Neil Brown

Hi, With Jim's help, I have just fixed the same problem on my 1987 FZ600! Here's a bit more info for you... Firstly disconnect the 8 way connector. This is the regulator / rectifier connections. On the wiring loom side of the connector (ie not the regulator side) you should have the following wires: Red - goes straight to the battery + ve Black - goes straight to the battery -ve Green & brown - goes to the brushes on the alternator 3 whites - goes to the stator coil in the alternator 1 empty space Ok, heres what to do to confirm that the alternator & wiring is OK. Take a multimeter, set it on the resistance range (Rx1). Start by shorting the meter's black & red test leads together. you should get a reading of near to zero, mine read 0.6 ohms. Make a note of that reading, because it is the resistance of the test probe leads. Now go back to the wiring loom side of the connector & choose two out of the 3 white wires (doesn't matter which two, we will test all possible combinations!) touch your test meter probes on those connections- you might need to press hard to get a good connection if they are corroded, or dirty. You should see approx 1 ohm between each combination of pairs of white wires. Your meter might read more than this. Mine read 1.6 ohm, so then subtract the value that you measured earlier to compensate for the resistance of the meter probes. If any of the pairs measure much more than 1 Ohm, there is probably a problem with the stator or white wires. Now measure the resistance between the green and brown wires, that should be around 4 Ohms (taking into account probe resistance). If either of these two measurements are far out, you might need to check the joins in the cable loom. remove the right hand seat panel & under there you will see connectors joining the 3 white & brown & green wires. Disconnect these & measure the side that goes down to teh alternator. you should get slmilar values to to those I mentioned above. If these all seem Ok, switch you meter onto DC voltage range and measure between the red and black wires on the 8 way connector (loom side) you should get the same voltage here as you get directtly across the battery terminals. Next, set your meter to the Diode range, and taking the regulator side of the 8 way connector we will measure the 6 regulator diodes. Start with your probes on one of the white leads & the red one, you should get either a reading of about 0.5 or open circuit, now swap the red & black probes over, you should get the other one of the two readings above (this is because the diodes in the regulator only conduct electric current in one direction. Now do the same with the other 2 white wires to Red (should measure the same for each one) Then measure the 3 whites to black. You should again find the same readinbg for each white / black combination. Have a go at all this, then poost back your findings & we'll take the next step. Good luck. Neil

Jim, Thanks again for your help, I cleaned all the connections between the reg / rect and alternator & it improved things a bit, however while doing that, I noticed some burn marks on the white cable from the stator, so I tried replacing the cabling. 3 wires direct from rectifier to stator, no joins. The diference was amazing, I now get 14.5 Volts at 4k revs with all the lights on. To celebrate, I went out & bought a freshly re-covered seat on Ebay!! I have learnt a lot from you all here, and now have a bike I can be confident in. Thanks again. Neil

Thanks Jim, The brushes are good, they are about 5mm longer than the scribed line. Rectifier is good - Diodes check out OK. I have the finned regulator / rectifier with the green brown wires which go to the brushes in the generator. (rotor) They have 10.5 volts accros them at 4k revs. I guess the regulator varies this voltage in order to control the charge voltage...? or maybe it's not that clever? At 4k Revs with no lights on I get 13.8V, no change for sidelights on, but it drops to 12.3 ish with dipped headlights. I tried disconnecting one of the headlights, ie halfing the load - no improvement. Some of the connections at the regulator are dirty, I'll try them next unless you have any better ideas. Cheers, Neil

Ewen, Really sorry to hear about your bike... I have a 1987 FZ600 with similar electrical problems. I always assumed that older bikes were not so vulnerable to theft, but I'll be a bit more careful now! Jim, I hope you don't mind me jumping in on this thread, but it is so refrehing to fond somone who really knows the electrics of these bikes...!! I bought my FZ600 in July (an E-bay special cheap first bike!) The previous owner had had charging problems & put a new regulator / rectifier on it - It worked well enought for me to get it home!! It charges the battery (I put a new one on it) well at 13.5 volts with sidelights on, but when I put dipped headlights on (which should be normal riding practice) the voltage drops to just around 12 volts, and after about 2 hours of riding of course gives up & won't start the bike again. I have checked the alternator brushes which appear to be OK, springy enough & the rotor slip rings are reasonably clean. Stator coils measure about 0.4 ohms as per the manual. Other useful info is that I have a trickle charger which keeps it topped up lovely, I just can't trust it for long runs out. I'd really appreciate some assistance with where I should look next. Thanks, Neil