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Echo srm2400 trimmer

Discussion in 'Mechanic and Repair' started by Ocalalawns, Jul 26, 2008.

  1. Ocalalawns

    Ocalalawns LawnSite Member
    Messages: 73

    I put new diaphrams in the zama carb and a newer throttle shaft as the old one was worn. Now I can't get it to idle low enough to stop the trimmer head from turning. Is there a air intake problem thats causing this? The unit has been sitting around for about a year and wouln't keep running that is why I overhauled carb. Is it possible the base gasket is the problem?
  2. Phil G

    Phil G LawnSite Senior Member
    Messages: 843

    Is there an adjustment for the throttle cable? Might no be enough slack, or, have you got two mixture screws and one throttle stop screw. By a careful balance of the throttle stop and low speed mix screw you should be able to lower the idle, even if it's running v slightly rich on tick-over.
    Good luck Phil :)
  3. Ocalalawns

    Ocalalawns LawnSite Member
    Messages: 73

    There are 2 screws low and hi. I have the idle stop backed off all the way. I have played with the mixture screws for 2 days with no luck on getting it to idle low enough without it not stalling on either idle or acceleration.
  4. echoman8

    echoman8 LawnSite Senior Member
    Messages: 293

    Here is what I would try:
    1: Disconnect the throttle cable, start, test to see if idle is too high. If the idle is solved, there is an adjustment with two nuts on the throttle cable.
    2: If #! did not solve, get a spray bottle of water and spray anywhere that the motor can leak air: intake manifold(near carb), cylinder to crankcase, inside front housing (gets to front motor seal), essentially anywhere you can spray. if the engine dies, the air leak is in the area.
    3: Inspect the throttle butterfly on the new shaft and look at another butterfly on some other trimmer or chainsaw. I think the butterfly can be assembled 4 different ways, but only one is correct.
    I can think of nothing inside the carb that would cause only fast idle.

    Good luck Dennis
  5. Phil G

    Phil G LawnSite Senior Member
    Messages: 843

    There's every possibility the carb's knackered. If you've done the initial setting of 3/4 to one turn out on the L screw and 1 to 1 1/2 for the H screw. Then it has a fault that requires it to be taken apart. Do you have a repair shop near you that can Ultra-Sonic clean the carb? To be honest, if the rest of the machine is in good order I'd look for a new carb' or have you got an identical one from another machine just to see if it runs up?
    Good luck Phil:)
  6. Breezmeister

    Breezmeister LawnSite Bronze Member
    Male, from South Jersey
    Messages: 1,739

    Just on the off chance that it might be the clutch stuck open or a broken spring. If it's sat around for a year, there could be some rust or dust keeping the shoes from closing completely. Just pop the engine off just to check.

    Good Luck
    ericg likes this.
  7. jkason

    jkason LawnSite Senior Member
    Messages: 546

    What is the compression reading for this unit?
    At an absolute minimum, it needs to be 100 psi. It will run at this, but not great.
    With a worn throttle shaft, you sucked in dirt/dust, guaranteed.

    This thing may be toast. Check the compression.
  8. Ocalalawns

    Ocalalawns LawnSite Member
    Messages: 73

    The weedeater shaft and head are from a srm2400 that the engine went bad. The engine I put on was from a pe2400 that I don't use. I finally got it to idle. I put in newer low and high needles and adjusted the metering lever to .012 specs. Also I used a throtlle spring that had more tension. NOW the only Problem is when I first start it up it stalls at full throttle unless you feather it a few times. Does it need moere adjustment on low or hi or both. If so open or close....TKS
  9. Phil G

    Phil G LawnSite Senior Member
    Messages: 843

    Best way I find to tune these little buggers is
    Get the engine to operating temperature.
    Hold throttle full open and slowly turn anti-clock the H adjuster, keeping the throttle full open until the engine starts to run 'lumpy', almost 4 stroking.. It's now running too rich, slowly screw the same H adjuster in, keeping the throttle fully open, keep turning until you hear and feel it's at max rpm. This will be too lean for using so back the adjuster out a tad 1/2 turn maybe.

    Throttle down to tick-over and re-adjust the L screw the same.

    Then go back and repeat the main jet L setting as first described.

    It sound a pain in the arse to do, but in reality only take a minuet or two.

    When I've adjusted any two stroke piece of equipment I try and have it set so it will start (when warm) in any throttle position.
    Try this out,
    Good luck Phil :)

  10. echoman8

    echoman8 LawnSite Senior Member
    Messages: 293

    Hi phil,

    About that fast idle, Have you sprayed around the throttle shaft while it is running? I bet the carb housing is worn and leaking air around the new shaft.

    This would cause the fast idle but still perform good at high speed.

    Good luck

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