making it harder to start the engine. Fuel System Problems: Problems with the fuel system, such as a clogged fuel filter or fuel lines, can restrict the flow of fuel to the carburetor. This can result in insufficient fuel reaching the engine, making it difficult to start. Air Leaks: Air leaks in the intake system, including the carburetor gasket or intake manifold, can disrupt the air-fuel mixture, causing starting issues. Even a small air leak can have a significant impact on engine performance. Compression Issues: Low compression in the engine can also make starting difficult. This could be due to worn piston rings or cylinder walls. A compression test can help diagnose this problem. Carburetor Adjustment: The carburetor may require fine-tuning of its settings. Ensuring that the air-fuel mixture is correctly adjusted and that the carburetor is clean and free from debris is essential for smooth starting. Quality of Fuel and Oil Mixture: Using the right fuel-oil mixture and good-quality fuel and oil is crucial. Old or contaminated fuel can lead to starting difficulties. Choke Operation: Be sure to use the choke correctly during starting. Depending on the engine and temperature conditions, either a full or partial choke may be necessary. If you've already ruled out issues with the carburetor and spark and are still experiencing difficulties starting your trimmer, it may be beneficial to inspect and address these other potential causes. Additionally, consulting with a small engine mechanic or technician can help identify and resolve the specific issue with your trimmer, ensuring it starts reliably. I hope this has helped a little and give you at least some idea about whats going on in your engine/carburetor complex Craig

[@vicentetush2672]

Ok i have a husqvarna 143r 11 trimmer so that s why i am asking you so i will not have worrys to work with

[@nafvol5053]

mine starts with choke but turns off when i turn choke off,turns off when i accelerate and have unburned fuel from exhaust,does it mean too much fuel in chamber?

[@fordman7479]

Unless it has an air screw instead of a fuel screw like yours, then it's opposite, turning it in richens it and turning it out leans it.

[@dekkermargo6]

Hi Craig my husband want's to know how many turns does one make on the screw setting for a perfect mix.

[@letsgobrandontrump2024]

It’s trial and error just turn it 1/8 or less of a turn each adjustment and you’ll find the sweet spot

[@gbt722]

Oh my God. You are a Don making this video.

[@steveperchinsky5833]

i have a g9 yamaha gof cart, new carb, new fuel pump, it won't run right unless i hold the choke out??? everythings clean, engine rebuilt last year,hardly ever used? tis is a clean lifted well taken cared for cart, I am steimied? When the choke is on it runs smoothe as silk.HELP/

[@mad2strokeguy694]

Hi there T.R.S I have a brush cutter with this carburetor I found it quite hard to adjust and I didn't find it efficient or effective ( even when running well) I had then put a chainsaw carburetor and what a difference more power more efficient on fuel and just far better than the single screw barrel

[@Cjs.bullies]

How Many turns out shud this screw be matey ?

[@SuperGutta123]

I love you❤🔥🔥

[@jamielihi3791]

Hello! I have trimmer CG-430 which couldn't choke .

[@lastpaceended5866]

Hey mate. Just wondering if you could help me trouble shoot a 2016 tohatsu 30 2 stroke. Starts and runs fine, but idles reasonably high. brand new spark plugs. Idle screw inside cowling is right back. Any ideas what else to check??? I've your videos man keep up the good work

[@TheRepairSpecialist]

Thank you for your nice feedback. I really appreciate it. It might help to take a look at this video first. Its on chainsaw adjustments but the principles are pretty similar for most two strokes. Here it is: kzbin.info/www/bejne/e6CZmoiKn8iEbrM Here is another: kzbin.info/www/bejne/bWXTanmCoq6eodk I hope these help. Thanks again. Craig

[@robjuliano4272]

Awesome

[@TheRepairSpecialist]

Thank you so much. Craig

[@jamalgoldenfalcon5]

Where is the restrictor located is it between the carb

[@tomread5603]

Hello. I have a hedge trimmer with a new single screw carb. It starts and idles but have no high speed. I can a adjust the bog out but still high rpm. Any idea would be great. Great Video.

[@kingcanada2588]

Turn it in a few turns and out a few turns and just fine tune it

[@panagiotiskent.5964]

Hi Craig! I just bought an old, used Kawasaki TH48 brush cutter 48cc/3hp, which is in excellent condition. The carburetor has a single adjuster screw. Tuning it by ear, it sounds best about 1/4 to 1/2 turn out from the point where the line head starts to spin when on idle. My question is: With single adjuster screws, is it correct to turn the screw clockwise until it's tight and then counterclockwise 1&1/4 full turn and go from there? Or is it completely different than the classic H, L, T screw carbs? Thanks a lot for everything you put out there! Keep on keeping on!

[@TheRepairSpecialist]

Hi. First of all thank you for your nice feedback, I really appreciate it. As for your question. Are you meaning the Idling screw? or the fuel/air mixture screw? The idling screw should be turned out so that the head just stops spinning (as you have done) and the mixture screw should be adjusted when you are using the machine at full throttle. Turn the screw both ways just a little and get the engine to sit its RPM in a kind of mid point between engine RPM lowering on one side and RPM lowering on the other. When I am at that mid way point, I just take the screw out very slightly (not much at all) to make it a little Rich. I find this helps better when starting the engine and keeps more fuel mix going into engine to lubricate the components. I hope this helps. Craig

[@panagiotiskent.5964]

@@TheRepairSpecialist Thank you for your reply! Yes, I have turned the idling screw to the point where the head just stops spinning. As for the air/fuel mixture screw, is it supposed to be "hidden" or something? I asked a local small engine mechanic about this and his response was that some of these particular Kawasaki TH48 models have an air/fuel mixture screw, and some don't. Is this possible? Thank you!

[@TheRepairSpecialist]

@@panagiotiskent.5964 yes it is possible. I have come across a few that don't have adjustment screws. Have another god look for it, but maybe it doesn't have one. If it doesn't then this means that keeping good servicing of your Carburetor and good quality fuel, fuel filter and oil is a must to keep your machine running well if you can't tweek an adjustment on it. It's a must for all machines having said that though. Craig

[@vincentlongep6577]

❤ nice

[@TheRepairSpecialist]

Many many thanks

[@whojanickabollockoff]

Hi Craig, I have a trimmer which is not working properly, I have changed the fuel filter and fuel lines, stripped down and cleaned the carb, spark plug has good spark after I got rid of the carbon build up. When I fire it up with choke on it dies after 2-3 secs, it will not fire up at all with no choke on, it has a single adjuster screw which I have turned every conceivable way but to no avail, i did notice it was a damp on the air filter so i changed that as well even though i did not think it was necessary,what next please ?

[@TheRepairSpecialist]

Hi. Well, I have had this issue with trimmers in the passed. I have done similar things as yourself and found that sometimes new parts have to be fitted no matter how well things have been cleaned and serviced. For instance, I cleaned a spark plug on a recent hedge trimmer thinking I would be ok. It was perfectly clean and had a spark. It would not run correctly until i changed the spark plug for a new one. Another instance was a chainsaw, which I cleaned and serviced the carburetor perfectly, but it did not run correctly until i fitted a new carb. I'm not saying this is definitely the case for you but just a consideration. Its quite difficult to diagnose machines from computer screen because there are so many little things a mechanic notices when they actually get there hands on the item. I hope this helps a little Craig

[@jonathanlee8942]

Hello I have a bs52y trench wacker 1998 the carb only has one screw which move the lever the throttle cable is attached too. The problem I'm having is when I open throttle the revs don't go high enough to start wacking properly. If I open choke revs go up and it starts wacking,would you know if carb needs a service.

[@TheRepairSpecialist]

Hi. Thank you for your comment. I used to work on these Wackers quite a lot when I was a Plant Mechanic and I found there to be two adjustment screws behind two tightened screws labelled H and L. Once the tightened screws have been removed you can access the adjuster and set the carb. If yours is a variant of the ones I know of, having no adjusters, then, ye,s you are absolutely right. After making sure you have a clean fuel filter and air filter and fresh fuel, you may need to clean out the carburetor. I did have to clean the carbs on these quite regularly because of the dusty environment these machine sometimes work in on building sites. I hope this helps. Craig

[@GmGarlo]

so to adjust that screw to the perfect setting , would you need to set it at the recommended rpm with an rpm reader gauge?

[@skipgate]

Soooo.. What is the right adjustment and how to do it. As far we need to screw in?

[@thevoxofreason8468]

Great vid. I know how this type works, but I'm still trying to wrap my head around the advantages/disadvantages of this type when compared to a 2 cycle carb with high & low fuel mixture screws. Also, how is this type maintaining a proper mixture on idle *and* at full throttle?

[@MrMaddog76]

these type of carbs do have a low mix screw also it is in the top. look for a small black silicon plug

[@nickyogorman1590]

But do you set it at idle or flat out ??

[@choppergirl]

Turning that screw does absolutely nothing at all. I took it off, took a syringe full of Berryman's B12, and shot it through with no obstructions. After spending 5 hours yesterday surgically cleaning this thing inside and out, I'm done with it. I just ordered a new one. I've spent hundreds of hours trying to clean carbs out all hopeful every time now it's finally going to run right, and it never does, so rinse, repeat, ad nauseum. On and off again, over and over. Humanity should of been 100% done with carbs 75 years ago...