$400 question; Igniter for ATV

Nick Hull: Year and model number of ATV ? .... and how many cc engine? electricitym

There was a simpler (for us to see) way in the past....a mechanically advanced "breaker plate" which originally mounted the points and later perhaps just a pickup. For the manufacturer, what you have is likely simpler. As it sounds like you got your igniter apart, is it repairable (or was it a destructive process.....potted etc)? Most likely what you have is a pretty simple circuit - why not reverse engineer it and either repair what you have or build your own with similar but perhaps more readily available components. Your cost to buy that unit has little to do with the cost of its component parts and more to do with supply and demand and typical lack of standardization.

You mentioned a failsafe mode but then answered your own question by noting that it might take extra circuitry to insert the delay (just one possibility for failure). One such system used in the past was to trigger the ignition coil (i.e. to be an igniter) via a capacitor discharged using an SCR (CD ignition) - Timing voltage was picked up via a coil being swept by a magnet on the flywheel (small engines). Advance and retard were effected by nothing more than a simple RC circuit (fixed time constant) which was overun as the engine sped up (capacitor didn't have time to charge or delay the build up of the trigger for the SCR). These types of modules often had nothing more than a few diodes, couple of resistors and caps and of course the SCR. They MAY have used a seperate supply coil (Dirt bike with no battery) which built system voltage just before the ignition was required......this could have been supplied by a battery as well though (as supplied by for cars and trucks).

With older mechanical technology you faced similar problems to what you've experienced. The breaker plate (or perhaps just a moveable breaker cam) could be "stuck" at some advance anywhere between low and high speed (not to mention the points themselves, if used). The only thing is with this "cave" technology is that you might dig out some lube and basic tools and fix it right there. A good thing with electronics is that you might go a long time before needing a fix....it's all in whats acceptable to YOU.

It sounds as if what you think you want could easily be much more complex than what you're replacing (hopefully an engineer, ANYWHERE, will read this and take heed!) Keep in mind the operating environment for this circuit or problem as well....do you want anything that is adjustable or prone to corrosion, immersion, high heat, extreme cold or mechanical failure in this severe environment, considering the consequences involved (you walking 20 miles home out of the bush for example).

Just meant to be food for thought and to sure not deter you from your pursuit - from someone who's been thar 'n done dat.

Gord

Igniter was not potted, but the IC is covered with a secondary PC board with surface mounted items so I can't read any numbers on the IC. It might be repairable but I don't have a circuit diagram.

CD sounds like an interesting alternative, where could I get some info on the design of the RC delay circuit. The board I have does not appear to be CD since I see no big caps. I'm guessing the power device is eother a transistor or a power mosfet (did they use power mosfets before

I'd probably prefer ancient tech breaker points, I've fixed them many times in the field, but in this case I don't have that option since there is nowhere to put a breaker point. Of course I really want it all, long life and ability to field repair or drive in the 'broken' condition. I've driven a lot of broken stuff; cars and tractors with broken steering, no clutch, no brakes, broken fuel system, etc.

This 3-wheeler almost never leaves my hundred acres and I can usually tow it or carry it with my farm tractor. One of my principal uses is to use the 3-wheeler to repair a broken tractor in the field, and the tractor helps repair the 3-wheeler.

Howdy Nick......by your reply I can see that you know already most of what I mentioned :) I don't recall power mosfets back that far but it's possible. Wouldn't rule out that the device, especially if it's a TO-220 or similar package isn't an SCR or similar either. I'll draw up a schematic of an era CD box I unpotted and repaired for a Can-Am motorcycle which is right at hand and shoot it off to you. The RC circuit can basically be found in any basic electronics text book with the formulas for finding instantaneous charged voltage etc....some experimentation will be needed to find your offset though. There were quite a few CD ignition kits around at one time and articles in various electronic mags and project books so some digging there might be real helpful.

Gord

CD sounds interesting but there are 2 questions; IIRC CD was sold as an accessory to regular ignition points to take the current so the points would not burn. The points were used to trigger the CD and the mechanical spark advance was still used. This is all guessing from old memories, I never used CD back then. I recall one of the arguments was that if the electronics failed (as it did too often back then) the CD system would revert to the regular points to keep the car running.

In addition to the mechanical advance, CD used a big cap to zap the coil. Apparently I don't need the cap since my present system just pulses the battery voltage.

If CD did use the mechanical spark advance it won't help me much. I need to find a simple electronic spark delay, even if it is only a simple fixed 30 deg delay, to pack for emergency use.

Ironically, I could really use CD for my tractor. It goes thru points too fast, BUT it is 6-volt and positive ground and I have never seen a CD for a 6-volt positive ground.

I could see here the possibility of using a variable delay line and a $14.00 4-wire GM ignition module say like form a late 1970's Monte Carlo, Not sure how to make a delay line that would preserve the correct pulse shape from the coil, however I am sure it is possible. One would rout the signal from the pickup theu the delay to the amplifier module --> coil. Having successfully used 4-wire GM modules to replace the two ignition modules on a KZ-550LTD streetbike before because the spark amps from Kaw were more expensive than the old bike, I am sure it will work, your only problem being the timing advance, the KZ had mechanical advance.

The advance (delay) is the real problem because it is not constant in time but must vary with crankshaft rpm even when a constant 10 deg BTDC is needed at low speed. That's the part that has me puzzled.