Weak spark? Chime in

[BULLET99Z28]

This is my first R, and 1st 2-stroke in aboout 15 years, so bear with me. I got the kill switch wired up, and had the spark plug connected to the coil, and was crankin it over by hand looking for spark. I was just verifyin the wiring was correct. Anyway, I could not get a spark, even though it was wired correctly. This motor and harness together ran when I bought the parts bike it came out of. So I let it be for awhile, and then I really gave the kicker hell, and i got spark.If i keep working the kicker fast, I keep gettin spark,and figure maybe the plug laying on the cylinder head isn't the best ground, compared to being screwed all the way in. My question is, how fast do you gotta crank the kicker to get the spark generating? Just curious to see if I might have a weak coil or cdi, or perhaps something down in the stator area.

FYI- I have the entire harness exposed, its not spliced anywhere, in great shape, and am not running the on/off or light switch,just a Pro Design kill switch.

[wilkin250r]

I don't have any hard numbers, but I think you definitely need to kick it to get spark, you're not going to get anything cranking it by hand. The flywheel needs to have some speed to it.

I know some of the dirtbike CDIs actually have a minimum rev limit built in, if the motor isn't spinning fast enough when you kick it, the CDI actually grounds the spark rather than sending it to the plug. I don't know if the 250r is actually built this way (I don't think it is), I think it's more just a matter of the physics of electricity. The flywheel needs to be spinning fast enough to generate enough voltage to spark.

If you can see a spark when you hold the plug against the head and kick it, and the spark looks nice and blue and it appears to be sparking every revolution, then most likely it's good. Without a proper spark waveform analyzer, the best way to tell is to try it.

[RyanWsly]

there is a minimum RPM that must be met if you still have the stock analog style CDI box. can't remember the number for sure, but seems like 500 rpm or greater guessing

[C-LEIGH RACING]

At least 750 rpm, for the ol stock TRX ignition to produce a spark, so it needs a good hard kick on the kicker to rotate the crank fast enough.

CR ignition system, real low rpm rotation.
Neil

[wilkin250r]

Well look at that, even I learn something new every once in a while. :p

I'll have to dial-down my little setup to check the minimum RPM, I'd like to actually see this in action. So far all of my testing has been in the upper revs to see how the voltage drops, it never occurred to me to check anything in the lower RPMs to see how it behaves.

[C-LEIGH RACING]

Yeah, that was one things about the ol stock ignition, you realy had to jump on that kick starter, make it turn to make her spark.

I know you remember ol Teamgeeks from MacDizzy, that dude was the 250R ignition guru.
Learned me something about a stock R ignition system, mater fact, thats how come good part of my hair is gray from just not giving up & trying to make the ol stocker work, dye hard I guess you could say.

Life is soooo much easier now with the CR set up on the ol 250R.
Neil

[BULLET99Z28]

Thanks guys, the minimum RPM answered my question. I can get good spark by really crankin on the kicker by hand. So I tidied up the harness and am good to go. Probably gonna be a real bear to start for the first time- fresh 310 topend, hi-comp.....

[bhatch21]

Hi. I thought I'd chime in with my stock spark experiences. For the longest time I could only get my 250r to spark with a 400ex cdi. I eventually learned it was for a few reasons.

One, the stock pulse genrator was bad but checked good on the meter. And the 400ex cdi didn't care, it would spark and run the bike to half through and then stutter out.

Next, I bought a new Electrosport stator and pulse generator. It was my only option besides a Ricky Stator with it's bad rep. But still, it only sparked the 400ex box. After putting a meter to the pulse leads and getting negative voltage, I determined it was wired backwards from the factory. Switching the wires around in the connector gave me spark with the 250r cdi.

And finally, what I learned was: all aftermarket stators/pickups may be made at the same place in china (read shoddy), and my stock 250r cdi boxes would only spark by kicking them, thanks to the minimum RPM requirement.

[wilkin250r]

Originally posted by bhatch21
One, the stock pulse genrator was bad but checked good on the meter.

That's really odd. Are you sure the mounting tabs weren't bent, causing it to be mounted too far away from the flywheel to pick up a good signal?

The reason I say that is because the pulse generator is such a simple mechanism, it's just a coil of wire around a metal core, there's only so much that can go wrong with that. Either the wire is broken and creates an open circuit, or the insulation has melted and it's no longer several coils, just one big one. Either one of those issues would show up in a resistance test. The only thing that wouldn't show up is if the metal core is broken, but that's not likely without also breaking the wire.

[bhatch21]

That's the only thing I've changed. Well, that and the stator together, but it also ohmed out good on the meter. But I also haven't put either stock one back on there to double check them.

My stock pulse generator could have some internal corrosion since there was moisture in there and a tear in the gasket when I originally removed the stator cover.

[DnB_racing]

Originally posted by bhatch21
Hi. I thought I'd chime in with my stock spark experiences. For the longest time I could only get my 250r to spark with a 400ex cdi. I eventually learned it was for a few reasons.

One, the stock pulse genrator was bad but checked good on the meter. And the 400ex cdi didn't care, it would spark and run the bike to half through and then stutter out.

Next, I bought a new Electrosport stator and pulse generator. It was my only option besides a Ricky Stator with it's bad rep. But still, it only sparked the 400ex box. After putting a meter to the pulse leads and getting negative voltage, I determined it was wired backwards from the factory. Switching the wires around in the connector gave me spark with the 250r cdi.

And finally, what I learned was: all aftermarket stators/pickups may be made at the same place in china (read shoddy), and my stock 250r cdi boxes would only spark by kicking them, thanks to the minimum RPM requirement. I think you initial problem was that you had a 86 harness and a 87 up cdi or vice verse, as the pulse generator leads on the cdi are different between the two types

[bhatch21]

I thought about that too. I tried swapping them around them around at the cdi with the old pulse like someone suggested and got no spark. And the wiring diagrams in my manual show all the wires in the 4p connector in the same position before and after 86. I've got 3 stock cdis all with the '89 HB9-CF552 part # on them.