most unseasoned techs will throw parts at 2 cycle engines till they run….dont guess…..test!!! before you dump 15 dollars into a carb kit that you cant get your money back on……. try these simple test procedures before rebuilding it




  1. @ MFL92028, before you criticise folk try to get your facts correct, your lack of knowlege as to where the fuel goes in, the fuel inlet pipe, and where it goes out, the jet assembly, shows your ignorance. The primer sucks the fuel from the fuel tank, where do you think the fuel comes from ? What is he testing with the pressure test ? simple, basically two things, one that the needle valve is seating and sealing and second that the diaghphragm and its gaskets are intact and not leaking.
    This is just one of many tests on these carbs and it found a fault before it was dismantled, saving time, another is a vacuum test.
    Jeremy has covered this task of pressure testing very well, if he covered the whole testing and as you suggest ( "explanation & understanding" about what all is going on in the carb ) the video would then get too complex, too long and involved and defeat his object of describing simple quick tests.

    Keep up the excelent work Jeremy.

    P.S. MFL92028, why don't you produce and post on YouTube a technical instructional video so all can see how it should, according to you, be done.

  2. Very good tutorial.  Only question I have is where to find a new needle and diaphragm?  Those things don't sound like something I can just pick up anywhere.  I would pay good money to be taught a class like this.

  3. Hi Jeremy,  Great info here but I need some clarification.  Question:  When you are using the thumb pump to test are you only testing the seal of the gaskets or is there some carbs that have a one way check valve in them that you are testing?  I have a rotary carb on a Echo that I rebuilt and works fine but after sitting for a couple of days the gas in the primer bulb leaks back to the tank.

  4. Finally a good, comprehensive and realistic video showing what has been my overall impression on rebuilds.  Compared to all these other videos claiming how easy it is and acting like every rebuild is a success and where have you been, I like your approach and explanation the best.

  5. For those looking for a pressure tester, one version is STENS # 705-020 (expensive). Will update when I find one at reasonable cost.
     Careful, it says Not compatible and warranty void with equipment using greater than 10% ethanol-blend fuel, so don't let it suck up any fuel into it.
    Another alternative is the Mityvac mitmv8500, it provides both vacuum and pressure at the flip of a switch.

  6. I replaced the fuel lines on my troy built weed eater and now all the gas will leak out after use… Used Oregon yellow tubing….. only used the thing 5 times in past 10 years… lines rotted so I replaced now leaks like hell after use and before if left sitting with any gas in it….

  7. Great work, I have the same sthil fs 45. My question is about the idle trim screw, is there a initial setting for it? Thank you for everything.

  8. yall ever just thought about buying a 10.00 manual blood pressure cuff ? it has a guage already has a hose and a release valve  and a sqeeze pump lol and after your done you can stick the hose back on the cuff and check your blood pressure lol

  9. Help on the conversion. Your gauge reads in Megapascals abbreviated Mpa. You said, "0.5." I think you meant ".05"  which is equal to 7.25 psi. Each .01 Mpa is equal to 1.45 psi

  10. Hi, I face an issue of Fuel Economy, Power & Pick Up
    Kinetic ZX Zoom 2 Stroke (2001) 110cc
    The carburetor seems to be leaking.
    I recently got the bike serviced & the mechanic changed the float pin/needle. Earlier before this the bike gave me a modest 35-45 kmpl. But now it's dropped down to 15/20.. Kmpl. Also the initial pickup & instant pickup of the bike has fallen drastically. Besides, when I open full throttle the bike stops after a minute or so.
    Kindly help & instruct me as to what needs to be done.

  11. I really enjoy watching and learning from you! My question is on these carbs do we perform pop off pressure test or is it the max test pressure of 10 psi? I've been watching John Pace's carb testing videos and am a bit confused because I have seen videos where the pop off test was applied on two cycle equipment. If you could elaborate that would be awesome! Thanks for all your great videos!

  12. Hi sir,Great tutorial thank you.I had a leak in my carb just like your`so I bought the correct carb kit,and it still leaked but slower bubbles,I noticed when inspecting the carb,I noticed very fine scratches that lead to the ends of the carb,I figured that air was running along the scratch pattern and out it was coming.
    My question is`will the new gasket seal once fuel starts to enter the carb,as the diaphragm should swell and fill any very fine scratches or will it not.?
    also wonder is there a way to smooth the very light scratch lines out?

  13. Please advise, my walbro wyl carb pops off and reseats at 2.5psi In operation the fuel inlet never reaches pop off pressure.
    Fuel is drawn in by carburator. What does pop off pressure test?
    Is my carb bad?

  14. 1. Perform a pressure test. 2. If it's leaking down, take your 5 lb sledgehammer and completely destroy that disposable carburetor before being tempted to waste your money and time on a rebuild kit. 3. Buy a new carburetor.

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