The Whole Fuel Priming System Explained - In a 2-Stroke Carburetor.

A Fascinating Explanation showing how the WHOLE Primer System Works Inside the Carburetor. For Quick and Reliable Starts, Preventing Engine Flooding, Fuel Efficiency, Reduced Maintenance and Repairs, Equipment Longevity and Safety.
- So let's begin: A Two-Stroke Carburetor Primer Bulb System is a feature commonly found in small engines, such as those in line trimmers, chainsaws, or leaf blowers. It serves the purpose of simplifying the starting process and ensuring a smooth flow of fuel to the carburetor. Let's break down how this system works to help you understand it better:
Primer Bulb: The primer bulb is a small, flexible rubber bulb located on the side of the carburetor. It's easily accessible for the operator to press.
Fuel Circuit: The primer bulb is connected to the fuel circuit of the carburetor. This circuit is responsible for delivering fuel from the fuel tank to the carburetor.
Fuel Suction: When you press the primer bulb, it creates a partial vacuum within the fuel circuit. This action results in the suction of fuel from the fuel tank into the fuel circuit.
Fuel Enrichment: The fuel drawn into the fuel circuit by the primer bulb is typically mixed with air. This enriched fuel mixture is essential for cold starting or restarting a warm engine.
Filling the Carburetor: As you press the primer bulb repeatedly, it fills the carburetor with the enriched fuel mixture. This is particularly useful when starting a cold engine because it ensures that the carburetor has the right mixture for ignition.
Cold Starting: The primer bulb system is most beneficial during cold starts when the engine needs a richer fuel mixture to ignite. The enriched mixture makes it easier for the engine to fire up and run smoothly in cold weather conditions.
Reducing Flooding: The primer bulb system also helps prevent over-flooding of the engine. By manually controlling the amount of fuel delivered to the carburetor, you can avoid an excessively rich mixture that could lead to engine flooding.
In summary, the Two-Stroke Carburetor Primer Bulb System simplifies the starting process by allowing the operator to manually enrich the fuel mixture for cold starts. It provides a quick and effective way to ensure that the carburetor has the right fuel-to-air ratio for ignition, making it especially useful in situations where smooth engine startup is crucial.
This principle works for most types of Chainsaw saws, and the following also helps with Chainsaw maintenance. So, whether you are using a Stihl Chainsaw, Husquvarna Chainsaw, basically, all types of Petrol Chainsaw are valid for this principle, as well as many types of or a 2 Stroke Engine. The Electric Chainsaw, of course, escapes this whole principle!
Thank you so much for watching.
Craig Kirkman (Owner and Creator of the 'The Repair Specialist' Channel and its copywrited content)
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...
#PrimerBulbSystem
#EngineStarting
#FuelEnrichment
#CarburetorTechnology
#SmallEngine
#ColdStarting
#FuelDelivery
#MechanicalComponents
#SmallEngineMaintenance
#OperatingPrinciple
#FuelMixture
#EnginePerformance
#StartingProcess
#MechanicalEngineering
#OutdoorPowerEquipment
#UnderstandingEngines
#FuelSystem
#EquipmentMaintenance
#PrimerBulbOperation
#EngineIgnition
The creation of information in this description was helped by ChatGPT

[@TheRepairSpecialist]

Hi guys I just wanted to Introduce to you my other Channel "Kirkman's Academy" - which i'm just getting started. It's a go-to channel for simple explanations for hard to grasp subjects such as physics, maths and chemistry etc. Here is the link: www.youtube.com/@kirkmansacademy/videos . Thank you so much for looking, and if these topics interest you then I hope to see you the there. Many thanks indeed. Craig 😊👍

[@dwilliams2794]

I've watched dozens upon dozens of "How-To" videos for the various projects that I take on. I watch anything from motorcycle repair, auto repair to carpentry. My friend, this is by far one of the very best tutorials I have ever seen anywhere. It's simplicity along with your visuals are fantastic. I had to pause the video to make this comment so I will get back to it now. Thank You !

[@ibkoool1]

If I had a teacher like you when I was a lot younger, I would have been a rocket scientist. I have never seen any one explain anything as through and clear as you do. You sir, were born to be a teacher and should continue to do so. Thank you very much for your contribution to the sharing of knowledge. At 13:58 in the time line of this video, can you please illustrate exactly where that check valve is and how it functions in the Stihl Zama carburetors for the HT75 pole saw.

[@unappreciatedtreehouse821]

That was a hell of a good breakdown of a two stroke carb. Very good! Extremely helpful.

[@foreverwood1963]

I have worked on my small engines for many years ( self taught ), and I do know most of what you stated here, but i must say it is still a great video. Your explanations are on point. The best I've seen!

[@dhirajlad7146]

There are teachers and there are teachers like this geezer. Even a plank like me can understand so beautifully explained in a layman’s terms. Hats off to you sir 🫡

[@yogsothoth9515]

This video alongside your metering and fuel pump video allows someone to completely understand a diaphragm carb. You sir are a genius.

[@DavidJones-smiley]

I get smarter ever video I watch of this dude! I love it

[@TheRepairSpecialist]

Thank you for your kind feedback. Craig 👍👍👍👍

[@johnmorkham7954]

Human ingenuity in a complex, intricate, delicate but robust piece of precise engineering. And once again explained brilliantly with diagrams to match. Thank you again.

[@donadwyer]

Brilliant explanation. Opened my mind to the inner workings of all those flaps and holes, suction etc.

[@danielfletcher253]

An excellent instructor. I watch every video uploaded. If you want to understand how small engines operate then this is the place.

[@mr.cryptobull1520]

I have worked on small engines for 30 years, Honestly, this is the first time I understood how these small carbs worked....GREAT JOB

[@MrEddieBasketti]

Thank you very much! A major confusion I faced was knowing which line is the supply side and which is the return. Now, not only do I understand that with no doubt whatsoever, I also understand the reed-valve membrane and all other functionality of this mysterious chunk of parts. Again, thank you for your very kind generosity in putting this video together.

[@meeekstubbular]

Well this one blows me away! I felt your simple diagram video I watched just before this one was a little too ... little, but here you're not holding back! Diagram and real carbi together is just so right and so helpful. I read a comment saying you should be a teacher...I would be quite amazed if you weren't already one. Thanks a lot for sharing

[@RushWorkingMan]

This is the best instructional video on how something works I have ever seen. My first thought was if my teachers were this good not only would school been easier but I would have enjoyed learning more. Thank you

[@hwally777]

Another excellent video. I have looked for a long time to find such a detailed description of how 2 cycle carburetors work. Thank you.

[@johnsmith-no8rj]

Best dang video on zama carbs and priming problems on youtube. I hope you're making money on this video. You deserve it.

[@DethBy3ToeSloth]

Fantastic video. Best explanation I have seen on KZbin hands down. One thing I would offer is that the carburetor you have only has two check valves on the diaphragm, not three. In fact, I think most of not all 2 cycle carbs have only two. One at the inlet (upstream of diaphragm) and one at the outlet (downstream of diaphragm) if you’ll notice, the two that you have drawn downstream of the diaphragm are redundant. Again, thank you so much for the explanation.

[@Dovafish.]

As all of your other videos the full and thorough explanation leaves the viewer in no doubt about what is happening. Thank you so much for making these to help people like me to understand the workings of the carburettor. I am certain that my repair work has benefitted from watching all of these because I am able to think about the process before making a diagnosis and clean and check the carb in the order of fuel flow and can be relatively certain that it will work when refitted. I would suggest that there are many occasions where a new carb has been fitted that simply didn't need to be. Thanks again. Super stuff.

[@TheRepairSpecialist]

Brilliant, thank you for your kind comment

[@wolfgangagrocock5832]

I completely agree with tompfbear I can't thank you enough

[@joeshmoe5935]

woah. That was an incredible explanation. Thanks

[@dezman237]

My primer bulb won't come back up once I push it down to create suction. Any advice?

[@bartpsenicnik7743]

Mine was doing the same thing, primer bulb not coming back up, and would run good for a few minutes then just die. I just took the gas tank off and found the fuel lines inside the tank were broken. There are a few excellent videos on how to fix those lines here on u-tube.

[@choiceblade]

I've just spent 3 days trying to learn how a carburetor works. BEST explanation anywhere. Got my sub,.

[@TheRepairSpecialist]

Wow, your message just made my day! 🌟 I'm thrilled to hear that my explanation helped you finally understand how a carburetor works. It can be quite a complex topic, but I'm delighted that I could simplify it for you. Your subscription means a lot to me, and I'm grateful for your support. If you ever have more questions or need further explanations on any topic, don't hesitate to reach out. Keep that curiosity alive, and happy learning! Craig

[@alext8828]

I really appreciate your hand-drawn diagrams. Best explanation on the planet.

[@duanepinsent5882]

There’s plenty of excellent and very helpful channels on youtube to help us diagnose and fix our small engine problems but there’s NO ONE that does it with such in depth detail of the total inner workings of small engines that help us truly understand how they work and help us actually come up with our own diagnosis. You rule!! Thanks for all the effort you put into your videos and the time to take to explain them.

[@joriver69]

You Sir, are an excellent teacher. Thank you so much for the effort that you put into this video.

[@stroys7061]

Excellent use of props! You are a great teacher. Thanks

[@rickbales1880]

Outstanding, I got alitle repair shop in my garage, The fuel flow has been a mystery for some time. Got it, thanks so much.

[@Idshyguy]

Thank you!! That explained alot to me and how all them ports and vavles work. I appreciate you taking the time to explain in very good detail!

[@1234tric]

It took me a minute to see how the gas went into the combustion chamber but now I got it, and can see how some time a motor runs and then stops. You made it so clear. Once again thanks!

[@arturoc6362]

Wonderful tutorial, sir. Thank you for taking the time and effort to teach the rest of us. I have always wanted to learn more about small engine repair, and yours is by far the best instruction on the matter I have ever seen.

[@tammysteele9881]

I think you are a very educator and teacher. Thank you for your efforts. You have helped me in mechanical repairs. Keep up the good work. Brian

[@dangermouse6642]

Excellent explanation. I ended up here because the bulb on my chainsaw split and I was researching how to replace it, this video is an education with really clear commentary and diagrams. Now I can replace the bulb but more than that I know how it works.

[@josepeixoto3384]

You're a Grand Master; i am an automobile engineer,for 40 years,and i did not know this; Thank you very much for sharing.

[@robertgary3561]

What that was absolutely fantastic. Very good explanation.

[@johnhoth6992]

The most complete video that I've ever seen. My hat comes off for such a great job. If one doesn't get this, maybe they are too young to do this type of work.

[@Jeff-rk8hq]

Very well thought out and executed. Particularly, I like your combined use of visual aids and narration paired with your ability to relay information in an unusually digestible way. Thanks for taking the time to do this. Much appreciated from IN USA

[@markd6022]

Absolutely love all of your videos. This is probably the most comprehensive break down and explanation of a 2 cycle carb I’ve ever seen. Cheers mate and thank you again for your content

[@joemusicman64]

This was an amazing tutorial. I just had issues with my weed trimmer and I had the lines connected backwards. Then I went to see how to connect them and the video I found had them backwards!!! No help at all. lol.Then I went to learn how the primer bulb worked and found your video. Wow did I get my moneys worth here. 5 stars my man. You're an incredible teacher. I know exactly which one connection is is which and why. PS: Subscribed.

[@jeffnahas2161]

He sounds like an engineer to me. Great job here and it sounds like others u put out there too. Thank you

[@stuartcrawshaw122]

Brilliant explanation, had no idea how these little carbs worked or how they managed to work at all angles, I do now. Thank you.

[@southpark4151]

This is one of the best videos I've seen of any kind!!! That's what I call teaching people something! Thanks for teaching us. This was really excellent.

[@Crest591]

Once again, a great video that explains very much. Keep it up.

[@antoniomancusa4259]

Finally! Thank you so much for the great video. I've learned the intricacy of how these little carbs work in so much detail and now understand what I have to do to fix mine.

[@TOMAS-lh4er]

ONE of the best exsplenations ive heard and perfect drawing .ive seen!!!!!

[@clintonandrews1538]

Outstanding video! It clearly explains not only how a primer bulb works (contrary to the popular misconception that the primer bulb pumps fuel into the carburetor, it draws air out of the carburetor, replacing it with fuel.) It also explains that the carburetor contains its own inline fuel pump, metering diaphragm and metering valve to control fuel flow into the carburetor. I wish I had the benefit of this knowledge 50 years ago when I first began tinkering with small gasoline engines. Bravo!!

[@ckpankratz]

Outstanding video. Excellent graphics and explanations. Thank you for taking the time to make this video.

[@patricktatten]

An amazing teacher and gentleman. A Scholarly approach to conceptualizing small engines. Well done, as always

[@TheRepairSpecialist]

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

[@curtflory7147]

EXCELLENT video! Wow, I understand now why my trimmer carb isn't drawing fuel into the bulb and where, and why, to look. GREAT job, thanks so much. I couldn't have done better if I had tried.

[@toonybrain]

Clear, concise, illustrated. Thanks for the time you put into this for our benefit.

[@Ranger11413]

I have been trying to figure out why my weedeater will not run properly. It has a new primer bulb so I know that isn't the issue. I've taken the carb off and sprayed it out with carb cleaner. No luck. Even tried a carb from another just like it. I am befuddled as to what the problem is but the video has been a great instructional video in understanding these carburetor functions. I can't thank you enough for this education.

[@davidhay782]

This video taught me what I needed to know to diagnose and correct the starting issues on my 26cc gas trimmer, thank you :)

[@kirkjohnson4636]

Have watched several of your videos, all brilliant!!! Made by a person that knows their craft inside out.

[@TomBuikema]

This video helped me a TON. Thanks a bunch for the thorough explaining and all the drawings!!

[@TheRepairSpecialist]

Thank you very kindly for your positive feedback. It very much appreciated. Craig

[@evildiesel1709]

Wow! Great explanation of such a complicated piece of engineering! I had no idea it was so involved

[@yachtwork]

Wonderful explanation and drawings. Thanks for all the video editing work.

[@anniversary4]

great as usual. Thanks for your dedication to helping others

[@uuutooob9]

I love the excruciating detail. Leads to better understanding and recall. Like your other videos, simply excellent! Thank you!

[@jaywhited1174]

That was fantastic!! I wasn't sure if mine was working correctly and now I understand exactly what I should find. Thanks very much and keep up the good work!!

[@brucerichards6531]

In a word, brilliant ! Thank you explaining, so clearly, how it works.

[@TheMarkEH]

A fabulous, insightful and (in my case) helpful explanation of this system. Thank you.

[@MichaelHollandOne]

this is exactly what I needed! Excellent details. I have subscribed and will be checking back here often, especially after our house is built and I can get back to my own lawn work. This will definitely help me finish fixing my dad's leaf blower. I was wondering why it still wasn't working after I replaced the fuel lines.

[@T0xIcNigHtMarE]

Wow.. To think that someone actually made something this ingenious and complex is just simply mind blowing.

[@glrgnicar]

Brilliant video and well explained,took my stihl blower out today after sitting for pretty much all of winter, purge bulb had no fuel in it, tryed priming numerous times. No fuel arrived into bulb and bulb very slow to come back to shape. Stripped out carb, cleaned up with some carb cleaner, checked bulb while not connected to the carb to see if it would draw fuel, it did! Ensemble everything back together but still won't draw fuel???

[@MartinIDavies]

great 'devil in the details' video.. I really like your step by step schematic overview of explaining what is going on before I start on a repair. I have several 2 stroke engines including grass mowers, weed wackers, air blower, chain saw and branch trimmer all with primer bulbs. In the past when one of my devices stopped working (invariably a 'fuel' issue) the solution was to take the device to my local small engine/mower repair shop to be repaired. Typically it's going to cost anywhere from about $75 plus parts to get my machine back in action (and, if this happens in early spring, I may have to wait 2 or 3 weeks for the shop to get to it. these how to vids of yours not only save me money (lots) and reduces my frustrations but also provide me a great deal of personal satisfaction of being able to effect repairs myself. thanks for taking the time to share your knowledge and skills with us.. BTW.. I have found during the 'off' seasons when I am not using them if I keep them filled with fuel and then every few weeks (3 or 4) I fire them up and let then run for a about 5 mins.. I have found that this preserves the plastic fuel lines and they dont become brittle and crack as a result of sitting dry and idle over the winter.

[@daveperry9111]

After searching the web, you have made the best explanation I can find. Thank you.

[@joeshmoe6686]

Brilliant exlanation, awesome diagrams, clear and simple. Thank you very much. Bravo Sir.

[@TheRepairSpecialist]

That you so much for your awesome feedback. I really appreciate it. Craig 👍👍

[@perssoh11]

As a process engineer I must salute you for this video. Extremely well explained. Only "mistake" is that you should use underpressure instead of vacuum.

[@TheRepairSpecialist]

Ok, thanks 👍👍

[@Jaguartmb]

Absolutely brilliant explanation, gone is my notion to bypass it and now i will purchase a new primer bulb. Mine corroded and imploded. Thank you once again for the effort. Brilliant.

[@margaretsewell9507]

Excellent job. Reminds me of my training classes when I worked for the airlines as a mechanic before I retired.

[@Aaronsutube1]

Thank you, that was effective teaching! Great visuals; please post more!

[@douglieuwen1661]

That was one of the best instructional videos I have ever seen. Well done! Thanks!

[@gibbonspider]

Remember that this type of carb (diaphragm) will allow the engine ,and carb, to be run upside down or at any angle. Not at all like the old style motorcycle carb, or mower engine. So any part of the fuel circuit that does not seal off a port (or a split primer plastic bulb)correctly means that it will NOT draw fuel correctly. A new diaphragm kit and absolute cleanliness when doing the repair and making sure that all ports are thoroughly cleaned out with some sort of pressurised aerosol spray usually results in a good working carb again. Nice video presentation, thank you.

[@TheRepairSpecialist]

Hi, thank you for taking time to give me your feedback. I really do appreciate it. Craig

[@Leroyjac]

Most have said what I would say - one of the best you tube videos I have seen. Going to fix a couple of carbs that have haunted me now that the mystery of operation is now resolved. As for the 139 that disliked the video, I feel for you...

[@EddiesCustomsandRestorations]

Extremely detailed explanation. I have no more questions, thank you. All was covered in your video

[@watsinit4me]

Awesome video, you explained everything very well so that even a novice such as myself can understand what is going on. Thank you.

[@robertlumsden942]

such a great explanation. it is really incredible the design of something like that. simple but almost complex. my gas bulb had a hole in it and i could not get my weed eater to start. i sort of figured that that little bulb was important. and i find out it is. no gas coming into the bulb so now i have to find a replacement. thanks for you video. was very good.

[@touretteslife]

You are absolutely brilliant, thank you for helping me understand what's going on when I push that little bubble! Now it makes sense why I've just thoroughly cleaned the carburettor and it's still not starting and I'm having issues with the primer . I think I need a new carburettor. I didn't realise how easy it is for a problem to arise in this complex little vacuum system.

[@roneverist5040]

Very thorough explanation. I never really understood how the priming system worked. Good job.

[@richardkradel7730]

Ron Everist xq

[@GodlessHeathenScotland]

Thanks for sharing this. A fantastically clear explanation of how this works.

[@archieneisz2910]

Superb dialog & diagrams. Thanks!

[@jeffzhang394]

This is absolutely brilliant video. Thanks. I was able to diagnose the problem with my weekwracker. It was the one way check valve inside the primer bulb that was broken so the motor dies every time I pull the trigger. Tried every method online trying to solve the problem but none worked for me. Finally I saw your video and boom problem solved after I replaced the broken valve. It seems rare but that was exactly the cause of my problem

[@bksaun]

Great job Sir! Cant thank you enough, absolutely the best explanation of operation I’ve ever seen!

[@notnilzab1]

A brilliant exposition of the working of a 2 stroke carb. Many thanks.

[@geoff8253]

Incredible description of how the carburetor operates. Very well done. P

[@nov51947]

Absolutely incredible video! Thank you for a thorough explanation.

[@trouts4444]

Best explanation of this type of carb operation I've ever seen. Excellent graphics and descriptions in an orderly way through all phases of operation. Impressive. Thank you.

[@TheRepairSpecialist]

Wow. That's some really awesome feedback. It's very good of you. Craig 👍

[@StevenChmielnicki]

Really just a fantastic video. Subbed and looking forward to the next one.

[@geojor]

an amazing explanation how this works, it's by far the best on youtube, congratulations on your hard work to put these valuable videos together, now a lot more DIYers will be happy ...

[@TheRepairSpecialist]

pei broker, wow, thank you for your feedback. It's comments like yours that motivate me to continue making these videos.

[@geojor]

you're welcome ...

[@ObsequiousV4]

I had no idea that these little fuel plungers were so precisely engineered. Thanks for the in depth explanation.

[@TheRepairSpecialist]

All Episodes -for 2-Stroke Carburetors Here. Thanks. Craig: kzbin.info/aero/PLrlXp3PlwgRI5OLvm3P91LJr1CYnO5TRD

[@John-rr4zz]

a very clear expert class . From a master tech. and I've been in the trade 35 years.

[@CarminesRCTipsandTricks]

THAT Sir, was invaluable information, indeed definitive, on the Primer Bulb and Main Jet function of these tiny 2-Stroke Carburettors!! 👏👏👏👏 I'll be getting my first 2-Stroke Engine, in a 1:5th Scale Gas Buggy. As a Retired Auto Technician, specializing in full size, motor Car Carburetors, I was a little lost.... Something that happens when you've learned *too* much about something similar, yet different in form and function. This has been a tremendous help. Thanks!

[@davidsewell7846]

Truly excellent explanation! Solves a mystery that I have for 50 years. Maybe now I can get my leaf blower fixed.

[@TheRepairSpecialist]

David Sewell excellent, thank you for your positive feedback

[@leeisenberg]

Same here.

[@jessecoleman2271]

This is perfect work. Really got to admire the science in these carbs.

[@gregsmith8686]

Thank you for taking the time for the in depth explanation and drawings

[@andyscott5978]

Lovely illustrations. You really have gone to a lot of work. Thank you, great job.

[@TheRepairSpecialist]

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

[@codemiesterbeats]

Thanks, I have watched one of your videos before... I remember the way you say "carb-retta" here in North Carolina we call it a Carb-er-rator. You actually did an excellent in depth explanation. Greatly appreciated.

[@100amps]

Thank you! I’ve been trying to figure out why the priming bulb on my lawnmower engine needs 12-20 pushes before the engine starts. The engine runs well and the bulb doesn’t leak fuel. Now, I can begin to see how to troubleshoot that.

[@juanvera7088]

Genius, thanks from Argentina

[@TheRepairSpecialist]

Thank you very much. I really appreciate it. Craig 👍👍👍

[@martinlintzgy1361]

Bloody brilliant. These little carbs are very complex, thank for lifting the veil.

[@garrycoates2147]

The very best explanation of these carbs I have found. Excellent!!!!!!!!!

[@jamie57061]

Thank you for your help. My mower is curretly stopping and starting, which i know could be a number of things, but at least i now know why i have to prime the carb with the buld. Thanks for sharing.

[@cheskybaba4864]

100% fantastic. Thorough and insightful. Well explained. It's so easy to fix things when you understand the system.