Broke Down Today, Ignition Problem, Accuspark Potential Cause

Discussion in 'Mech Tech' started by chrisselby, Apr 19, 2017.

  1. can i disconnect at the dizzy cap?
     
  2. Dubs

    Dubs Sponsor supporter extraordinaire

    Your best bet would be an original Svda with Leccy ignition module imo.

    Yes you can pull leads at the cap, but best to use well insulated grips if you want to avoid involuntary break dancing...
     
    earlylatebay likes this.
  3. The best ones are rebuilt original Bosch ones but £££££. The Accuspark SVDA is OK. I have one as a spare that I used until I had my Bosch one rebuilt.

    Before you go out and spend lots on a new dizzy, get the fuel pressure checked out, and make sure that the two butterflies in the carbs are defo opening at exactly the same time. As you have one carb cold and one hot it does suggest misfiring on the RH carb. Very unlikely that this is the dizzy. I am betting on fuelling.

    It can end up costing loads.
     
  4. Just a thought, could it be down to an air leak on the right hand carb?
     
  5. Definitely!!!!
     
  6. Not always easy to spot. brake cleaner gives better results than WD40 in tracing air leaks. Use the straw to spray the stuff in specific areas. listen for any change in idle speed. most likely place is the carb base gasket or manifold gasket. but it can also be the joints on your balance pipe unions. Are the small brass vac take offs on the carbs both blocked off securely?
     
  7. When nigel had it to sort the linkage he said there was an air leak on the left side, so he used some sealant on the carb to manifold gasket, and changed the manifold to head gasket for a metal one.
    I'd fitted a fibre one.
    I guess I could do the same on the right side.

    That could explain the lumpiness then
     
  8. mikedjames

    mikedjames Supporter

    Did you rebalance the carbs after moving one vertically with a different spacer ?
    Fixing one side may have caused the problem on the other side.
    Start with it symmetrical in terms of spacers then check the linkages.. but most likely its a vacuum leak..
     
  9. If you have moved a carb, you will have upset the balance as the arms on the linkage will be out of balance.

    The way to check is. operate the throttle crossbar by hand. to open the throttle butterflies. move to full throttle. BOTH butterflies should be in exactly the same position.

    The metal gaskets are a nightmare. They are asking for air leaks, especially with the Empi manifolds. Fibre ones every time.
     
  10. Also, as the metal ones are thinner, the heights will be different. This will put your linkage out, not by a lot but it will have changed.
     
  11. UPDATE

    so tonight I tackled this.

    Looking for any signs of an air leak I discovered the right hand carb could be moved by hand on the manifold, about 4mm!!!
    bingo I thought. the nuts were loose. tighten them right down, solid.
    ok, go out for a drive, starts up fine, warm up, pull off and drives away nice, up to 30mph, cruising, lumpy, wtf, turn around to come home.

    nigel (my mechanic mate) had it in for the linkage sort adjustment, and said there was an air leak on the left hand side, which he sorted with a smear of hylomar on a new metal gasket, so I thought id do the same on the right hand side, I had some new metal gaskets and some hylomar.
    whilst waiting for the engine to cool down so I could touch it to remove the manifold I notice the screws that hold the top on the carb were a bit loose, so I tightened them up.
    removed the manifold with the carb still on it, and replaced the gasket as recommended, reassembled, fired up lovely, checked carb balance which was still bang on 7 each side on my sync-meter.
    start up, drove off, 30mph, no lumpiness!!!! BINGO!!!

    drove around, all gears, lumpiness seems to have gone :)

    got home, head in engine bay, touch the right hand carb, still noticeably cold compared to the left hand side.

    then I remembered to try removing the ht leads from the plugs as @earlylatebay suggested, tried 4, drop in idle speed, tried 3, drop in idle speed, tried 2, drop in idle speed, tried 1, no change. the spark still jumps the gap between the dizzy cap and the ht lead though?? but def no change in idle speed.

    now it sound like its idling on all 4, drive like it on all 4, I've fitted new rotor arm, dizzy cap, pertronix ignition, newish ht leads, replaced the plugs for the ones removed from the last service, so any ideas guys?
     
  12. It may be that it is running fine. How far did you go? The RHS of the engine does run hotter than the LHS. give it a good run. This will let everything get nice and warm. Take out no 2 plug and check the colour. Are they a nice straw brown? They should be. If it is black and sooty, its either running too rich or not firing. If it is wet and fuely, its not firing. It may all be fine. if you have it running on all 4 at tickover then it will be running on all 4 at running speeds. give it a good run and let the oil get up to temperature. Maybe 20 miles or so.

    what colour were the plugs you took out?
     
    chrisselby likes this.
  13. If it's driving fine now then leave well alone! I don't think mine drops revs if I take off lead 1 either.

    From bobbing about on the forums for about 20 yrs (if they have been going that long?!) I do recall others saying at idle it is not unheard of for icts to not fire on all the cylinders, but run fine otherwise. Quite why I have no idea!

    Just on an aside, I don't know if petronix have changed in the last decade but the module was not transferable between 009 and vacuum dizzys.

    Glad it works!
     
    chrisselby likes this.
  14. Ps i would do what earlybay said re plugs too
     
    chrisselby likes this.
  15. Exactly this.
     
    chrisselby likes this.
  16. will give it a good run over over the weekend.

    the plugs i took out where a browny white grey colour.

    but they hadnt been in long.

    i may clean them up and put them back.

    they are accuspark ones. i was just trying to track down the issue i had :p
     
  17. If all the plugs were in a similar condition you are probably firing on all 4, drive and enjoy
     
  18. Did you gap the plugs ?
     
  19. The Bosch ones I've just fitted I happens gapped to 0.70 but the accuspark ones have 3 prongs around the electrode and I couldn't see how you would gap them?
     
  20. I must admit I only fit NGK plugs and I make my own leads
     
    77 Westy, mgbman and snotty like this.

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