Jaguar CDI, mild porting, four stroking?

Discussion in '2-Stroke Engines' started by SeanPatrick, Jul 15, 2015.

  1. SeanPatrick

    SeanPatrick Member

    Hi guys,
    Been lurking for a while, first post, and I need some help. I'm running a Jaguar CDI, a high comp head and I have done some mild porting, widened intake and exhaust, took the piston and matched the skirt to tdc on the intake, and relieved the piston to match the exhaust port at bdc. If I raised the ports any, it was minimal. The widening was also mostly minimal. I am using my Jag cdi as it came in the mail and the problem I have currently is that I have good low end power and good mid range but as I reach top end ( I have no tach) the motor starts to "4 stroke", usually above 30mph. It will hit sometimes and I can feel the power pick up and the exhaust note change. It will keep doing this until I drop the rpm considerably. So, I'm pretty sure I need to open my jag and mess with the jumpers? Any advise or tips?

    Thanks, Sean

  2. crassius

    crassius Well-Known Member

    could be you're just going a bit rich at that point
  3. Waxxumus

    Waxxumus Member

    Mess with your spark plug gap a tad. I went from .024 to .031 and noticed a MAJOR difference in the amount of 4 stroking.
  4. Waxxumus

    Waxxumus Member

    You just need to grab the metal contact and pry it back without touching the tiny iridium core in the ceramic.
    I did it with a generic 1 dollar pair of pliers.
    You can too.
  5. BWB

    BWB Member

    Does your Jaguar CDI have internal switches?
  6. jaguar

    jaguar Well-Known Member
    "Retarding ignition timing reduces four-stroking, as it allows more time for scavenging to take effect. "
    To fully retard the ignition of the Jaguar CDI you need to engage all three of the switches on the triple post switch. Move the levers towards the ON side. (look for the small print)
    But usually 4 stroking at high RPM is just a jetting issue. Put a leaner jet in your carb.