Severe lack of power when baffle is in

Discussion in '2-Stroke Engines' started by Jamieoz88, Dec 20, 2014.

  1. Jamieoz88

    Jamieoz88 New Member

    I have a 66cc zbox with the stock carby, when I have the baffle out the bike runs ok just a little rough with no power loss whatsoever. When the baffle is in I have next to no power and the idle seems really low sometimes dyeing when the clutch is in. Any suggestions will be much appreciated I am changing the spark plug today, could this be the problem?

  2. crassius

    crassius Well-Known Member

    sounds like it is running rich - see if dropping the needle down makes it better, then decide on whether a main jet needs to be smaller
  3. Fabian

    Fabian Well-Known Member

    You need to jet the carburettor so that the engine runs optimally with the exhaust baffle in place.

    Whenever you make a change to either the intake side of the engine or the exhaust side of the engine, you will need to rejet the carburettor for optimal engine operation.
  4. Jamieoz88

    Jamieoz88 New Member

    Cheers for the replies dropped the needle in the carby and put a new plug in and it's running great
  5. gator joe

    gator joe Member

    Gator joe here. ..I agree with Fabian. Y did you remove the baffling in the first place. And i assume you are speaking of the exhaust baffling ..? Did you want ur bike to sound tuff lol.. I have news for u as u should well know. It's only a little bike motor. And there are many more draw backs to making ur bike loud. .ie..cops..I am thinking of putting a expansion chamber. .any one know about those. .also I want to get a 36 tooth sprocket with adapter clamp. .I just broke my first spoke yesterday
  6. Timbone

    Timbone Active Member

    In reference to the broken spoke issue, I have a few comments as a guy who has built many sets of bicycle wheels:

    My 8 month experiment with two motorbikes has led me to believe that the rag joint thing is a pretty good functional design!

    Bicycle wheels are unique in that the spokes serve in terms of pull only. Although a 14 gauge spoke is quite strong, it offers zero in terms of push support. It is the net combination of many different spokes pulling that give a wheel its strength.

    Most bicycle wheels fail because a spoke has too little tension at a certain spot or spots when the wheel rotates. This very quick detensioning/ tensioning causing a slight movement that, over time, acts like the bending of, say, a metal coathanger. Keep working it over and over and eventually - POP! - the spoke will break, usually at the j-bend.

    I was working on my rear wheel today, checking for tension (I had a few loose spokes) and trueness and I think the rag joint serves to stabilize the spoke even if it works loose due to torque/vibration. I had not had issues with spoke breakage - I've had issues with the rear rim being distorted due to the powerful torque of the motor and hitting rough spots on the road at high speed.

    I've really come to like and have faith in the good old rag joint. :)

  7. Fabian

    Fabian Well-Known Member


    That's why you get yourself a wheel truing jig and a Park Tool spoke tension meter:

    and if you have a wheel with bladed spokes, you need to get this device to ensure they don't twist when tightening up the spoke nipples:

    I have had brand new wheels measure up with wildly different spoke tension on individual spokes.
    My current set of wheels were atrociously bad, with one spoke measuring up at 13 on the Park Tool spoke tension gauge and the spoke next to it (on the same side of the hub) measring in at 22 on the Park Tool spoke tension gauge. All other spokes measured in somewhere between 14 and 21.

    No wonder people experience broken spokes, especially with the extra weight and extra torque that is placed on the spokes in a motorised bicycle configuration.
  8. Jamieoz88

    Jamieoz88 New Member

    Gator joe, I removed it to clean it and wanted to see if it would run with it out as it was not with it in, not to make it louder