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2T stutters at WOT

Discussion in 'Technical and Troubleshooting Torque' started by blackjacket, Feb 25, 2008.

  1. Hey guys,

    I got a cagiva mito and recently it's started having this problem. When taking off rapidly at WOT to the redline (11k RPM) the bike sputters at around 10k RPM wheras before it would pull on a bit past 11k RPM.

    However if I slowly raise the throttle speed up to 11k RPM, it gets there without trouble.

    It only seems to have started after the bike has been sitting for a week while I was waiting for a footrest part. During that time, the carby seems to have emptied as it took a few seconds of cranking to fire up for the first time. The spark plug is probably due for a change now too, would be several thousand K's old.

    Any ideas?

  2. I would say its the powervalves, not opening quick enough. Might need some adjustment.
    If its not the PV, then maybe your carbs need a clean.
  3. Spark plug.

    Try a new one.

    Ride it hard on the freeway for 10 to 20 minutes and then see how it goes.


    Trevor G

    PS It is always better to open the throttle gradually, in line with the way the engine is responding, rather than just give it a big handful.

    PPS The power valve would be opening somewhere closer to 6,000 rpm, so it shouldn't be the issue.
  4. Replaced the spark plug this morning, and seems to have fixed but I haven't given it a proper run yet. The removed plug gap was almost 1mm :shock:

    But I muffed up... I didn't know you have to unscrew the cap on the plug electrode to fit the lead on... I thought I'd got the old plug's electrode stuck in the lead. Managed to screw it up completely. :oops: :oops:

    Luckily I could get a new NGK spark plug boot, so hopefully that will fit in nicely.
  5. Spark plug boot went on nicely and the new plug is going strong. No more stuttering. The engine sounds a lot more crisp like snap-snap-snap now.

    I've got a weird problem now though, seems like I've lost power down low, used to have decent power at around 5k rpm for taking off, but now I have to rev out to 7k. Not sure if this is because of the new fuel I put in yesterday.

    I also replaced the fuel hose from the tank to carb yesterday because I split the old one. I made the new one much longer for access purposes.. would that have any effect?

  6. Unlikely, but it's not always a good idea. How extra long is the hose? Is it absolutley free of any chance of kinking? Can you make sure it does not drop down below the level of the fuel entry into the carb.

    I know it shouldn't matter, but it could.

    All the best