Weird rpm signal
 

The bike wount rev past 6500 rpm, it just looses all power. At the same time the needle of the tachometer is going bananas! Im thinking that a faulty ignition signal could be the cause of my problem. Ignition pulse generator? ICU? Could this be the result of a broken R/R?

Not R/R related, I would check the pulse gen first, you should have 0.7V peak (need peak hold Multimeter), try it at higher RPM If correct, I'll try to swap the ICU with a known good unit

Borrowed a ICU from a friend but it did not make any difference. Put the bike in the Dyno and we could see that the ignition signal at both coils gets crazy at ~7500rpm. It dissapperars, comes back, dissapperars and so on. I'll try to find another puls generator, it must be that fucker who is causing the faulty ign signal. Any other ideas?

bad coils? is your timing in spec?

nope, the coils are ok. Tryed it before I've tested another ICU. I'll try a new pulse generator next week.

How's your battery voltage?

Battery voltage was checked when the R/R was replaced, but how would the voltage of the battery affect the ignition signal? I'm pretty sure that the timing is ok since it runs perfect through the low and mid range. It seems like it looses the ignition signal when the rpm reaches 6500 rpm

2nd the battery voltage question. My VFR had the exact same symptoms when its R/R went bad. After a bit of riding, without sufficient R/R battery recharging, there wasn't enough juice to run the tach or ignition. Bike can't rev past a certain amount, tach goes bananas.

The battery wasn't holding a charge for long, as the R/R going bad had over time caused the battery to go bad. Didn't really notice anything until one day I get all these symptoms. New R/R & new battery, then all was well.

So, how is your battery voltage? And after you recharge the battery, how is the battery voltage several days later? I'm thinking bad battery, and maybe a bad R/R (which caused the bad battery).

I replaced the R/R after it burned, now there is a R1 -01 R/R with fins mounted. I've checked the battery voltage but only at idle, not where all the problems start. But it is no problem to start the bike after it has been standing for some weeks so it seems that it holds the charge. I will still measure the voltage in the hole rpm range or try an other batery.

Well, no difference with another pulse generator....I also replaced the battery but the bike wount rev more than ~6500rpm. I am thinking of a new (used) cable harness, any other ideas? Could bad spark plugs give thoose sympthoms?

Check voltage at battery when you rev up the motor.
It should swing upward toward 16 volts. no less than 15. @ 4000 rpm
If the R/R has an internal short( meaning its going to die soon) it will do this same thing.
To eliminate the R/R from your troubleshooting equation, pull its plug and leave it disconnected with a charged up battery... and test bike. If symptoms change, like it can rev up now, the R/R had a short between diodes.

Aha, good idea!I'll measure the battery voltage and dissconect the R/R tomorrow, it wouldnt start today since the battery was empty. I measured the resistance of both ignition coils and it turned out to be 17,9 kohm (front, both circuits) and 17,3 kohm (rear, both). Can't find any informtion on coil resistance but i know that I have seen it somewhere in this forum, any one?

Alright, tested the battery voltage when reving the bike and there were not that big difference from the voltage at idle, 13,7-13,9. I also tryed to disconnect the R/R with a fully charged battery but the bike still wount rev up.

Next , unplug the stator plug near the gas tank bolt, and check for continuity to ground (beep) from each of the 3 leads comming FROM the stator side.
If any of the 3 stator wires beep to ground you have direct short in stator pulling your system down.

There were no continuity to ground on any of the wires. However I found that the axle to the TPS was broken giving a constant signal of 400 ohm. How would this affect the performance? Could this be the reason why the bike doesnt rev up?

try unplugging the TPS .. It will still rev up without it, just not quite as punchy.

1st rule of the service department - broken doodads are never good. lol
fix the broken doodads before good diagnosis can happen.

Alright, I guess I'll need a new TPS then. I've heard that they are expensive.....

Honestly you can fit about any TPS there with minor modifications, they are all about the same, just bring it to a junkyard and get a similar one, specially when they only drive the ignition advance, I would not do this on an injected bike that use the TPS as the main load input (Alpha-N algorithm)

Well to verify if this is your problem, unplug it and see if it will rev up without it attached. You won't have full power, but it should still rev to redline with it unplugged.

Edit: and IIRC Honda Civics have very similar TPSs that just have the wireing connect from a different angle.

Thank for all your help, I'll get back when I have some results.

Just a thought, check the coil voltage supply while reving the engine, in case that a bad wire would cause a voltage drop as the duty cycle increase. Same could be done for the ICU, there's very little components left from the ignition system except the wiring.

I just checked the coil resistance you posted, this are not the primary winding, it should read 1 to 5 ohms, unless those coils are different from what I'm used to, I'll measure the resistance of mine and report tonight after work. When coils fry from too much voltage, they go from the primaries.
They don't look like smart coils, they are rather dumb units (no ignitor built in)

I get 14 ohms to primary

How do you measure the coil resistance? The figures I posted was the resistance over the spark plug cap and the each one of the two wires in the 2pcs connector as shown in the picture. Reading was 18 kohm

I measured the two leads of the connector, this is the primary winding, the one that usually let go.

I start thinking that this bike is possessed, maybe hire an exorcist :shock: