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Yamaha Zeal Flat Spot

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Zealadin, Feb 2, 2009.

  1. Its been a while since I posted, but I've had my 98' Yamaha Zeal (FZX250) since I first started riding about 2 years ago.
    Since then I've had minor work done, as well as slightly more major work when my tank started to rust and clogged my carbi's.
    Since that time I've had quite a few issues with the bike, from it being very hard to start in cold weather, to hugely inflated fuel use, and a flat spot appearing but not frequently. (The tank was resealed inside to stop future rust and it was all cleaned out, including the carbi's etc)

    Most recently the flat spot has been a HUGE issue. It seems to crop up mainly when I go for a long ride and get stuck in traffic, meaning I'm going very slowly/not at all and on and off the clutch quite a bit.
    (To be honest I might ride the clutch a bit in these situations)
    It also tends to vary where the flat spot appears, and usually culminates in the bike sounding very clunky, and revving in a strange manner, as in it won't rev hard, at which point I normally have to stop and let the bike cool.
    I don't get any overheating lights on the console, but I do know the overheating light works, as it turns on briefly when the bike starts.
    The flat spot is basically a point where there is absolutely no acceleration but if I give it more throttle after a certain point there is a huge surge, which can be quite dangerous. :(

    I'm careful to change the oil often enough, and have been wondering about dirty fuel, or clogged fuel lines, but don't really have the knowledge without someone looking over my shoulder to take stuff apart and take a look.

    What is strange is no one else I've heard with this issue have had it only some of the time, and mine won't be an issue at all on short rides, or long rides if I'm not clogged in traffic in really bad heat.

    Can anyone shed some light on this issue from their own experiences or knowledge, would greatly appreciate any help :)

    *Edit: Just to add some extra information as an after thought.
    This has happened at different fuel levels, and with fuel from various stations (I normally buy vortex 98)
    The bike has just kicked over 40k kms of which I have done about 7k in my time riding (generally use it every day for short distances)
    Also the bike seems to be running very very rich at the moment (no the chokes not on).**

  2. the vaccuum hose to the tap is getting hot and leaking, resulting in a leaning of the fuel to the carbies.

    Replace it. For good measure replace the fuel lines too and make sure all the connections are good. Clear the tank vent for good measure too.

    Easy and cheap fix, if you get the hoses from "Repco"
  3. Awesome thanks, hopefully will get time to head out to Repco tomorrow before work so I can have it back up and running at 100% asap.
    Will post again once its done, thanks again!
  4. Sounds like your plugs are fouling up a bit. Try checking your spark plugs, and tuning your carbies (or getting someone else to) if need be. If the plugs are fouling, they'll be all black (but dry).
  5. Checked the hose/lines today, most are new and in good condition, the hose looked shabby but seemed fine(judging by the rubber tubing), replacing it tomorrow anyway, missed the shops by the time I got round to actually starting (was too hot earlier today)
    Also replaced the spark plugs, but the old ones didn't seem too bad either, they had the heated metal look to them, but where not blackened (they where also the right measurement too)

    Getting the bike tuned next friday after I get paid since I don't have the expertise :D

    The air filter was in pretty good condition, and replaced the oil and oil filter.
    Something I hadn't thought about either was the fact the exhaust seems to have something loose inside it recently, so took that off and am putting a second hand (but in better condition) replacement on that I got at a wreckers. That being said I don't think it was effecting the exhaust flow.

    *Edit: Also getting a new fuel filter tomorrow**
  6. Ok well changed the hose, put in a new filter, and put on the newer less damaged exhaust, and thought I would probably be sweet as long as that fixed whatever the problem was...

    Went for a ride saturday, in that extreme heat around 1pm, probably got about 10km's of 40-60km/h riding with light traffic along pacific highway and stopped for petrol with no issues, got about 2-3k's from the petrol station and once again the flat spot appeared and I couldn't even get the bike to chug along, managed to get it down a side road and had a quick look to see if I could see/smell a fuel leak. It seemed fine. No overheating lights, but damn was it hot. Again the engine wouldn't rev properly, and was almost dieing while idle. I put the bike in the shade and trudged back to the petrol station for something to drink and one of those concoctions to put in the fuel to clean it out a bit, got something along the lines of 'cleans injectors and carbies'.
    It took about an hour between stopping making a few calls, then heading to the petrol station for drinks and heading back to the bike and it started alright and ran fine. Only had to go about another 10-14km's and got there no issues.
    On the way back I was almost home and it felt like it was starting to have the problem again, but managed to make it home without it really kicking in so not sure if it was my imagination or really happening.

    With the new'er' exhaust on its smoking quite a bit when it runs, on and off, but despite everything its still having the problem....

    Its still booked in for a tune on friday, but I'm wondering if it could be an issue with the fuel pump?
    Any other ideas what could be causing it?

    I park it outside in our garage which only has shade cloth not actual 'cover' so if it rains it rains on the bike, and in wetter weather and winter I try and keep it covered, but in this warmer weather when its dry I don't always cover it because I use it alot. My dad says after using it when it sits there uncovered it damages the bike...
    Is this really true? Its covered most of the time but not all, and not when I take it places unless its a long trip.
  7. Tank vent is the next most likely candidate.

    Make sure it is clear.

    In the short term it doesn't matter if a bike gets wet. In the longer term it's better if it's kept under some cover.
  8. Had the tune done today, and it is running beautifully, but haven't been able to figure out whether the tank vent is breathing properly, I can't see any gunk or sealage in the open spots, but I also can't tell whether my tank is sealing, for instance when opened it doesn't make a pressurised sound, nor a sucking noise, but the bottom of the fuel tank lid gets a kind of petrol condensation on it.