Capacitor in a Boyer system?

I fit capacitors to boyer systems as backup in case a battery goes dead, saved my bacon at least once. Bit of a lottery if you can kick start it but all will start with a bump start. You have to pull the fuse so the electricity goes to the 2mc and not the dead battery. Remove it for now if its failed but replace it at some point.

I have the Lucas 2MC capacitor in many of my hybrid bikes, with the Boyer or Pazon ignition. I did not know that my Ranger 750 had a duff battery as the capacitor kept it going. I put the battery into my 1973 Triumph T100R Daytona, and then I found out that the battery had gone bad. That capacitor is a very good extra for bikes that do not have them. The system was designed by Lucas to run with out a battery. I once forgot that I had not fitted the battery, and it started with out it. That was a test that Lucas recommended to find out if your capacitor was still working ok.

" Thanks,, if I remove it should I join the 2 wires that connect to it?   " Definitely not - one is live the other is earthed (assuming we're talking about the 2MC).....

The 2MC capacitor has a shelf life, so it's not worth buying a secondhand one as they are likely to fail.  RGM sell an equivalent replacement for about £15 to £20, there are two varieties i.e. a 2 wire and a 3 wire version.

The one on my Mercury saved the day when I was on route to the NOC rally in Holland.  Just remember to turn off the lights before trying to restart the engine.

The one I sell costs £8. I am very happy to have the one mentioned above back for investigation and replacement. (Can RGM do this?)

But going back to the original question the capacitor does not matter a hoot if there is enough battery to run lights for several minutes, it will start the engine. 

There cannot be a 3 wire version, maybe one of the terminals has two connections as the original 2MC did. Yes the original 2MC is well passed its sell by date. New versions are far more reliable.

Suggest you buy such  ie Electronic items from someone who understands them and can supply back up. aoservices

Hope this isn’t hijacking the subject, but  where (and how) do you fit a capacitor in an electronic ignition setup? I have Boyer units on my Triumphs and will use a Pazon on my Dommie (when it’s finished). However, I haven’t a clue about fitting a capacitor or how it manages to start the bike if there’s no battery. I’m guessing that the capacitor charges up when the bike is running, holds the charge and then delivers its voltage  to the ignition coils when the bike is kicked over, but I don’t know if that’s correct or not - I just don’t understand how it all happens. Apologies if everyone is saying, “Blimey, don’t you know anything?” to which my answer is, “Nope!”

Thanks

Regards

Tony

Tony, the alternator supplies alternating current to the rectifier. On the two output leads from the rectifier where you have direct current, you fit the capacitor. The capacitor must be connected the right way, as it has one positive and one negative side! If your system is upgraded with a rectifier/regulator, the capacitor shall be on the output side. If you have an empty battery, you have to remove the battery fuse in order to start the bike. There is of course other  places to fit the capacitor. Hope this helps.

Thanks Mikael. Just to be sure I’ve understood it correctly, the capacitor is fitted in parallel with the battery. Does the capacitor get warm (so should it be fitted in a position where it gets good air flow?

Thanks again

Regards

Tony

Hi Tony,

Consider the capacitor as a second battery that can charge and discharge very quickly. Fit it effectively across the battery. Positive to positive and negative to negative.

While the battery is ok, the capacitor will do nothing much. If the battery is flat, you need to disconnect the battery. Then when you kick or bump the bike, the alternator will charge the capacitor sufficiently to provide volts to the ignition, being electronic or traditional.

If you leave the battery connected, all your starting efforts will go into charging the battery.

You do not need to worry about it getting warm by itself, but keep it away from any hot items.

Regards

Tony

Most above is correct. The capacitor does NOT get warm, in fact if it does get warm disconnect it quickly. (it might be reverse connected). it is in effect a sub miniature battery that will charge/discharge on the moment. Do not fit it across the battery directly. (should it go faulty/short then the bike wouldn't be protected by the fuse.) The output of the rectifier or Reg/Rect (same place) is where you fit it. As well as helping with starting with a flat battery, kicking casually (no or flat battery) then you stand the chance of a kick back, but with the capacitor this kick back will be reduced.

As an aside, fitting the capacitor will reduce the ripple on the battery line (especially with a reg/rect) as a result the average voltage rises a little and the charge current rise a little.

Tony and Al, thanks very much. I’m using electronic ignition systems (Boyer Mk4 and Pazon Surefire) which need a minimum of 10 volts (Boyer) or 8 volts (Pazon) on startup to prevent the ignition system going into fully advanced mode. Low voltages result in kick backs and misfiring when starting, so does the capacitor somehow manage to prevent the electronic ignition going fully advanced when attempting to start the engine?

Thanks again

Regards

Tony

Hi Tony,

The capacitor will not make any difference if the battery is charged and connected. 

With the battery disconnected, the capacitor will only prevent the 'low voltage kickback' situation if you can kick it over hard enough to generate the volts required.

Tony

As it’s probably not possible to generate 10 volts from the capacitor by operating the kickstart once (a wild guess - I may be wrong)  does that mean there is little point in fitting a capacitor on a bike fitted with an electronic ignition system?

I’m just thinking that, if the voltage from the capacitor can’t reach 10 volts before the engine fires, the ignition will be in the fully advanced state and so is bound to kick back and the engine won’t start or run.

Regards

Tony

It depends on the electronic ignition. The old Boyer could actually be anywhere between full advanced and fully retarded if the volts are low. I had this problem on my Commando MkIII when using the electric start.

I now have Pazon Altair that works down to a much lower voltage and either fires or it doesn't, no kick back.

It also depends on how hard you kick! Bump starting may be the only guaranteed method.

Tony