Questions About Rectifier Testing

Where on the bike is that located?

That doesn't look like the OEM ground lug at all--the factory lug doesn't have yellow insulation on it and is located in the vicinity of the RR.

That looks like someone's attempt to fix a ground problem, but where is the wire?

Yes you could just add a ground wire jumper from the green at the ICM to a known-to-be-good ground point, but there are a multitude of other green wires that are intended to be grounded also--and you really should trace and fix the root cause and make sure ALL the grounds really have a good path to chassis ground and the battery negative terminal. If you want to make the jumper just to make a quick test whether it will start and that the ICM is okay, then that might work okay, but don't try to run it without proper return ground paths for all the circuits--otherwise you could really burn some stuff up.

 

It's just about midway down the right side of the bike. I haven't sat on the bike yet or know what my body position would be, but I'd say it'd be next to your thigh. Those two yellow ring terminals are empty. There's a third on the very inside. You can't see the terminal, but you can see the Green and Green/White (I think) wires in the pic. They're connected to that inside ring terminal. Not sure what the PO's intentions were with those two yellow ones.

Where is the stock chassis ground? I didn't see anything near the R/R. Then again, my subframe has had a decent chunk cut off the back.

Yeah, I know there's a whole lot of stuff branching off that green wire.

 

I found the break in the wire. Whoever cut all the excess wire when making this thing into a trackbike did it wrong. First I followed the wire out of that grounding lug, and just stripped a little piece of wire from the right turn signal and the horn, and they both showed continuity. As far as I could tell, the horn is the end of the line for the green wire towards the front.

I then followed the green wire out of the ICM, and saw that it dead ends where a PO cut off the rear light cluster wires. Tested for continuity between the dead end and my small test strip just outside the ICM and there's continuity! Double-checked for continuity between the dead end and the grounding lug, and I got nothing.

Good, I'm half way there.

This part was easy. Just strip the rest of the green wires in that cluster and see which one leads back to the lug. I found it, then tested for continuity between that wire and the wire from the ICM and got nothing. Perfect!

It's looking good so far. All I should have to do is join the two "flagged" wires, and we should be good to go! Hopefully this works out.

 

So there still isn't any spark on any plug. I don't get it. The ground wire is fixed, there's good continuity between that green ICM wire and the (-) battery cable.

I rechecked all the coils, and they're still good. Kill switch, sidestand switch, clutch switch, clutch switch diode, and starter relay switch were all re-tested and good. I can't check the neutral switch. All fuses are good.

All the instruments have been removed from the bike, as well as all indicator lighting. I see that the ICM wires up to the tach, I wonder if the tach being gone has anything to do with it. I'll go jump the tach wires and complete that circuit... I'm thinking it's a long shot, but you never know...


EDIT: Nope, jumping those wires didn't make any difference at all.

 

ok, so you have removed the instruments, Hmm -then it's a different matter. I read somewhere once that somewhere in the wiring harness has to be jumbes/shortcout, if instruments are to be removed. good hunting on the web.

 

Ignition circuit VFR 750,1990-on



This is from Clymer Honda VFR700F & VFR750F * 1986-1997,
from Primedia Intertec, Kansas P.O. Box 112901, Overland Park, KS 66282-2901

 

So, you see the neutral indicator and sidestand indicator light has to be pressent.

 

That diagram helps a lot, the Haynes isn't quite as clear about that. I was just going to jump each pair of instrument wires together, but I guess I'll jump those two.

It's funny how many problems I've found (and fixed) while troubleshooting this.

EDIT: I spliced the wires from the two indicators together and connected them to the mutual Black/Brown wire. Still nothing. I've got to work all day, so I'll have to wait until tomorrow to take a closer look. Damn.

 

Great that you found the missing ground wire! Bad news that someone got happy with the wire cutters...you may have more cut wires to discover along the way to getting this bad boy running.

To troubleshoot the ICM
Remove the ICM connector and with the key ON and the kill switch to RUN, verify that you have battery voltage present on the Black/White wire measured with respect to the green wire.

If so, then verify that you have normal resistance of the pulse generator coils (450 to 550 ohms at the ICM, 200 to 400 ohms at the 4pin connectors at the pulse generator) between the yellow and white/yellow, and between yellow and white/blue. So 300 is probably okay if they are both the same.

If that is good then verify continuity of the neutral switch line, light green to ground. Continuity when in neutral, open circuit when in any other gear.

If that is good verify continuity of the side stand switch, green/white and ground. Continuity with stand up, open circuit when down.

If that is good and you are getting no spark on all four, then the ICM is likely bad.

The only other test i can think of is to actually measure the output of the ignition pulse generator coils to verity that a voltage pulse is being created. Maybe the magnets have been damaged or the gap is too wide to get a decent pulse...

 

Whoever tried to track this bike wasn't too careful about cutting wires. I would've probably done the same thing, though. Chop off everything unnecessary and not think twice about it. Then scratch my head when it doesn't start!

Looks like I'm in the market for an ICM?

 

Since somebody got stupid with the wire cutters all bets are off.

Verify continuity of the wires from the ICM to the coils.

If you can try to measure a voltage from the pulse generators to verify they are making pulses. An oscilloscope is the best way to actually measure the voltage, but a meter on AC can indicate that at least something is happening or not.

Maybe track-boy removed the magnet wheel to save weight and go faster. You almost have to remove all the side covers just to discover what is or isn't still on your bike after somebody gets an idea to strip her down...

It may be that the ICM got fried inside when the green wire was cut and there was not a return path. Normally that wouldn't be a failure mode, but in your case it is. Better verify everything is intact before hooking in the new ICM. Maybe can find a known-good used unit for testing.

 

I imagine the PO as a guy with a sawzall and a bloody lab apron, laughing maniacally...

Continuity is good through all the wires... From the ICM connector, at least. I don't know how to tell if anything is getting through. Just put the meter leads between the colored and black wires on each coil can hit the starter? And set the meter to AC?

Speaking of the wires, can you verify that they're on the correct terminals? rjgti said that the colored wires go to the green terminals on all coils. I have no reason to doubt him, but the manuals aren't really clear. Plus, if they're all wired backwards, could that lead to a no-spark?

Here's mine now:



Notice that the Black wire is "across" from the plug wire.

Haynes:



Notice that the COLORED wire is "across" from the plug wire.

I also get the same impression from this page of the Haynes:



And also the FSM:



Does what I'm saying make any sense? I'd go out and simply switch the wires, but I don't know if I'll fry anything is they're hooked up correctly right now.

 

i can't verify the wiring for you, but someone put a Y on that coil near the green terminal and there is a Yellow wire connected. i suspect the colored wires go to the green terminal, but it may not really matter. The yellow wire gets grounded thru the ICM so that current flows thru the primary coil. When the current stops, then the secondary coil voltage goes high and pops a spark. It's a magnetic field collapsing and i don't think the magnetic polarity matters, but i got no proof.

If the pulser coils are not sending a pulse to the ICM then the ignition coils will not fire.

 

Polarity doesn't matter on either of my Yamahas, but I wasn't sure about the Honda. I'd love to blame it on my skepticism of the POs, but the coils on there now are actually a used set I picked up, so it's probably correct.

I'll see what I can find out as far as the pulse. Do I just hook the meter up to the wires that attach to the coils and press the starter? The ICM is something that the guy I bought the bike from specifically said that he replaced.

 

And promptly blew...

Electronic modules do not like to have the ground open--the electrons are looking for a path back home and if there is not one, then they will make one through whatever path is shortest.

i suspect the replacement unit is now bad--he replaced it because he had a problem that blew it, but never fixed the root cause. So the ICM became a big expensive fuse.

To check the pulser you would put a voltmeter (probably either ac or dc would work, try both if one doesn't give a reading), or oscilloscope and watch the waveform. It's probably a low voltage signal and there is an amplifier in the ICM.

 

So I tested the pulse generator. At the 4-pin connector, the voltage is 0 at rest, and goes to about a steady 0.10v when I hit the starter. At the coil wires, the colored and black wires, the voltage is 0 at rest and a steady .03v when I hit the starter.

I only tested the wires of one coil.

 

It seems like the pulser may be working although the voltage sure is at a low level--?, but i'm not sure what voltage level would show up on a meter--that is really an oscilloscope measurement to know for sure. But there are no specs on it in the manual.

Verify that you have power at the ignition coils. With the key on and kill switch in 'run' position you should measure 12 v at the black/white wire on each coil with respect to chassis ground.

Then measure the colored wires with respect to ground--they will read either nearly 0 volts or 12 volts depending upon the ICM logic, BUT they should pulse between nearly 0 volts and 12 volts when you push the starter button if they are getting the proper control signal from the ICM. On a scope you could see this, on a meter it may look like the voltage is jumping all over the place.

Either the pulser or the ICM, or both, are likely bad if it fails this test, and it is easier to replace the ICM than the pulser generator. But if a new ICM doesn't work then a new pulser may be needed.

 

I wish I had more of a need for an oscilloscope, bc I (as I'm sure everyone else does too!) love buying new tools. I can get cheapos like this on eBay for $60, but who knows if they're worth anything. Arm DSO201 Portable Pocket Sized Nano Handheld Digital Storage Oscilloscope AHN | eBay Plus, I wouldn't know how to use the damn thing, and I'd have to wait for it to get here from Hong Kong.

It'll probably be a few days before I can take a look at it. I'll post up what I find.

 

I've already got another pulser, so at least I've got that going for me.

 

It's been a while since I've posted here, but since the last update, I've:

-Replaced the pulse generator
-Replaced the ICM.

And wouldn't you know it, still no spark... I really don't know what to do next. I've replaced everything and all the wiring SEEMS to check out now. I'm lost.