Issues with my VFR 750

Hey guys, first time here...

Bike has been sitting for approx 5 months with a full tank of fuel.
Just got me a VFR 750 1987 recently with 44.000 km; battery is dead and tried to get it starting but starting to realise that isn't the problem. I've already tried bump starting and using a booster pack; the battery reads 11.8v which should be sufficient i guess.

Anyhow; i'm starting to think it could be the fuel system or either my carbs that are clogged, bike doesn't crank standstill but it does crank on the bumpstart but instantlly just shuts off after dropping the clutch from 2nd.

Anyone know the common issue procedure to these bikes or should i just check the fuel pump/relay and clean out the carburetors?

Thanks a lot!

 

A bike that doesn't crank has an electrical issue so I would not be worrying about the carbs or fuel system - yet. If you parked it for 5 months without draining the carbs then you probably DO have blocked pilot jets at least.

You need to provide some more clues about the symptoms so we can can give a bit of guidance. So when you turn the key on:
Do you get instrument lights?
Do you see the neutral light?
Is the killswitch in the run position?
Do you hear the fuel pump clicking to prime the carbs?

When you hit the start button:
Do you hear any clicking
Does then starter motor try and turn the engine over (even a little?)

Have you tried using a jump cable from a car battery?
Checked the fuses?

 

The 87 (in stock form) will not prime when the key is turned. It has to be cranking or running for the pump to run. Sometimes you might hear one click when the key is turned on.

 

Yes the instrument lights turn on; so does the neutral, killswitch is also in position & the fuel pump doesn't make a noise, when turning the key.

When i do hit the starter button; it's just constant electrical twitching basically trying to get the motor going but it won't. & i have only tried using a booster to try and get the batteries going; not a car battery with jump cables. & yes i've also changed the fuse with no succes...

 

Constant electrical twitching - you mean a buzzing or clicking from the starter solenoid? That is usually a sign of not enough current flow from the battery i.e. a battery that is sulfated or has developed an internal short. I would suggest trying a jump from a car battery before you go further.

 

Alright will do that firstly for sure! Thanks a lot brotha!

 

These bikes have a "safety feature" in that there is afuel cutoff relay which is designed to stop the fuel pump pumping if the engine is not running.

Normally the bike will start on the fuel in the bowls then the fuel pump will run.

Catch22 is if bowls are empty bike will not start so fuel pump does not run.

Trick is to prime carbs. Remove connector from fuel cut relay. Connector should have three wires - red/ yellow, black and black/blue.

With ignition on and kill switch off short the black & black/blue wires. The pump will run until the carbs are full. If the carbs overflow then you have stuck carb float needles.

Then with full carbs the bike should start.

 

The pump also runs when cranking, not just "running". It might take some cranking, but the pump is operating and will eventually fill the bowls.

But, absolutely you're right, priming is ideal. That's why I wire in parallel toggle switches so I can prime in the Spring after Winter storage without cranking the shit of it and running down my battery.

 

US bikes must be different to Europe as fuel pump relay will only pump when engine revs detected on red/ yellow wire are above 1,000 rpm.

 

Then how does a normal person start a bike when the bowls have emptied from sitting or draining? Honda does not design a bike you have to jump a relay to start when the bowls are empty, or just not full enough to start. So, I'm going down the road and start running out fuel but I don't get the fuel valve turned to reserve and the bike sputters and dies... well better start removing body work on the side of the road so I can get to the relay with my jumper wire so I can start the bike? That sounds safe. No. Turn to reserve and crank until the bowls fill back up, the bike starts and I'm on my way.

Wiring diagram (on Euro Service Manual) shows signal wire from the ECU splits, one going to the FCR and one going to the tach. How would a simple relay know what RPM has been achieved? It either senses an energizing signal or not. If that condition has been observed, then the bike has issues like a failing FCR or excessive resistence, not a different or special FCR.

I am not trying to be combative, but please back your statement up with some proof. The relay is the same unit used on many Hondas from that era in many different markets. It is energized by an ignition signal (red/yel or whatever it is) from either being cranked or running. A certain RPM threshold is not required, either the bike is trying to produce spark or not.


1986 VFR750F U.K. Fuel cut relay: 36100-ML7-013

1986 VFR750F U.S. Fuel Cut Relay: 36100-ML7-013


1987 VFR750F U.K. Fuel cut relay: 36100-MB1-701

1987 VFR700F U.S. Fuel cut relay: 36100-MB1-701

 

Have owned a 1988 VFR750 since 1991 and more recently at 1990 VFR750.

Agree it does not seem ideal. I have a short piece of wire taped under seat. I use both bikes for a couple of months in summer and drain carbs before storage. If there was another way of starting a dry carb bike I would use it to save having to take off seat, side panel and relay connector.

Have posted same information quite a few times to posters in your position on this and other, now no longer live, forums. And always been thanked for helpful post.

 

As I said in earlier posts this is based on experience with Europe market bikes. There are differences, for example the 90-93 Europe bikes have an On/Res/Off fuel switch which was not fitted to US bikes.

 

As your listening shows the fuel pump part numbers are different for 86 and 87.

The part number is different again for Europe 88 models (36100MN4008) and YS never got the 88 upgrades.

So your bike may operate differently.

It is possible your 87 may pump fuel while cranking.

But suggest you try the relay bypass, or open one of the carb bowl drain screws to check if the carbs have fuel or dry. At least you will have ruled out fuel starvation.

 

Your bike has a problem, not a feature. I posted a solution for you. Install a parallel toggle switch. FCR remains intact and "functional", carbs primed at the flick of a easily accessible switch. All of my bikes have one so I don't have to drain my battery to fill carbs. And I can get home when my FCR fails. Has happened twice, once in the middle of a floating bridge.

 

The presence of an external fuel selector knob does not change how the electrical system related to the fuel pump operates. It was not redesigned to accommodate one, because it doesn't matter.

Again, think about what you're saying. Honda designed (wait... now RE-designed for 88 with a new "feature") a bike where if you run out of fuel and can't switch to reserve in time (even with a fuel valve right below your left hand!), you have to remove body work, untape your jumper wire, switch to reserve, let the fuel system prime, and then reassemble your bike.

They didn't. People all over the world select reserve, crank to fill bowls, and go on their way.

What may seem to support your theory for other people, is how long you have to crank to re-prime a dry system. It takes a while and they may think it's never gonna happen.

I know somebody with a Euro 88 here in the states. Bike operates like every other US bike in this regard.

 

"This logic is sound."

 

Euro 1988 VFR750F Fuel Cut Relay: 36100-MN4-008

Same part as used on US models below, plus A LOT more. I own a 92 VFR, 95 VFR, 88 Hawk GT, all of which take the same FCR. They work just like an 86/87 does.

• NT650A (88) MOTORCYCLE, JPN, VIN# JH2RC310-JM000007 TO JH2RC310-JM003038
• NT650A (89) MOTORCYCLE, JPN, VIN# JH2RC310-KM100011
• NT650A (90) MOTORCYCLE, JPN, VIN# JH2RC310-LM200001
• NT650AC (88) MOTORCYCLE, JPN, VIN# JH2RC311-JM000007 TO JH2RC311-JM001093
• NT650AC (89) MOTORCYCLE, JPN, VIN# JH2RC311-KM100019
• NT650AC (90) MOTORCYCLE, JPN, VIN# JH2RC311-LM200001
• NT650AC (91) MOTORCYCLE, JPN, VIN# JH2RC311-MM300001
• PC800A (89) PACIFIC COAST, JPN, VIN# JH2RC340-KM000015 TO JH2RC340-KM003896
• PC800A (90) PACIFIC COAST, JPN, VIN# JH2RC340-LM100001 TO JH2RC340-LM102558
• PC800A (94) PACIFIC COAST, JPN, VIN# JH2RC340-RM200008 TO JH2RC340-RM200980
• PC800A (95) PACIFIC COAST, JPN, VIN# JH2RC340-SM300001 TO JH2RC340-SM300869
• PC800A (96) PACIFIC COAST, JPN, VIN# JH2RC340-TM400001 TO JH2RC340-TM400849
• PC800A (97) PACIFIC COAST, JPN, VIN# JH2RC340-VM500001 TO JH2RC340-VM500623
• PC800A (98) PACIFIC COAST, JPN, VIN# JH2RC340-WM600001
• PC800AC (89) PACIFIC COAST, JPN, VIN# JH2RC341-KM000031 TO JH2RC341-KM000734
• PC800AC (90) PACIFIC COAST, JPN, VIN# JH2RC341-LM100004 TO JH2RC341-LM100483
• PC800AC (94) PACIFIC COAST, JPN, VIN# JH2RC341-RM200001 TO JH2RC341-RM200220
• PC800AC (95) PACIFIC COAST, JPN, VIN# JH2RC341-SM300001 TO JH2RC341-SM300140
• PC800AC (96) PACIFIC COAST, JPN, VIN# JH2RC341-TM400001 TO JH2RC341-TM400221
• PC800AC (97) PACIFIC COAST, JPN, VIN# JH2RC341-VM500001 TO JH2RC341-VM500090
• PC800AC (98) PACIFIC COAST, JPN, VIN# JH2RC341-WM600001
• VFR750FA (90) VFR, JPN, VIN# JH2RC360-LM000009 TO JH2RC360-LM000788
• VFR750FA (91) VFR, JPN, VIN# JH2RC360-MM100001 TO JH2RC360-MM101581
• VFR750FA (92) VFR, JPN, VIN# JH2RC360-NM200008 TO JH2RC360-NM200817
• VFR750FA (93) VFR, JPN, VIN# JH2RC360-PM300001 TO JH2RC360-PM300992
• VFR750FA (94) VFR, JPN, VIN# JH2RC360-RM400003 TO JH2RC360-RM401253
• VFR750FA (95) VFR, JPN, VIN# JH2RC360-SM500001 TO JH2RC360-SM501271
• VFR750FA (96) VFR, JPN, VIN# JH2RC360-TM600001
• VFR750FA (97) VFR, JPN, VIN# JH2RC360-VM700001
• VFR750FAC (90) VFR, JPN, VIN# JH2RC361-LM000011 TO JH2RC361-LM000227
• VFR750FAC (91) VFR, JPN, VIN# JH2RC361-MM100001 TO JH2RC361-MM100403
• VFR750FAC (92) VFR, JPN, VIN# JH2RC361-NM200006 TO JH2RC361-NM200186
• VFR750FAC (93) VFR, JPN, VIN# JH2RC361-PM300001 TO JH2RC361-PM300217
• VFR750FAC (94) VFR, JPN, VIN# JH2RC361-RM400001 TO JH2RC361-RM400268
• VFR750FAC (95) VFR, JPN, VIN# JH2RC361-SM500001 TO JH2RC361-SM500248
• VFR750FAC (96) VFR, JPN, VIN# JH2RC361-TM600001
• VFR750FAC (97) VFR, JPN, VIN# JH2RC361-VM700001
• VT1100C22A (02) MOTORCYCLE, 98, VIN# 1HFSC323-WA300001
• VT1100C22AC (02) MOTORCYCLE, 98, VIN# 1HFSC324-WA300001
• VT1100C2A (00) SHADOW SABRE, USA, VIN# 1HFSC430-YA000001 TO 1HFSC430-YA099999
• VT1100C2A (01) SHADOW SABRE, USA, VIN# 1HFSC430-1A100001 TO 1HFSC430-1A199999
• VT1100C2A (02) SHADOW SABRE, 97, VIN# 1HFSC323-VA240001
• VT1100C2A (02) SHADOW SABRE, USA, VIN# 1HFSC430-2A200001 TO 1HFSC430-2A299999
• VT1100C2A (03) SHADOW SABRE, USA, VIN# 1HFSC430-3A300001 TO 1HFSC430-3A399999
• VT1100C2A (04) SHADOW SABRE, USA, VIN# 1HFSC430-4A400001 TO 1HFSC430-4A499999
• VT1100C2A (05) SHADOW SABRE, USA, VIN# 1HFSC430-5A500001 TO 1HFSC430-5A599999
• VT1100C2A (06) SHADOW SABRE, USA, VIN# 1HFSC430-6A600001 TO 1HFSC430-6A699999
• VT1100C2A (07) SHADOW SABRE, USA, VIN# 1HFSC430-7A700001
• VT1100C2A (95) SHADOW 1100 - ACE, USA, VIN# 1HFSC320-SA000001
• VT1100C2A (96) SHADOW 1100 - ACE, USA, VIN# 1HFSC320-TA100001
• VT1100C2A (97) SHADOW (2-TONE) - ACE, USA, VIN# 1HFSC320-VA200001
• Show More

 

I got it running!!! Hahahahaha basically just a dead battery, got myself another one… Bike does sound that it’s running quite rich. I assume that might have to do with the carburetors being blocked or not cleaned in a long time.

edit: i’d love to show y’all what it sounds like running! It’s sick, first vfr xp

 

Great! Terry nailed it.

 

Congrats, Janko....woohoo! And a tip of the hat to Terry!

I think I will try a jump on one of mine that doesn't want to start when I press the start button. Good way to start the troubleshoot process!