1986 Interceptor 500 fuel problems (petcock and ect)

Discussion in '1st & 2nd Generation 1983-1989' started by forgriffindor, Apr 24, 2018.

  1. forgriffindor

    forgriffindor New Member

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    Hello everyone, this is my first time posting my own thread so forgive any mistakes in formatting and such.


    I purchased my 1986 vf500f off craigslist for a pretty good price and I finally got it running and on the road about a month ago. It had a leaky petcock which wasn't a huge issue because I got caught up in the excitement of riding. Well last week I finally got around to ordering the gaskets to fix it. I got it all put back together and installed on the bike, but on my initial test ride it would ride really well for about 10 miles before shutting off. I figured it was because I was low on gas, so I filled it up and got it going again. Well a few miles down the road it shut off on me again. After a couple of minutes I got it going again and I was on my way, only to have it cut off on me again. It did this repeatedly until I tilted the tank back and the carb started pouring fuel out, so I assumed that the carb wasn't getting enough fuel because that has happened before when it started getting fuel after being dry. So I figured it wasn't getting enough fuel from the tank/petcock, probably my DIY fuel line. Anyone know where I can get a proper fuel line and possibly a new petcock? I can't find anything searching online.


    Now to the scary/serious bit, I finally got around to taking a look at the petcock/gas starvation problem today, and when I went to start the bike to let it idle/burn the remaining fuel in the line it wouldn't crank. I thought it was a dead battery so I hooked it up to a jump pack, still nothing. Jumped to worst case, the engine is seized, so I decided to pull out the plugs and see what I could find out. Right when I pulled plug #1 (left rear) and turned the bike over it spit out gas. I pulled the rest of the plugs and none of them spit out gas. I assume this is because it was on the kickstand and thats the lowest carb and the carb leaked out. What can I do to fix this and stop it from happening in the future? Is this a serious issue that requires me to pull the engine to fix?


    TL;DR:

    1986 Honda VF500F leaks fuel from the petcock and carb into the cylinder. I think it was hydro-locked till I pulled the plugs.

    -where can i find a new petcock?

    -is there a good aftermarket alternative?

    -what can I do to keep the fuel from getting into the cylinder?

    -is this a serious enough issue that I need to pull the engine?


    Again I'm sorry if this is a long post but I just wanted to provide all of the information I could about this issue. Any help resolving this would be greatly appreciated!
     
  2. Gator

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    I just went through this on my sons DRZ 400. He was away for about 4 months and the bike had been sitting for a few months before that. It had gas with ethanol in it. The petcock diaphragm failed and the float valve o ring failed and I found about a gallon of gas in the motor. I rebuilt the entire fuel system, replaced the stock petcock with a Yamaha Raptor one that does not use engine vacuum. A bunch of oil changes later and it runs great now. I have a DR 650 and will eventually replace the petcock in it too as it uses the same kind of vacuum one.
    I'm not familiar with carbed VFR's but there are a lot of guys that are. I do know carburetors in general. It seems your VFR's problem is one that is common on mikuni carbs that do not have an overflow tube. When the petcock fails, the fuel will not shut off, then the float valve in the carb fails (usually the little O ring) and the fuel seeps into the head then eventually down to the bottom of the engine. You have a classic hydrolock , fluid, gas in this case, does not compress. Drain the oil, find a petcock that fits, probably a bunch that will, then do a complete rebuild kit on all of the carbs. I'd check/clean the tank at this time too and replace all of the fuel lines. I only run Rec 90 in all of my carbed bikes and machines.
    [​IMG]Reply
     
  3. Gator

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  4. Captain 80s

    Captain 80s New Member

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    Unfortunately the 86 VF500F petcock is a 1 year only unit (in the U.S.) 84-85 are different and can not be modified to work as the bolt spacing on the tanks is different.
     
  5. Gator

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    Measure the holes , I bet there are more than 1 aftermarket that will fit it. A search on here and VFRD should come up with one. I put a Yamaha Raptor one not eh DRZ. Simple on, off and reserve. The reserve is a bit less than stock but thats one as long as you know.

    Captain, is the stock one vacuum activated? If so he will have to plug the port on the carb. I bought one of those bag full in assorted color and sizes for a few bucks.
     
  6. forgriffindor

    forgriffindor New Member

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    I changed most of the gaskets on the carb when I initially had them off. I'll probably go back and check out that o-ring. I managed to find a o-ring that works for the petcock, so maybe I can stop that leak. Also got it to not let fuel through when it's in the "off" position so that should keep gas out of the line. Thanks for the replies. I did find a generic petcock and an adapter for the tank, but it won't work with the switch on the side of the tank without modification.
     
  7. Gator

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    Grinding the lever of a Petcock down is a common mod. A lot of guys do that on the Raptor one used on the DRZ. I used the spacer off the stock one and managed to route the fuel line so it would not kink so no grinding required.
     
  8. forgriffindor

    forgriffindor New Member

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    Okay a little update, I got the petcock back together and so far it doesn't leak. Also got the carbs apart and put an o-ring in the first carb and that appears to be keeping the gas out. Now I'm running into the issue of the bike feeling slow and like it's not getting enough fuel, I have reason to believe its the o-ring I put in or my home made fuel hose from the tank. Now on to that issue. It doesn't like to idle so I think it's starving for gas, any thoughts would be appreciated. Thanks for the help
     
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    Did you check all of the float levels? Did you change any jetting or clip positions on needles?
     
  10. forgriffindor

    forgriffindor New Member

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    I got the bike back together and it doesn't leak anymore, I got the petcock to work and not dump fuel in the carbs/on my driveway. I've now run into another issue, after riding the bike for a while it slowly starts to lose power, and occasionally it will feel like the bottom just falls out of it. It dies immediately when I pull the clutch and it takes some starter fluid to get it going again (now I carry it when I ride). This wasn't a problem before I fixed the fuel petcock so I think the carbs are drawing so much fuel it's making suction in the tank and limiting the fuel coming out through the line. the reason I think this is the issue is because before it was probably relieving this suction through the petcock where it was leaking from when off, but now that the air isn't getting in it has to come through the gas cap. Which leads me to my next point, I think the gas cap vent isn't working and is limiting the fuel allowed into the system. I read another post about something similar and it turned out the bike wasn't firing when it got hot, I just checked mine while it was still pretty hot and it still fired. I have a new gas cap on the way so I guess we'll see if it solves my problems.


    I should also mention I did the vacuum bypass that Daugherty Motorsports has detailed on their website.


    TL;DR: I fixed the leaks and I think it's making suction in the tank and not letting the gas flow properly, tracked it down to (possibly) the gas cap.
     
  11. forgriffindor

    forgriffindor New Member

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    Update: Got a new gas cap, fixed the problem marginally but it's still not running right. After a while of riding it just stops getting fuel. I pulled up the tank and the fuel filter is not getting fuel. I just barely trickles out. That narrows my problem to the petcock, again, so now I have to figure out why it isn't letting fuel through after I have been riding for a while. Has this happened to anyone else? Do I need to just bite the bullet and buy an adapter and generic petcock?
     
  12. squirrelman

    squirrelman Member

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    Try blowing some compressssssed air backward into the tank through fuel line with the cap open with tank drained and dry.
     
  13. beeton

    beeton New Member

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    Off chance but have a look at your fuel pump as well. It may be on its last legs and overheating which you are mistaking as a fuel-flow issue with the carbs. if you detach the fuel outlet line after the pump and filter (and yes, check the filter if it is an opaque one), you should get a strong, steady flow when you are running...until the carbs empty out. As for the petcock. not a standard fit. I am trying to find the x ring to rebuild mine.
     
  14. forgriffindor

    forgriffindor New Member

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    Sorry to abandon the thread here. I ended up fixing the problem by replacing my fuel filter and running a new line from the tank to the carbs. The '86 vf500 doesn't have a fuel pump, they got rid of it in favor of a gravity fed system. Still thanks for the suggestion
     
  15. beeton

    beeton New Member

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    Very odd as I have an 86 and it has a fuel pump. As for the filter change, that was probably it as the stock one is opaque and hard to tell if it's cruddy within. I use a clear one.
     
  16. jeremyr62

    jeremyr62 New Member

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    In most (all?) countries the 86 was an updated model and the fuel pump was deleted. Quite a lot of frankenbikes out there by now I expect. I have an 85 myself with a 86 engine in it.
     
  17. beeton

    beeton New Member

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    So, I have an 86 which may have a tank from an 85 (it was painted black), or a tank from an 86 with a petcock from? as it has been modded to omit the vacuum BUT I have a fuel pump as well. I rebuilt the petcock (removed rivets, drilled and tapped, mounted new bolts after cleaning the x ring and softening it with a bit of silicone grease. Did not leak at first. Then leaked a bit. Now stopped but I won't park it over my driveway for fear of a leak as that will chew up the asphalt. I ordered 2 x rings and am awaiting those. They are coming from England. If they don't work, I will seal up the petcock selector in the res position and add an inline on-off between the tank and pump, even though the pump will prevent flow-through.
     
  18. forgriffindor

    forgriffindor New Member

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    I had the leaky petcock as well, I had a problem with it leaking even after I replaced the o-rings. Ended up just sealing it with gasket maker, not the prettiest solution but it works.
     
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