Forum

[will]

Please help i am a electric dummy.
would like to run my crusader batteryless, but would like to keep it true to its age, so no modern frills or gadgets.At present i just have a 6 volt alternator attached to a rectifer which is just dangling from crancase, oh and a Lucas 6 volt coil in a box. So please help what happen next. Advice will have to be simple and very clear. Yes i am that thick. Many thanks

[Les H]

The shortest answer is that you need to replace the battery with a large value electrolytic capacitor …around 10,000 uf. (Micro Farads). To charge the capacitor at kickover speed you will also need to have both sets of coils (High and Low O/P) from the alternator connected together to provide sufficient low rpm current. This is simple to do. Also is the wiring standard and do you have a “modern” silicon bridge rectifier? (old ones were very inefficient Selenium type). Some here might recommend a Boyer power box to you but this is not really necessary, especially if you want to keep your electrics at 6 volts (not recommended…but obviously the cheapest method). So once you start modifying the electrics there are more comprehensive changes available, most will improve the performance and reliability of the electrics, but none are free. The capacitor will cost only a couple of quid 50V rating should be sufficient or use 75V if not much costlier. A new Silicon rectifier will cost £2-5.

[Mark M]

Will, a small point: are you going to have lights on this bike? If it is a Trials type it need not have any lights fitted at all but if you do have lights your MOT tester will need to see them working without the engine running. You could cheat and fit a battery for the test of course...
REgards, Mark

[John M]

Mark, I think you may be mistaken, lights can be MOT tested with the engine running, to quote the testers' manual, "On machines without a battery or with an insufficiently charged battery, it will be necessary to run the engine."

[will]

Many thanks
Bike will be a trial bike so no frills just kick and start. bike is very orginal it has no wiring just regulator,rectifer and coil.
I just do not know where to start. I was told to change regulator to 12 volt by linking cables, but then i need a zener diode and a heatsink.So i am very confused. Would like someone to hold my oily hand and get me through this in very simple terms, thank you all. Yes I am that thick.

[Les H]

I'm not going to hold any greasy hands but if you have no lights and just a coil to power, then a zener diode is going to be overloaded. With little electrical knowledge, my suggestion to you now is that you buy a Boyer (or other make?) Power box and follow the instructions carefully. You will also need to obtain a 12v coil.

[Mark M]

John, I was under the impression that it was necessary to have a parking light function on bikes fitted with lights but that quote from the manual seems to suggest not. I will amend my remarks in future accordingly. It was on my mind as I MOT'd my Works Replica the other day and the Tester was complaining about people who advertise a "Daylight MOT". "No such thing!" he said!
REgards, Mark

[will]

Many Thank wanted to stay away from mod-con's trying to keep bike true to its age. just need to give her a heart beat. but just do not have the skill or knowledge.

[Les H]

Will. If you want to keep it simple, 1) just replace the battery with the electrolytic capacitor with both alternator coils joined together and feeding the rectifier. This will keep the 6V system (No zener available for 6v!) ..........2nd...why not fit a small capacity lead acid battery and just use the LOW output from the alternator (bridge rectifier still required) This way you will have power to fire the coil and not boil the battery by overcharging.....Otherwise the 12 volt ZENER diode system MIGHT be Ok without a battery in circuit and you might have enough power from using just the High output alternator coil (not paralleled with the low o/p, like this there is less chance of exceeding the dissipation of the zener (less likely to burn out), changing the alternator connections is quick and easy to do to get optimum results. So if you want to try that method you will need the capacitor, a new 12v coil, a zener diode with heat-sink. The zener diode has only one lead (The body of it is earthed so you must choose a + or - type to suit your bikes chosen earth polarity...it makes no difference in practice) It must be positioned in the air stream and then run the zener lead/wire to the supply that feeds the coil, which will be the "SW" terminal of the coil. The "CB" coil terminal goes to the points as normal. You have posed a difficult question as you have not said what wiring the bike has and what switches and whether you want to use just a basic simplified wiring. The zener diode + heat-sink + capacitor + bridge rectifier is not cheap and probably dearer than a combined rectifier/regulator power unit, which are very small and can be hidden in the position of the original battery. The wiring for both methods is very simple. Some food for thought but you could try option 1) for very little cost and effort.

[John M]

I would be tempted to convert to 12volts only because most modern stuff is 12volts.
It is my understanding that the Lucas 3 coil alternator was used as a 6volt system via a complex switching arrangement simply because the voltage regulators weren’t up to the job of sorting out all three coils at the same time.
The existing alternator can be converted to 12volts by connecting the green / black wire to the green yellow wire and using a modern regulator / rectifier.
You can use any voltage regulator / rectifier, I used one from a Honda CG125 on a 1980’s Suzuki that I converted to 12volts, as it is small and I had one on the shelf. The ones sold for Chinese pit bikes are very similar. If you are not going to use a battery you could probably get the bike to run without one, but if you wire in a CAPACITOR 2MC, pattern PART No.:LU/54170009 from our hosts at £14.00 it will make starting the thing a much more pleasant experience.