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Spada - Rough Idle, Jets and Plugs

Discussion in 'Technical and Troubleshooting Torque' started by Captain115, Sep 24, 2012.

  1. Hi all,

    As mentioned in another thread, my friend just bought a 1989 Honda Spada. After having some trouble with the oil measurement (see ) we've got her running fine and he took it for a hour or so ride today.

    When we first got it the other day, periods of idling would sometimes results in the revs dropping and the bike stalling. I assumed it was due to some crap in the carbs so took off the floats and sprayed around in there with carb cleaner. Also took the slow and main jets (and holder) out and cleaned them and made sure all the holes were clear.

    Put it all back together but no luck, it will still begin to die while idling unless a little throttle is applied to keep the revs up. Idle is set at roughly 1400 by the way. I checked the plugs after the ride and have attached photos.
    The front cylinder seems to be darker than the rear so might be running slightly richer? Both are whiter on one side too, but I assume that doesn't mean its running too lean due to the other tan colour. Also, choke doesnt really seem to work as application of choke just means the revs bog down more and the bike stalls.

    Anyone want to take a gamble at the problem using the info of what I've mentioned and the plugs? Oh and as a side note, no I didn't strip the entire carbs down for a clean as the phillips head screws in the rubber boot clamps burred by practically looking at them.



  2. How long roughly did you leave it idling for?
  3. Various times, 10 minutes, or sometimes just when we'd pull up to the lights. However I just took the float bowls off again and there is ruse in there again.

    Hmmm....open up the tank for a look (it was full of fuel since he bought it) and wow look at that the whole thing is full of rust too. So now what? And would this be causing the aforementioned idling problem?


  4. Rust in the tank is definitely a problem. What you'll likely need to do is:
    1. Fit an inline fuel filter (do this ASAP even if you don't plan on doing any other work)
    2. Strip and clean the carbs
    3. Flush and seal the fuel tank with something like this:
  5. Ok cheers for that jd, I'll go ahead and try to fix the tank and then report back. Here's hoping it all goes smoothly!

    Thanks for the help,

  6. So grabbed the first two products in the KBS motorcycle kit (the only kits they had in were the large, 45L ones which we don't really need for the 11L Spada) which were the cleaner/degreaser and the rust converter:


    AquaKleen: http://www.kbs-coatings.com.au/kbs-aquaklean
    RustBlast: http://www.kbs-coatings.com.au/kbs-rustblast

    The actual tank sealer we didn't get as they a) didn't sell it separately and b) we are going to do that one my friend is back at work and hence won't need to ride the bike, since it takes like 4 days to cure.

    So took the tank off, poured in the AquaKleen and water and shook it around, then drained,filled with water a bit and then drained again and filled with RustBlast. This stuff you have to keep moving and coating all the surfaces so every few minutes I'd pick up the tank and gives it a shake and roll. Poured it out and most of the rust seemed to be gone which was great!

    I also made sure to leave enough of the two product so I can use them when it comes to do the tank again in a fortnights time. Hooked it back up and put the jets and float bowls back on (they were off for cleaning) and started her up....and nothing really. Huh, look down and the petcock vacuum hose wasnt attached so I plugged it back it. Tried again and although it was trying to start, no luck.

    I thought perhaps there was still some water in the bottom so I drained the float bowls to get rid of any water (does this even work?) and realise that there wasn''t any fuel coming out of the front cylinder bowl. So I pulled off the fuel hose connecting to the front cylinder and tried sucking on the vacuum tube...out pours some fuel.

    Took the front bowl off, and the jets out, sprayed around with carb cleaner and then put everything back together. Also replaced the front spark plug.

    Tried again and she came to life!!! I was pretty worried there but all good. Still has the unstable idle though, so didn't fix that. Hopefully no more rust coming through though and reinstalled the inline fuel filter to remove the chance of that happening.

    So would someone (jd?) like to have a crack at guessing what the problem is with the idle? And is it ok to use the bike for a week or so with the now de-rusted tank and filter before putting the sealer in?

    PS full disclosure; I didn't do a full carby strip since the rubber boot host clamps screws are still burred. Probably doesn't help hey.


  7. a Choke will bog the engine down once it is warmed up somewhat.
    (in cars atleast) the choke will restrict some of the air flow into the carb (hence 'choke') so that the engine gets a richer fuel/air mixture to start and warm up.
    depending on the vehicle, it may not even need the choke on to start on nice warm days. i know with my mates spada, he only used the choke on cold mornings and nights.

    make sure you change the fuel filter. if this is full of rust, it will restrict the fuel flow.

    change (or atleast test without) the air filter

    and of course, the third thing in the pyro's triangle is spark. change ignition leads,
    and if im not going to 'car', inspec the dissy cap and rotor button.

    with all that new, it will prob. run like an even bigger dog untill you do a tune :)

    i love old engines :)
  8. Shouldn't hurt to ride as it around for a week as it will take a while for the rust to come back and in many ways riding it is actually better than leaving it sit.

    As for the rough idle it's hard to say. Could still be some rust in the carb - or the previous owner may have tried adjusting the idle mixture to compensate for the rust. Since you know bits of rust got into the carbs I really think a full strip and clean is the best option.
  9. Ok, so we went for a ride today but my friend noticed that the Spada would drop revs or become unresponsive to throttle input. Throttle cables are all tight and so on. Once out of first or high in the revs it would be fine but with no throttle input at idle, it would idle really slowly and then cut out.

    I also noticed around this same time that the front header was cold to the touch. I assumed it has fouled the plug but when I took it out it looked ok, a little black (too rich) but still no enough to cause it to foul. We tried screwing the idle up and while that did sort of get rid of the problem somewhat, it would randomly rev up.

    What I think might be happening is that the font cylinder is cutting out for some reason. This means the idle drops and the bike is sluggish. If the idle is adjusted so the rear cylinder is running at around the 1300rpm mark, when the front cylinder starts to fire again, the revs pick up.

    I've checked both the leads for spark and they seem ok, but then again it will idle ok sometimes (both cylinders) but then randomly will die and my guess this is when the front cylinder drops out. Any clues on what to do here? I'm guessing it might be electrically based as opposed to carb etc?

    We gave the battery contacts a clean and had a quick look at both the leads and it seemed ok. Tested the resistance of both coils and they both read 3.5 ohms which is high than what is recommend (2.6-3.2) and the connectors in the spark unit which were reading 432 ohms not the recommended 310-390. However this may have just been due to my cheapish multimeter and the fact that both coils and connections (from both the working rear and intermittent front) read the same resistances\ make me think that it's not that big a deal being over.

    So where now? Recheck the leads?


  10. Does seem like the ignition system might be stuffed.

    As a temporary fix you could try switching to Iridium plugs - they require less voltage to generate a spark and are less prone to sooting up.
  11. to start (before you foul any more plugs) pull off the dissy cap, look inside (i am guessing since it has 2 cylinders) it should have 2 metal contacts on the inside (under where the leads connect to) and one in the center (going to your coil). if one of these 2 pins are damaged, that will be a part of your problem. if this is the case, get a new dissy cap, rotor button, points(if applicable) leads and plugs, because it looks like the previous owner has neglected the ignition system.

    if the contacts have plenty of 'meat' on them, try swapping the leads over (the whole leads, not just one end) if the back cylinder fails to fire, get some new leads.

    for some reason, most people concentrate on oil and air when doing home services, but the ignition system is just as important.

    the leads should be replaced every 2-3 plug changes (depending on how ignition sensitive your particular engine is) and plugs should be inspected every oil change (i usually change my cars every oil change, makes it easier to remember the last time)
    of course, if you are using iridium or other high end 'long lasting' plugs, replace the leads with the plugs, and the plugs as necessary.

    the dissy cap, rotor button and points (if applicable) should be inspected every oil change, clean off any build up (being careful not to remove too much of the conductive material, the spark gap is quite important) and replace as necessary.

    (inhales) /end rant over people not taking care of their vehicles.
  12. Good luck finding that on a Japanese motorcycle.

    I think you'll find most (including the Spada) have transistorised electronic ignition - which like most things digital will either work, or not work ;)
  13. i didnt think they had electronic ignition on many things at that stage (that werent like super expensive) though always happy to be proven wrong. my logic is mainly coming from cars, but most of it is transferable.
  14. Pretty sure the original CB750 featured electronic ignition back in the 1970s.
    In fact I'm struggling to think of a Japanese bike that was fitted with a distributor - other than maybe the pre-war Rikuo Harley Davidsons.

    Edit: Of course I where you're coming from. I went looking for a distributor on my first bike as part of my usual post-purchase service, only to find there was nothing to fix/adjust - just something painfully expensive to replace.
  15. odd to think that it wasnt mainstream in cars (even japs) untill late 90's or even to the naughtys.
  16. Not that odd when you consider that bike engines, especially 250cc bike engines, are in a much higher state of tune than any car engine. So any change in the ignition timing would have been immediately noticeable, and they never would have got the power figures and service intervals they did otherwise.

    I think the main reason they were introduced to cars in the 90's was more to do with making them more adaptable to the varying octane ratings of unleaded fuel (much easier to integrate a knock sensor with electronic ignition than mechanical).
  17. Hi everyone,

    So here is an update of what has been done to the Spada over the past week since I last posted:

    Finally got the carbs off (the screws in the hose clamps around the rubber intake boots were really burred, but replaced them with allen head ones so shouldn't have a problem next time. Cleaned the carbs up, all the jets, checked the float and needle, checked/cleaned the choke (bi starter valve), cleaned the air cut-off diaphragms and the main needle and the pilot screws.

    So carbs were completely clean and also went ahead and re-cleaned all the leads, contacts from the coils, battery etc and made sure everything was firmly seated together. I also checked the spark from the front cyclinder at low and high revs and got a nice blue spark which was promising. Oh and also installed a new fuel filter.

    Put it all back together and got her running again. Front cylinder was firing like it should and I adjust the pilot screws a little so the front wouldn't run so rich.

    Good, everything works. Now to wait for the front cylinder to drop out so I can start testing electrical connections....

    Huh.... it hasn't. So i guess it might be fixed? But I'm a little uncertain seeing as how last couple of times it was a bit into the ride when it happened so not sure if it only occurs under load or what. Below I've linked some similar sounding problems:

    Spada, had a bad coil that would break under load:

    Has a miss in low gears (same problem as currently), think it ends up being the R/R:

    Also sounds similar, only running one single cyclinder. Mightve been coils or leads: