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Troubleshooting: Two Strokes

Discussion in 'Technical and Troubleshooting Torque' started by rodgerdodger, May 10, 2006.

  1. Hey,

    What are the typical causes of a badly smoking two stroke?

    (Bring on the two stroke jokes you bastards :grin: )

    It started a while ago though the bike was idling badly so I thought it was just carb related. Since then I've had the carb cleaned and tuned and it idles perfectly. Next suspect was some of the oil; I've been caught on longer rides and had to buy a small bottle of mineral based oil (yes, two stroke). Since then I've flushed that through with the semi-synthetic stuff I was using before without any problems.

    Same goes for the air filter, I did clean and re-oil it with the mineral stuff (might as well use it if I've got it) but since then I've cleaned and re-oiled with the semi-synthetic so that's out.

    Finally I thought it was the rings so after calling a few Yamaha dealers (the best response I got was "hmm... you'd be looking at... ohh let's say... 80PSI") I ran the compression test and got perfectly consistent 90s. For an engine that runs a compression ratio of 6.7 : 1 that sounds about rightish and is kind of backed up by the ever-so-helpful Yamaha team.

    So I've got no idea what else it could be? Ideas? What else should I be checking?

  2. Your injection pump timing is it out ???

    Not sure but is the yamaha an engine speed pump or a cable operated rate pump ???

    On my old RG the pump was operated by the engine but it had a split cable line to the accelerator and when the cable was worn it would stay open dosing the engine with additional oil leading to heavy smoking

    Also your compression is well on the money but how many ks has it done, because if your crank seals are shot they can draw oil from the transmission and be down on power.

    PS I hope you didnt use two stoke oil on your air filter as its not the best for the life of it as it contains ammonia
  3. Ok im no expert on 2strokes ........... Nadeen says takes at least 4 strokes to get me going ! :LOL: :p

    1st off yeah, id reclean your A/F and then oil it back up with the proper A/F oil.
    It sounds like as Brucey says, your oil pump timing is out, BUT before you go to far and spend a few waisted hrs looking for a problem that isn't there,
    Drain your oil tank or turn it off if you can? AND mix up the correct ratio oil/fuel and run it straight from your fuel tank for at least 2 tanks and see if the problem stops.
    If it does stop then yeah its an oil feed problem
    If it dont stop then its else where and you'll need to see about striping her down and replacing the crank seals etc.
    2 strokes are damn easy to repair as long as you know where and what your looking at, but do try to find out whats causing the problem before you just jump in

  4. Trouble Shooting twostrokes.

    You bet, they are so flitting they are a bugger to hit. I mean 4's take a little to get off the line so you can really get your site down on them...

    Oh... you don't mean Shooting Twostrokes...

    I'll shutup now :p