VFR750fl 1990

[Paco]

Hi all,

Looking for a bit of advise. I have a VFR 750FL 1990 and my problem is that I nave no neutral light coming on due to a regulator overheating the battery.

The bike will not start as she thinks is in gear.

Tested the light green neutral wire from the neutral switch to the neutral light and DID NOT GET CONSISTENCY. I have replaced the neutral bulb as it was gone and

the positive wire to the neutral bulb is showing consistency. I have tested the neutral switch and it seems to be working.

My problem now is where to look for the most likely wiring problem on the light green neutral wire and an easy way to test it to see where the problem is.

My understanding is that the green neutral wire goes into the wiring loop and goes under the throttle bodies, removing the throttle bodies would

be beyond my capabilities and I am wondering if there is a better way to find where the problem is in the green neutral wire or if it is possible to bypass it.

I have read in a previous post that the light green neutral wire goes into a relay switch, which is under the throttle bodies, so I am wondering if there is an easy way to test it without removing the bodies. And where is located?

All the other electrics seem to be working except the two right hand indicators.

I would really appreciate if anyone can point me in the right direction.

Many thanks

 

 

or 

[Captain 80s]

Does the bike start with the side stand up and the clutch pulled in? 

 

Does it stay running when then put into gear?

 

There is no relay/switch under the carbs.

 

You say the neutral switch "seems to be working".  That is not very definitive.  It either is working or not, and can be tested to find out.  How did you test it?

[Paco]

Hi 

no the vfr does not start with the clutch in or out or with the side stand up or down and neither in neutral or in gear. I tested the neutral switch on a voltmeter and, strangely, it did show consistency in and out. I did put the earth wire against the chassis as an earth to see if the green neutral light would come on and did not. Any thoughts would be great! Thanks

[Captain 80s]

You have more problems than a neutral light / switch then.

 

Bypass the sidestand switch to eliminate that possibility.  Not just unplug it, you have to jump 2 wires on the harness side connector.   Just did my 92, but can't remember what 2 wires off the top of my head.  Refer to the wire diagram.  Does your sidestand switch light function on the dash at this time?

 

Bypass the clutch switch on the clutch master cylinder to eliminate that, but be sure the bike rolls in neutral before any subsequent start attempts.

 

Sounds like the clutch diode on the wire harness has failed and is possibly what you are referring to in your first post you read about.  Can't remember exactly where I noticed it was located on my 92 recently, but it is not located under the carbs, I know that.  Likely on the right side near the coil, to perhaps the rear tank mount area.

 

It is possible that every function got fried somehow, but is unlikely.   I'm pretty sure there's a combo that will still allow the bike to start even with a bad diode.  Bike doesn't think sidestand is down and believes the clutch lever is pulled in.

 

There are people here way better at walking thru diagnosing electrical problems than me.  Well, at least better at explaining it and the logic.  But eliminate the suspects until it starts and then start re-introducing them until it doesn't.   Guess that's all I got right now.

[Paco]

Many thanks for taking you time to help me and tomorrow I will start again at the vfr 

 

[Captain 80s]

I am assuming you have checked all fuses already.  Does your headlight go out when you press the Start Button?

 

The Clutch Diode should be on the main wire harness, right side, above the coil for the Right Rear Cylinder. 

 

[Paco]

Hi 

yes all fuses are fine 

when you press the starter absolutely nothing happens but yes the headlights do become dimmer 

Greetings from Ireland 

[Captain 80s]

"dimmer", but not cut all the way?

 

Also, just for giggles, have you jumped to a car battery (not running) and tried to start?  I know, I know, you're gonna say the battery is just fine.  But have you tried?

[Paco]

Yes the headlight is dimmer but does not cut all the way out 

in fact the battery is not good at all so I had it jumped to a car when doing the testing on the vfr had it now for 25 years so I would hate to have to break it up for parts 

[Captain 80s]

Ok.  Keep on keepin on.. You'll get it.  It is possible the battery is so bad that it's not letting enough "juice" thru.

[Grum]

Hi Paco.

Further to the good advice from the Captain.

Absolutley make sure you are working with a healthy Battery and your battery terminals are clean and tight. 

Assume you are NOT hearing the Starter Relay clicking when you Press the Starter Switch? You should measure 12v on the Yellow/Red wire at the Starter Relay every time you press the Starter Switch with Ignition to On, measure this, what do you read? If this is good then you need to verify the Ground path being the Green/Red wire, through the Clutch Diode then through the Neutral Switch to Ground. refer above Starting Circuit Diagram.

 

Concentrate on getting your Neutral Light and a Neutral start working. Refer to the Starting Circuit Diagram the Captain supplied above.

1. Verify the Neutral Switch operation - Are you able to unplug the wiring directly at the Switch? If so put your meter into Buzzer or lowest Ohms range. Preferably place the Black meter lead on the battery Negative and the other lead on the Neutral Switch terminal. Go from In Gear to Neutral many times - make sure you have Continuity/Zero Ohms whenever you are In Neutral and NO Continuity when In Gear.

2. Using the diagram the Captain supplied, reconnect the Neutral Switch wiring and locate the Light/Green wire at the Clutch Diodes (see attached picture for Diode location). While in Neutral probe this wire again making sure you have Continuity to Ground on the wire.

3. Measure both Clutch Diode these work like One Way Valves, allowing current flow in One direction only. Select Diode mode on your meter, place the Black lead on the Light/Green wire junction then place the other lead probing the other two ends of the diodes you should measure current flow, reversing the leads should show NO current flow. Given the problem you're having you'd be looking for an Open Circuit Diode = No current flow in either direction.

 

See how you go with these tests to start with.

 

[Paco]

Many many thanks Captain 80s and Grum this is so helpful for me and have given me new hope that my Vfr will see Road again 

[Paco]

Hi Captain 80s and Grum,

 

I have got a bit of time yesterday to wok on the VFR and I did follow your advice Grum and I might need a bit more advice from you 🙂

 

1. I have checked the starter relay and I got a reading, only when I pressed the starter, on the yellow/red wire of 172 with the setting ACV in 2K. Am I doing things correctly?

2. The neutral switch is working.

3. I am getting continuity from the neutral switch right up to the clutch diode switch, however, I am not getting continuity from the diode switch earth green wire to the neutral bulb. I did run a wire from the neutral bulb and earthed on the bike and the bulb did work. Not sure if this confirms that I have a problem with my earth green wire running from the diode switch to the bulb.

4. I have checked the clutch diode switch and does not show any current flowing in neither direction. Grum, I could not find a diode mode on my meter, so what I did was to check the clutch diode switch with all modes that I had on the meter and no current was showing at all. So, I am presuming, there is a fault in the switch. The clutch switch, does it need to be Honda or can be aftermarket?

 

Many thanks!

[Captain 80s]

It seems to me that the only way this is possible is that your clutch diode AND your clutch lever switch (on the clutch master cylinder, left handlebar) are bad. Or possibly the wiring for the Clutch Lever Switch is suspect if you have jumped the wired connectors.

 

But it is early and I am only half way thru my coffee.  

 

Paging Mr. Grum to the Red Courtesy Phone.

[Paco]

Many thanks 

Captain 80s

[Grum]

22 hours ago, Paco said:

Hi Captain 80s and Grum,

 

I have got a bit of time yesterday to wok on the VFR and I did follow your advice Grum and I might need a bit more advice from you 🙂

 

1. I have checked the starter relay and I got a reading, only when I pressed the starter, on the yellow/red wire of 172 with the setting ACV in 2K. Am I doing things correctly?

2. The neutral switch is working.

3. I am getting continuity from the neutral switch right up to the clutch diode switch, however, I am not getting continuity from the diode switch earth green wire to the neutral bulb. I did run a wire from the neutral bulb and earthed on the bike and the bulb did work. Not sure if this confirms that I have a problem with my earth green wire running from the diode switch to the bulb.

4. I have checked the clutch diode switch and does not show any current flowing in neither direction. Grum, I could not find a diode mode on my meter, so what I did was to check the clutch diode switch with all modes that I had on the meter and no current was showing at all. So, I am presuming, there is a fault in the switch. The clutch switch, does it need to be Honda or can be aftermarket?

 

Many thanks!

21 hours ago, Captain 80s said:

Paging Mr. Grum to the Red Courtesy Phone.

Roger that Captain, Red Courtesy Phone in hand! 

 

1. Oh dear! Ah No, you are not doing it correctly and your results are not making sense, why ACV AC volts?. Have your meter set to DC Volts and if it's not auto ranging set it to the 20v DC range. You should see 12v on the Yellow/Red only when the Starter Button is pressed. Clip your Black meter lead to the Battery Negative terminal. 

You also need to confirm that the Green/Red wire from the Starter Relay has continuity back to the other Diode terminal AND that the Green/Red wire has continuity to Ground when both Sidestand is Up and Clutch pulled IN. refer the drawing the Captain supplied.

 

3. If you have NO Continuity on the Light Green/Red wire from the Globe to one of the Diode conections then you have found your Neutral Light issue.

 

4. The Diode is not a switch! As mentioned it acts like a one way valve, allowing current to flow in One direction but not the other. Are you absolutely sure your meter doesn't show a Diode symbol on the Resistance range of your meter? This is most unusual not having a Diode mode on your multimeter! You need to confirm that both diodes show a reading only in one direction, it would be highly unlikely that Both Diodes could be open circuit. Again, check your meter and compare one diode to the other.

Diode Testing - Have a close look at the two photos attached. Note the Diode symbol on the meter dial selection.

 

Good Luck.

 

Diode Test forward bias = Current Flow

 

Diode Test reversed bias = No Current Flow.

[Paco]

Many thanks Grum!

 

Apologies for my lack of knowledge and you’re right, of course, about the mode on the multimeter.

The thing is that I seem to have current of 370 running each way through the diode. So, I am not sure if the diode is the problem and needs to be replaced.

 One thing that I don’t understand is that I am getting no continuity between the earth wire at the neutral bulb to the clutch diode switch.

Would this not indicate that the green wire is damaged between those two points?

 Thanks for all your help!

[Grum]

Your meter is showing good forward bias to both Diodes  Now do the same thing with the meter leads reversed, ie Red lead at the centre terminal, you should have a reading as per my reverse biased photo. And if that's the case then both Neutral Diode and Clutch Diode are Good.

9 hours ago, Paco said:

One thing that I don’t understand is that I am getting no continuity between the earth wire at the neutral bulb to the clutch diode switch.

 

As mentioned you have a Neutral  Diode and a Clutch Switch Diode, commonly called the Clutch Diode. Not a "Clutch Diode Switch". The globe earth wire goes to the Neutral Diode.

 

Again....The wire from the Globe is a Light green/ Red wire. (Look at the Drawing), it goes to the Neutral Diode. So you Must have zero ohms/continuity from the globe to one of the Diode terminals, if Not then you have either a poor connection or damaged wire, this will be why the Neutral light is not working. 

 

Go through the checks mentioned on my previous post. You're making a lot of hard work out of this!

[JZH]

By the way, I'm not sure about Aussie models, but UK and the other European models do not interrupt the headlight circuit when the started button is pressed.  They expect riders to have the headlight switch in the OFF position when starting the bike.  US models, with their always-on headlights, do not have headlight switches.  The starter switches in the different models are, therefore, also different.

 

Ciao,

 

JZH

[Captain 80s]

7 hours ago, JZH said:

By the way, I'm not sure about Aussie models, but UK and the other European models do not interrupt the headlight circuit when the started button is pressed.  They expect riders to have the headlight switch in the OFF position when starting the bike.  US models, with their always-on headlights, do not have headlight switches.  The starter switches in the different models are, therefore, also different.

 

Ciao,

 

JZH

 

Thank you!!   All the clues are there, I just never put it together that they didn't cut the headlight.  I knew the rest of world got headlight switches, I so wish US models were like that.

[Paco]

Many thanks Captain 80s and Grum for your help and guidance! Grum, I am forever grateful for educating me on how to use a multimeter!

 

It seems to me that I may have a bad starter relay. The reason I thought that it was a wiring problem it is because I just replaced the starter relay with a new one after the battery melt down, but I got it on ebay cheap. Also, it could be possible that wires touched when installing the relay as the red cover had melted away (see photo). I will get a new cover as soon as the bike starts.

 

Am I correct that a bad starter relay could stop the neutral light coming on?

 

The multimeter results:

1. Grum, I did what you recommended it and I set the multimeter at DC 20V range then I put one lead on the yellow/red wire at the starter relay and the negative on the battery negative terminal. I pressed the starter and got no reading.

2.  When I putted the multimeter on the yellow/red wire and red wire, at the starter relay, and I putted the negative on the battery negative terminal, the starter motor did turn over which gave me hope.

 

Wiring:

1. The green/red wire at the starter relay has continuity to the clutch diode switch. I looked and looked and I was unable to find the neutral switch diode. Could it be possible that there is none on Irish/UK VFR_ As in the diagram that Captain 80s supplied there was no neutral switch diode. But I did put the multimeter on Diode Mode. I putted one on the earth of the clutch diode switch and the other on the earth of the neutral bulb and did get a good reading.

2. Interesting to see that the clutch showed continuity whether the clutch was pulled in or out. 

3. The clutch switch was working. The side stand showed continuity on the earth wire with the side stand up and no continuity when down.

4. The neutral switch works fine and the earth green wire from it showed continuity up to the clutch diode switch, so do you think that a new starter relay would solve most of the problems?

 

Many thanks to both of you!