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Fuel flow problem...

Discussion in 'Technical and Troubleshooting Torque' started by spawn, Jun 2, 2008.

  1. Hi,

    On the last 2 NR rides I've been on I've had issues with fuel flow on my VT250. The problem manifests as a loss of power while cruising usually at >80km/h speeds, and more noticeably at freeway speeds. It appears that either the bike is not getting enough fuel. Sometimes the engine dies completely but restarts fine once I have stopped/slowed down. This is intermittend and doesn't always happen though.

    I had the bike in for a service recently and I asked them to check the carb needles and floats. They said there was nothing wrong with them.

    I have a suspicion that there's debris in my fuel tank that is blocking the fuel flow and that this only happens when cruising (as the fuel isn't sloshing around much) at speed due to the amount of fuel flow at these speeds I suspect the debris is getting sucked onto the petc-ock filter inside and blocking the fuel flow but then clears when the fuel demand is reduced.

    When I got the bike last year there was a plastic type lining around the fuel cap, probably some kind of sealing, but this lining has deterorated and come off, I suspect it's dropped into the tank and is causing the problem.

    My question is, how do I go about cleaning the tank out (at home)? Would it be sufficient to:

    1) Turn petc-ock to OFF.
    2) Remove fuel lines.
    3) Remove tank.
    4) Open petc-ock and drain tank into a container.
    5) Close petc-ock and use kerosene to 'rinse' the tank out (turn it upside down).
    6) Let it dry, refit and then refuel?

    I would prefer to actually remove the petc-ock and inspect and clean it properly but I'm concerned about refitting it properly - does it have a gasket for sealing that would need to be replaced?

    Finally, doing this at home poses as problem with fuel drips and disposing of the used kerosene. Any ideas?

    If anyone has facilities and could help me this would probably be a better option.

    Appreciate any help.


    (Note, p-e-t-c-o-c-k is getting blocked by the profanity filter!)
  2. I've seen stuff on the 'net about certain types of tank liners breaking down over time and clogging filters, particularly the latex based ones (which is why I'm hesitant to use tank sealer myself).
    Not sure if the Spada needs a gasket for the fuel tap but other bikes do just have a rubber seal. I'd definitely be taking that out though just to check if the filter is indeed clogged, and also to see if it's been damaged in any way. It'll also make cleaning and flushing the tank a lot easier.
    Also be a good opportunity to fit new fuel lines and an external inline fuel filter.

    As for disposing of the kero, this is what matches are for ;).
    Or you could do the right thing by bottling it and taking it to a proper waste disposal facility.
  3. I had a look at the workshop manual I downloaded for the VT250 but it doesn't show much detail on the tank fuel tap, I'll have a look under the tank when I remove it to see how it's fitted/sealed. Would prefer to know before going ahead with this though.

    An additional inline filter, is that a good idea? The fuel tap one not good enough? Where would I get one as well as some fuel line in Melbourne?

  4. The filter in the tank should be enough, but if it fails any crap in the tank will then go straight into the carbs and can leave you stranded somewhere. Having that second filter not only stops that stuff, but being external and visible means you can also tell when the tank filter has failed.
    Fuel line and filters are usually available from auto places. Car lines are often a lot thicker but as long as the internal diameter is the same still work fine. Replacing all the hoses should only cost a few bucks at most and is a lot better than waiting for one to split/crack (which if they're still the originals could be anytime). Filters are usually only a couple of bucks as well though sometimes finding one small enough can be difficult - in which case bike shops or even lawnmower places are worth checking.
  5. Yes. Will cost a few bucks from an auto store for what you need.
  6. Took some quick pics.

    Fuel line.
    Checked and the pipe is in good condition. Will replace in any case though if I go ahead with an inline filter.

    Tank cap:
    Notice some of the sealing has come off, probably in the tank. Also a bit of corrosion on the tank cap itself, is this a problem?

    Fuel tap:
    This is underneath the tank. There appears to be a rubber seal and two bolts. Looks like I'll be able to remove and refit without getting a new rubber?

    Edit: hmm, don't actually see a rubber disk under there, is that a gasket?
  7. Cleaned the tank out last night. Didn't find any signficant debris. Also the fuel tap tubes inside have a large surface area so it would be difficult for them to get blocked. Anyway, I did discover the fuel tap uses an o-ring (which was in good condition so I didn't need to replace it) and the fuel tap uses a vacuum tube to open/close the flow to the carbs.

    So I'm still wondering what the problem is giving the symptoms I described....

  8. Possibly a slight leak in the vacuum line resulting in the fuel tap closing slightly?
  9. Ok, there's something not right here. Yesterday on the way back from work I noticed the bike would start stuttering at higher rpms, I have noticed this before but it went away. This morning on my way to work I decided to open it up and the problem is still there. Seems it's getting worse.

    I could probably start by replacing the fuel tap and fuel lines but I don't know where I could possibly find a replacement tap - and it did seem to work fine when I was draining the fuel manually (I sucked on the vacuum pipe), but that doesn't really prove it's working properly. What else can I check?

    Should I take the bike to a Honda dealer and have them check it out?

    Help please!
  10. Yes
  11. you have one of two problem.

    1. Tank vent is not clear.
    2. Vacuum line to the tap is not sealing properly or has a crack in it.

    clear the tank vent first. If that's fine then replace the vacuum line. don't muck around with the existing one even if it looks good.
  12. You can check if your filler cap vent is blocked by leaving the fuel cap open (best try this on a quiet road when the fuel level is low and on a straight road to avoid a lap full of fuel) and see if the problem goes away.
  13. Well I just paid Peter Stevens a visit in the city and they don't service pre-2000 model bikes :roll:

    Got myself some fuel and vacuum hose and some fuel-system cleaner additive (to clean the carbs although not sure how well this stuff works). Will do some work this weekend and check the vent while I'm at it.

    Guy at the dealer said it could also be electrics, might be worth changing the HT leads too. Will see how I go...
  14. Well the bike is running worse than ever now. I went up for to Halls Gap on Thursday and got back today, bike was running badly most of the time even died a few times, but strangely enough it still has periods where it runs just fine. Bike is basically fine for commuting but when I'm on the open road it acts up, might be something to do with cruising at freeway speeds - maybe carb floats or something but I need an expert now:

    Can someone please recommend a decent mechanic/shop that can help me out, as in not take ages to diagnose and get it fixed first time?
  15. Does your fuel tap have a prime position? If so, take fuel line off at carburettor and turn tap to prime.
    A steady flow of fuel eliminates blocage in filter or lines.
    Next step would be to ride the bike, and when it does this, switch to prime. If no joy, open tank cap as said above.
    These steps will test fuel line, fuel delivery, vacuupm operation of fuel tap, and fuel tank venting.

    Regards, Andrew.
  16. Unfortunately it doesn't have a prime position. I have replaced the fuel line and vacuum line. Also flushed the tank and checked the petcock itself. When I did this I had to drain the tank by sucking on the vacuum line so it was working.

    I tried venting when the bike was acting up. Basically I would pull over turn the bike off open the fuel cap and then close it again. Restart and the problem is still there. Doesn't want to rev up when I open the throttle, actually if I open the throttle wider it stalls. I does recover if I leave it idling for a while before driving off. Is it possible it's actually flooding and not starving?


    Regarding the flooding possibility, I noticed what appeared to be liquid on the exhaust but it had been raining so I can't be sure, also the engine backfired at one point while this was going on which apparenty can indicate flooding (spark plug covered in fuel). I'm probably trying to make the symptoms fit the diagnosic based on what I've been finding with google so who knows.

    If the engine stalls when u apply too much throttle wouldn't that indicate flooding?

    I would like to eliminate the carbs as the problem and would like to get them inspected properly and cleaned. If it's going to cost and arm and leg for labour for a shop to do I might consider doing it myself (I have done this before but it was ages ago when I still rode a Yamaha DT50!)
  17. Yes. Can you smell fuel when this happens? If it's flooding, you will be able to smell fuel in teh exhaust system, next time it happens, give the tailpipes a good close sniff.

    Regards, Andrew.
  18. Just edited my post above before u posted...
  19. How old are your spark plugs?
  20. Bike was serviced 2 weeks ago.

    Had them check floats and they said they were fine although I can't be sure they actually did anything (I'm not sure about Sumuto's service department credability).