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.

High & Strange Idle (Honda Spada)

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Kit, Mar 19, 2008.

  1. I've just got my Spada back on the road and she's performing wonderfully again with the exception of one point.

    When cold, she'll idle a little below 2,000rpm, which might be a touch high, but I'm not too fussed. After revving the engine a little when cold, she'll settle back to a little below 2,000rpm. So basically, no problems when cold.

    When warm, she'll idle a little above 2,000rpm, which is a bit too high for my liking. After revving the engine a little when warm, she'll drop back to 3,000rpm and stay there for quite a while before slowly dropping back to a little above 2,000rpm.

    If I have the clutch out a bit to force her down to 2,000rpm (or lower) when I'm getting impatient waiting for her to get there, she doesn't subsequently creep up to 3,000rpm - she'll sit at 2,000rpm like a good bike.

    My throttle stop screw is all the way out, my throttle and choke cables don't seem to be pinched or routed oddly (although, I will check this again). One of my idle screws on my carbs was incorrectly set, but after setting this back to the factory settings (2.75 screw turns out?) I have not noticed any effect.

    The most recent changes on the bike are a new battery, drainage of some oil after overfilling, new plugs due to fouling (probably from overfilled oil), cleaning of carbs (which weren't really that dirty either).

    Any ideas? I don't have gauges to sync carbies, but would that be responsible for this odd idle? I really love wrenching on her and would like to think I have managed well, but this one little thing is really annoying me.
  2. check that the rubber mounts are tight enough, a little air getting in will cause that to happen

    also check the throttle links are clean and freely moving and not sticking open at all, a bit of silicon spray would not hurt

    finally check that the springs on the butterfly's or where ever they are mounted are set correctly, if adjustable (on and su they are adjustable to give more or less spring pressure for each carbie)
  3. I'm assuming the idle speeds you mention are without using the choke.

    If not, make sure the choke is OFF and the engine warmed up fully before adjusting idle speed. Anything screwed all the way out should set off the alarm bells so start with the throttle stop screw.

    An idle speed of 2000 rpm+/- is too high - you need to be around 1000 rpm +/- a couple of hundred rpm - as low as the engine feels comfortable at.

    Check for air leaks round the carb rubbers, check carb settings. You've already checked the cable is not pinched, but also make sure it isn't kinked or damaged from another time. Also check the choke isn't sticking on.
  4. Choke lever is completely off at all times. Actually, she's been starting without the choke at all lately.

    Hadn't thought about the carbie rubbers - will take a look tomorrow morning when there is light.

    With the choke cable, if I disconnect them from the carbies will that act as though the choke is off, or is it ill advised to disconnect them? I figure I can isolate the cable as a problem at least.

    Many thanks :]

  5. No need. Once the engine has warmed up, if the chokes were still on it would idle extremely slowly, if at all. The chokes would produce a very rich mixture if on.

    What about throttle free play?

    At the twistgrip you should be able to rotate (looking at the join mark which is usually on the grip) at least 2 - 3 mm before feeling any resistance or pull from the carb butterflies. You might have something holding the butterflies open...

    Did you adjust or play with the sync rod which connects the butterflies on the 2 carbs? If so you will need a vacuum gauge to get it right gain. One carb too high will prevent a correct idle


    Trevor G
  6. does it still idle at 3 grand if YOU close the throttle grip completly? ive got the same problem at the moment with the VTR250, but i know this is a choke routing problem. i might disable the thing completly, i never bloody use it any way.
    short of choke, vacuum leak perhaps. carb balance wouldnt cause a rapid idle. it will cause an unstable idle, and cause one cylinder to run rich while the other lean, if you know what to listen and smell for, you can almost get it on the money without a gauge.
    no bullshit, i pulled my carbs out once, farked around with the balance screw, ran like shit, played around with it till it ran and smelt better, checked it two weeks later with a mercury gauge and she was ony just fractionally outside the service limit by 2mmHg.

  7. The choke staying partly on can never cause a hot motorcycle engine to idle fast. It will cause it to blubb-blubb (or eight-stroke to use the correct terminology) or quit altogether. The choke on these bikes is not at all like a car system, where fast idle is also applied when the choke is on.

    Motorcycles in general and these in particular use a fuel enrichening jet without any fast-idle-via-throttle-valve adjustment. That is why it is so important to not warm up a bike by idling it on choke, since it is only a very rich mixture that keeps it running, not extra throttle opening.

    On the recent spanner night in Yarraville I adjusted a Spada with fast idle (about 2,000 rpm) simply by synchronising the carbs using vac gauges. It looked as if someone had tried adjusting the balance rod to adjust the idle. By the way, it idled smoothly, no roughness or instability at all while it was still way out of adjustment.

    All the best

    Trevor G