Jaguar CDI upgrade

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 mouser.com (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:
http://www.epemag.wimborne.co.uk/solderfaq.htm#howto
http://www.epemag.wimborne.co.uk/desolderpix.htm
http://www.epemag.wimborne.co.uk/solderpix.htm
http://www.appliancepartspros.com/how-to-solder.aspx

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 http://www.dragonfly75.com/motorbike/5curves.html

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

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.

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.

HeadSmess said:

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!

Click to expand...

That's exactly what i want

HeadSmess said:

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

Click to expand...

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

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

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.

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

Top end has been ported and polished