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750ss Carb Model Not Starting

Discussion in 'Technical Help' started by Sideshow, Apr 1, 2020.

  1. I had no heater pipes on my 900 monster - it suffered icing on cold mornings
     
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  2. wiresf.jpg
     
  3. Me too;)
     

  4. I figured that's what they must be, my other bikes are from the 70's so this is a modern set up for me !
     
  5. Update

    alright so I found I had fuel to the carbs. I pulled off one of the float chambers and it looked pretty grim inside, so the carbs came off. I broke them down and put them in my ultrasonic cleaner with some R33 carb cleaner, you can see the difference it made. I dint have spare o rings or gaskets, and I kind of knew that the carbs would probably leak when re built, but as its lock down, and i find myself with now, probably lock down until the 26th of April, it was worth a try to just get the bike started. It went back altogether , and i turned her over , fuel started leaking from gaskets as I guessed it would, but the bike did backfire before I called it and turned the ignition off and the fuel off. Im assuming Im not far from it starting, or rather hoping. New Carb service kits are on their way !
    Thanks for everyones help, i will add to this post when i have more news. For now, I will go back to working on my Laverda's
    IMG_2391.jpeg IMG_2392.jpeg IMG_2401.jpeg IMG_2407.jpeg IMG_2409.jpeg
     
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  6. I would love a carb manual if anyone has one
     
  7. it's unlucky that your bowl gaskets are well and truly flattened, i've re-used those gaskets nearly everytime and have been fine. It sounds as though you would have worked it out from experience but the hollow brass hex fixing that holds down the jet holder assy is only just up to the job so nip down carefully (too late for this time). I shudder to ask, but how are your idle mixture screws? - both come out ok I hope. From what I can see of the screw heads it looks as though they've rarely been touched - can be a good thing/can be a bad thing!.
     
  8. This link will get you instructions for rebuilding the Mikunis as fitted to a Suzuki GS1000. There are 4 carbs inline but they are basically the same as those on Ducatis. Not quite a manual but it's near as you'll probably get.
     
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  9. Thanks mate.
     

  10. Hi Chris. Everything is pretty much chooked inside the carbs. I have ordered some rebuild kits where I can replace all the seals, O rings jets etc. hopefully they will be here next week
     
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  11. That guide looks useful Derek but I wonder about the float setting, does the 750ss have BDST 38’s same as the 900 ?, if so the float heights need to be 14mm (assuming the intake and exhaust isn’t highly modified).
    Update; just looked at the OP’s photographs, floats same as 900, go for 14mm.
     
  12. Yes, the 750 has the same carbs as the 900 but with slightly different jetting. I agree, 14mm float height. Worked for me.
     
  13. Sideshow, when you set the float heights measure on the longer oblong float not the small diamond shaped one.
     
  14. I had my SS floats set at 14mm but Al recommends less than 14mm and I can see the logic behind this, as this will give a richer mixture. Ducati struggled to get these engines through emission tests and had to set them up rather lean as a result.
    If you read the Ducati workshop manual, it hints at this problem while avoiding recommending running the engine richer in as many words.
     
  15. Going back a bit...... I don't think you've said what it was in the workshop for originally. Doesn't sound like you need to start playing with float heights; just a thorough carb clean to start with, as you're doing.
     
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  16. Al did set his floats to 12.5mm but he had gone away from standard with his air filters, not sure about his exhaust, on my 900ss I have a K&N panel filter and virtually straight through exhausts and I set my floats to 12.5mm, it runs well, but speaking to Nelly he said he uses the standard 14mm (not sure if he goes away from that if the bikes modified), on my M900 I have baffled carbon cans and a standard air filter, 12.5mm was too rich, I’ve returned it to 14mm and it runs well.
     
  17. Not suggesting he plays around with the float heights Keith but he needs to check they are correct.
     
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  18. Re: checking float heights on Mikuni BDST38, just to quote Brad again:-

    "I don't think I've ever checked one that has been wrong. Certainly not one that hasn't been played with anyway. If someone has been in there trying to make it right it's usually not."
     
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  19. Interesting.
    I had race cans and a semi open airbox and I never did get my fuelling spot on with 14mm
     
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