82 Seca 750 - Help

Well, I got some good news. After trouble shooting the hell out of it, I finally figured out one of my problems. I was using the wrong wiring diagram. That would have saved me a lot of time and profanity had I clicked on the right one from the beginning.

Anyway, with the right diagram, stuff started making sense. Everything on the dash is still lit (even though the obvious ones should not be, like stand, headlights, etc.) Also the check buttons on the dash dont do a darn thing either. If the button itself is faulty, could that make all the lights stay on?

I just took a scotch lock and connected (I think) the red/black and the blue/black wires coming out of the right side handlebar controls. Then the headlight and aux lamp worked, including the relays and on/off or hi/low switch. Took all the stuff out of the equation for the turn signals and everything checked out OK. Put it all back together and now the turn signals work. Put a new fuse block in too, and replaced the inline one inside the bucket.

My lean condition and hanging revs are probably not being helped by the fact that the bike has no mufflers. Its just straight pipes because the old ones rusted off. Im gonna go to the junkyard and get some off of a similar bike to get that thing quieter and get a decent tune on it.

Thanks for the help so far. By connecting those two wires and the headlights working, would that be indicative of a bad diode block? Checked all the relays, flashers, and even the cancelling unit. Everythings good so far.

 

If all the LCD alerts are staying lit, the computer isn't running. A bad check button wouldn't lead to that, but a bad signal from the alternator/diode block might, as I don't think the test starts until the engine is started. I'll double-check when I get home and let you know.

Please remind me: is your headlight off when the ignition is turned on, but coming on when the engine is started?

 

I suspected diode block, but dont have anything to test it with. The headlight now comes on as soon as you turn the key on. Kicks off for starting. The LCD panel still doesnt go off even when I go down the road.

 

RickCoMatic....Thanks VERY much for the simple fix for my BATT warning staying on. My small town Radio Shack only had 2.2K resistors, not 2K, and didn't know how critical the resisitance was, so I bought a package of five 1K resisitors, and put two in series (same result as a 2K). I wired them in line from the taillight to the battery sensor, white w/red stripe, wire coming out of the wiring harness. Shrink wrapped all the exposed, bare parts, took the bike for a short ride and everything is great.

Thanks again!

Lynn

By the way....the package of 5 resistors was only $1.28, including sales tax. I did ruin two resistors by getting a little overzealous twisting the tails of the resistors and wires together to solder them, but was a bit more gentle the second time and the solder joints held everything together nicely. I zip-tied the whole works to the rest of the taillight and turn signal harness so it can't flop around.

 

OK. Just checked mine. When the key is first turned on, the headlight is off, and the warning center has all LCD's displayed (STAND, FUEL, OIL, etc) and the red lamp on solid. The only active display is the four bar fuel gauge.

When I start the engine, the headlight comes on and a second or two later, the red lamp starts flashing and the LCD cycles through its test - normally turning off everything except STAND (if the side stand is down).

Your headlight coming on when the switch is turned on is not normal. This may be another symptom of the same root problem, or it may be a coincidence. What's the history on these problems? Have they always been like this since you got the bike? Can you ask the PO about anything he/she might have done regarding headlight relays and such?

BTW, the same alternator wire that triggers the headlight relay looks to trigger the warning center, but the warning center is on the other side of the diode block from the headlight relay. You might try unplugging the diode block and see whether that changes anything for the warning center.

 

Wow, thank you sir. Seems like you are going over and beyond what most people on the internet would do for someone else on the internet.

Anyway, I jumpered the wires to make the lights work, so that probably explains why my headlight comes on early. The only thing that works is indeed the fuel gauge. No luck on talking to the PO. Got the bike on a mechanics lien for 250 because of the starter clutch.

I didnt think about simply unplugging the diode block. Figured I would have to jumper some wires, and didnt think of which ones I needed to jumper. Maybe thats the problem then. The warning center is not getting the signal to cycle through stuff. Anyone know of a place to get (or make) a working diode block as a replacement?

 

First question is how you jumpered the headlight.

Second question is whether unplugging the diode block makes a difference.

Then, if needed, we can worry about replacements.

 

I just put a scotch lock on two wires coming out of the right side hand control unit (aux/kill switch). I believe that it was the red/black and blue/black wires that I connected, which made the headlamps work. Didn't cut anything, just connected them.

Ill get that diode block outta there and see if that changes anything. Figured that I would have to send power to the outputs of the block or else it would just dead end there, unless I don't understand how a diode works.

 

Red/Black to Blue/Black wouldn't do anything but make your Aux lamp stay on all the time, once the headlight relay was engaged.

Red/White to Blue/Black would power the headlight as soon as the ignition was turned on, but would also be placing extra load on your ignition circuit and fuse... load that that fuse and wiring were not designed for.

 

Red/White must have been what I did then. Hasnt blown anything yet, and I just needed it to ride it home since it was night time.

Took the diode block out, and no change. Doesnt do anything different. All the lights come on, and dont go off or cycle through, even after started and riding.

Ideas? Id rather have this working correctly since Im thinking about selling it soon. I dont need 5 bikes, since I only ride two of them regularly, and another one is no longer a bike persay.

 

Sorry to say, but it sounds like the computer itself is bad.

The Yamaha price on that part is stupid expensive, even if any were available, which I don't think there are; but enough people have removed their stock clusters that I would think someone on here would have a working unit they could part with for reasonable money.

For the headlight, I'd be a bit more concerned with melting the R/W wire's insulation somewhere from the extra load it's carrying. Headlight adds about 5 Amps... Aux lamp would throw another 2 or 3 on there. Another more subtle side-effect you might see is reduced spark intensity because the supply voltage to the coils will be reduced due to the extra voltage drop on their supply wiring.

 

Well, heres more data. I undid the wiring I had for the headlight, so its back to stock. Took the diode block out, and put 12V to the white wire going to the computerized monitor. It started cycling through the tests! The only thing on was the BATT because I dont have the "correct" battery, but thats easily fixed.

So I guess I'll order a new diode block and see what happens. Or do you know of a replacement?

 

It's not the diode block. At least not for the computer piece. It's the white wire, the regulator/rectifier connector, or the alternator winding itself. Check the connector under the left side cover that carries the white wires. You should have continuity from one of the white wires there back to the white wire are the computer.

You may find that the contacts in that plug are burned or melted. Cleaning them up and treating the connector with electrical grease (bulb socket grease from an auto parts store) may help, or you may need to replace the connector and socket.

By the way, that white wire is also the source of the signal to engage the headlight relay, so that's probably why your headlight wasn't coming on as well.

This sounds like good news.

 

I checked real fast before I had to get to work. I have continuity between the white wire at the diode block connector, and all three wires under the seat. Also checked at the R&R connector, and good there too. Cleaned up the connectors, and getting good signal through them. Took off the alternator winding cover and all three white wires go to the winding, no problems.

I will check the wire directly to the monitor, and the wires going into the R&R once I get some free time (finals this week).

I did notice that the innermost magnetic stanchion sticking up in the cover was broken off. Could this effect anything?

 

Any idea on the magnet being broken off inside the Winding cover?

If I take a switched 12V power and just have that go into the monitor as a signal rather than having the alternator give it the signal, would that cause maliciousness?

 

That would not provide the correct behavior. The point of getting the signal from the alternator is to trigger the headlamp relay and computer test cycle once the engine is started.

Assuming all the connections are really good, then it sounds like your alternator is not producing output on the phase that is connected to the computer and diode block. You could try switching that white wire with one of the other two white wires at the connector from the alternator to the regulator/rectifier. If that fixes things, it's a solid indication that your alternator needs to be repaired.

 

Hey Nightviper19 and SQLguy,
Did you ever resolve your dash lighting activity issue?
I have an 82 XJ750 that i'm now having some problems with not starting.
History:
When i drive bike it will suddenly stall (electrical type dead). Most of the time it would start right back up. Thought it was the Kick stand safety, so I bypassed that wire, along with the dash indicator wire for the same and tied all of them together (3 wires)..

Worked fine after that....but yesterday drove down the street again died...
This time it wouldn't start.
All Dash indicator lights are on, but no starter action. Can't get the dash to do its checking or respond to hiting any of the buttons.
Its almost like i need to reset the computer like we do with other electronics.
Bob

 

Have you rebuilt or replaced the original fusebox yet?

If not, there's the place to start.

 

I rewired the main fuse, when i bought the bike as those cheap little spring metal holder fingers break so easy.
I'll check the other fuses, but they looked okay.

 

Those cheap little metal holder fingers crystallize over time and can be cracked and you wouldn't even know it. My very first "XJ rude surprise" was one that broke all by itself without being touched.

The fusebox can be rebuilt with new real metal clips from Radio Shack, replaced with a new original style, or (recommended) replaced with a modern, blade-type fuse box.