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Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Monkey Magic, Dec 24, 2013.

  1. #1 Monkey Magic, Dec 24, 2013
    Last edited by a moderator: Dec 25, 2013

    PROBLEM: I've a spada that won't start.

    When I press the starter button the bike cranks fine, once I pull back on the throttle it clunks or makes what I can best describe as a Schhitumph noise. If I crank for a 10-20 seconds it attempts to backfire. It has backfired once.

    It was running rough so I checked the valve clearances and the done some disassembly on the air filter down to carb level. All was reassembled properly. I'm no slouch but this one has be and a mechanic stumped. Maybe somebody has come across this either with a honda or another bike before.

    1. It's getting juice because I've loosened the overflow screws on the carbs and i got juice.
    2. It's got plenty of spark on both plugs
    3. The Juice is new so no issues with stale petrol
    4. The ignition switch is on
    5. I've tried both using and not using the choke
    6. I've checked the valve clearances, all good.
    7. I took the carbs off and checked them, all good.
    8. The plugs are new and the HT leads are good
    9. Idle and carb settings are set to factory settings
    10. Checked both heads with a compression gauge and all is within normal levels there.

    The schitumph sound can lead to a backfire but that's only happened once, it sounds like it wants to backfire but it doesn't.

    Can anybody help. Plugs are new, electrics seem fine, head compression are both at 190ish. I can post a video on Youtube if it helps because then you can hear the sound. Well can you help?
  2. Is it possible to cross the plug leads on that bike?
    IE. Put rear cylinder lead on front and vice versa
  3. im sure Justus can help, lol
    • Funny Funny x 1
  4. Were the Valve clearance's checked before or after your problem of a none running bike?

    I'd recheck the valve clearances, ensuring that you are a TDC.

    sometimes the feeler gauge is not quite flat, giving the feeling that the clearance is tight; when in fact it may be way out.

    Just a suggestion! as this is where I'd start again.
  5. If you've got juice and spark, I'd look at fuel quality. Has it not been used for a while? Has it sat exposed to weather? (I'd suspect this before I'd suspect anything else, if the bike has not been worked on, and has sat a while)

    Pull a sample from the bottom of the tank. Is it clean? Is there water? Any tries I'd do, would be with new PULP. Another easy possibility is spark plugs that are arcing deep inside rather than at the tip due to carbon build up. Generally, though, this is a two-stroke problem, and can be fixed either with a change of plugs or by poking a fine wire deep into the plug to clean the area where the ceramic insulator meets the sides , then blow it out with compressed air. Protect your eyes.

    Two easy things to look at. Third? Kill switch.
  6. Ignore this.

    My first thought was flooding but you reckon you know enough about carbs, so I'll trust that it's not running rich. If you haven't yet though, crank without the plugs in to see if fuel comes out.
    My second thought was to check how much oil is in the crankcase, you may have got petrol in it. Drain it and check the consistency. Put the measured amount in.
    Beyond that I can't really think of anything else, by your description it certainly seems mechanical rather than electrical. Maybe look at timing?
  7. Check you got the cam timing right when you did the valve clearances. If you're only a few teeth out you'll be lucky if it runs at all, and smacking a valve into a piston is a very real risk.
  8. KISS method, If it was OK before you touched it, check everything you touched. If you have spark and fuel and compression, the spark and fuel arent meeting in the cylinder at the right time. backfire would also suggest this. check the timing. Re read of the OP. Running rough could be vacuum leak, hole in carb diaphragm. manifold leak etc.. check the easy stuff first, could be as simple as a bad plug or lead..
  9. If you meant me, that's exactly what I did. The OP changed the valve clearances. That often requires lifting the cams. The bike ran before that but not after. It's possible to put them in slightly out of position if you're not careful.
  10. The OP seems to have vanished. The question was his first and only post, no introduction. It's a wonder this thread wasn't locked/deleted.
  11. Hi folks,

    Sorry for my absence but I've been pulling the little hair outta my head for the last few days. As everybody who replied here there are a few basics that I should have checked, which I did, with no success. I did find the problem.

    The workshop manual I have for the spada is the one everybody else has and it indicated that the Right coil fed the front spark plug opt whichever it recommended. I had the leads on this way. When i gave up on a mechanical problem I went through the electrical and everything checked out. the only thing I hadn't done was swap the leads over on the coils. I did this and the bike started first go. Ah Jebus Cripes I thought to myself.

    Anyway It ran OK for 2 days and died on me, luckily I had ordered 2 new air ducts, the rubber boots that the carbs sit on, mine were kinda in bad shape. Since then the bike has been running pretty good and apart from some adjustments to the air mixture I think all is good.

    I didn't disappear and will be back here plenty as I do a lot where bikes are concerned. The workshop manual screwed me over where the HT leads are concerned but I really appreciate the thread not being deleted and want to thank everybody for their input.

    Ciao Fir Now…..
  12. And what was my very first question?
    Should have checked back and tried the suggestions.