Potential CDI issues?

Discussion specific to the 1995 - 2006 KDX200 (H Series) and 1995 - 2005 KDX220R (A Series) models sold in the USA
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MotoArts
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Potential CDI issues?

Post by MotoArts »

My 1997 220R is having issues with what sounds like a rich pilot/needle circuit in the carb.
New jet block gasket, carb is spotless, 38/142 jets, PC pipe and silencer, rest is stock.
Removed the top end just to inspect PV's and obvious slap hackery, and everything looks peachy keen.
Can't get this random dead miss/rich bog out of it, no matter what big swing I take with needle position or air screw. Jets are already lean enough... and it is not using trans oil, has no exhaust spooge either.

Suspecting a faulty CDI unit. I'm thinking the timing is going shotgun scatter until it reaches a certain RPM, then it generally runs and sounds downright rippy... as in a bad component or components, board, wiring...

Has anyone tried the adjustable unit I've seen online?
Anyone have a known good unit for sale or lend/lease?
'97 KDX220, '84 YZ125, '81 YZ250, '78 RM250C2, '80 RM100T, '04 KTM 250SX,
'82 Yamaha Seca 650 Turbo, survivor
90SDKDX
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Re: Potential CDI issues?

Post by 90SDKDX »

http://www.kdxrider.net/forums/viewtopi ... 15&t=19538

That article is from a issue I had with my E series. Not really sure if it is similiar to your issue, but it may help you. I am also in the process of installing the adjustable CDI.
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Jaguar
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Re: Potential CDI issues?

Post by Jaguar »

the lower the RPM the lower the voltage from the stator coil which the CDI has to use to drive the high voltage coil.
If the stator plate or the mounting screws are getting rusty then that presents resistance in the circuit because that is a ground path. Make sure that metal to metal contact is clean.
If the stator coil has a partial short then that would lower the voltage which would demonstrate as a low RPM problem. Next I'd suspect the high voltage coil. I'd replace it with any of the Honda CR coils because my testing of various coils has shown that to be the most powerful. You can find good used ones on EBay. Make sure the bolt hole spacing is 55mm center to center.
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/
MotoArts
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Re: Potential CDI issues?

Post by MotoArts »

Thanks guys.
Yes, yours is the CDI unit that I was referring to, Jaguar. I did not know that you were "the" designer ;)

When I first got the bike last year, it did not run. Had random intermittent spark, as in either good or no spark. Checked the ignition coil first with a known good unit, no dice. Disconnected kill switch and lights and again, no dice. Verified bullet connectors to CDI, but did not spend time cleaning them. Removed flywheel, removed stator plate and found corrosion between plate and case. Cleaned, added light coat of dielectric grease, and now we had consistent spark. Also a note of interest at this point is that the lighting coil was trash... winding was no longer wound but not to the point of a birds nest, so my lights wouldn't have worked anyways. I left the lighting coil alone, figuring that it was one of the last things that I was going to need anyways. The bike had more pressing needs...

Engine does consistently start easy cold or hot and idles reasonably well. When cold, it runs like there is a direct gas line to the intake manifold... lots of tailpipe smoke, lots of "airbox" noise (like flipping the air cleaner lid over on an old Quadrajet equipped Chevy... us '50-something gearheads know what I'm talking about :cool: ), and typical power reduction till full operating temp arrives.
Even so, it hasn't fouled a plug yet.

I lean towards electrical issue now since:
1) - I've made jetting swings with no expected changes.
2) - There's a small random dead miss sound as it accelerates through any gear. If it had a tach I could better describe a RPM window, but it's just off of idle to maybe 2/3 of its usable RPM curve. It doesn't really "lean surge" like I've felt many times in the past of various vehicles, just pulls erratically. Once up on the mainjet, it sounds and runs like gangbusters. If the dead miss is there, I can't hear or feel it.

Maybe you two are on to something regarding heat soaking of the source coil. The rest of the day riding, even after it sits for a while during a break, it doesn't seem to "load up" as much as it does when stone cold.
'97 KDX220, '84 YZ125, '81 YZ250, '78 RM250C2, '80 RM100T, '04 KTM 250SX,
'82 Yamaha Seca 650 Turbo, survivor
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Jaguar
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Re: Potential CDI issues?

Post by Jaguar »

the bike is around 10 years old so its probably time to replace the crank seals. Have you checked them for leakage?
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/
MotoArts
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Re: Potential CDI issues?

Post by MotoArts »

Wet side seems fine, uses no trans fluid over several tanks of gas. I've had bikes with bad wet side seals/bearings before, this one I'm going to call OK.
On the dry side, I just checked flywheel/crank play and all seems perfect.
If it were sucking air, I would think with my lean 38/142 jetting and needle all the way down (clip in top slot) it would be lean surging, pinging, running hot, etc. Instead, it sounds and feels rich. And, the volume of gas that it eats is astounding. Fuel mileage is horrific... but it doesn't foul plugs or spat spooge anywhere.
It literally gets half of the mileage that the CR250 does.

I'm tellin' ya, it's a real toughie to figure out. I will remove and inspect the source coil from the plate itself next. I can't remember if I did that before or not.
'97 KDX220, '84 YZ125, '81 YZ250, '78 RM250C2, '80 RM100T, '04 KTM 250SX,
'82 Yamaha Seca 650 Turbo, survivor
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Jaguar
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Re: Potential CDI issues?

Post by Jaguar »

I would suspect the carb then. Maybe the valve to the float is not sealing completely
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/
MotoArts
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Re: Potential CDI issues?

Post by MotoArts »

Today, 7/4, I removed the source coil from the stator plate, cleaned its contact points to the plate. I had previously cleaned the plate to case interface, and rotated the advance back and forth a few times while I was there just to ensure good ground contact.

No change in run quality whatsoever.
'97 KDX220, '84 YZ125, '81 YZ250, '78 RM250C2, '80 RM100T, '04 KTM 250SX,
'82 Yamaha Seca 650 Turbo, survivor
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