1986 VFR 750 Problems

I bought this 1986 VFR750 recently I came across it for a pretty good price or so I thought. It had been sitting for almost 10 yrs without being ran. The guy I bought it from told me he got it running with starting fluid, but it only ran for a couple minutes because the carbeurators had become varnished. After I bought it I got the carbs cleaned yet I still cannot get the bike to start, I believe the problem lies between the Gas tank and the fuel pump, when I attempt to crank it over gas won't come out of the line from the fuel pump to the carbs. Any suggestions? The local shop charges $130hr just to even look at it. Any help would do. thank you.


P.S. Also any suggestions where to get tires and a chain online?

 

hi,
Stuka has said the right things to do. But check this : disconnect the fuel line from the pump (I mean the tube that arrives to the carbs). Now try to start : does the gas come out from the pump ? (be careful with the gas !) If not = bad pump. If gas comes out then you have an electrical problem. In this case, check spark plugs. If spark plugs are ok, there's only a possibility : in the head of front cylindres there is a little gear that feels the crank speed and activates the PK (a switch that leads the spark unit). iF THIS GEAR IS BROKEN, THE PK DOES NOT ALLOWS THE SPARK UNIT TO SEND SPARKS ON THE PLUGS AND THE ENGINE CAN NOT START...WELL, LET US KNOW.
LAMPS TO YOU AND GOOD LUCK !

 

Thanks for the Suggestions Stuka and Carmine-I disconnected the fuel line, attempted to start it and NO gas, I'm going to get a new pump. Also I took the gas tank off and emptied it to see if the interior was varnished, it does look a little rough in there but gas still leaks through. I also removed the fuel reserve sensor, it looks as if the gas ate away at the protective cover of the wires, so I definitely need a new one of these right? Also i was wondering if anyone knew where to get a diagram for the fuel hoses on the bike. Thanks Again.

 

Before you get a new pump, be sure to test it first. It may be that the fuel cut-off relay is bad...(if it has one)

 

before to buy a new pump, try this : first, remove the black cap of the pump (there is a screw on the side), You will see a mechanism similar to a bridge, this bridge has the function to open/shut a metallic contact (when the carbs are full of gas this contact is open, when carbs are empty this contacts alternatively open/shut to send gas to the carbs). If this contact (a brass dot) is only dirty, try to brush it with thick abrasive paper (hope this is the name) and/or clean with electrical contact cleaner. If the pump is not "burnt" this could be the way to reactivate the pump. Also, check, if any, the correct position of the fuel filter : it MUST be between two sections of the line that comes from tank to pump, with an arrow pointed toward the pump inlet. When you switch ingnition key "on" if you hear a noise near the pump it is a good sign : the pump begins to run.
Lamps and good luck !

 

hi, masonv, glad to see other guys who love "old ladies" as '80s VFR.
Lamps to you !
Carmine

 

Carmine; When I turn the key to the "On" position, I do hear a clicking sound, and also feel the pump turn on, but yet when I try to start it no fuel will come out of the fuel line to the carbs,(like you said to do earlier) Also I cannot spot a fuel filter, so I'm guessing this model does not have one. I'm off to attempt to clean the contact on the pump to see if that makes a difference. And masonv how do I find out if the fuel cut off relay is bad? Thanks for all the Help.

 

In the manual, it should detail how to perform a fuel flow test. Usually, it is performed by shorting the valve cut relay which powers the pump on all the time. Do not short across the ground or you will fry your relay. On my bike, it is the black and white wires in the relay (green should be ground).

Little lesson on early V4 Honda fuel systems(82-86..yours may be different due to the redesign in '86):
1. The fuel cut relay is triggered by the coils. So it doesn't actually get a solid supply of power. It only gets it when the coils fire - in another words, only when the bike is attempting to start, or is running
(this is a safety feature to cut off the fuel pump in case of a wreck/fuel leak and the bike stops running. Otherwise, even with the bike not running, the pump would keep pumping gas until no more gas, or no more electricity, or no more pump {explosion}).
2. If this relay is bad, the pump will never get power.
3. The fuel pump is a really low pressure pump (like 3psi). So when the float bowls are full, the float needle closes off the fuel flow and the pump cannot pump against the gas back pressure anymore so it stops. As the fuel is used in the carb, the float needle opens and the pump can now overcome the gas backpressure.

When you turn the kill-switch on and off, some residual voltage crosses the coils. So you may hear the pump click. This is a slow method to fill the carb float bowls. I usually short the relay or provide power directly to the pump until it slows/stops pumping.

 

Didn't I just see a thread about removing the pump all together? The jist of the thread was that the bike should run just fine on gravity feed.

http://vfrworld.com/forums/first-se...89/7094-fuel-pump-woes.html?highlight=gravity here it is.

 

Are you sure a 1986 VFR750 is compatible for a gravity feed? Are the carbs supposed to create a vacuum?

 

uhmm, gravity feed is possible but remember that carbs are in a higher position, so when you have no enough gas in the tank (1/4 of its capacity) carbs can not get gas by means of gravity. I think that the Masonv's test for the relay is very good. After that, and after the control to the pump contacts I do not see whatelse to do. Only a question : are you sure that fuel hoses are in the right position ? I mean : tank hose towards the pump inlet and carbs hose towards the pump outlet. Once, I changed my hoses, and I inverted their position : the pump tried to run (click sound) , the engine ran for some instants and then...no way to restart....untill I replaced the right position.
LAMPS !! At least, you are having a goog knowledge of your bike !!!
Let us know, I am sure we will "wake up" your VFR !

 

use the jumper wire trick to send power to pump and bypass relay.

the pump has 2 internal valves (in and out)) that could become clogged, so blow compressed air into inlet to clear that valve and test the outlet valve by using your breath to blow into outlet side, where you should not be able to blow air through it.
if you suck on inlet, no air should flow; and if you blow into outlet, no air should flow.

if fuel is getting to the pump, and if pump clicks, then evidence points to bad pump diaphram, meaning a new pump is needed.

 

Hey I Just wanted to drop b and thank you guys again for the help. The problem was the fuel pump indeed. I put the pump on as soon as I got it and after a little coaxing it started up beautifully after 10 years of sitting if someones garage!!! I was very suprised. the chain is extremely rusted, the grommets are falling off and the tires seem to be dry rotted, But atleast she starts. The parts are already ordered and on their way, so I will be soon to ride! Have a good day to all.

 

you will need a new chain and 2 sprockets as well as tyres.....

 

Yeah at first I didn't believe the people at the honda dealership thinking they were going to tell me I need this and that when in actuality I didn't. But they did convince me to buy a new sprocket set, new tires, and a high performance chain. Hopefully it will come together just fine. I did take her for a small ride around the neighborhood and i was suprised how much power the 86' has, my friend had a 06' suzuki 600 and the Vfr seems to put it to shame.

 

How about some pics of your sweet lady?

Regards,
Rollin

 

Here's a Couple Pics of the Ol' Lady.

 

It looks in great shape!! Congrats!:strong:

 

I bought a similar project (not quite as clean as yours though), and my fuel pump would only buzz and get hot. The factory pump is very expensive, so I bought a small "facet" brand pump from Checker Auto Parts (about $50) rated at 1-4psi. I adapted it to the bike, and am running it off the factory wiring harness. It seems that the factory wiring, without the use of the relay on the factory pump, is live whenever the key is on, but hasn't overloaded the carbs yet. Just a thought....