Engine flooded in fuel. Help needed!

Discussion in 'Mechanics Garage' started by Traveller, Nov 5, 2022.

  1. Traveller

    Traveller New Member

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    Hey all,

    I really really need your expert help on this one.
    A few days ago I had a day off and went to take my '96 VFR 750 out for a ride.

    The bike had been sitting since July but this was not unusual. Unfortunately, other engagements are keeping me from riding much the past few years, but I've always tried to at least do a yearly check up/service even if I don't ride much.

    Anyway, the battery was flat so I jumped started it and the bike fired right up. However, it immediately started spewing fuel from every seam in the exhaust pipe; mid pipe, tail pipe... you name it. Interestingly, no fuel was coming out of the actual exhaust and the bike was running and sounding just fine. And we are not talking about a few drops either. The gas was gushing down like a mini waterfall.

    I immediately turned the bike off and took the tail pipe out to see if fuel was pooling inside the pipes but there was nothing. I started the bike again and again, fuel was spitting out. At about that moment the engine cut out and I realised that the tank was completely empty.

    I went to get some fuel and then decided to look at the oil. Lo and behold, as soon as I unscrewed the dipstick, a mixture of gasoline and oil started spewing out like a fountain.

    Doing some reading I saw that if the carb floats get stuck they may lead to flooding, but what really puzzles me is that the VFR also has a fuel pump inline. This seals shut when the power is off, so how could something like that happen?

    So now for my questions:
    1. How can I make sure this never happens again?
    2. What can I check (and how) in order to find the culprit?
    3. Where can I find fuel lines? Every damn part I need from lines to the pump are all discontinued.
    4. How on earth do I get the carbs out of the rubber boots? It feels I could hang the whole bike by that assembly and it still would budge.

    I really could use some help with all this!

    Cheers
    Nick
     
  2. Traveller

    Traveller New Member

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    To also add a couple of things that may be of relevance.

    1. Before removing the fuel pump, I turned the petcock on and let fuel go in and I was watching for signs of leakage. Nothing.
    2. I drained the oil today and it was super thin and a lot more than the 3 litres that would usually be in there.
     
  3. rc24dk

    rc24dk New Member

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    Remove the side fairing so you can see the carburettors and motor. Then if you start the engine you can see if the caburettors are leaking. This can happen with old O-rings. I tried it and the next day they were tight. When they are wetted with fuel they apparently tend to expand a bit and tighten up again.
    As some of the fuel enters the motor it is more likely a float valve that is leaking. Cleaning the caburettors and checking floats and float levels may be "all" you need to do. If you do this I recommend replacing the fuel line seals.
    I once worked the carburettors on a VF500. It was a pain. Do you have a workshop manual?

    Here it is: https://archive.org/download/Honda250/Honda250.pdf
     
    Last edited: Nov 5, 2022
  4. rc24dk

    rc24dk New Member

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    Fuel system, see p106ff in the service manual linked to above.
     
  5. squirrelman

    squirrelman Member

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    use the off position on your petcock during storage, and test that the vacuum petcock shuts off fully when engine is off. some modified petcocks do not stop fuel flow when off.
     
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  6. rc24dk

    rc24dk New Member

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    Now I think of it ... isnt the ON position vacuum controlled and the RES used for priming (not requiring vaccum)?
     
  7. squirrelman

    squirrelman Member

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    depends upon which bike.
     
  8. Traveller

    Traveller New Member

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    Thanks for the replies guys.

    So, do you think that the leak didn't occur during storage but actually happened real-time when I started the engine?
    Otherwise I just can't see how on earth could so such fuel through a stuck float into the engine with the fuel pump being off.

    Here's my reasoning on this and do correct me if I'm wrong: if the floats were stuck, then they would only let through whatever is in the bowl and the lines from the fuel pump downwards -which isn't all that much at all (maybe 200-300 ml?)

    The fuel system on the my VFR goes like this:
    Tank ----> Petcock ----> Fuel Pump ----> Carbs

    The petcock seals completely when turned off. (Checked)
    The fuel pump also seals when off. (Checked)

    So that leaves the carbs and whatever fuel is in the lines. But this still doesn't explain how the fuel tank could have emptied out. Unless the fuel leak happened after I actually ran the engine the other day. Stupidly, I didn't check the oil level before running the bike to be able to tell.

    Now I have stripped the bike and I am currently trying to yank the carbs out but this is proving to be impossible. Any ideas? I've heard good things about WD40 and heat.


    Rc24dk, the Gen 4 doesn't have a RES on the tank petcock. Only on and off positions.
     
  9. rc24dk

    rc24dk New Member

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    There are three ways into your engine oil:
    1. Inlet (forwards through carbs)
      1. Eventual overflow gets sucked into combustion chamber
      2. The overenriched mixture misfires
      3. Compression forces some the fluid pass the piston rings
      4. Rest fluid is send to the exhaust/muffler
    2. Outlet (backwards through exhaust/muffler.
      1. Same principle - except you dont have fuel source on this side.
    3. Breather
      1. Similar to 1. as well but requires also a fuel source to the breather case to work. If all tubes and hoses are installed and tight this source would also be one or more leaking caburettors.
    Looking in the section 6 in the service manual I linked to, the fuel tap seem not to be vaccum controlled. I guess so as I see no secondary hose attathed for that.

    The fuel pump can give up to 0.9 lt/minute but only when running. You did run the engine for some time. Since we dont know the running time, not the initial amount of fuel in tank nor the amount floating through the exhaust nor the volume added to the engine oil it is guesswork, but were it me I would check the carburettors.

    For removal of the carburettor assembly try to loosen both upper and lower clamping band to get a little more flexibility. A little lube may help but only if you can get it in where it is needed.

    My advise is not really backed by experience with your bike model. The VF I worked was maybe 6 years old at the time and your bike is a bit older which possibly affects flexibility of the rubber.
     
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  10. rc24dk

    rc24dk New Member

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    As far as parts go, you may be lucky so you only to clean the carb (work only) and a few O-rings, which are likely available somwhere.
    Once you get inside post some pictures of what you find.
     
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  11. Simon Edwards

    Simon Edwards New Member

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    A little heat from a hair dryer can work wonders to soften up the old boots and get the carbs off. But its not a cure.

    Then buy a new set off FleaBay or your favourite supplier before you refit the carbs.

    Note positions of the clamp screws carefully as you take them off, top and bottom of each boot. To avoid fouling the carb bases when you reassemble later.

    If you don’t get that right you can block access to the mixture screws or simply prevent the body seating down properly.
     
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  12. rc24dk

    rc24dk New Member

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    Illustration: service manual p6-4, pdf p109
     
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  13. airwalk

    airwalk New Member

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    Look for v4dreams.com, he has lotsa carb tutorials & other helpful stuff, in “maintenance” category, well illustrated w/pics!
     
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  14. squirrelman

    squirrelman Member

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    better than any hair dryer, get the engine running for a few minutes to build heat and soften carb boots.

    post-3647-0-38585400-1334096436.jpg
     
  15. Traveller

    Traveller New Member

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    So, reading again the first post, I realise I didn't give a proper explanation for the incident.

    The whole thing happened as follows:
    The moment the engine fired up, I started seeing liquid coming out from the exhaust pipe from 2 places: from the pipe joint right after the bottom collector and from the slip on itself (I guess the ends are not sealing properly with the carbon fiber body)

    (Same exact pipe like this one)
    [​IMG]

    Within about 15-30 seconds the fuel was literally rushing down, almost waterfall like.

    I didn't let the engine run more than that of course and I turned it off to figure out what was happening.
    In the tank I must have had about 4 litres of fuel and when I restarted the engine to see if more fuel would be coming out the bike run out of fuel.

    I definitely didn't see 4 liters of fuel rushing out the exhaust; maybe 0.5 to 1 litre? So I presume that the rest had gone in the engine.

    When I took the oil out it was definitely a lot more than the 3 litres that should be in there.
     
  16. Traveller

    Traveller New Member

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    So, I finally found some time over the Christmas holidays to work on the bike.
    What I found inside was quite interesting. Have a look guys and tell me what you think.

    First, I took the carbs out to clean them out. I found quite a bit of red gunk in there, mainly on the bowls and caked on the jets. The jets themselves were not clogged, just had this red varnish on.
    [​IMG]

    [​IMG]


    What was even more interesting though was the state of the throttle bodies' butterflies.
    They appeared to have a fair amount of dark residue on them. Possibly overly rich mixture?
    [​IMG]

    [​IMG]



    Sparkplugs have definitely seen better days.
    [​IMG]


    Here's what I did so far:
    1. Cleaned the carb jets, pilots and needles in an ultrasonic bath cleaner.
    2. Cleaned up the carb bowls, the throttle bodies and the carbs with the help of some carb cleaner (nasty stuff that!)
    3. Replaced all sparkplugs
    4. New set of carb boots as the old ones were hard as marble
    5. Cleaned the exterior of the carbs and polished the throttle bodies
    6. Washed and reoiled the KN air filter
    7. Changed the fuel line from the tank to the fuel pump as it was leaking slightly

    Speaking of the fuel pump, I tried testing it for leaks and it seemed alright, but I had no idea if that was part of the problem that lead to the flood.
    The points switch was in rather sad state, so I decided to order a repair kit from the UK just to be on the safe side.
    [​IMG]


    The fuel tank itself had some rust and pitting inside which I am suspecting was what caused the fuel flooding in the first place, so I decided to let the professionals handle it and went to a very experienced shop that specializes in fuel tank coatings.
    When I removed the petcock and filter I was shocked at the amount of gunk that had gathered at the bottom of the tank.
    [​IMG]


    Looks like coating the tank was long overdue!
    While I am waiting for the tank to come back I decided to change the coolant, put new oil/filters and got a new pair of tyres; the previous ones had given up the ghost a long time ago.
    [​IMG]
     
    Last edited: Jan 6, 2023
  17. Traveller

    Traveller New Member

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    So after all the above, it was time to try and start her up.
    However, much to my disappointment the bike refused to fire no matter how hard I tried. After trying for over 10 minutes the battery finally gave up the ghost so I called it quits.

    I must admit, this was not expected. I had changed and cleaned up mostly everything and I had fresh fuel coming in...
    And then it dawned on me to check whether the carbs were getting any fuel. I opened up the bowl drains and nothing came out; they were dry as bones.

    I started suspecting the fuel pump. I knew that fuel was going there (as the fuel filter was clearly indicating) but nothing was coming out.
    When I was pressing the starter, I could hear the fuel pump click once but that was it. What's interesting is that both the fuel pump relay and the fuel pump itself were quite warm to the touch, so they must have been doing something, but probably not what they had to.
    Changing the tips might not have been the straightforward job I thought after all...

    New fuel pump coming in as we speak... To be continued.
     
  18. 50th VFR

    50th VFR New Member

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    Fuel cut relay will only allow pump to run when engine is running.
    With try carbs it will never start.
    Remove fuel cut relay connector and short the black and blue/black wire. Turn on ignition, pump should run filling up carbs and stop if no leaks.
    If all OK full choke and operate starter.
     
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  19. squirrelman

    squirrelman Member

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    don't trust any $ 25 chinese pump; do what 50th vfr suggests above first b4 replacing pump. pump relays fail more often than pumps. unless it's very cold, try using no more than 1/2 choke or you might flood the plugs. be prepared to dial back the choke about 20 seconds after it starts then adjust idle speed to about 1200 rpm using the black knob.

    the red dust is from a rusting fuel tank and is very common on older bikes., so be sure to replace the main fuel filter.
     
    Last edited: Jan 6, 2023
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  20. 50th VFR

    50th VFR New Member

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    Full choke is winter starting routine here in Scotland. Given poster is in Finland full choke is appropriate.

    Just leave the throttle alone.

    Honda pump is made in Japan and is very robust except that points can fail beyond 100k.

    Repair set of new points is all that is required.

    https://www.davidsilverspares.co.uk/VFR750FV-1997/part_141058/
     
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