5th gen shutting off after hard braking

Discussion in 'Mechanics Garage' started by Bercedes-Menz, Sep 7, 2016.

  1. Bercedes-Menz

    Bercedes-Menz New Member

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    Hey all, I have a 98 VFR800 with an issue. Under hard braking, the engine will shut off. I can be rolling in first gear, hold in the clutch all the way and squeeze the brakes, and it will shut off. I have adjusted the clutch lever so that it doesn't touch the bars when pulled in all the way.

    Here's some info on the bike:
    ~2500 miles, stock
    Low-sided it on the highway (left side) about 200 miles ago
    New battery around 150 miles ago

    I can't remember if I had the issue before the wreck or not. Does anyone know what it could be? Thanks.

    Edit: Here is some more information. It only happens in situations when I'm braking to a stop, like at stop lights and stop signs. I can be coasting and then hit the brakes, and often times it will stall. Rarely, the rpms will go very low on the verge of stalling, and then come back up to normal. The bike idles fine, but recently I've been having to pump the throttle slightly to get the motorcycle running when starting.

    If I brake moderately at higher speeds with the clutch in, the bike won't stall until it is completely stopped, so it doesn't stall when at speed.
     
    Last edited: Sep 18, 2016
  2. Terry Smith

    Terry Smith Member

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    Has to be a loose connector somewhere. Given the new battery, I'd start at the battery connections/ground connector, but in reality it could be elsewhere like the sidestand switch. The clutch switch is unimportant as this only stops the starter motor from running with the bike in gear, not the sparks. There is also a bank angle sensor under the instruments that is intended to stop the engine when the bike lies down, maybe that is able to move under brakes?
     
  3. SlideRule

    SlideRule New Member

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    My buddy had the same problem after we re-assembled his CBR after sliding down the highway. The bank-angle sensor was loose and would kill the bike on hard braking; in order to restart the bike he had to cycle the kill switch. We pulled the sensor, jumped the outer two pins and it fixed the problem until we could reorder a new one and mount it correctly.
     
  4. Bercedes-Menz

    Bercedes-Menz New Member

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    Okay, that makes sense. It was a pretty hard drop around 80mph, so I could have broken it. When I put on the new fairings later on next week I'll take a look at the sensor. Thanks for the info guys.
     
  5. Bercedes-Menz

    Bercedes-Menz New Member

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    I've added some more information that could help narrow it down. I have not checked the sensor yet as I'm wanting to do it when my fairings arrive. Should be next week. I don't think that's it because if it was It would shut down while I was still at speed, but I'll still take a look at it later on.
     
  6. NormK

    NormK New Member

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    Back to SlideRuls post, shut down under hard braking, something is moving when braking
     
  7. Sniper

    Sniper New Member

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    I had a Honda 919, that I put an Ohlins rear shock on. Upon reassembly,I managed to put the bank angle sensor on sideways. When I hit the gas hard, the bike would die. My buddy found a lot of humor in that. It was a easy fix.

    I knew another guy that supposidly, somehow wired the kill switch to the brake lever. When the victim hit the brakes, the bike would die. Sounds kind of dangerous.
     
  8. squirrelman

    squirrelman Member

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    maybe a good clutch bleed would help cuz if the clutch is dragging just a little it could pull the revs down. also you could try boosting the idle speed a bit.
     
  9. SlideRule

    SlideRule New Member

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    If the clutch plates are dragging a little, wouldn't an easy test be to engage/disengage the clutch at idle? If that were the case, wouldn't the rpm's would vary when the clutch was in or out??

    Edit: a similar test would be to idle the bike in neutral on the center stand; if the rear wheel is spinning, the clutch isn't releasing properly. See if it varies clutch in or out.
     
    Last edited: Sep 19, 2016
  10. Bercedes-Menz

    Bercedes-Menz New Member

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    Filled up the tank, and now it doesn't do it anymore. This time I used 87 instead of 93 since that's what it calls for. So, if it happens when I'm low on fuel again, then something in the fuel system is restricting the flow. I'll dump in some Seafoam later to see if it helps.
     
  11. Terry Smith

    Terry Smith Member

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    In my own experience, my 99 5th gen is very prone to stalling if the idle speed drops too low. If you didn't already know, the idle adjuster screw can be accessed through the small hole in the right frame spar, screw in to raise the idle speed. The manual specifies 1200 rpm unless you are in California, then it is 1300 rpm.
     
  12. Bercedes-Menz

    Bercedes-Menz New Member

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    Alright I'm back. Got the fairings back on as well as a slip on, and I've narrowed it down a bit. Whenever I get to around half a tank, I start experiencing the shut off issue. It gets progressively worse the lower the tank gets.

    The bike usually idles around 1300-1400rpm, but there are times where it will drop down to around 1100. The bike stalls at 600 or so rpm. Also, I am having trouble starting it up the next day. It takes a good 4 or 5 tries to get it started (turn on choke, start while twisting throttle a bit, and modulate the choke until it starts up). After it starts and warms up, I can shut it off and it will start up fine immediately after.
     
  13. fink

    fink Member

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    Is this starting problem since your off or has it been gradually coming on?
     
  14. NormK

    NormK New Member

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    Sounds like the tank is gravity feeding and the lower the fuel gets the less fuel is getting through. I didn't think fuel would have been able to pass through the pump if it wasn't working or working properly
     
  15. RVFR

    RVFR Member

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    I'm with Norm here. though I'm late, the first read was telling how odd, can it be a fuel slosh not getting fuel thing, but then there''s the pump in the middle of this that would have to be checked out. interesting sounds to me from the get go to be a fuel issue IDK it's one of those things ya have to get a feel for, but for sure check the fuel system. just seems odd if the pump is working, then Hmmm??? if not well there ya go.
     
  16. Bercedes-Menz

    Bercedes-Menz New Member

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    It has gradually gotten worse. It is getting colder, though. Maybe that has something to do with it.

    So, you're saying the fuel pump isn't working, and that the engine is only getting gas through the weight of the gas and gravity pushing it down? That could be it, but I do hear it prime whenever I switch the bike on.

    Due to the amount of variables at play here, I might just bite the bullet and ride it over to the honda powersports shop down the street. While these problems aren't huge dealbreakers, it is pretty aggravating.
     
  17. NormK

    NormK New Member

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    It is a total guess at the moment, but it sounds like something is wrong with the pump, doesn't make sense but something is going on with it. Just remember the dealer will just replace the pump straight up and regardless of the problem you will be billed for it, better you fault find it yourself. Plenty of cheap pumps out there to test with and remember the dealer will replace with a genuine Honda pump and you will feel that in your wallet
     
  18. Terry Smith

    Terry Smith Member

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    The FI system will not work (at all) without the fuel pump; injectors won't inject. However I can confirm that fuel will happily pass through the pump when it is not running, under gravity, as I discovered when I replaced the FPR and got a shoe full of petrol...Also leaky injectors will allow fuel to flow into the cylinders/crankcases when the engine is off.

    Maybe there is a dodgy electrical connection at the fuel pump, and more sloshing when the fuel level is low aggravates that? Or maybe there is crud that is mobile and occasionally blocks the fuel intake at the pump? I'm sure that as soon as the pump either stops or loses flow, the fuel pressure would drop and bike will shut down pretty hard. Would be worthwhile pulling the pump assembly out of the tank and taking a look I think.

    Don't suppose you have some water in the fuel tank?
     
  19. Bercedes-Menz

    Bercedes-Menz New Member

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    Oh wow, they aren't cheap. Partzilla has them for around $310. Ebay has some cheaper used ones that I might test.

    Another thing that is occurring is whenever I give the bike some throttle when I'm cruising at a higher gear, it will bog down slightly after a few seconds (say, 75% throttle in 6th gear). It isn't that feeling where you're in too tall of a gear and you give it too much gas. I can feel the engine hesitate and bog a bit. If I let off slightly, it will respond better.

    Whenever I give it some throttle when I'm in the lower gears, the power will occasionally plateau. Again, if I let off the throttle a bit, then it will respond better. If I keep the throttle where it was at, it will work through it eventually. When I rev the bike at idle, it'll periodically hesitate slightly and then start to rev.

    All of these point towards fuel delivery, but it also shares symptoms with spark plugs, and maybe the oil. Or it could be the slip-on and I need a PC3 + tune.
     
  20. kennybobby

    kennybobby New Member

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    Heart of Dixie Georgia Boys mighta been usin' dat
    It sounds like it could be water in the fuel or an unmeasured air leak.

    i'm not a fan of trying to use chemicals to cure mechanical issues.

    snake foam aka sea oil
    from the msds

    pale oil 40-60% (diesel fuel)
    naptha 25-35% (coleman lantern fuel, or gasoline)
    IPA 10-20% (Isopropyl alcohol + water, Isopropanol)


    Drain your tank and catch the contents in clear plastic gallon jugs so you can examine the contents and see any water.

    Check for air leak at the idle speed actuator (paraffin actuator?).

    Good luck--those intermittent problems are the hardest to solve.
     
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