possible TCI problems on `90 FZR

[mattfromthepier]

I'm hoping to get some help with a 90 FZR600 that I havent been able to get running any any help would be greatly appreciated!
As of now the bike struggles to start, sounds like it wants to but just wont fire up and sometimes lets out a loud backfire!

Things I've already tried include 3 new sets of spark plugs, two factory NGK sets and one set of little bit
hotter NGKs, all of which fouled very quickly and plug life got shorter and shorter throughout the 3 sets. The first
set i thought I fixed the problem as it ran for a couple days of short rides around town.
The second set didnt last but a day of riding and the third only got me down the street( had to walk it back!)

Other stuff Ive tried: taking apart the carbs to check for anything abnormal, dirty or clogged,
checked valve clearances (all were within spec), checked sparkplug coil and wire resistance(good to go).
There is spark when i checked at cylinders 1 and 4, only reason i know is becuase the boots are broken and i
can arc them to the frame because the plasctic boots are broken. I've also replaced the stock VR with YZF VR.

Anyway, I've been thinking about replacing the TCI because the bike has some "weak spark symptoms" that i cant seem to diagnose.
The DC volts at tci w/ key on read: red/white- 11.99v

grey- 11.99v
orange- 11.99v
black/blue- ~ .9v

Other plug:white/red- .59v
white/black- .59v
grey- .05v

The DC Volts at tci while cranking read: red/white- 9.0v
grey- drops to 9.0v then drops when cranking stops to ~1.0v and kinda stayed there (????)
orange- drops to 9.0v then goes back up to 11.99
black/blue- 1.07

Other plug:white/red ~1.0v
white/black ~1.0v
grey- 0.3-0.5v
Im not so sure about that grey wire, does any one have any idea what up with my FZR? I feel like i need a little
more info on the TCI before i go cutting it open or replacing everypart part two or three times until it runs. LOL Thanks for any response! -Matt

[DonTZ125]

Hi, Matt.

It sounds like you've got a fried coil driver - the grey wire on the 6-pin connector grounds out the 2-3 coil, allowing current to flow through the primary winding and building a magnetic field in the core. Once the current is chopped off, the field collapses, sending a voltage spike through the secondary winding that arcs across the spark plug. There should be full battery voltage at the terminal under 'stand-by' (key & kill switch on, engine stopped). The fact that you have only 1vdc for that pin indicates that current is flowing rather freely, which will kill your coil as well.

Ummm... You might want to replace your spark caps before you damage anything else.

Excellent diagnostics, by the way! Your readings make good sense.

6-pin connector:
R/W - +12v from battery
B - GND
B/Y - NCS safety switch input (neutral, clutch, stand)
B/L - pump ground switch
Gy - 2-3 coil ground switch
O - 1-4 coil ground switch

8-pin connector:
W/R - crank pick-up wire #1 (variable reluctor, AC signal)
W/B - crank pick-up wire #2
Gy - tach output

I'm (FINALLY!) just about to hit the start button on my business with parallel refurb/exchange program; see here. viewtopic.php?f=76&t=7386. I should have a working TCI for exchange by next weekend.

EDIT - if your battery is reading 12v at standby and 9v at cranking, it's pretty messed up. Check the electrolyte levels' you may have some dry / low cells. A desulfonating charger may be able to help, or the battery may simply be toast.

[mattfromthepier]

Thank you Don! This is great news for me! I'd like to use you're program for a replacement, let me know when you have a TCI available and Im ready. I will make sure take care of my battery and spark plug caps before I install the new TCI. Thanks again for the great response! Hope to hear from you sometime next weekend. -Matt

[yamaha_george]

I would say your battery needs attention the voltage should not drop that low.

check that all the cells are full of electrolyte and that no cell has a set of grey sludge across the bottom shorting it out which is what I believe has happened for your battery to go that low.

[mattfromthepier]

Thanks yamahageorge. you were both right about the battery, it was dry and may have had some sludge at the bottom. I'll try desulfonating charger thing and filling it up sometime this week. I may wait till the tci is replaced, and other loose ends are tied up before i buy a new battery.

[yamaha_george]

Thanks yamahageorge. you were both right about the battery, it was dry and may have had some sludge at the bottom. I'll try desulfonating charger thing and filling it up sometime this week. I may wait till the tci is replaced, and other loose ends are tied up before i buy a new battery.

M,
cool got this from my sparky mate"Ooopnorth"
QUOTE:-
The first port of call with any electrical problem is, check the battery (as stated above). I.E voltage, electrolyte levels, & the security/condition of the battery terminals.

Take a reading of the battery voltage, then take a reading of the voltage delivered to the coils (Red/White wires) if the voltage is low compared to the battery voltage you possibly have corroded connections, which will result in a weak spark!

The main suspects are.

The Ignition/Main switch connector, it’s forward of the radiator cap, your looking for a 3 pin or maybe a 2 pin connector (these differ from continent to continent). The wire colours are Red Brown & Blue, ensure that those connector/s are clean and free of corrosion, especially the Red & Brown wires.

The Run/Stop switch connector. Wire colours are Red/White Red/Black, again ensure that connector is clean & free of corrosion.

Now we turn our attention to the coil Low Tension connectors, they are under the airbox. One is coloured White the other is Yellow, wire colour’s are Red/White (the power source to both coils) Orange for coil #1 & #4,  Grey for coil #2 & #3. Disconnect those connector's, again make sure they are clean and free from corrosion.

That said, the coils on the FZR are 12 volt (no ballast resistor) If the voltage delivered to them is less than battery voltage (12.5V) your will have a weak spark, especially when the starter motor is engaged.

I.E. if battery voltage (12.5V) is not delivered to the coil primary windings. When the starter motor is engaged the voltage to the coils will drop dramatically (as yours does to 9.0V ) resulting a very weak spark, the bike will not start.

A faulty TCI will not result in a weak spark scenario, either #1 & #4 and/or #2 & #3 will have no spark, due to a fried ignition transistor.

regards

oopnorth

HTH

[mattfromthepier]

Dang! Thanks a bunch guys, I think my FZR deserves a new battery, i have no clue how long its been in there and i've put the poor thing through hell at this point. Im going to go a head and replace it. Hopefully it works, if not, check the tci readings again and with all the info here i think I have a great chance of getting the bike running again!