Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

Hot Hornet - unstable idle, stalling, rude sounds...

Discussion in 'Technical and Troubleshooting Torque' started by mattb, Nov 6, 2009.

  1. G'day All.

    Just fishing here for something I might not have thought about.

    '98 Honda Hornet 600, 43,000km, known the bike for 3.5 years (owned it one month) and no problems (was ridden two times a week). Been mostly sitting this year (hence sold to me), done 3500km trouble free in last month, but...

    Today, two-up, an hour non-stop from Altona slowly over the bridge and then in stop start traffic around the city. Idle begins mildly, noticeably wavering (say 800 - 1300, up and down, up and down). Feels now and then like will stall (falls somewhere below 1000rpm). Then starts to stall now and then, when coming off the throttle, but also feels like it will when sitting (but if I blipped it idle stabilises) - so, problem happening in slow stop start riding (fine at any stable speed). Then, does a very very mild backfire - more of a gentle 'pop off' such a child does, intermittently, in the stop start stuff. On heat, was at bar three of the five little thin bars (about two-thirds up the heat register?), and when I stopped I noticed the fan had come on. About 20 degrees out there? (Melb)

    Stalled a couple of times in the past, at slow speed, having just come off throttle. Usually run 91 octane, put 95 in there first time yesterday (mate always ran 91). Mate always ran without baffle in the Staintune, but I have it permanently in (we know nothing of PO and so of jetting etc - got it from Spot On). Normally idles fine. Just had major $1000 service (whatever that's worth?)

    Thinking simple:

    Will put carb cleaner through

    Will check the plug colour (where the hell are they???) - hard to determine yet if lean or rich

    Maybe throttle cable adjustment could be better (rolling off too far)

    Any ideas, Hornet experiences of this type? I look at my SR when there's a problem and think, Whatever!; but this bike frightens me!
  2. Check fuel and vacuum lines. Also check for air leaks after carbies and intake blockages. Also fuel tank vent for goo measure.
  3. The fan comes on at about 3/4 on the temp guage, but I wouldn't have thought that it would come on at all on a 20 degree day, even in traffic.... If the engine is overheating it could be effecting the fuel coming into the carbies, perhaps even vaporising it?

    If the carbies are dirty, etc, what did your $1,000 pay for?

    Spark plugs are accessible (just) without taking the tank off.
  4. Sounds similar to an air leak I had on the way to phillip island last year. The Vtr has 2 carbs, and they sit on a pair of rubber boots that sit on the intake runner. One of the boots had a split in it, and the volume of air getting in was only enough to cause problems at low rpm, and off throttle. At full noise, you couldn't notice it.

    Alternatively, if you get a loose spark plug, the same thing can happen where you get air defeating the o-ring and changing the mixture in the cylinder at low rpms.

    An easy check for the fuel mixture to be too rich, is to just stand behind it when it is idling, and observe the odor. If it smells fuelish, it is probably rich.

    If the smell goes beyond a petrol smell, and instead smells like rotten eggs, it is definitely running too rich.

    Good luck with it.
  5. If the temp is ok during normal running, I'd be looking for an air leak in the intake.

    Spray some startya bastard around there and see if the revs rise.

    The next step would be carb sync etc.
  6. Hot Hornet - unstable idle, stalling, rude sounds...

    Sounds like Hornet! pmsl! ducking from Paul!
  7. :rofl: Do attempt to stay On-Topic, please people :rofl:
  8. stupid double posts!
  9. High temperature = running lean
    Mild backfires / pops in exhaust = lean
    Poor idling = lean sometimes

    Air leak in intake system = lean
    On the Ducati, a leak in the exhaust system can make the bike run lean. (Weird, but common)
    Putting the baffles back in = richer

    So yeah, check the colour of the plugs (before using carb cleaner), smell of the exhaust, colour of exhaust outlet (black = rich, light brown / grey = lean), or get it tested with a gas analyser.
    Probably not the throttle cable.

    Maybe it sitting around for most of a year has resulted in cracked rubber intake boots. I'd definitely be looking for air leaks into the vacuum side of the fuel system, making the mixture leaner.
  10. Thanks guys. Will pull the tank off tomorrow and have a look around. From a glance, the fuel hose is aged with spidery cracks, so might be the same elsewhere. Will start with replacing any such hoses and go from there. Asked my mate about it, and the problem was there when he owned it - he thought it was just a Hornet thing. But he didn't commute on it so I guess it didn't strike him as enough of an issue.

    Pulling into Cohuna yesterday the temp gauge in the town read 35, but the gauge on the bike was low - the bike is having no problems at all when at speed. Which is good - I reckon we're in for a hot one!
  11. and the problem was there when he owned it

    aha, the dreaded FTM

    Financially Transmitted Malady :LOL:

    Hope you get it fixed mate, Hornets run smooth as glass usually...
  12. Thanks. After all this time on old bikes, I'm feeling pretty confident with this one!

    Just gave her the first oil change - man, runs so much more quietly! I love new oil! (Valvoline XLD Premium 20-50). There's a noticeable sound coming right from where the cam chain is, might look into that as well - I hear the tensionors give out or something... (Mind you a guy who owns a bike shop nearby looked all over it when I pulled up to show off, and he thought all sounded fine.)
  13. Hey Matt,
    I tend to agree that it's most probably running lean. You just had a service eh?
    Do you know if they checked the carb balance? If so, they may not have refitted a blanking plug/hose properly . These hoses/plugs are fitted to the bottom of each carb and are removed when doing a carb synch. Not refitted properly will create vacuum leaks causing the engine to run lean.
    As for fuel, I have found that my H6 runs best on caltex premium unleaded.
    re: The tensioner .. there is a mod I have performed on mine that takes 10 min, and costs sweet FA... stops the tensioner from coming back.

    Good Luck.
    If you need assistance, and don't mind riding to Dandenong ... feel free to pop in

    Oh .. one more thing. One of those hoses supply vaccum to the fuel tap. If it is not fitted properly you will experience:
    1: Lean mixture
    2: Lack of fuel being drawn from the tank to supply the carbs
  14. Thanks Vinnie - I might cruise your way sometime for help with that tensioner mod if you don't mind (unless - even better - you'd rather go riding sometime and show me in the shade of a nice tree somewhere far from the madding crowd).
    Showed the bike to a mate tonight, who's not a mechanic, but is pretty knowing, and his opinion upon listening to the bike start up, is that I should get the carbs balanced first - that they are certainly out and this might be the problem. I'll go hunting around the hoses, but put this on the agenda (how much does a carb balance usually cost?).
  15. Anytime ... let me know what you find.
    Not sure what a carb balance would cost. But it took me about 1-1.5 hrs. The tank must be removed, hoses hooked up, an intravenous fuel drip attached ( you cant feed off the tank due to not having the vacuum hose hooked up to the fuel tap ).
    Getting to the adjusting screws is a PAIN in the ass, but adjustment usually does not take long. If you have time on a Sat morning, I have a Carbtune kit I just purchased from the USA, I could give you a hand setting it up.
    I've yet to make up some kind of intravenous feed, but I'm sure to sort something out.
  16. Wot, no PRI position on the tap?
  17. Nope .. not on the H6. I guess Honda felt the savings were justified :rolleyes:
  18. Don't give Pat any ammunition to slag off Hondas. He'll never stop!
  19. Damn what was I thinking QW?? especially after reading comments from Pat like this one below:
    Oh well .... some people need to whine about something, and it's usually something they've never experienced ... like post 90's 'Honda Reliability'


    I feel an earth tremor on it's was from our Western shores :p
  20. Well, the man has based his opinion on a lot of experience.

    I know a few people who feel the same way about Hondas.