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It's Going! (or Maybe Not...)

Discussion in 'Supersport (1974-2007)' started by jimmer, Mar 16, 2016.

  1. If you can't find the info here, I'm happy to go through it again, but I have been a bit short of time the last few days.
     
  2. @Desmoquattro thanks for the tip, swapped the wires on the pick up coil and it ran on both cylinders! Mega chuffed

    Had forgot to check it before but when researching the forum on @Arquebus advice I found someone who’d had the same issue and that was the fix.

    Bike seemed to be running lean as the revs were hanging so took the fuel screws out to 3.5 turns from fully in and tried to set the idle. Was running much better but still hunting a bit and the revs are still hanging a little, also getting a bit of backfiring so I think there must be an air leak somewhere.

    Took the bike for a spin around the block and it pulled perfectly, picked up nicely from low revs and nice and linear all the way through the rev range. Checked how much load each cylinder is taking by pulling one plug lead at a time while the bike was running, very little difference pulling the front plug and a bigger drop pulling the rear one so figure that the carbs are slightly out of sync.

    So a bit of tuning to go to get it all right but it’s running properly for the first time in 3 years! Thanks for all the help and advice
     
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  3. Goods news, Ive had the same probelm in the past, ran like a dog, but ran nontheless.
     
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  4. Not a huge amount of progress but stipped off the air box, carbs and intake pipes to try and source my air leak. Gaskets on the intake flanges were completely shot so cut some fresh ones and fitted them up. Rubbers from the carbs to the intakes were a litte loose and had lost one of the internal ribs so I fitted a spare set that are in slightly better condition. Refitted everything up and will hopefully give the bike a run this weekend to see if I've managed to improve things.

    Have also managed to source a decent set of exhaust headers locally which I'm collecting on Sunday amongst a few other bits and bobs, with any luck the bike could be ready for an MOT within a week or two! :party:
     
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  5. Little bit of progress again. First off thanks to @HairyWolfhound for the exhaust, it’s in much better condition than the one that came off the bike! To try to preserve this I’ve given the headers a few coats of high temp paint.

    Fitted the new exhaust up and ran the bike briefly (too cold to be hanging around outside) and it definitely runs better, sounds good too! Struggling to get the exhaust in a position where it’s not hitting the swing arm though, think I need to slacken everything off and try and manipulate the whole arrangement a little.

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  6. I had a similar problem with my 750 albeit it had twin cans......ended up making my own hangers and turning the outlet caps to suit as well.

    From what I can see in your photos, it seems to me you need to reverse the hanger bracket on the can, and rotate the can so the bracket is upright; then remove the end cap rivets and turn the end cap and re-rivet so it is in the right position.
     
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  7. Yeah I figured it would require something like that. Didn’t want to go too deep into it last night as it was late and cold. I think I’m going to slacken all the clamps and see if I can manipulate the outlet from the headers so that it exits at a slightly better angle too.

    A job for Sunday!
     
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  8. This should give you an idea of what I did.

    One pic as it was when I first got it.
    One pic after I had dealt with them.

    P1000039a.jpg now1a.jpg
     
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  9. Cheers for that, very much appreciated!
     
  10. Well a bit more work undertaken, belts changed, upgraded the starter cables and fitted a new battery. Been at it again this morning and still can’t get it to run right.

    First up it needs full choke to start and then revs close to 4000rpm. I have to then balance the choke to try and lower the revs a bit but also keep it from stalling.

    Then once it’s warm it stuggles to hold an idle or any steady revs below about 2750rpm. Also noticed it backfires a bit under 2750rpm when trying to hold steady throttle. Above that it’s great, rides well, pulls well, no obvious flat spots or stutters.

    Upped the idle at the adjuster scree and no change. Tried leaning out the mixture a little going from 3 turns out to 2.75 but all that’s achieved is a bit of rev hanging, if blipped.

    Thinking it’s idle circuit on the carbs, I really don’t want it to be as I can’t be arsed taking them off the bike again.

    Took a couple of vids to help diagnosis if anyone has any ideas, they’ll follow once I get them uploaded.
     
  11. Sounds as though the idle circuit is completely AWOL...
     
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  12. Oh and also battery drain seems to be a major issue. Seems to be charging ok when running but when sitting with everything off the battery voltage seems to drop off very quickly. It’s already killed one battery, I don’t want the new one to go the same way. Have it on an Aldi trickle charger in the mean time
     
  13. Dammit! ‍♂️

    I take it my course of action would be to strip, clean and rebuild again? Could float height cause a similar set of symptoms? I can’t see how it would but I’m not sure I did the best job of setting them...
     
  14. @Derek is really hot on electrics and used to have an SS.
    I'm sure he can help you diagnose whether there is an issue and how to pinpoint what it might be.
     
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  15. Al ( @Arquebus ) has strong opinions on float height and is adamant that the 14mm that used to be accepted as standard is wrong.
    He's definitely your best bet when it comes to carburation on these bikes.
     
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  16. Brill cheers for the pointers I’ll spend a bit of time reading up before pestering folk. Such a pain in the arse this bike, you feel like you make a stack of progress and then a whole new set of issues pop up!
     
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  17. Tell me about it...
    I've spent the last three months (off and on) chasing red herrings in trying to get my 999 running and starting. All sorted now but couldn't have done it without the help of knowledgeable, kind and patient folk on this forum.
    Notably Derek and Chrisw with Exige being really helpful too.
    I never did get my SS carburation spot-on but I suspect Al did. I did get it pretty serviceable though.
    Have you replaced the needles and main jets?? They do wear...
    I found it hard to measure the float height, so made a crude one-size version of the adjustable factory pro gauge
    The 14mm dimension, you make to whatever Al recommends.
    upload_2019-3-23_12-3-52.png upload_2019-3-23_12-3-52.png
     
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  18. We have video!

     
  19. I would suggest from your video that it is either idle circuit, or an ignition problem. I chased an idling problem for ages until I discovered that it was a dud coil that would work fine when revs were higher. As soon as it tried to idle it was all over the place.
     
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  20. In for a penny in for a pound, new coils time, probably needed anyway!

    Will give the carbs another going over for good measure.
     
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