CHAINSAW CARBURETOR DIAPHRAGM: 'Fuel Pump Diaphragm' Causing BOG, Won't Start!

Mastery of the Chainsaw Carburetor: Unveiling the Mysteries of the Pump, Bogging Down

Very few people know this, but there is a very special Pump inside your Chainsaw Carburetor, and any malfunction of the pump and can cause a whole host of problems (bog, incorrect running and starting issues, to name just some). Powered by the fuel pump diaphragm, this pump is the heart of the 2 stroke chainsaw carburetor. The diaphragm, in turn, is powered by the 2 Stroke Engine.

Removing the fuel pump cap on the 2 stroke carburetor will expose the Fuel Pump Diaphragm. So lets now see how all of this works. Fuel is sucked through into the fuel inlet pipe where it's drawn down internally towards the carburettor body. When it gets there, the first thing it meets is the one way valve flap that it part of the Fuel Pump Diaphragm. The fuel passes this one-way valve and continues to be drawn down a second hole that is the entrance to the fuel pump chamber/reservoir, all situated underneath the Fuel Pump Diaphragm. So the pump, above, moves up and down due to alternating positive and negative pressures from the impulse line generated by the up and down movement of the piston during engine running.

Each time the negative suction pressure from the upward travel of the piston draws the fuel pump diaphragm up (via the pulse line, attached to a special connector on the fuel pump cap above the fuel pump), it sucks fuel in, underneath it, from the fuel tank. When the piston travels downwards, this sends the positive pushing pressure, via the impulse line, to the top of the diaphragm, which then pushes it downwards. This pushes the fuel out from underneath it. Upon doing so, the fuel can only go one way because of the valve flap system built into the fuel pump diaphragm. The flap that the fuel came through when the diaphragm rose up

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!

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I hope you find this video useful, and I really hope you enjoy it.

Many thanks indeed

Craig Kirkman (Owner and Creator of The Repair Specialist Channel and its Copyrighted diagrammatic content)

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#EnginePerformance
#ChainsawMaintenance
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#FuelSystem
#FuelPumpPrinciple
#EngineDiagnosis
#ChainsawTips
#ChainsawRepair
#EngineComponents
#FuelFlow
#2StrokeEngine
#ChainsawKnowledge
#CarburetorFunction
#ChainsawMechanic
#PetrolChainsaw

[Hydrogenblonde]

This is the best explanation of the two stroke fuel pump system I've seen on YouTube.

[NesianDope]

I understood it!
People actually pay for this kind of explanation in a classroom.
This was for free in exchange for views, we all benefit from this system.
Thank you for the videos!!!

[peterbaumgartner]

This is the first time I understood how the pump works. Thanks you very much for clear explanation and the lot of work that went into the video!

[GuysPlayingWithTools]

Nice video. Not many people think about how the gas goes uphill to the carb with no external pump

[beebester]

44 years old and finally a simple articulate explanation of a carburetor. So we'll explained that I feel I will actually; remember it.

[kenward]

Absolutely the best explanation of how the carburetor works I have ever seen. I finally know now what all the holes and flaps are inside and their functions.

[joeorapellojr]

Best explanation of 2 cycle fuel pump. Thank you for this video. Excellent!! I’m 63 years old and finally understand it.

[lucian]

When I saw the illustration on the thumbnail I knew this would be the best video on 2 cycle carbs

[IRDeezlSmoke]

Absolutely awesome teaching and explanation. I have a whole new understanding now of the service needs of my older saw. This video also somewhat explains why some prefer to pull the start rope a few turn overs before turning the switch on. The piston pulse will freshen the fuel load in the carb chambers and make starting easier.
Thank you so much for taking the time and efforts to make such an awesome educational video. I definitely hit the like button and may subscribe after browsing your channel for a bit.

[vg]

I just found you through your *Setting 2 Stroke Carburetor | This Happens Inside - How to Tune, * which I fortunately found, and this one was suggested next. I have to say that I love your work! So descriptive with such brilliant illustrations. Thank you, Mr. Craig, and Good Day across the pond.

[twizz]

Epic,
I can't believe its not been seen more!
Hopefully that will change for you
No cutesy BS
Just knowledge in a clear understandable way.
Thank You Sir✌🏽

[cm]

Long time mechanic, short time 2 stroke mechanic so always looking for more knowledge. I’ve encountered other common problems with lower end equipment, crank seals going out very early in life, and rubberized parts including carburetor parts that simply do not appear to be fuel rated materials. I have a pile of chainsaws that I keep threatening to bring back to life.

[jamesnicholson]

Thankyou for such a good demo of how the carburetor works and really really appreciate the effort you have gone to using diagrams to explain their wordings. Jim from AUSTRALIA.

[gronowens]

You have made a fantastic set of videos !!! I use these carbs on RC Planes and they are exactly the same Walbro type carbs. I now know exactly how they work and have now invested in a pressure tester! Again, many thanks.

[thadrepairsitall]

I'm glad to hear I've been doing things fairly well for years. I definitely learned a few things since I'm a fuel injection guy.

[stuungar]

Brilliant thanks, you've made an essential function of a diaphragm carb, easy to understand.

[DavidJones-smiley]

Thank you sir I learn more and more each video I watch!

[kiteglinton]

Yet again another superb video with clear explanation, it's really helpful so thanks for taking the time to share your expertise Craig

[thediddly]

Thank you, you added all one needs in this video to understand the topic

[michaelglynn]

Very well explained, great graphics too. Thanks, I learned something there. 👍