'86 VF500F Not Starting After Service

Discussion in '1st & 2nd Generation 1983-1989' started by HamHock, Nov 16, 2020.

  1. HamHock

    HamHock New Member

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    Hey everyone, I've been working on my VF500F but I've run into a bit of a snag. First a little back story, I picked up this machine about 3 months ago with 22k miles on it and it was running less than great. The bike would start up but never ran well. It would feel like it was starving for fuel while cruising down the freeway. Sometimes it would bog down and I couldn't get it to rev up to save my life.

    Poor drivability and low power were the reasons I decided to take the bike off the road and have a look at things. I came up with more than a couple plausible seeming reasons for the above mention symptoms, everything from a bad petcock vacuum, the evap system, the carb vents and the petcock screen.

    While I had the bike apart I have done the following:
    • Carbs cleaned out and bench synced
    • evap system completely removed, all hoses are either capped or merge with each other
    • valve inspected and adjusted. All of the valve were tight with the exception of the inside exhaust valve on cylinder #4, which had its lock nut come loose and the tappet had backed out. Miraculously there was no damage to either the valve or the follower.
    • petcock modified to simple on/off/res, without vacuum operation.

    Now I've got the thing reassembled and I have fuel in the float bowls and I have spark but it is not starting or even firing. Not even a cough. I suspected that I had reconnected the coils backwards, so I switched around the wires with no change.

    I should add that this is far from my first time adjusting valves or cleaning carbs. First time on this machine, but I've been turning wrenches my whole life.

    Where do I start? Should I blow it all back apart and start over with the valve adjustment? Other than valve timing I don't know what else could be going wrong. Any ideas or help will be greatly appreciated.
     
    Last edited: Nov 16, 2020
  2. Captain 80s

    Captain 80s Member

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    My knee-jerk is that you have misinterpreted the needs of a de-smog. I believe your capabilities, but that's the biggest change.

    If you've got the skills, your valve adjust is not it.
    The fact that you know what a "bench synch" is, and how to do it... won't keep it from starting.

    This is ALL assuming a bigger problem does not exist.
     
  3. HamHock

    HamHock New Member

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    I'm not sure if you are familiar with the California carbs/evap set up on the '86, but let me try to explain what I did to get rid of those parts. I removed the two canisters, I removed the purge valve. So on the '86 carbs fuel is fed to two carbs via a Y fitting. Each carb has a bowl vent that would go to the cannister but I have them connected together on the front carbs and same on the rear. The carbs are now vented by a central vent line that is open to atmosphere. The fuel tank vent is also open to atmosphere. I followed what other members here had reported doing when removing those components.

    While I am confident in my skills, I have been wrong before and these valves were not easy to adjust. I thought I had all the right tools for the job but when I got too it they were sufficient to complete the job but a longer square drive tool and better, angled, feeler gauges (which I ordered last night) would make it easier to do and I feel that if it is easier to complete the accuracy could be better.
     
  4. squirrelman

    squirrelman Member

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    TEST COMPRESSION

    dija flush out the tank before hooking up the carbs ?
     
    Last edited: Nov 16, 2020
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  5. straycat

    straycat Member

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    Just a simple suggestion, did you try and squirt a bit of fuel down each carb throat to see if you can get her to fart ?

    Float bowls may be full, but that will guarantee you'll know for sure if it will fire with fuel in the cylinders.

    If it fires, then id keep looking at the Carbs or Evap incase something has interfered with their function. (im no expert on the evaporation systems)
     
  6. Captain 80s

    Captain 80s Member

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    It sounds like you de-smogged it the right way. Be sure you plugged any vacuum port spigots below the carb insulators that are now empty.

    Also, did you turn the idle adjustment back up after bench-synching?

    In the future, use 2 feeler gages at the same time, one for each adjuster on the forked rocker. The adjustments will be more consistent.
     
  7. HamHock

    HamHock New Member

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    Sorry it took so long to get back to this. I did a compression test on the front 2 cylinders and only got 30PSI in each cold. I did the test with the plugs out and the throttle open. Given the low compression reading I assume the valve are loose. I tried to get back to them but had to abort before I could make any progress. I have bought new tools since my first attempt. I had bout the motion pro tappet adjusting tool set, which included an 8MM wrench and 3MM square drive but they don't fit very well. I purchased 2 new angled feeler gauges, a different 3mm square drive that I have welded into a deep socket so I can actually hold it steady when tightening the lock nut.

    I have read about people taking measurement from where the cam lobe rides on the cam follower. I believe the rocker arm ratio on the VF500 is 1.5:1 and if valve clearance is .15mm at the tappet it would be .1mm at the cam, is that correct? I've been using a single feeler gauge between the cam and follower to double check and I'm hoping some one can confirm that I got my math right.
     
  8. squirrelman

    squirrelman Member

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    valve adjustments probably won't improve the compression #s enough for a properly-running bike, so you're screwed, and another VF500 goes to the scrap pile. :(

    low compression #s cause hard (or no) starting.
     
  9. HamHock

    HamHock New Member

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    I wish I had taken a compression reading before tearing into it. It was running, albeit poorly, before attempting to adjust the valves. I am going to continue trying to dial in the valves and hope for a change, after all adjustments are free. If this bike is done for it's sad that it died with only 21K miles on the clock. This is my second VF500 and I knew full well what I was getting into. I knew the engine was a time bomb no matter what and have had dreams of a banshee 350 swap...........
     
  10. raYzerman

    raYzerman Member

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    Before writing it off.... little story, buddy brings an '85 650 Nighthawk, runs on 3 cyl. Tested compression, a couple were like 30 psi, two others 90 psi. Pulled the carbs, a jet in #3 was plugged, but we got it running decently enough. Didn't do anything special but run it for a while to full operating temperatures a couple of times. Compression check later showed all over 100. Rings loosened up I presume and got some oil lube.
    You could dump in some Yamaha RingFree, say a couple of tablespoons in each spark plug hole and turn it over to distribute, then let sit a couple of days..... instead of Ring-Free, can use another product (most have naptha) or mix up some naptha and a bit of oil.
    Basically we didn't do that, but it ran better after going for a couple of street rides putting it under load, etc.
     
  11. squirrelman

    squirrelman Member

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    ^^ worth trying.

    you could also try to determine which factor might be causing low compression, rings or valves.
     
  12. HamHock

    HamHock New Member

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    This bike isn't done yet! My compression tester, as it turns out, is missing an O-ring. I readjusted all the valves and checked compression with a working gauge and got 150PSI in all four holes cold. Put some gas in the tank and after a lot of turning over it fired up. It didn't want to idle or stay running but it did start and it sounded very healthy.

    Now I've got to take it back apart and get some sealant on the valve cover gaskets (both are leaking) and double check the carb settings. After that I'm hoping it's just a matter of getting the carbs synced and I'll be back on the road. Thanks for being a sounding board as I work through this bike.
     
  13. squirrelman

    squirrelman Member

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    good news then. now you'll need to clean the carbs to improve running and idling.
     
  14. Jim McCulloch

    Jim McCulloch New Member

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    Good job! Stay at it. In the face of huge odds against you with a VF500F you can sometimes win!
     
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  15. HamHock

    HamHock New Member

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    The carbs were cleaned out prior to adjusting the valves. They are spotless inside but I need to double check what I have the pilot screws set at and my new main jets have arrived so I've got to decide if I'm gonna pull the carbs again or not. My carb boots are in good shape and with a little grease they go on and off pretty easy. I'll post back when I've made more progress.
     
  16. straycat

    straycat Member

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    It may be worth cleaning this Carbs again. its hard to see dirt in the various passage-ways and orifices of the Carbs. Float Bowl area being clean wont guarantee that the necessary passage-ways are similarly clean and that may be the reason the bike is running poorly. Its simple enough to pull the carbs, so I'd recommend another cleaning. Be sure to remove the rubber diaphragms etc before/if you use Carb Cleaner, that stuff will turn them to black goo.

    lots of good videos out there on cleaning V4 carbs.

    Ultrasonic cleaners do a good job if you have access to one.
     
  17. squirrelman

    squirrelman Member

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    ^^ sometimes the only way to be sure an idle jet is clear is to pass a .010" steel wire through it.

    post-3647-0-85981000-1347898810.jpg
     
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