1986 VF500F almost back to life

Discussion in '1st & 2nd Generation 1983-1989' started by Chocula, Sep 19, 2014.

  1. Chocula

    Chocula New Member

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    I have an 86 VF500F that had been sitting in my garage for many years. Fuel system has been cleaned out, carburetors rebuilt, new coils, plugs, fluids, etc.

    It starts up and seems to run fine, but after a bit it starts to sputter and dies as though it has run out of fuel. If it sits for a bit, it will restart and run for a few minutes. I have confirmed the fuel is fresh, clean and flows from the petcock. I was thinking this was a kink in the fuel line, but I did not have much success trying to correct that. I have not completely ruled that out, but it seems unlikely at this point.

    Has anyone experienced anything similar and found a solution?
     
  2. Maggot

    Maggot New Member

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    I have no experience with the '86 VF but try running it with the gas cap open. Some older bikes have a vent in the gas cap and with time the little hole can rust shut.
     
  3. NormK

    NormK New Member

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    My first test would be pull the tank and run it on a fuel bottle straight int the hose feeding the carbs and see how that goes, eliminates a lot of things you can't see
     
  4. jeremyr62

    jeremyr62 New Member

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    Instead of letting idle in your garage, the best thing is to ride it. Putting it under load does wonders. You will flow more fuel and probably clean the blocked circuits. Trying to diagnose problems without riding the bike can be very misleading in my opinion. However it's your bike, your circumstances. It does sound like a circuit blocked in the carbs.
     
  5. 74ullc

    74ullc New Member

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    Not sure if the '86 500 has a fuel pump, but if so that's where I would look.
     
  6. NormK

    NormK New Member

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    and that is the reason for using a fuel bottle you bypass all that stuff, blocked vent, relay,fuel pump,kinked hose blocked tank feed, rusty tank, anything that can cause problems, put fuel straight to the carbs.
     
  7. 74ullc

    74ullc New Member

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    Agreed NormK.....that's the first thing I did when I got my '84 VF700F, it would start and run for about 2-3 seconds then die. Give it a minute and it would start back up. So I bypassed everything and then it would start and stay running. I pulled the pump and filter, jumped the pump and let it clear some crud out and then it was fine.
     
  8. Chocula

    Chocula New Member

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    There is no fuel pump and I connected a bottle today. She seemed to be burping a lot of air back up the fuel line, but she was initially running as she should while the choke was one. I could see her drinking the fuel in the line as well as through the fuel filters. Once she warmed up and sounded like she was ready for the choke to be off, I noticed most of the air had been burped out and that is when she decided not to run. I was able to hold it at about 3000 rpm using the throttle for maybe 20 seconds after that before she stopped. She was neither happy with the choke on or off at this point. Before she was warmed up, the throttle was responsive and I could take off the choke as long as I held the rpm's up a little, but once warmed up, she did not want to run. There seems to be a very distinct point where she goes from happy to unhappy.
     
  9. 74ullc

    74ullc New Member

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    Do you have a timing light? I would wait until it started running bad and see if I was getting spark on all four. It sounds electrical, the way you describe its runs fine and then, boom, runs like poo. I know you said you have new coils but maybe its possible you got a bad one? Coils can drop out when they get hot. Or could be a CDI box.

    I'm not too familiar with the '86 500 but on the '84 700 there are two CDI boxes, one controls the tach and two cylinders, the other one controls the fuel pump and the other two cylinders.

    Seems like electrical gremlins are the toughest to work out.
     
  10. Chocula

    Chocula New Member

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    I will test the coils in the morning. I used to have a timing light, so it should still be someplace in the garage. Does the timing light provide the same information as the "dynamic" test except you don't have to pull the wires? My multi-meters are easier to find so I will check the resistances as well. She was in a shop over the summer getting the tank and carbs cleaned out as I don't have the needed facilitates for that. They indicated they replaced the coils, but I can't personally confirm it.
     
  11. 74ullc

    74ullc New Member

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    You can use the timing light to check for spark. Just hook it to each wire one at a time and see if it strobes. You're not checking timing, just checking for spark. On my bike I had to lift the tank to get at the rear wires.
     
  12. Chocula

    Chocula New Member

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    Today I pulled out the coils, both physically looked good. One measured 3.0 ohms on the primary and 14440 ohms on the secondary, the other measured 3.1 ohms and 14400 ohms. After re-installing the coils and finding my timing light, I hooked up a bottle and she ran beautifully. Warmed up nicely and I was able to set the idle. No hiccups and the timing light flashed consistently for all cylinders. One difference is there was very little air coming back up through the line.

    Since my petcock does not stop the fuel completely when off, I have to get the tank almost completely empty before disconnecting the hoses, hence I want to have it run well for another few tests before I put the fuel tank on and refill it again. I also want to get a better routing for the fuel line, as mine currently has some undesirable kinks.
     
    Last edited: Sep 21, 2014
  13. Chocula

    Chocula New Member

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    I was not able to get it to fail in the last few tests so I cut some new fuel hoses to reduce the sharp bends and re-installed the tank. She warmed up fine so I took her for a 15-20 minute test ride and so far so good. I will probably get some highway testing in this weekend.

    Thank you everyone for you support and suggestions.
     
    Last edited: Sep 25, 2014
  14. NormK

    NormK New Member

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    Ok glad to hear it is working but you say the tap doesn't shut off properly so before you come back with a problem of a bent con rod due to fuel leaking into a cylinder, do yourself a favour and fit a fuel shutoff solonoid
     
  15. Chocula

    Chocula New Member

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    Well, I have ruled out it being a fuel starvation issue. Sometimes works great, sometimes not.
     
  16. Chocula

    Chocula New Member

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    Update: Took the tank off today to try and install an inline shut-off valve and discovered evidence of the hose having a kink in it. I shortened the 1/2" hose to where I had just enough room to make the connection and get the clamp on while my wife was holding the tank up for me. Put about 25 miles on the bike today with no issues. My hoses were altered by a shop this past summer, I would love to see a photo of how things looked originally my manual doesn't show this very well.

    My intention was to put in a manual shut off valve, but there is no way the one I have would fit how I have the hoses at the moment. I have not been able to find a 1/2" inline solenoid, hopefully I will be able to find a rebuild-able petcock on ebay or something.
     
  17. NormK

    NormK New Member

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    Ok so are you by any chance calling the hose 1/2" by measuring the O/D of the hose? I would think the outlet from the tank would be 5/16th" and you just get a 1/4 inch BSP solonoid valve and get barbed fittings to take you back to 5/16th" tails, fit that straight out of the tank outlet and then I used a bolt together barb connector so that all you have to do is undo the nut and the hose is apart,10 seconds, none of this crap trying to get the hose on and off while trying to hold the tank up. Hose goes down infront of the rad expansion bottle and the up to the carbs if you are not running a fuel pump Not exactly if the 500 is the same, mine is a 750 but I'm sure they are close enough
     
  18. Chocula

    Chocula New Member

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    A 1/2" inside diameter hose fits over the petcock and goes to a "Y" connector with a 1/2" inlet and two 5/16" outlets which go to the carburetors. I did not look at it prior to taking it into a shop to have the fuel system flushed and cleaned, but I suspect the original hoses were shot. There was a small piece from what I think was the original with a preformed 90 degree bend. I speculate that it originally had the rest of this hose which was preformed to flow nicely. The '84 and '85's had a different petcock with a smaller outlet as well as had a fuel pump.

    I was able to put in 45 miles on Sunday as well as 10 more yesterday with no apparent issues. I did find a 1/2" barbed inline solenoid, not sure how I will have to change things to get it to fit.
     
  19. NormK

    NormK New Member

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    Thanks Chocula, I would love to know the thinking behind this setup, 1/2" fuel line sounds bizare you can run a big block Chev on less than that. You just have to think about how quickly you could empty the fuel tank through a half inch hose and how far you can ride on a tank of fuel. 5 min to empty it through the hose or 2 hours riding which proves you are only drawing a fraction of what the hose can pass
     
  20. jeremyr62

    jeremyr62 New Member

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    Honda assumed we would be riding WOT, all the time, everywhere.
     
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