CARBURETOR EXPLAINED: Primer Cold Start System!

2-Stroke Carburetor Working it's Fuel Primer BULB System
A 2-stroke carburetor primer bulb fueling system is a mechanism commonly used in small engines, like those found in line trimmers or ATVs, to facilitate the initial startup of the engine and ensure a sufficient fuel supply. Here's how it works:
Primer Bulb: The system includes a rubber or plastic primer bulb, which is typically located on the side of the carburetor or the engine's housing. The primer bulb serves as a manual fuel pump.
Fuel Line Connections: The primer bulb is connected to the carburetor through fuel lines. One line runs from the bulb to the carburetor's inlet or fuel pump side, and another line goes from the carburetor's outlet side back to the fuel tank.
Fuel Pump Action: When you press the primer bulb, it compresses and then springs back to its original shape. This action creates a pumping effect. When you release the bulb, it draws fuel from the fuel tank into the bulb and then pushes the fuel into the carburetor.
Priming the Engine: Before starting the engine or after the engine has been off for a while, you typically press the primer bulb several times (usually 3-6 times) to fill the carburetor with fuel. This is necessary because 2-stroke engines don't have an oil sump like 4-stroke engines, so they require a premixed fuel-oil mixture.
Choke Activation: After priming, you might activate the choke, which restricts the airflow into the engine. The choke enriches the air-fuel mixture to aid in cold starts.
Engine Start: With a properly primed carburetor and the choke engaged, you can then pull the starter cord or use the electric starter to crank the engine. The engine should start more easily due to the presence of a well-primed fuel system.
Warm-Up and Choke Deactivation: As the engine warms up, you should gradually deactivate the choke to allow normal airflow. This prevents the engine from running too rich once it reaches operating temperature.
Primer Bulb for Restart: The primer bulb can be used again if the engine stalls or needs a restart. It helps ensure a sufficient fuel supply to restart the engine when it's warm.
In summary, a 2-stroke carburetor primer bulb fueling system is a manual pump that assists in getting the engine started by delivering a fuel-rich mixture to the carburetor for cold starts. It's a simple and effective mechanism commonly used in small engines like those found in line trimmers and ATVs to simplify the starting process, especially in colder conditions.
The fascinating Fueling Priming System of the 2 Stroke Carburetor shown and explained 'visually' throughout all of the intricacies of the epic Two Stroke Carburettor.
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
Craig Kirkman (Owner and Creator of the 'The Repair Specialist' Channel)
#PrimerBulb
#FuelingSystem
#SmallEngine
#2StrokeEngine
#StartingProcedure
#LineTrimmer
#ATV
#EngineStartup
#ColdStart
#ChokeOperation
#FuelMix
#CarburetorPriming
#SmallEngineRepair
#OutdoorPowerEquipment
#EngineMaintenance
#LawnEquipment
#MechanicalDevices
#StartingTechniques
#EnginePerformance
#QuickStart

[@TheRepairSpecialist]

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

[@madyottoyotto3055]

This is not a single adjustment carb This exact carb HAS A hi and lo mixture screw The initial setting for air is done by the idle screw and air is naturally limited after this The screw you call the air/fuel mixture screw is actually the lo flow mixture screw The hi flow mixture screw is on the opposite side of the carb to the prime bulb Look for the brass collar/screw and remove the rubber tube from the centre of the brass collar revealing the hi flow mixture screw Hope this helps

[@dansynness6295]

Best educational video on KZbin covering carburetor operation

[@mfilipovic99]

You're such a good teacher, explaining in a way that everything seams logical and it's easy to understand. Thank you for your video lessons!

[@promechanics2395]

This demonstration is much better than previous one of bulb function because in that you make a little miatake that when we press the bulb the pressure goes back to metering area but actually there are two valve inside bulb as clearly explained in this video ,,,previous video was also very informative but this has cleared the concept completely.

[@timc3600]

Thanks. Been looking at this exact problem today on a Zama carb. Now I know where to look for the problem.

[@bobross9332]

I used to have such a hard time starting my chainsaws and weed whipper. Did as instructions said.. prime 3X then pull cord, keep pulling cord. Now that I know I can't flood the cylinder by priming many times they start right up by getting all the air out of the carb. These 2 cycle tuturials are absolutely fantastic... those carbs are a lot more complicated than I thought.

[@TheRepairSpecialist]

Thank you for your comment and nice feedback. You are absolutely right. These types of carburetor are quite complex and absolutely ingenious in the way they work. Thanks again. Craig 👍

[@mvmcali6900]

That is one of the best explanations of a technical process that I have seen ! Excellent

[@TheRepairSpecialist]

Wow, thanks!

[@metheewatchakittikorn4796]

I just know how it works from your video. Thank you so much.

[@edwardcarter6408]

Great explanation and thanks for sharing!

[@erbid]

I've been looking for a rebuild tutorial for a H129f-2C (Ruxling?) carburator and this gave me the info I needed to get it going again. Thank you!

[@TheRepairSpecialist]

That’s awesome. Thank you for letting me know. Craig 👍

[@philipoakley5498]

Excellent !

[@TheRepairSpecialist]

Thank you! Cheers! 👍

[@michaelsawyers1002]

Great job!have better understanding how the primer bulb work

[@brianb5779]

If you hold the return port with some pressure from your finger should you see fuel squirt into the venturi?? Just trying to see if there is a simple bench test for checking operation. Thank you also for all your teachings, incredible.

[@dboser1]

This is a GREAT video description of the primer bulb circuit. Can I ask you further explain the function of the “special hole” that are open all the time ?

[@Aaronsutube1]

I'm looking to make a P&ID of your drawing. Have any advice?

[@geojor]

sometimes the primer bulb is on top of the pump, and sometimes it's on top of the metering area, am I right in that, and if so, does it make any difference ? thank you ...

[@chrismots6479]

I have seen some carburetors without a primer bulb, there's just a metal plate where the bulb should be. How these carburetors work? Or the plate is there temporary?

[@joegarza9505]

I'm no mechanic in any sense of the word but I'm trying to learn. Maybe this is a dumb question but I notice that the fuel stays in the primer bulb and never dries out after I store my leaf blower for a week, it's still there ( blower will not start). On my other two stroke engine machines, the bulb is dry every time I go to use it the next week or two.

[@darkbidding]

Why does it seems that there’s always still some air in the bulb? I can never get the bulb to be filled completely with just fuel. Is the vacuum pulling some air down the main jet? Sometimes there’re even some bubbles that will travel out the fuel return line as I pump the primer bulb. Are these just cavitation bubbles? This happens even though the priming system is completely primed.

[@TheJiminiflix]

Im not getting fuel into the bulb.

[@oliverwilliamson2243]

Try replacing your fuel lines, thats what I had to do!