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Need help with my Bandit 1200

Discussion in 'Tech' started by andy342, Nov 19, 2011.

  1. Tunersricebowl

    Tunersricebowl Fog, onward through.

    The bike sat up too long and the fuel turned to varnish which clogged the pilot circuts which will cause exactly the problems he's having.
  2. loser

    loser Well-Known Member

  3. Vitamin-E

    Vitamin-E cornerin lo in the 3-1-fo

    Yep!! OP, I would seriously give it a try. It'll be easier than another carb cleanout and very well might work. It fixed the sh!t out of an R6 that was doing roughly the same thing...I know they are very different bikes, Yamaha/Suzuki, carbs/FI etc...but, often times, parts such as TPS's are supplied by Tier 1 manufacturers such as Keihin etc and are very similar bike to bike.

    If its not that, I would next go to the carbs again and make sure you get a good manual or illustration on how to clean them. A fueling problem is way more likely than skipped cams or other problems with the long block.
  4. afm199

    afm199 Well-Known Member

    check carb vent hoses. Are they lying on top and getting pinched/
  5. turner38

    turner38 Well-Known Member

    Bikes with clogged pilot circuits don't normally Idle well. The only thing inside the carbs I could see giving this problem would be if the needle jets had a thick layer of varnish on them, the odds of that happening are very low.

    On a carburated bike the TPS has VERY little effect on how the bike runs it changes only the amount of ignition lead and has zero affect on fuel trim.
  6. Tdub

    Tdub Say what???

    I have even disconnected it on my 450 dirttrackers and seen a smoother graph and higher HP...
  7. afm199

    afm199 Well-Known Member

    check the vent hoses. If you had the carb rack out you probably laid them back in the wrong place and they get pinched when the tank comes down.
  8. ed who?

    ed who? the opposite of eharmony.

    pinched vent tube WONT do what he is saying. If it was, the bike would fall on its face from midrange ALL way up, would never clear out.

    Its just a matter of getting float level right and gearing to. Those bikes were terribly tall geared. The bog is very common and it'll never go fully away, but if your bike is this bad, stop guessing, take to a known dyno tuner, have him run it and lets see the air fuel ratio? Im betting the air fuel dips WAY rich just off idle as they all do.
  9. Vitamin-E

    Vitamin-E cornerin lo in the 3-1-fo

    I dig it. He says he's already rebuilt the carbs so that's why I'm suggesting this relatively easy procedure before he does the carbs again. When mine messed up, it was sending bad signal in only part of the range. It would idle (more or less), but barely run from 2,000 to 7,000 and then come back over 7. Screwing the ignition up would do this even on on an old carber.
  10. turner38

    turner38 Well-Known Member

    No, it wouldn't. Even with the TPS disconected it will still run normall on a carbed bike, you'll notice a slight loss in fuel mileage and maybe just a tick in light throttle response.
  11. Vitamin-E

    Vitamin-E cornerin lo in the 3-1-fo

    Unplugged it sends no signal. The ECU can deal with that better than an effed up signal. OP should give it a shot as it takes about 5 minutes. Easy stuff when troubleshooting.
  12. fastfreddie

    fastfreddie Midnight Oil Garage

    intake boots.
  13. andy342

    andy342 Well-Known Member

    Wow. I didn't mean to start ten arguments.

    Boots are fine, I routed the vent hoses down between the carbs so they don't get pinched, and no, the pilot circuits are not clogged, or it wouldn't idle perfectly. TPS moves like it should. The resistance changes when the throttle is moved, and I have it set back to factory spec. Slides are not modified at all. The kit I got called for cutting an inch off the slide springs. I put stock length ones back in to eliminate that as a possibility.

    I think I finally found the problem. The needle jet ( the brass tube that the main jet screws into, suzuki calls it 'Holder, Jet,' part # 17 in the carb microfiche) has major grooves inside, where the needle passes through and rubs. This is on all four carbs to varying degree. The needles do not look scuffed at all. A big leak there, in the lower part of where the needle travels, could explain it all.

    I have heard that these wear out, but I have never seen it with my own eyes and I have been inside more than a few carbs. Factory pro makes these with a nickel plating so they are supposed to last longer than the stock ones.

    Thanks for all the ideas.
  14. ACDNate

    ACDNate Well-Known Member

    Those usually only wear out on the first gen B12's 2k and back. Do you're carbs have a throttle position sensor on them?
  15. Vitamin-E

    Vitamin-E cornerin lo in the 3-1-fo

    Don't sweat the arguments. Arguments are fun!!! :D Glad you got it fixed.
  16. andy342

    andy342 Well-Known Member

    Not fixed yet. Gotta call factory pro and throw the last hundred bucks at the problem in the morning.

    I never knew to look inside these things. You have to hold them in the sun at just the right angle.
  17. andy342

    andy342 Well-Known Member

    Update since I referred someone to this thread.

    The factory pro parts did not fit after they assured me they would. Wrong type of tubes. I had to order oem ones after all.

    Then after a long backorder, a couple of the oem emulsion tubes (holder, jet as they were called) were not machined very well inside. One had visible steps in the tapered inside, which should of course be smooth.

    They were still better than what I started with. Put them in anyway, the bike ran a lot better but still not quite perfect, sold it cheap.

    Anybody want a bandit 1200 ignition box and advancer cheap?
  18. afm199

    afm199 Well-Known Member

    This is my thought. Those tiny pilot jet holes get a even tinier bit of pflug in them and the low end turns to nada.
  19. andy342

    andy342 Well-Known Member

    No, please read the whole thread

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