Hi KCValue, thank you very much for that, much, much better. Ur question about the minature pots fits in perfectly with the next step I was meaning to describe;
continually variable initial timing setting between a point a bit advanced of the normal most advanced setting, thru to the most retarded setting by using a minature 25 turn 250 ohm vertical trim pot. As HD said, vibration can be a real problem (tho the multi turn pots cope with this much better). The answer would be to tune using the pot, then remove it without changing the position of rotation, then measure from to find the resistance across it & make up a resistor of the same (or as close as possible) value to solder in. (In a race type CDI I wouldnt want jumpers).
So, u wiuld need;
an 18 ohm resistor;
a 51 ohm resistor;
a minature, 25 turn, 250 ohm vertical trim pot.
The trim pot is a little plastic block with 3 connections (pins) exiting the bottom & a small screw head at one end on top.
U would replace the 16 ohm resistor with the 18 ohm. Remove the 220 ohm & 120 resistors & their jumper pins.
Now u will want to use the trim pot as a variable resistor rather than a divider so u will connect the (variable) center leg to one of the end legs. Use ur multimeter to work out which one to connect it to, so that u know when u turn the screw u know whether ur making the resistot bigger or smaller (with regard to the way that u r turning the screw).
The trim pot cam go on the board where one pair of jumper pins were with the 51 ohm resistor then connecting the trim pot to the cathode of the SCR (where the 220 or 120 ohm WAS, depending on which spot u use).
So now, with the trim pot at its full value of 250 ohms the initial firing point will be slightly ADVANCED of the most advanced setting (no jumpers on the 220 or 120 ohm resistors) previously available. (basicly increases the 16 ohm to 16.984 ohms).
With the trim pot at its smallest value of zero ohms, the initial firing point will be roufhly the same as if u had a jumper on both the 220 & 120 ohm resistors. (basicly decreases the 16 ohm to 13.304 ohms).
To read the value of the trim pot once u have found ur ideal setting, u will first need to remove it from the circuit.
To then make uo a resistor of the same value u can put resistors in series, which adds their values together, or in parallel (use an online calculator to make it easy, google parallel resistor calculator), or a combination of series/parallel to get the value u need if it isnt available.
I think I'd be inclined to try leaving the minature trim pot in circuit before making up a fixed value resistor as I really think it might handle the vibration. When u see how they're constructed u'll see wot I mean.
So hopefully u can all understand my description of wot u need to do. If not, give me a yell asking about wot u dont understand & we'll try & clear it up.
With regard to the timing cap for use with a high reving race type motor, I think that changing from a 4.7uf to a 3.3uf will be enough of a reduction to allow the kind of revs needed for a race motor but this isnt something I have tested. My motor is ported & tuned for a wide midrange power band for use with a shift kit & 8 speed cassette, so my CDI is set up with just a smidge more initial advance & just a tad steeper retard curve (small extra capacitance), to keep it on the pipe which has slightly longer header.
By the way, nice job on the key lock ignition there KCVale, nice looking bike also, wot we can see of. The 3 position switch for the timing caps isnt a bad idea either, for a daily ride type aplication. For a race type motor I think I'd first tune the CDI to suit the motor's requirements, then solder all components in properly, just to ensure nothing could go wrong.
Cheers
