Capacitor Installation to avoid Starting Problems ?

[scooterfan]

Since I joined this Forum it became clear to me that many owners by times experience engine starting problems with their scooters. I also experienced an engine failure / no start situation, and the problem on my scooter was caused by a dying  DC CDI. In my case the original CDI has been replaced as a matter of "thumb sucking", while I was only hoping that a new CDI would solve the starting problem. Fortunately luck was on my side - the original  DC CDI was indeed faulty, and a new DC CDI solved the problem.

But since the new CDI installation on my scooter some comments at this forum clearly indicated that low battery Volts on scooters can also cause starting problems - even when the battery is still capable of swinging the engine. More reading on the Web confirmed - the batteries on scooters with DC CDI's need to be fully charged - otherwise the CDI's will not be able to deliver sufficient Volts to assure a proper spark at the spark plug - and the scooter will battle to start

Since this information started sinking in I did more reading about this subject and to my surprise I discovered the following:

If the Voltage on the battery on my scooter is slightly too low (probably less than about 9.5 Volt) the Kick Start on my scooter will become useless. Simply because the battery Voltage will be too low to generate a proper spark at the spark plug.
I only realized this after some intensive reading about DC CDI's, and after realizing how it actually works:

!. The purpose of a DC CDI's is to transform DC Volts (from a battery) to a Capacitor inside the CDI - which release Volts to the ignition coil - which releases  much higher Volts to the Spark plug.
This means on scooters with DC CDI's (like mine) the battery (and ONLY the battery) "feeds" the ignition Coil and Spark Plug spark plug with power - the spark plug's power does NOT come from the scooter's stator.

2. A Hall sensor on the scooter's flywheel only triggers the CDI's Capacitor to release stored power (Volts) to the ignition Coil and spark plug - again, the spark plug's power does NOT come from the scooter's stater.


With this information in mind, I started wondering about the possibility of installing  an additional Capacitor as "battery standby" on these scooters - just in case a battery is on it's way out - or even to replace a battery completely.  There seem to be a lot of available info on the Web in this regard.

Has anyone ever tried something like this on a scooter with DC CDI ?

https://www.team-bhp.com/forum/motorbikes/199120-diy-eliminating-motorcycle-battery-adding-capacitor.html

[CROSSBOLT]

Yager 200i had a plan to do this very thing several years ago. It was one of his many projects for his Yager. I found all sors if stuff on youtube.com about this and thought it a viable project but never personally ventured into it. The East LA custom car guys have been using one farad capacitors in their ridiculously loud sound systems to cushion the huge drain on the car battery/alternator while "doomp, doomp, doomping" down the road. Should work...

[scooterfan]

I was actually thinking of just keeping one capacitor (maybe like the first picture at this link https://www.team-bhp.com/forum/motorbikes/199120-diy-eliminating-motorcycle-battery-adding-capacitor.html ) handy - just to somehow connect to the CDI when the battery fails to  supply sufficient Volts to the CDI.

To my understanding a single capacitor (like the one at the picture) will supply enough Volts to activate the CDI's capacitor to produce a proper spark at the spark plug when the Kick Start get used to start the engine. The extra capacitor obviously need to be linked to the voltage regulator and ignition switch , because the capacitor will need continuous power supply from the stater to keep the engine going once the engine started.
 A modification like this (one smallish capacitor) will only be suitable for scooters with carburetors. The fuel pumps on  FI models need too much Volts / Amps to drive the fuel pump. Fuel injected systems obviously need continuous pressure in the fuel line before the engine starts - therefore I think a mod like this on scooters with FI systems will simply not work.

On mods like this the scooter's Kick Starters need to be used to start the engine - the small capacitors will not suitable to drive the engine's starter motor.