mike, I don't see on your list that you adjusted the idle mixture. It sounds like it is too rich. Adjust it with the engine running and turn it lean until it smooths out.
Kevin1 --- In [email protected], Mike Willis <m...@...> wrote: > > Hi guys, > > As previously mentioned I¹ve been experiencing a throttle stumble that seems > to be getting progressively worse. This is on my Alon A2 with a C90 and MA3 > carburettor. 6 months ago there was nothing apparently wrong. > > The main time it is exhibited is at take-off, when advancing the throttle, > albeit slowly to avoid a rich cut, still results in a stumble. It ticks > over at 1,000 no problem, and once above 1,500 it runs smoothly. If you > advance it very slowly it is OK, with carb heat on it doesn¹t happen either. > It is exactly the same running on each of the magnetos. > > It therefore appears to be a carb. problem with maybe a fault in the > accelerator pump or a leaky manifold gasket. > > A strip down revealed > * a little bit of dirt in the float chamber > * a leaky inlet manifold gasket on no. 3 cylinder > * a very small slit in the accelerator pump washer > * a corroded main jet packing washer. > > In addition the > * needle valve has been replaced > * the primer system checked > * the fuel flow measured from the pump (10+ USG/hour) > * the float level checked > * the jet size is correct > * ignition timing is correct > * new set of plugs fitted > * magneto earthing checked > * cylinder compressions seem fine > > And guess what, no change! It is exactly the same. > > If anything the engine seems to run rich and lumpy and fuel consumption is a > little on the high side. > > The next plan is to get all the cowlings off again and start checking the > mags and harness. > > Anything else we have missed? > > Best regards, > > Mike > > m...@... > www.ercoupe.co.uk > > Alon A2 Aircoupe > A-188 > G-HARY > -- >
