View Full Version : Boosting ignition output at low engine rotation speeds

Billy Golightly
05-10-2008, 10:12 PM
My question is, is there a way to increase low engine speed ignition output (IE, kicking over the engine so slow that the coil is not firing unless its spun over quicker).

This is on my ATC/CR 500 conversion that I short track race with. I have to use a Blaster kick starter to fit around the frame and brake pedal. I'm using an 01 CR250 digital ignition setup modified to fit on the 500 and also have a flywheel weight. The problem is, even with the splines on the kicker shaft adjusted all the way forward so I get the most rotation out of it, when I kick it the motor is only making about 1-1.5 revolutions and is not sparking consistently because its not turning over enough. I'm already at the very start of the throw and putting my entire weight using the tip of my boot to "flick" the kick starter, so there pretty much isn't any technique tricks.

Now, I can pull the plug out and then kick it over slowly, about the same roughly as I do when its in and the motor is under compression, most of the time it isn't firing, and then sometimes it will. When it does, its a nice big fat blue spark.

BUT, I can kick the motor over just a little bit faster (but fast enough that I can't do it this quick with the plug in) and it sparks nice and blue on every kick, because the engine is getting enough rotations/speed to generate the ignition output it needs to spark. There is nothing wrong with the ignition system because it came off of another running machine and if you pull or pop start it, it runs perfectly, or if you just turn the motor over quicker it fires enough to bust your ass if your holding onto the plug. Its just the slower speeds, and less rotations out of the motor I'm getting when I have to kick it that its not getting a spark.

I have played with various plug gaps, and went on just about everything between .012 and .030. I'm using a regular old B9ES plugs...I've read in quite a few places that the split electrode plugs really don't make that big of a difference, besides I don't really think its the plug anyways but the ignition system itself before it gets to the plug. I've also already lowered the compression ratio about 25lbs and that did help to get the motor to turn over faster but not enough. I suppose I could add yet another base gasket but thats gonna really screw up my power output and the head design. Kick starter lengthening is out of the questions because if it gets any longer my foot/boot is going going to be hitting the silencer even worse then it is now. Bump/Pull/Accessory starts are out of the question because I'm not at a drag strip and when my class gets called to the grid I need to go. Besides that I'm by myself most of the time anyways.

I realise there are fuel additives and such (I've already done the 5% acetone trick) but they arent gonna do anything for me if the thing can't spark enough.

Harry in chat suggested using a condenser wired inline with the + wire coming from the stator to the coil, with the idea that it would hold what spark energy is generated at the lower speeds and then release it once its charged. I think I might give that a try and see what happens. Anyone else have any suggestions?

Billy Golightly
05-10-2008, 10:54 PM
Thats some real good info John, that was another idea Harry and some others had suggested in chat was some sort of an auxiliary battery wired between the + side of the stator and the coil. I've seen some custom drag race systems use 9v batteries and one of those would be simple enough to wire up and easy to hide. My only concern was the systems polarity, I believe but I'm not certain that it is DC out of the stator up to the coil, at which point it is converted to very high voltage A/C so that it can jump the plug gap. Does that sound right?

The ignition system should still be triggered to fire by the pulse generator (The little pickup coil setup that the flywheel has a small external magnet for) and since it isn't generating any power and is operating as an interrupter type switch only it shouldn't (to the best of my knowledge atleast) be hindered by the lower rotation speeds.

The Goat
05-11-2008, 02:33 PM
This may not be similar, but there is no kick starter on my 200x, sometimes when I go to start it when cold, it will not start. If I connect a battery charger with a ten amp boost, it doesn't turn over any faster, but it starts instantly, less than a full rotation of the engine.

I'm wondering if you couldn't do the same thing?

Billy Golightly
05-11-2008, 03:45 PM
After many hours of discussion in chat last night (from about 11:30 till nearly 2:00AM) we covered a whole lot of ground on this issue/predicament (Thanks a lot to Harry and Gag_halfront for helping me get my brain wrapped around this electrical stuff) and settled on the following plan:

Between the stator and the CDI box on the hot wire coming from the stator (DC polarity of varying un-regulated voltages) wire in a momentary switch (Normally open style, so that when its pressed your "closing" (completing) the circuit and letting a 12v accessory battery exactly like Swinehart has above which would be 8 AA batteries help juice the system and fill the capacitor in the CDI quicker. Once the CDI is filled, the pulser releases the charge into the coil and then it of course generates the extremely high voltage needed to jump the plug. The momentary switch would have to be released as soon as the engine cranks so as to not overcharge the batteries with the unregulated voltage from the stator.

It took a hell of a lot of head scratching, but I think we're onto something here and I'll be taking a trip to Radio Shack tomorrow to pickup the necessary parts to see what I can make happen.

Hey Goat...that sounds pretty much exactly like what my plan is, your charger is helping juice/fill the CDI in addition to the normal system and thats allowing it to generate the power to spark quicker/faster then it takes the bare system by itself to generate. Sounds like the plan should work then :)

05-11-2008, 07:45 PM
Billy, you should check out some of the old school enduro motorcycle ignition setups. Some of them werent powerful enough to start themselves from just the stator, so they had a small battery implemented somewhere in the ignition system for the sole purpose of boosting the ignition system enough for the bike to start. Maybe if you checked out a wiring diagram or something from one of those bikes with that setup, it would give you some ideas of how to merge the idea into your 500R.

-Nick :TrikesOwn

05-11-2008, 10:43 PM
I had an msd enhancer ignition on a cr125 back in the day that worked real good that thing used a battery too.It started first kick every time.

Billy Golightly
05-11-2008, 11:18 PM
Well we'll see how it rusn out, I'm off to radio shack in the morning and buy the parts I need and then I'll start hackin away at it to see what I can get to happen.

Billy Golightly
05-12-2008, 07:31 PM
You guys are not going to believe me, get a load of this.

I got my parts today, they didn't have a 8 AA battery pack like I was wanting so I got some 9V contacts with the tires, and a momentary switch like I needed. When I got home, after some debate I stripped 2 wires WITHOUT cutting them. They were the solid GREEN ground from the pulse generator and the solid BLUE from the stator. I wanted to test the theory before I went any further and I just skinned and wrapped the wire from the 9V contact around these bare places. I put the 9v square battery in, and had my dad turn the kicker over slowly.


I'm talking real slow, like just enough power to make the thing spin around one time and its arcing. Not a real bright blue, but a pretty good sized white spark at least, for sure more then it had been at such slow speeds. So I'm thinking SWEET, this is actually going to work! So I un-wrapped the wire and told and was getting my stuff together when I told my dad hey row it over through slowly again, I wanted to see the difference in it.

Well I'll be damned if the freakin thing didn't STILL spark at low speeds just like it had been when I first hooked the battery up!

So we keep rowing it through to see if it was going to die down or anything and NOPE, it just kept doing it every single little rotation just like it should have been doing from the beginning. Sooo....I put all the *Edited**Edited**Edited**Edited* back on it, taped everything up, and on the THIRD kick it cranked right up. So I shut it off, kick kick kick BAM! Third kick again. This repeated SIX TIMES! All six times it cranked on the third kick. I then went and rode it some and lost my kickstarter (I found it , but it came off heh) and then had a little issue with it starting hot, but I used the ole wide open throttle trick (Which is how I use to crank it all the time when it was hot) and then 4 kicks it cranked right up. This is WAAAAY better performance then I was getting with trying to start it before.

My theory is that it somehow "charged" the CDI, I don't know how long its going to last but I soldered in the contact for the 9V battery and taped it up under the harness and I will either just "hook in" the battery every once in a while or I will go ahead and wire up a system as I had described above. I didn't really get the switch or battery box setup I wanted to do so for the time being I'll probably just plug it in once in a while. I got a race this weekend with it but I think it'll be fine for that.

Some crazy *Edited**Edited**Edited**Edited* how that works huh?

05-13-2008, 01:48 AM
If it is anything like the 250R electrical system, then the stator has a 200 volt AC coil and a 12 volt AC coil. The 200 VAC goes only to the CDI box for the ignition then gets rectified to DC and charges the capacitor for the spark discharge. So what you would want would be a small inverter circuit to step up 9 volt (or whatever battery config you use) DC to 200 VAC. Then you could run this with a toggle switch and it would have the CDI constantly charged with switch on for starting. I don't know how much time you want to put into this since it would mean making a small circuit, but that's just my opinion on how to fix the starting issue.

05-13-2008, 01:29 PM
Although it sounds like you are happy with the way you got it working now, I'll make a suggestion just in case you decide to "finish" it some.

The part where you mention you would have to disconnect the batteries quickly after starting can be avoided by installing a properly sized diode in line. This will prevent any back charging of the batteries.

Just be sure to get a diode rated properly for the voltage/current that will be trying to back feed the batteries once it's started.

Once you get that installed you can leave it hooked up full time without worry unless I have misunderstood something on how your electrical system is set up.

05-13-2008, 03:02 PM
That's pretty slick Billy! Kinda interesting how something so small makes that big of a difference....maybe I shouldn't have got rid of my CR500 and just done this :P

Billy Golightly
05-13-2008, 07:54 PM
Hey 1BFC, how exactly would I wire that Diode in? Hell maybe I'll get one of those and just leave that 9v (or maybe even 2 of them to make 18v) on the damn thing full time.

05-13-2008, 10:18 PM
a diode only lets electricity flow one way through it. looks much like a resistor.
you would put the IN side on the + battery side of the wire, then on the OUT side of the diode, you would run to your starting system.

so basically, cut the positive battery wire, and install the diode in between. then the power will only flow to the motors electrical system, not from the electrical system into the battery :D

Billy Golightly
05-13-2008, 10:22 PM
That sounds simple enough. Now how do I determine what size/type of diode I need?

05-13-2008, 10:57 PM
well, you need to know the voltage at the opposing side of the wire. if the pulse generator is putting out 100 volts, you need one rated at 100 volts. if its 200, you need one rated at 200 volts. all ya gotta do is figure out how many volts the pulse-generator puts out. Personally, i would give it about an extra 50 volts higher than the rated output for the pulse generator just to ensure no problems will arise from a possible high-rpm voltage spike.

i seriously doubt you will need a diode that can withstand high current flow, as that 9 volt wont be pushing much amperage through it, so probably something 250-500milliamperes will do just fine.

so, if the generator creates 200 volts, grab something around 250 volt resistance rating, and 250-500milliamperes current carrying capacity.

Havent been to radioshack for diodes, so you may not even get an amperage rating choice. this isnt too critical anyways, as it doesnt affect the diode's one-way flow characteristics, just how much amperage it can handle flowing through it.

OH and the diode should have an arrow on it. pretty obvious, the arrow points in the direction of the electrical flow. arrow should look like this

05-14-2008, 01:18 AM
300rman has it already answered pretty well :)

You can get a diode from Radioshack or www.digikey.com

Here's one that would probably do the trick with a ton of over kill built in. This part cost about $0.40 too... not exactly expensive.


datasheet for it: http://www.onsemi.com/pub/Collateral/MR850-D.PDF

if you want to look at others, do a search on diode rectifier on digikey.

Good luck with it!

Billy Golightly
05-14-2008, 10:45 AM
Thanks for the input guys. I searched around onthe radioshack website and found a few that I think will do the trick, hopefully they are instock at the one here in town. It'd be nice to have this thing all wired up and ready to go permanently by this weekend.

Billy Golightly
05-14-2008, 08:59 PM
Well I don't know what the hell I did. I made up the battery pack using a 9v, soldered and wired in the diode (was wrong direction the first time but I redid it and got it right). I grounded the battery and run the positive down to the wiring harness in the same place I had the old 9v snap connector soldered in...and now I have the exact same amount and type of spark as I did to start with before I did anything. It wont spark worth a *Edited**Edited**Edited**Edited* at low speed and is awesome once the motors turning over. UGH what a piece of *Edited**Edited**Edited**Edited* I can't believe I had it going and working, tried to get rid of the cob job and now its back to the same stuff again. Damnit.

05-15-2008, 08:22 AM
Billy - did you install the diode yet? Maybe you have it in backwards.

Billy Golightly
05-15-2008, 09:23 AM
Nope, Diodes in straight tested it with a volt meter and that'd mean the battery is still up too. I'm gonna go over my solder joints and stuff today and see if I can figure out.

05-15-2008, 10:19 AM
You probably already checked this, but a battery can show voltage and still be "bad". If you have another one to try, give that a shot too.

You'll find the gremlin...you KNOW it works, which is a big help.

Billy Golightly
05-15-2008, 11:40 AM
Well this morning I figured I'd give it a try and see what happened, maybe it fixed itself overnight :lol: This time, with nothing changed from last night except for putting the spark plug back in and the boot on, it kept back firing a lot when I would kick it. I determined that perhaps the charge from the battery was disrupting the spark timing in the CDI box. It still didn't spark good at low speeds like it was before, but had excellent spark at faster speeds which has been the issue all a long.

So, I opened up my plastic case that held the battery and simply un hooked it. Put the snap connector and diode back into the case, screwed the lid down and clamped it back to my frame.


Shut off


shut off


shut off


shut off.

And I kicked 50 times on the damn thing last night with the battery hooked up to it and never even so much as farted. No back fires, no pops, NOTHIN. I have not pulled the plug and wire again yet to visually check the fire at low speeds but from the ease of it cranking I'm sure it is. I cannot get my head wrapped around this, it makes no damn logical sense at all! BUT its working this time and I'm gonna leave the MFer alone cause its cranking easy again and that was my goal to begin with.

05-15-2008, 03:32 PM
Sure sounds like a bad connection somewhere to me.


Fiddle with wires...

Doesn't work....

Fiddle with wires..

Works again...

I bet when you actually ride that at some point it will revert back to "Doesn't work".

For your sake, however, I hope I'm totally wrong on that :)

05-16-2008, 12:15 AM
I'm sorry but I don't see how putting 9V DC into a high voltage AC circuit is going to help it.

Billy Golightly
05-16-2008, 12:19 AM
I don't either and I don't have any explanation for how exactly it worked but it did, thats all I know.

Billy Golightly
05-16-2008, 07:46 PM
I cranked it up again before I loaded it into the truck this evening, 3rd kick and it popped right off!

Billy Golightly
05-20-2008, 08:59 PM
Cranked up really easily at the track. 2 kicks when cold with no throttle, 3-4 with the throttle wide open when it was warm and had been ran a bunch. Still an infinitely better setup then it was before thats for sure.