Dash display

Still sorting my 750 seca .started it up display work,checked out the new clutch shut it off started it back up now the display is lit up all the time it doesn't go through it check list,any body know what look at cause I am lost. Thanks

 

The Computer Monitoring System (CMS) is initialized by a white wire that runs from the AC Generator to the CMS. If this wire is open or the AC Generator is not functioning the CMS will not be initialized.

The same leg of the AC generator also applies power to the Headlight Relay, but takes a different route through the diode block to rectify the AC signal. Does the headlight come on and latch when the bike is started?

 

Not sure if there the problem the cms has all check lights on including the warning light .

 

Yes, and it will stay in that state until the bike is started and the AC Generator outputs a voltage to initialize the system, which is when the system checks begin.

 

After the bike is started the cms does not go through its checks,thevwarning light stays on.is there a relay the triggers the cms?

 

No relays are involved to initialize the CMS. As stated earlier it is the AC Generator output that initiates the self test function when the bike is started.

And, just to ask again, is your headlight latching on when the bike is started?

 

For clarity's sake; latching means that the headlight stays on after you use the kill switch to shut the engine off.

 

Sorry I didn't state it but the headlight does stay on after statingand now my neutral does not light up at all.

 

Well now I have the CMS working it was plug not fully seated it the headlight,but now I am back to the original problem of the neutral light being on all the time unless the side stand is down

 

Annnnnd...... this should have been in that thread. Jumping around without context makes it much harder to help you solve the problem.

 

In the other thread you had you found an issue with a shorted diode in the diode block causing the neutral light to illuminate continuously with the side stand up. Did you replace the diode block or repair it? If so, did the neutral light work correctly after that, and now has suddenly failed?

Are you having any issues with the safety circuits for the starter cutoff? Starts in neutral OR in gear with the side stand up AND clutch pulled in? Won't start in gear with either the side stand down or clutch not pulled in?

Did you ever verify relays were in the correct spots as suggested in that earlier thread?

 

I replaced the diode block that looked to melted but it didn't fix the neutral light problem the only time the light goes off is when the side stand is down the bike won't start with the stand down,the kill switch works as it should .the clutch lever swich has been eliminated cause the switch was broken.I am thinking my neutral switch is faulty.

 

Could be, but it can't fail in such a way as to cause the neutral light to be controlled by the side stand switch.

With the side stand down does the neutral light illuminate when in neutral?

Did you verify the correct starter cutoff relay is in the proper location?

From: http://www.xjbikes.com/forums/threads/the-ultimate-relay-switch-sensor-and-diodes-guide.27543/

on all 1981-83 XJ750 Seca models: under the gas tank, in-between the frame tubes, on a welded bracket just behind the flasher self-canceller relay.

small metal (original) or plastic (replacement) "cube" relay, inked 4H7-00, 4H7-01, or 12R-01 on the top face.

Do you have a meter and know how to use it? If so check the diode in the starter cutoff relay and the diode in the new diode block.

To check the diode in the diode block ohm between the L/W and G wire. With the DMM set to diode setting you should have and open in one direction and approximately 600 ohms in the other direction.

To check the diode in the starter cutoff relay use this diagram.

 

The neutral light does not light when the side stand is down,the relays are original 4h7-00and tested fine with ohm meter and is in the very rear location witch I believe is correct I will check the diode block next

 

Is the diode block the one in the headlight

 

Yes

 

I just tested the diode block its 843 ohms

 

Not all XJ diode blocks are alike, even though the plugs can be. Are you positive that you have the correct replacement?
Somewhere I think I have the specs for the 750 Seca block. I'll look tonight.

 

I just tested the diode block its 843 ohm

The diode block came from yamaha if that means anything

 

A bit on the high side, but that may depend on the meter and it should only read in one direction. So if 843, then reversing the leads it should read open?

The XJ750 Seca should be a five wire device Part Number 4H7-81980-M0-0 and is used on many different models. It has 3 diodes and a resistor and it appears that only 2 of the diodes are used for the 750 Seca. D1 for the safety circuit and D2 for the headlight relay.

Starting to think you got PO'd and some creative wiring was done to compensate for a defective neutral switch. Kmoe suggested this as the very first reply in your other thread regarding this.

Do a continuity check at the diode block mating connector checking the pins corresponding to the D1 diode. This should be Sb to L/Y on the main harness. If the clutch switch is bypassed (wires shorted) you should read the starter cutoff relay diode in one direction and high resistance in the other direction

And just to be sure the diode tested OK in that relay? Remember a shorted diode here with a clutch switch bypassed would cause the side stand to affect the neutral light

 

There hasn't been any creative wiring done all wiring looks to be factory the only thing I did was uplug the clutch switch wires in the head light plug them together thus bypassing the switch this does the same thing as pulling in the lever.if I unplug them the light goes out the bike won't start

 

Bingo!
I say bingo sirs!

Check the diode in the safety circuit relay.

 

And once you get this sorted you can deal with the other issue (no neutral light with side stand down) that is likely a defective neutral switch.

 

Didn't get a chance to check it out yesterday I'll do today,the safety circuit relay is the very back one right

 

Yes, see post 13 on page 1:

on all 1981-83 XJ750 Seca models: under the gas tank, in-between the frame tubes, on a welded bracket just behind the flasher self-canceller relay.

small metal (original) or plastic (replacement) "cube" relay, inked 4H7-00, 4H7-01, or 12R-01 on the top face.

 

With 12v coming in there is power to the sb wire and the by wire but nothing to the other rw wire. I don't think this is correct?

 

Could be depending on the state of the safety switches. Since we are looking for a shorted diode check using continuity.



Remove the relay and lay the relay on the table with the connector pointing up and tabs facing as pictured.

Set the DMM to ohms:
Check from the upper right terminal (R/W) to lower left (B/Y) - should be about 100 ohms
Check from the upper right terminal (R/W) to lower right (R/W) - should read open
Change DMM to diode setting
Place the positive lead on lower left terminal (B/Y) and the negative lead on the upper left (Sb) - should read approximately 600 ohms
Reverse the meter leads so the positive lead in now on the upper left (Sb) and negative lead on the lower left (B/Y) - should read open.

 

Checking my relay with the last diagram my relay test a closed circuit on sb-by diode in both directions

 

Replace the relay.

 

Well I had the diode replaced in the relay fixed that problem now as another member mentioned the neutral switch is stuck ,anybody know an easy way to remove it,i don't think I can get a socket on it.

 

843 ohms is the resistor in the block used in the oil light setup .
you want to put your meter on diode

have you checked the neutral light bulb?

 

First thing is to be absolutely sure it is the neutral switch that is causing the issue as I believe you have to remove the collector to change it. So, it is visible from the left bottom side of the engine and you can momentarily ground the screw / terminal to the frame or motor and make sure the neutral light illuminates.



If the wiring checks out isolating the fault to the neutral switch, then you can try running seafoam in the crankcase to help clean out any sludge buildup before committing to replace it.

 

The switch is the problem I've checked that the bike has a 4 into 1 on it I can see it just can't get a socket on it does it take a special socket

 

Yes it does. Chacal sells them or you can make your own.

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."

Seems I remember you just had the engine out for repair so it should be clean in there, but check out this other thread where a member had very good success with the seafoam. Also since you have the 4 to 1 it's just a matter of getting the right tool.

http://xjbikes.com/forums/threads/neutral-switch-replacement-procedure.68194/

 

Before you pull the switch (which is a PITA with the engine in the frame) put 3 ounces of Seafoam in the crankcase. The most common problem with the neutral switch is gumming up from years of sludge accumulation. Run the Seafoam for a few hundered miles to break up the sludge, and see if that corrects the problem.

 

Will do thanks for all the help