1. Zausel

    Zausel Genosse Forum Donor

    Zausel just got a Mikuni from Trabiteile.de but won't start. I have 20l of fuel, I've got 450ml/min flow out of the fuel line (going through both the petcock filter and an inline filter per Trabiteile.de recommendation), I've got sparks from both plugs, there is fuel getting into the carb.

    I pull the choke wide open and give it no gas. It just spins and spins and spins. I drained the battery trying to start it.

    Any suggestions from anyone who has done the Mikuni upgrade? Am I missing something obvious? I also have the MBZA and it was running fine with the stock carb.

    Thanks all. It's summer and everyone else is cruising, why can't I?
  2. A Spooky Ghost

    A Spooky Ghost Loyal Comrade

    I've delt with a few of these carbs(on motorcycles, and the like). A random guess would be the float is stuck, or jammed from shipping. Also the throttle slide could be installed backwards. It only goes one way.

    Other than that, a clogged passage, or maybe one of the cables are holding something open.
  3. Andrew353w

    Andrew353w Puttering Along

    When I've done call-outs to a non-starter I look for 3 things; Fuel, air and spark. I'd start by checking things in the following way:
    1/ Take the plugs out of the cylinders and rest them on the top of the engine block, so that they can earth out through the engine frame. With the ignition ON rotate the engine using the fan belt and confirm there are 2 sparks, one from each plug and the they're at the right time in the engine cycle. So far so good? If not, adjust as necessary. Put the plugs back n to the cylinders. Now stage 2:
    2/ Confirm the fuel really IS getting to the cylinders, by pouring a little neat fuel directly into the throat of the carburettor while trying to start it. If this causes the car to make an attempt to start, there might be a problem with the carburettor.
    3/ 2-strokes need effective seals in the cylinders although in a different way to those in 4 stroke engines and if these seals are damaged there's no compression, so it won't start. A compression test might help here.

    As you've only changed the carburettor and not disturbed anything else I expect it's something more obvious than what I have suggested, so check that all the flaps and connections can move freely and smoothly, which might help.
  4. kev the builder

    kev the builder Loyal Comrade

    i would check the float level it needs to be right if its to low the fuel wont enter the jets to high and it floods its a trial and error job to get the right level as theres no instructions on what it should be also worth checking it that the carb adaptors sealing to the engine as an air leak will limit the vacuum to the carb
  5. Zausel

    Zausel Genosse Forum Donor

    Thanks all. The carb is definitely flooding. I'm going to try a new set of plugs. I have spark on the old ones. The float might be stuck, I'll check that, but the carb came from spaet-bremser and is meant to arrive set up for Trabi.
  6. Wartburg353W

    Wartburg353W Loyal Comrade

    If the engine has spark and fuel isn't burning then it may be the carb isn't seated properly or something else is open causing a large vacuum leak.

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