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Damn hissing noise!

Discussion in 'Technical and Troubleshooting Torque' started by blue_muppet, Mar 11, 2006.

  1. Righto people, I did a search on this problem and couldn't find anything so here goes (sorry if it is there mods)

    My bike has been behaving badly of late. It started playing up a few weeks ago. I had just switched back to normal fuel (I usually run premium) just for fun and it really "seemed" to make a difference.

    It was pissing me off the lack of response and crappy fuel consumption (30km less out of a tank) so I went back onto premium a few days ago but its still running like crap!

    The problems are:
    1. Poor throttle response (especially in first)
    2. I now have to grab the front brake really hard to slow down.
    3. Bubbles on top of the oil, when I tip the bike back onto its side stand, the bubbles remain on the view port.
    4. Call me paranoid but there also seems to be a funny hissing noise coming from the engine.

    My thoughts are that the last batch of fuel really fouled up my engine or something has gone wrong with my front brakes and they might be slightly engaged while riding.

    The bike just had a oil change 300km ago and the brakes were bled 3000km ago.

    HELP! I hate it when my bike is broken. The lack of riding is giving me a twitch.
  2. Might not be related but I had problems 1 and 2 on the Kat recently (same engine as the bandit). In my case I also had an air leak between the airbox and carbs - whilst fixing that I also gave the inside of the carbs a good clean. Still not entirely sure which was causing the problem but it's definately gone now. My advice would be to remove the tank and airbox (much easier to do on a Bandit than the Kat) then spray some carb cleaner down the throats of the carbs (most auto stores sell it).
    Edit: Obviously check for any air leaks whilst doing this too ie any obvious gaps or damage in the rubber connections between airbox and carb.
  3. if you've got the clutch in (ie coasting) do you still need to apply more front brake than you used to?

    If so, then it's probably not a brake problem, but just more force exerted on the engine when the throttle is closed.

    Does the bike idle higher than it used to?

    Higher idle is one sympton of a leak in your manifolds (connection between the carbies and cyliners). Another way to diagnose this is to undo your (idle) throttle stop until the throttle butterly is all the way closed. (eg there's a gap between the end of the screw and butterfly). If the engine doesn't stall, then you've got a leak somewhere, as there's air getting through when it shouldn't!

    Hope that helps,
  4. Took a trip down to my local bike mechanic (prohonda) and got them to check it out for me. No problems with the brakes whatsoever, plenty of pads left on both front/back and not touching.

    The thing that stood out was the seriously loose chain. I tightened it up just before so that its just touching that rubber looking thingy under the swingarm. I'm about to take it for a ride so i'll get back to you on that.

    I asked them about the lack of performance (shut up, i know its only a 250 :p) and he said it might be in a need of a tune. Getting the carbies rebalanced ect. I've got the 30,000km service coming up in about 2000km so I think i'll get it done then.

    Oh and that hissing noise was from the loose chain i'm told! lol.
  5. Loose chain? Hissing?

  6. Hissing noise, bad fuel economy, bubbles in the oil.

    Ring problems or head gasket.

    I hope I'm wrong.
  7. Maybe it was meant to be a "buzzing" noise. Loose chains do make a bit of a racket.
  8. Well it’s definitely a buzzing noise now!

    Adjusted the chain (pretty steep learning curve I must say) and its still really loose because the tighter I have it, the worse the noise is. When I spin the back wheel I get a rubbing kinda noise once a rotation.

    I'm going to take the chain off on the weekend and see if its the chain or wheel thats making the noise. But neither of those problems really could be blamed for the decrease in performance!

    Also, the rolling resistance (when it’s not running) hasn't changed, which suggests to me that it can't be anything wrong with the bearings ect because that would make it much harder to push. Right??

    AAArrgggg. I was kinda pissed of at Prohonda the other day too when I waited for 1 and half hours for the guy to tell me my chain was loose. Not to mention that he had forgoten I was there and was rude to me every time he spoke to me.

    Might let my feet do the talking and go somewhere else in Brissy. Does anybody know of some good mechanics in this area? I really think this problem is over my limited knowledge of bikes.
  9. If you're getting a noise once in a rotation, and the chain was really slack, then you are reaping the rewards of bad maintenance. The chain has a 'tight spot' and that usually can't be fixed short of replacement.
    As to the decrease in performance, that has to be related to the change and then the change back in octane rating of the fuel, surely?
  10. Hate to sound like an ass but I have been extremely diligent as far as maintenance. The chain has been sprayed with the proper stuff every 200km since I got it and has been regularly cleaned. Granted, I have never adjusted the chain because I didn't know how to do it properly :oops:

    Well, from what I can tell, the engine is running fine. It just seems to be labouring against something. So whatever is making my bike slow down quickly after backing off the throttle also would be hampering the performance. I assume :cool:

    The fact that I only noticed the decrease in performance when I swapped to a lower quality fuel yet it is still screwed now that I’m back on premium would suggest that it may not have been the fuel, just merely a coincidence.
    GGGrrrr, i really don't know what I’m talking about here :-# so I think I’ll shut up before I get flamed.
  11. Just to put this out of the question, after you've been riding for a while (just normal street riding, nothing fast, nothing slow) - check the temperature of your brake rotors. You might want to just carefully check them first incase my suspicion is correct as they may be very hot.

    I'm thinking that one of the pistons in your front brake has been ejected at an angle and has jammed. This in turn is causing the brake to constantly if only slightly bind on. This would also explain the hissing noise as that's similar to the noise a bedded in pad makes when rubbing against a rotor. This may also explain the poor braking performance as you now only have the stopping power of one less caliper piston.

    Hows my logic there? :)
  12. Lurking mechanic here,
    Sounds like Hornet 600 hit the proverbial nail on the head as far as the chain goes,ditch it & get chain sprockets as a set. (the front sprocket that you can't see does3 times the work as the rear) and is the initial cause of all chain sprocket wear,tight spots in chains happen to lots of bikes,even if your'e diligent with your lubrication-chain tension is just as important.
    As far as the hissing noise goes, i would chek to see if the vacuum hose to the fuel tap hasn't come off,(very common cause of fuel-performance-idling issues etc.).The fuel tap on the tank has 3 positions,on/res/pri(prime)
    On/res only allow fuel to flow when the engine is running.Prime allows fuel to flow freely from the tap without the engine running (but also places the carb float needles & seats to undue pressures{we all need some time off:)}.
    The vacuum hose that operates the fuel tap runs from one of the intake manifolds,it is this hose that turns the fuel tap 'on" when you start your bike.
    Possibly,? you have had to run the bike in the prime position to run it, which allows the bike to run,but also lets it run with one of the inlet manifolds having a huge air leak(eg.poor economy,running on,etc)
    Its a small hose about 6 mm in O.D which lwhich should connect up to a small spigot on the back of the fuel tap.
    It is VERY common for this to happen. Cheers
  13. hey blue_muppet, sorry if I sounded like I was putting you down, bad choice of words. As you've found out, it's great to keep the chain lubricated but it has to be regularly adjusted too, and I do think that's your problem.
  14. I'm not here to offer much advice except the "prime" position on the 250 bandit is hidden. You'll have to unscrew a little bolt that prevents the tap facing up. Hence, "prime" is up and is unmarked.
  15. I'm concerned with the bubbles in oil. I agree with ibast, sounds like ring or blown head casket.
  16. What colour is the oil?? if its a greyish white then you have done a head or a gasket somewhere.
    I had a similar prob with one of my cars. Are you going throughmuch oil?
  17. No worries hornet! Sorry if I came across as a little over sensitive but I was having a very bad day :(

    As far as the bubbles in the oil, I havn't noticed them since I posted about it. I'll have another check after I have ridden to university. The oil colour is fine too.
  18. As far as good mechanics in brisbane go, the following two have been recommended to me by a good friend who is a motorcycle mechanic (but works in an import shop where they don't do repairs for the public):

    Tommy at MMM Motorcycles - 3290 3767
    Tony Bogarts Cycle Tune - 3219 9777

    They're both in / near Moss St, Slacks Creek.

    Hope that helps,
  19. Thanks for all the helpful suggestions guys, much appreciated.

    I just got back from university (damn you single 8am lectures!) :evil: and there is unfortunately bubbles in the oil. Only about 5mm thick on top of the oil and it sticks to the view screen when I put the bike back on its centre stand. BTW, they arn't there when the bike is cold.

    The vacuum hose is still firmly connected so I can't blame that. Also, the only time I ever run the bike on Prime is when I’m stuck in traffic and I run out of fuel. If I’m on the highway, I can just flick it over to reserve but if I’m not moving my bike conks out if I try that.

    Oh and it’s not hidden on my bandit. Prime at the top, ON in the middle and reserve down the bottom.

    As I said in a previous post, I’ll take the chain off tomorrow and if I can't see anything wrong with it, I’ll head off to the mechanics. I'll give Tony Bogart a ring now.

    Cheers folks!
  20. Because it's not a water cooled motor, the oil might not go milky.

    It may start to smell a bit and go black qicker, however.