Won't start (not electrical)

Discussion in '3rd & 4th Generation 1990-1997' started by bintings, Feb 10, 2017.

  1. bintings

    bintings New Member

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    This may be solved easily... who knows.

    I have been riding pretty much everyday with no issues - Apart from minor annoyances I haven't got round to fixing.

    Anyway, tried to start the bike today (1 Celsius here in the U.K.) and all I got was turn overs. I know my starter clutch is pretty worn, I hear snaps and bangs from it occasionally when starting. I have bought another with all the necessary bits, just haven't got around to replacing. I initially thought this was the problem today but after a few snaps and bangs it was plain old turn overs followed by a couple misfires.

    I then attempted to bump start down a hill near my house and it refused. The back tyre just slid to a halt.

    I am wondering if this is more serious than just a starter clutch. Could it be worn spark plugs?
    I have not noticed the common spark plug symptoms (although the bike is choppy at low rpms).

    Thanks in advance
     
  2. skimad4x4

    skimad4x4 "Official" VFRWorld Greeter

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    Sorry more questions than answers...


    OK the bike won't start - but what VFR are we talking about - the 3rd/4th gen category covers 750s and 400s.

    I looked at your earlier posts but I could not see the precise specs of your bike. It might be an idea to update your forum profile (Forum Actions + Edit Profile) to include the precise year/specs of your bike and an approximate location (City/Town is fine) so if you need help you may find someone nearby is willing to visit and offer advice - especially if you have a well stocked beer fridge:drink:.

    I spotted you have already had electrical issues with this bike - so did you track down and fix them? VFR's have a history of RR charging system issues so simply fitting a new battery is unlikely to provide a permanent fix...

    My first suggestion now is you quickly test the battery volts with a multi-meter. If the battery is drained/dead the chances of bump starting is quite low. So put it on charge overnight and then see if it runs OK.

    If the battery volts are good, then check the basics - a petrol engine needs - fuel, air and a spark. Pull a spark plug and check it is not fouled up and that you are getting a healthy spark. Can you smell fuel? If the air filter is badly clogged it can also starve the bike of enough air, making it very hard to start or keep running.

    Are there any other issues? You mentioned low coolant in an earlier post - has that also been resolved? If you are still losing coolant you might even have a failed head gasket - when the engine has warmed up is the exhaust reasonably clear or very steamy?

    Good luck


    SkiMad
     
  3. bintings

    bintings New Member

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    Specs: 1994, 750VFR, 76000 miles. Spark plugs have been changed within the last 12,000 miles (according to previous owner). Starter clutch never been changed as far as I can tell looking at the service history.
    Location: London, England.

    Electrical issues solved. Installed 'vfrness'. Removed burnt cables/connectors with new ones, haven't had any problems since (over a year since fixing).

    Coolant leak solved. replaced radiator cap + tightened hoses which seemed to do the trick. Haven't had any leaks since. Regarding this, oil looks fine (dipstick + one oil change since problems) and no white smoke with a warm engine.

    Battery tests perfectly normal on the multimeter - Charging is pretty much spot on. I ran down the battery trying to start it so will recharge and try again.

    Air filter has not been changed in a few years (although was cleaned a couple years ago). Will need to check its current state along with the spark plugs.

    I cannot smell any fuel. When there is a misfire, a loud bang and flames exit the exhaust momentarily with a slight smell but i can only assume this is unburnt fuel from trying to start.

    The main thing that puzzles me is the refusal to bump start. I have done this many many times in the past and always used it as a backup but this time, no use.
     
  4. squirrelman

    squirrelman Member

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    Maybe you're not getting fuel to the carbs, so crack a drain screw and check. Maybe water at the bottom of the petrol tank got into the carbs, so drain them all and try again. :biggrin-new:

    Most disagreeably, you'll need to pull off the mid-fairings to do anything, no fun.:grumpy:
     
  5. thurst

    thurst New Member

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    Just bought a 1990 myself and going through tear down. Here is what I would check in order based on your description of a sudden no start condition.

    Check that you have spark.
    Pull a plug, turn over and look for spark.
    If no could be kill switch shorted in the on position, bad coil(s), broken plug wires etc.
    Check plugs for evidence of fouling if you pull the plugs (for later)

    If spark then check for fuel
    Check fuel shut off is open, fuel filter clogged, check that pump is priming on start, open a carb drain and empty then go through startup again. Carbs should fill up.

    Assuming fuel and spark are there then the issue is likely in the carb itself
    Most likely pilot jets clogged that is the circuit that is used during startup. Could also be improper float adjustment running too rich/lean (the plugs will tell you this).An exhaust pop is unburned fuel in the exhaust that is being ignited during start. This is most likely caused by fouled pilot jets or improper float height as discussed. This happens after serious misfires and/or a cylinder or two not running and sending fuel out through the exhaust valve

    I would check these things first as they are most likely.

    Other more serious issues would then be possible valve adjustment out of spec causing low compression, bent valves, stuck rings all causing compression issues.

    Hope it helps check it out and report back.

    Trevor

    If
     
  6. NormK

    NormK New Member

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    What gear did you have it in when trying to bump start it?
     
  7. Diving Pete

    Diving Pete Member

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    I find 2nd gear has worked for me better than 3rd when bumping, however I'll also suggest it's a carb issue - suspect blocked pilot & slightly blocked main jets.

    This generally will not cure itself & can only be fixed by pulling the carbs off the bike.

    Pete
     
  8. Diving Pete

    Diving Pete Member

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    also you MAY need to pull the plugs for a clean - Use mulgrips / pliars & hold each one over a gas ring for a couple of minutes to burn off the fuel..
     
  9. bintings

    bintings New Member

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    Thanks for all your replies

    Welll....
    I checked all the spark plugs - looked pretty normal for the most part (I can attach a photo if anyone is interested). I decided to change them all anyway.

    Attempted to start the bike once this was done and it did... after some very unhealthy cranking from the starter clutch.
    I opened up the crankcase and I found the starter clutch bolts (gold ones) literally falling out. Paired with this, cracks in multiple areas of the starter clutch.

    After replacing this I fixed my long awaited slippy clutch with new plates and springs, closed it all up and added fresh oil.

    The bike now starts like a dream - quick and smooth. Haven't been for a test ride yet as I will allow the new clutch plates to soak overnight but will keep you posted.

    --
    - I generally bump in second gear and tried both first and second when bumping during the problem.

    - I had a look at the carbs and air filter. Air filter was pretty dirty and had not been changed in many years so decided to change this along with the fuel filter. The carbs looked clean to my amateur eyes.

    --
    Edit: A good 3 hour ride confirms everything better and somehow cooler than ever!
     
    Last edited: Feb 20, 2017
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