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Random loss of power

Discussion in 'Bling and Appearance' started by Hyssy, Dec 3, 2008.

  1. A question for those with a greater knowledge of engines than mine (that'll be everyone then).

    While riding, with no particular reason, my VFR will sometimes start to lose power. The best way to describe it would be as if you had quickly taken your hand off the gas and it had started engine braking. This would last about a second or so, then accelerate again, slow down again, etc. It would happen about 5 or 6 times in a row. The engine RPM doesn't seem to be affected but the speed drops. My first thought was the clutch slipping, but I've done only 17,202Ks so far on it and the oil levels are fine.

    It seems to be an entirely random event. It has happened twice. There is nothing I can do to replicate it at will. It started yesterday while I was riding from Homebush to the Northern Beaches and was quite sight on Forestway with a bunny hopping VFR.

    I've never mono'd it and haven't run it harsh throughout all its life so I can't think of any cause for mechanical problem, and would be very surprised if the clutch was worn out already.

    The only thing out of the ordinary that I have done are:
    A) Put the suspension 1 notch firmer.
    8) Used a petrol station (Shell on Parramatta road just past Flemington while heading toward Parramatta, quite an old looking station).

    I did make sure I had the right (standard unleaded) fuel and not E10 or anything like that (They were separately labelled). I only use standard unleaded and have used Shell VPower once a few months ago. As I said, I never usually go to this station. I have done 220Ks on this tank with 2 blocks left on the dial.

    This station

    I have spoken to Sydney City Motorcycles and they reckon it's the fuel mapping and the guy on the phone said he'd heard of it being a common problem with the VFR VTEC engine. I've booked it in for its 18,000K service on monday.

    Has anyone out there, VFR rider or not, heard of a problem like this? Any ideas are most welcome. I have a feeling it's related to the fuel, there is no other explanation I can think of for it suddenly developing.

  2. so your using 91 in a bike that is labelled to have 95 or higher only?
  3. From the owners manual:

    "Use unleaded petrol with a research octane number of 91 or higher."

    I'd like to see where you have read it rated as 95+, do you have a source?
  4. 91 is fine but there is fuel and there is fuel.
    It sounds like contamination (water?).
    The first thing I would do is dump whats remaining in the tank (keep it for the lawn mower) and fill up at another servo.

    Failing that its a shop job on these new hi-tech donks.

    EDIT: I'm not bagging Shell. I use it occasionally but regularly fill with Mobil.
  5. well i guess i stand corrected, only just about every fuel injected bike released since 2000 are usually labeled 95+
  6. Wrong again :LOL: :LOL: :LOL:
  7. 2Wheels, I wouldn't worry about bagging Shell. I usually use them but I just had a feeling about this particular station and didn't have time to go to my regular/anywhere else (looked for the brand et voila). Like I said I have concerns about this tank of fuel, but the problem is still irregular so can't pin it for certain.

    qbn, wouldn't want to question what you're saying. I've only been riding a few years and have pretty much zip mechanical knowledge of the things, much to my detriment. I just go by the owners manual and recall having a chat with my mechanic from where I originally got the VFR and the CBR600 I had before it. The Standard or Premium debate is enough of a mess already. I just went by the book with this one.

    So, looking at the tank, I would love to drain it. But as I said I have no mechanical knowledge of these. I'm guessing draining the tank wouldn't be recommended for someone like me. Unless someone has a guide or instructions or I pester my dad for some advice...

    Anyway, thanks for the input so far guys.

    Checking out the manual it only states how to get the tank in the maintenance position, and mentions "You do not have to drain the tank" which is kinda helpful. Anyway, failing some kind of epiphany I think I'll see what happens come Monday and will probably try to clear this tank out and get something else in it ASAP.

    Aaaan I've just realised this should really be in the troubleshooting forum.... Any mods, feel free :wink: :oops:
  8. Sounds like water contamination.

    Depending on how much fuel you have left in the tank, put in about 50mL of metho in the tank and go for a ride. The metho bonds with any water in the fuel and it gets burnt up and spat out the exhaust.

    Run the tank down quite low and then refill at a servo that gets a lot of traffic. When you're running it down, don't be shy with it.
  9. I'll be going out on it again shortly...

    The thing I can't quite grasp is the inconsistency of it. If it really was contamination, surely it would be more predictable or consistent.

    It's frustrating, anyway will see how it goes. Thanks for the help.
  10. Not hard to drain, and not mechanical. Simply open the tank, stick some hose down it, put the other end lower than the bottom of the tank. Might need to suck it for a sec to get the suction through gravity going, but then it'll just come out by itself.
  11. It's neither consistent or predictable when surging will happen. You have the fuel being sloshed around in the tank, various throttle openings etc. so it can happen at anytime. The water is heavier than the petrol so it will tend to sit at the bottom of the tank where you'll not be able to get it. Just use the metho.
  12. apparently i'm wrong oh well, just every fi bike i had seen built 2000 onwards had been stickered for it, oh well

    i actually get the same problem but on my storm, might only ever happen once on a ride then it could be weeks before it happens again, but mostly it's when strapping the bike with a full tank of fuel, actually come to think of it, it actually happens on the same corner each time

    no idea sorry
  13. Hi Hyssy, I ride a Viffer, just had 36k service and generally run it on 95 or above but when travelling sometimes have not had the option. Never had the problem you are experiencing but as others have said it sounds like fuel contamination. I would go with TP's Metho in the tank option and if that fails mention it on your 18k service when you take it in. Good Luck.
  14. Change the plugs, change where you get your fuel for a couple of weeks
    see how it goes.
  15. Well I gave it a good run around and got it into a good new tank of (Shell, from an old regular garage I used to frequent). I hadn't spotted anything recurring, thankfully and I took it for servicing and had a good chat with the mechanic about it.

    From what I described and of what he knew he was leaning towards a fuel problem. So as well as the servicing they paid attention to the fuel tank/lines cleaning etc (though I know that's kinda part of a service anyway).


    We shall have to see how things go from now. There were no stored codes inside the computer so it hadn't logged anything going wrong. We'll see.

    Thanks again all for your help (oh incidentally the spark plugs were inspected but not replaced.) You can rest assured you'll be the first to know if something goes wrong :wink: