With the pot set fully clockwise the timing will be static as per graph. Just off fully clock the timing will be "BDK RANGE". The timing is adjustable in between "BDK RANGE" and "DEGREES 29k-50,31Y/K-50,52Y-50 & 1UA-50" With the pot fully anticlockwise the timing will be standard to your particular cdi (degrees 29K-50,31Y/K-50,52Y-50 & 1UA-50) Note: the initial start point (degrees btdc) can be changed by advancing/retarding the stator plate. This will advance/retard the whole curve by the amount it is moved.
Cost of modifying a YPVS CDI is £140.00 + vat.

This is an example of fitting one of our CDi's to a Stan Stephens tuned 350YPVS, FII Race Bike, the Power Valves are fixed in the fully open position, it has Bored Standard Carbs with Ledair nozzels, Jolly Moto Pipes, with an airbox. 350MJ and C5 on the needle. Dyno1 Dyno2 The Standard CDi was 1UA-50.

We ran with the advance set at mid position, 12 O'Clock, and got more or less the gains shown, we jetted to suit, and then reduced the advance untill we started to loose power, this was about 11 O'Clock on the adjusting pot.

We have always tuned and prepared the LC's, YPVS350's and TZR's for racing, and as this has become more popular, we are now preparing more machines for racing. Obviously our main work is the engine, this is where our passion is, however with more and more rules, one has to stay ahead. Weight for these old machines has never been their strong point, so we have started producing light weight components, for example: suspension tie rods, and race wiring harnesses, hollow wheel and swingarm spindles. As I am sure you can appreciate, weight gains performance everywhere, cornering, braking and accelerating. Whereas HP only gives you better acceleration. Pictures below. The standard ones are 0.5Kg each, the new ones are 155g each.

The Tie Rods are £85 a set.

RD/RDZ 500
Power Valve Bhp/ Rpm
Power Valve Control

With the adjusting pot fully anti-clockwise the timing will be standard(47x or 1ge). Fully clockwise is the same timing asTZ500 (corrected for con rod,stroke length). The std ignition cuts out approximately 5% of the sparks at about 9800rpm increasing to approx 20% at 12000rpm. This circuit is completely removed and will not effect the timing even in standard setting.
We are currently charging £140.00 for the ignition(CDI) modifications and £140.00 for the p/ valve control units, however, if they are ordered/done as a pair we are charging £240.00 in total. The reason for this is that they do complement each other and it is easier for us to set up.

The Graph below shows the effect of changing the power valve timing on a Graham File Tuned TZR250.
This is the only change that was made, no jetting, ignition timing or adjustments of any kind.





Power Valve Control
Below are some of the options for changing the power valve starting to opening rpm and the fully open rpm's.
Above example was using the standard TZR250 1KT program. This was reprogramed to prog' 14 (Top Row). As you can see this changed the initial movement of the power valve from 5850 rpm to 6000rpm, and the power valve was not fully opening untill 10050rpm this was changed to 8550rpm, the power gains are seen above. The eg' for the RD/RDZ500 uses RD500 (standard) and is reprogramed to prog' 8, for mildly tuned engines or prog' 18 for highly tuned engines.
The switch options 1 to 12 are fitted so all the programs listed are available by turning different combinations on/off.

Clear as mud?
The cost of modifying a P,Valve control unit to do all these things is £140.00 + vat.