1985 vf700f needs help

So about a month ago my '85 vf700f left me stranded. I first thought that the problem was my fuel filter, (it was trashed and starting to fall apart), I replaced the filter and once again it died on me with the same symptom. When it died on me I was riding up hill at about half throttle and it felt as though the motor wasn't getting enough gas, but when I tried to accelerate the motor quit. I tried to start it by the side of the road but it wouldn't run for more than a few seconds without the choke on. I waited for a half hour and it fired right up and got me home.
So after this experience I thought it might be the fuel pump so I converted the bike to gravity feed. Once again it died on me with the same hesitating and lugging feeling.
I then took the opportunity to do some much needed maintenance which included replacing both sprockets, countershaft seals, oil pan seal, water pump seal and I cleaned the carburetors.
Once I got it put back together I rode it for one day and everything seemed normal again. Then as I was riding home yesterday (going up a slight hill) the bike died again with the same symptom of seeming like it is being drowned.
I left the bike to sit for a couple of hours and when I came back, it fired right up and once again got me home.

Needless to say I am at a loss.
I just cleaned the carburetors but will clean them again. I also synced them and they were a only a hair off between the four of them.
I am kind of worried also because I can smell gas in the oil and the oil level is higher than I last checked.

I know this was a long post but I could really use the input from anybody who might have a clue.

James :unsure:

 

What RPM level are you at? The only thing I could think of is that you are bogging down the engine, maybe try to downshift for the specific hill and keep the RPM's high.

 

Thanks for the input and I wish it were that simple. I cleaned the carburetors last night and some of jets had a little build up in them. I used carb cleaner and an air compressor to blow out all of the passage ways. I hope that this might do the trick but can any one suggest any other places to be concerned about. I only ask because the motor only dies at operating temperature which suggests to me that it could be an electrical problem.

Oh another thing I should add is that I have never taken the pilot screws out could this maybe have something to do with my symptom.

James

 

BTDT...tank or gas cap is not venting.

Usually happens when there is less than 1/2 tank.

 

So I just got back to working on the bike and have done a few more things to the bike.
Tonight I dismantled my gas tank and cleared the lines. I also made sure that the tank and cap valve were venting.
Over the weekend I had a few thoughts that I would like to throw in. I should have mentioned that the bike has died with less than a 1/4 tank and also with a full tank. I also should have added that my bike it is a California model with a PCV valve and whether or not it might have anything to do with the tank possibly not venting properly.

 

hi,
sometimes old vfr have problems with coolimg system. You can have a false reading on the temp.gauge. So you think that you are about the operating temp while the engine is overheating. Check the radiator (drain out the coolant, it is certainly dirty....), change the coolant with a good one. When the engine overheats, there is a major expansion of the pistons and the engine tends to block, also, the hot temp changes in a negative way the stechiometric ratio of gasoline that arrives in to the carbs. This not happens when the engine is cold...
Try this, anyway if I remeber well, your bike has not lateral fairings, so it is easy to reach the tube that goes from rad to the water pump.
Let us know,
Lamps to you
Carmine

 

Hey Carmine,
I will check the cooling system but the bike has died with both old and new coolent. Also when I drained the old coolent it looked clean. Do you know if there is any sort of thermal switch associated with the thermostat?

 

Hi Cirque,
well, on the right side of the engine you will find the thermostat (it is a bulb ; inside there is the thermostat valve that opens/closes the fluid to the rad depending on the water temp). then on the left side of the radiator (bottom) there is the fan thermoswitch that activates the fan when the temp in the rad reaches high temp.
well, i do not know if this is the cause of the troubles of your engine, but at least you will learn the exact way your cooling system works (if it works !).
To undetstand the origin of the problem you should verify if the current arrives to the spark plugs when the engine dies (if the current arrives the cause is a gasoline/carburation problem, on the contrary, you have to check coils/spark unit or some other electrical matter. Remember to be careful with electrical applications ! Danger of high voltage around coils and plugs !
Ciao, let us know !
Carmine

 

Last night reassembled my bike and it runs well. I made sure that I was getting good spark on all four plugs and I tested the coils and rectifier with a multimeter and could find no problems.

Another problem has surfaced though that could potentially have something to do with the original issue. The throttle response has become sluggish and I fear it could be that my carb slides might be causing the problem. When I say sluggish I mean that when I slowly rev the motor it hesitates around 2000 rpm then surges to 4000 and then continues to climb steadily. Then, when I back off of the throttle it takes several seconds to return to idle.

I don't know if this problem has anything to do with the first one but I would really like to figure them both out.

Thanks again all,
James

 

over heating and fans

Try getting your bike hot and see if the fans turn on. I had the same bike for 5 years with about 50k on it, still starts up fine but overheats in stop and go and fans don;t turn on so left in N. CA with my father in law to enjoy on short stretched where it will never overheat. Anyway my fans no longer turn on either due to a faulty therm/fan sensor or other, but know when you overheat it will do exactlr what oyu say, die as you try to accelerate, oil light also seems to turn on at the saem time. if your fans do not turn on you can do a quick fix and buy a switch from an auto parts store and put them on a manual switch to try to keep her cool. These bikes are notorious for overheating as they get old and the elctricla system starts to fry-out. Good luck, its fun bike but I decided to upgrade to a used 99 VFR, and man what a difference 14 years of tech can do.

 

Sounds like sticky carb slides or a clogged emulsifier tube. My '83 uses similar carbs, the emulsifier tube on mine is not easily removeable. I used a brass .45 pistol brush to clean mine. Pilot screws should have no effect at the speeds you're talking about, but if the fuel filter was falling apart, pieces of it may be blocking the float needles. There are little dome shaped screens on the top of them, so unless they were removed when you cleaned the carbs, they may be blocked... even if they appear clean.

You should change your oil. it's contaminated with a lot of fuel.

 

Was this post ever resolved? I have the same bike, I hope yours is still on the road.