Jaguar CDI upgrade

Discussion in 'Performance Mods' started by jaguar, Jul 13, 2013.

  1. jaguar

    jaguar Well-Known Member

    For racers the newest version can handle up to 10,000 rpm, due to a lower base value of timing retard capacitance. If you have a Jaguar CDI and have ported your engine for higher revs and want the CDI to match (if over 8,000rpm) then just replace the capacitor that I indicate in this drawing. The capacitor part number is 581-TAP335K010SCS from (cost is $.50) It should be installed with the side with alpha-numeric characters facing towards the components board midline, not outward toward the edge of the board. Typically you can gain 10% more top speed with this modification.

    JNMotors is not capable of making the upgrade for you or giving you any trade-in value for your old CDI. I could but being in south america it is a 2 month wait (due to long shipping times) and I doubt you can be without a CDI that long, especially in the summer now.
    Radio Shack sells a cheap kit for soldering.
    Online soldering tutorials for beginners:

  2. jaguar

    jaguar Well-Known Member

    If you have a standard engine then the retard timing capacitance has little effect on your top speed since your top rpm are not very high, normally 5500. If a modified engine revs to 7000 or more then you can notice its value making a difference.
    The old base value was 4.7uf and the new value is 3.3uf with jumpers able to increase the total value to 3.8, 4.3, or 4.8uf.
    To read about the jumper setting and their effect on the timing curve please go to
  3. Fabian

    Fabian Well-Known Member

    Can you post a diagram showing how to install 4 trim pots as a method of getting rid of the jumpers and allowing wide range adjustability of the timing curve in the low, mid low, mid high and high rpm parts of the ignition curve :bowdown:

    Even better still would be to have remote mounted (push button) handlebar selectable ignition curves to allow different options to be selected on the fly.
  4. HeadSmess

    HeadSmess Well-Known Member

    or maybe a full 16 bit microprocesser controlled CDI with magnetodynamic closed loop gain feedback circuit set by an easy to use digital panel interface with ipad compatability and a bootstrap buck converter with phase rectification? ooooh, and a usb port would be nice!

    a trimpot is a variable resistor. a jumper wire is a link.

    as far as im aware in jaguars design, the jumpers link successive value caps together. you cant replace jumpers with resistors. you could use trimmer caps like in a radio but they arent available in high values and are expensive.

    (maybe some resistors are linked via jumper so can be varied via trimpot?)

    you could wire a rotary switch or similar up so as to have all the "maps" selectable. or more. or less, depending how its wired and number of positions/caps used. caps in parallel add together, caps in series go by the 1/Ca X 1/Cb X 1/Cc..... or two equal values will halve when in series. (opposite to resistors which add in series and...divide? in parallel)

    rotary switches can be anywhere from 2pole 2throw up to 24 or so throws(clicks, positions) with multiple poles. the basic idea is just to vary the capacitance between the input wire and output wire from a minimum to a maximum. this is done by variously running caps in series, alone, or in parallel in various combinations, selectable by the switch. some careful planning before soldering and you could make a fairly effective unit.

    wired up via multistrand flex and it could be remote mounted. length of wire can be an issue with a circuit using a capacitor due to stray inductance. shielding may help. it may not. using DIL switches is much the same but they are those fiddly little switches you see occasionally hidden on circuit boards and are hard to reach. next option is rotary encoders/pushbuttons that leads into the microprocessor and digital field...

    then again, judicial application of a trimpot to replace one of the existing resistors to achieve a degree of adjustability.... ;) completely feasible.

    PS, dont ask me which one, i only do tube amps.
  5. Fabian

    Fabian Well-Known Member

    That's exactly what i want :banana:
  6. Fabian

    Fabian Well-Known Member

    Headsmess, you need to start building CDI's for these 2-stroke engines, with some serious extra functionality.
  7. jaguar

    jaguar Well-Known Member

    Fabian, just solder speaker wire onto each of the paired jumper posts and solder the other end of them to switches.
  8. gary schenaman

    gary schenaman New Member

    May I ask what are the values of the two metalized poly caps. The big and small brown caps that is. Also your upgrade there are only two caps showing my version has 3. 2 with 1uF at 25v and 1 at 2.2uF at 25v.
  9. jaguar

    jaguar Well-Known Member

    You have the upgraded version then.
    Have you modified your engine for high revs?
  10. gary schenaman

    gary schenaman New Member

    Top end has been ported and polished
  11. jaguar

    jaguar Well-Known Member

    Find out the engines natural top RPM (speed) with the muffler pipe on.
    Then if you have an expansion chamber put it on and then adjust its header length till you have the top speed you want, which could be equal to or anywhere around the natural speed, even up to 15% more.
    Then adjust the CDI to improve on that speed a bit. That way the CDI is being matched to the engine/pipe and not the other way around.
  12. kr1x

    kr1x New Member


    Jaguar, as we know stock cdi unit advances timing on higher revs. I can find video really advancing it on higher revs on youtube, but do you have similar video of your product retarding timing?

    We race bicycyle engines here in Estonia. Russian made predecessor as well as Chinese made products at same race.

    Greetings from Estonia

  13. jaguar

    jaguar Well-Known Member

    Soon I should have a video ready that shows the timing advancing and then retarding. The other day my timing light died and so I have to get another one from the States. Also I looked for my tester and couldnt find it. Stuff always dissappears from me when moving. I will look extra hard tomorrow.
  14. jaguar

    jaguar Well-Known Member

  15. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Awesome to hear that you are racing motorized bicycles in Estonia.
    Do you have a website or any videos online?

    Check out Socal Motor Bicycle Racing in California.

    Almost none of the racers use the Jaquar CDI but there is a new CDI on the market that will be raced on April 12th.
  16. jaguar

    jaguar Well-Known Member

    I predict a whole lot of detonation will be happening as a result of people using the standard CDI or the LIghtning CDI if they are running a high compression head and are running too lean. Possibly racing in the winter-time will present enough cooling to the engine to prevent it though. But be forewarned for summer! Thing is, you don't even know it's happening without a trained ear for it. But then you lose engine compression due to aluminum particles on the cylinder wall or the engine just stops due to aluminum particles shorting the spark plug out. Race that! ha! push that bike over the finish line !
    Last edited: Jan 17, 2014
  17. mrbg

    mrbg Member

    I'm new to this stuff how about a basic walk thru on installing the cdi and coil?
  18. jaguar

    jaguar Well-Known Member

    the Jaguar CDI connects to the high voltage coil by basic mechanical connections.
    The Jaguar CDI connects to the stator coil by soldering the wires together (although some people who believe in luck actually connect them with crimp connectors although they aren't even sealed against water getting in and creating corrosion).
  19. mrbg

    mrbg Member

    The internal coil inside the magneto cover stays and you swap out the stock cdi with the new one and bolt the coil to the frame and reattach the connectors and it's ready to go rite?
  20. mrbg

    mrbg Member

    I forgot thanks for your time we'll see how it goes