Safety Switches on Seca/Maxim xj750

I'm almost there. I just installed an '82 Maxim 750 into my '81 Seca frame. I had a bit of a brain-fart and connected the stator wires incorrectly. Here the thread that explains that fiasco:

(https://www.xjbikes.com/forums/threads/all-the-warning-lights-are-on-seca-750.119890/ )

Now the bike is running awesome, with one small problem. The safety switches aren't quite working correctly.

I "think" I've got all the connectors hooked up correctly. Here are the symptoms:
The starter will only engage if the side stand is up. It will not engage if the side stand is down. It doesn't matter if the bike is in neutral, or in gear. It doesn't matter if the clutch lever is pulled back to the handle bar or if the clutch is engaged... The only thing that matters is if the side stand is down or up.

In other words, if the side stand is down and the bike is in neutral - the starter will NOT engage. Even if I pull the clutch handle, the starter will NOT engage.

However, if I put the side stand up, and the bike is in neutral, the starter WILL engage. If I put the bike in gear, the starter WILL engage (which tends to be surprising.... and dangerous.) If I pull the clutch lever, or leave it alone, the starter WILL engage.

So the side stand is King - if it's down, the starter will NOT engage. If it is up, the starter WILL engage. All other safety switches are ignored.

One more thing - the neutral light never comes on now, even if the bike is in neutral.

Rustee Gold
1981/82 Seca/Maxim XJ750 Frankenbike

 

check the switch on the clutch it could have come apart at perch.
bike starting in gear with out clutch pulled in is like a jumper was put across the green connector for the safety switch . your clutch safety switch could be shorted
also unplug the clutch safety switch. if it is unpluged bike will only start in neutral. if bike will not start then look at the neutral switch
it sounds like your bike thinks it is in gear.
when i stop to park bike in gear I use the sidestand to kill the motor


the sidestand switch
test the neutral switch. if light never came on it is bulb or switch

 

Does the bike die when in neutral and the side stand is put down - normally it should not?

So the neutral light never comes on, like maybe with the side stand up does it illuminate, guessing no?

Double check the connection for the two bullet connectors where the wire travels with the pick-up coil wires to be sure they are correct - B/R to B/R and Blue to Sky Blue.

I suspect the previous issue with the AC generator was a swap with the side stand wiring - I could not quite confirm that with the wiring colors. Anyways, I see potential there if that were the case the diode block could have been damaged. A shorted diode would make the side stand King, but would not explain the neutral light.

Edit add: do you currently have any failures on the CMS?

 

The neutral light might could be explained by it being fed unregulated AC and burning out.

 

The neutral light was burned out. I replaced it and it works now.

The clutch switch is working. I disconnected the side stand relay and the start control cutoff relay, then I connected a DMM to the blue/yellow stripe wire from the side stand relay connector to the black/yellow stripe wire from the starter cutoff relay connector and i got continuity when i squoze the clutch lever and not when i released it.

I think my neutral switch is bad. I do not get continuity from the switch to ground when the bike is in neutral. Question... how do you replace the neutral switch. Is there a "how to instruction" on that process?

Problem still exists with the side stand... even though the neutral switch is not working, when the side stand is up, the neutral light comes on and the bike starts. If I put the side stand down the bike stops and neutral light goes out. The starter will not engage if the side stand is down.

Also when I plugged the connectors in wrong before, I plugged the white generator wires into the side stand switch wires... so I probably fried something... the wiring diagram in the Haynes manual shows a diode in the circuit... where's that diode? Do I need to replace something?

Rustee

 

The diode block is located in the head light bucket. It is a rectangular device covered in a rubber sheath and was likely damaged by the cable reversal.

The neutral switch is a pain to replace and usually involves removing the exhaust as it is so close to the frame tube. The write-up below from Len seems to indicate the tool he sells allows for doing the job without pulling the exhaust.

http://xjbikes.com/forums/threads/xj-parts-catalog-section-d-electrical-system.44641/page-2

"HCP15718 Aftermarket neutral position switch REMOVAL SOCKET. On many models, it's almost a physical impossibility to remove the neutral switch from the crankcase "well" without removing the exhaust system or removing the engine from the frame.....the left lower frame tube conspires with the exhaust system to make it unbelievably difficult to access the switch. This special "open side" socket is the proper size to squirm through those restricted spaces and make it possible to remove and re-install the position switch without going through a tremendous amount of effort. Standard 1/4" drive socket should be used with a 3" extension bar, or, it's even easier to use when attached to the HCP13516 flexible shaft driver listed below."

 

So it's on when you put the bike in neutral? If so then the neutral switch is fine.
Where are you checking for continuity at?

 

Yes you can check it with a DMM set to the diode mode. The best way would be to have it removed just to eliminate any parallel resistance paths. However, if you don't have easy access to it because of the fairing and you want to check it in circuit, then do it with the side stand down, out of neutral, starter cutoff relay removed, and side stand relay removed to reduce the confusion that might occur from parallel paths. Check L/Y at the side stand relay to Sb at the starter cutoff relay. I believe from there it should ohm as a standard diode. Here is a diagram to help with location and colors - D1 is the likely shorted diode in your case:

Standard diode with DMM set to diode mode approximately 600 ohms in one direction and open when leads reversed

 

Rooster,

Thanks for the diode diagram. I removed the diode from my blue bike and tested it. As you predicted D1 was burnt out. I stole the diode from my other 750 (red bike) and it tested good so I installed the good diode into my blue bike. Now the problem is different...

If the side stand is down it will not start. But I think I have a bad neutral switch...

Now here's the new problem... if the side stand is up, it will not start unless I pull the clutch lever. When I pull the clutch lever, the neutral light comes on, and then it will start. If I then release the clutch lever, the neutral light goes off but the bike will continue to run. If I put the side stand down it kills the bike.

I can hear the side stand relay click when I put the side stand up and down.

I can hear the starter cutoff relay click when I pull and release the clutch lever. I'm including pictures of the side stand relay and cutoff relay so you don't think I'm nuts... but I do think I'm nuts because I don't understand the clutch lever switch controlling the neutral light...

 

83 seca 750 diode block

DIODE ASSEMBLY
4H7-81980-M0-00


Related Fitment
This Yamaha 4H7-81980-M0-00 DIODE ASSEMBLY fits the following models and components:

Yamaha Motorcycle 1980 XJ650 - XJ650G ELECTRICAL - 1

Yamaha Motorcycle 1981 XJ650 - XJ650H ELECTRICAL - 1

Yamaha Motorcycle 1981 XJ750RH ELECTRICAL - 1

Yamaha Motorcycle 1981 XJ650LH ELECTRICAL - 1

Yamaha Motorcycle 1982 XJ750RJ ELECTRICAL - 1

Yamaha Motorcycle 1983 XJ750K ELECTRICAL 2

Yamaha Motorcycle 1983 SECA - XJ900RK ELECTRICAL 2

Yamaha Motorcycle 1983 XJ750RK ELECTRICAL - 1

Yamaha Motorcycle 1983 XJ750MK ELECTRICAL 2

 

opps got confused thought we were talking 82 maxim , its an 81 seca750 with a 82maxim motor



is bike in neutral when pulling in clutch and light comes on?

your bike thinks you are in gear with what you discribe

 

I can only start the bike with the clutch lever pulled in AND the side stand up. It can be in gear or in neutral... doesnt matter.

 

Well that looks like along with the bad neutral switch you also have a blown (shorted) diode in the starter cutoff relay, and likely in both bikes since it was swapped in the previous event.

Here is a diagram for the starter cutoff relay so you can check the diode. Note the coil should read about 100 ohms as a sanity check for being on the correct pins. Check the diode as mentioned above with the DMM set to diode mode.

That would be normal if the neutral switch is defective.

 

That would also be normal until a working neutral switch is installed. Ignition cutoff is side stand up OR in neutral - with a working neutral switch.

 

Yeah!!!

I pulled the started cutoff relay from the red bike and put in on the blue bike. Now the blue bike works as expected. No neutral light at all because the neutral switch is bad. But if I grind the sky blue wire the neutral light come on and the engine will start.

I'll be getting some parts from Len and pretty soon I'll have both bikes back on the road. Now I just have to find a white one so I can take them all the the Fourth of July parade...

Thanks again for all the help.

Rustee

 

I assume you mean "ground" rather than "grind the sky blue wire" ! Otherwise it could point to a different issue.

The sky blue wire should actually be thought of as a black wire (if you think like me) because it is actually a VARIABLE GROUND WIRE.........the neutral light gets 12V from the battery and only when a ground path is established (thru the neutral switch) is that sky blue wire serving as a ground --- and thus letting voltage flow thru the neutral light and thus illuminating the bulb.

The neutral switch actually has a spring-loaded plunger that fits into a dimple (or maybe it's a raised bump, can't recall at the moment) on the shifter drum, and thus when the drum is in the neutral position, that spring loaded plunger is either lowered (or raised..!) into a position that completes the ground circuit. At all other times (all other shifter drum positions), the plunger on the switch is either fully retracted (or extended!) and thus is no longer making a ground contact......and therefore the neutral light, even though it is receiving 12V on its "input" side, has nowhere to send that 12V to (ground), and thus the light stays off.


That starter relay schematic is pretty good. 12V comes into it but it has no place to go to unless:

a) either the neutral switch sky blue wire is grounded, i.e. the shifter drum is in the neutral positions, OR....
b) the side stand switch is in the UP position....and when the sidestand is UP, the sidstand SWITCH is now passing current to ground.

So either of the above conditions will allow the 12V coming INTO the relay to have a ground path.

And the importance of that 12V having a ground path (either thru the sidestand switch or the neutral switch) is that once a ground is established, then the flow of 12V thru that little spirally coil of wire (which is a tiny electromagnet, I presume) forces that little switch (in-between the 12V IN and the "TO SOLENOID" terminals) to be closed, thus completing the circuit from 12V to the solenoid. With 12V now flowing along this path, then the starter solenoid has power to it and can be activated when the START button is pushed.


Of course, all of the above may be wrong, and hopefully Rooster will tell me (and you) of my errant ways...........

 

Excepting in reference to the starter cutoff relay, the missing part is the working clutch switch to complete the current path to energize the relay.

Starter cutoff relay - In neutral OR in gear with the side stand up AND the clutch pulled in
Ignition cutoff ( side stand relay) In neutral OR side stand up.

And of course the two steering diodes, one contained within the starter cutoff relay and one in the diode block have to be in working order or weird symptoms occur as noted above.