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Mikuni RS38 Setup

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    #1

    Mikuni RS38 Setup

    The bike: 2004 Bandit 1200

    Mods: 1991 Katana 750 Dot head with 89 GSXR750 cams, pod filters, Black Widow head pipes with Yoshimura RS3 can.

    The Issue: No run or start. I know the carbs need to be set up but I can only get the bike to run by constantly cranking the throttle, i.e., using the accelerator pump. Carbs are brand new and not setup at all, so I knew they wouldn't be perfect, but I was expecting them to at least start and idle.

    I am thinking needle position, since opening up the idle screw did not do much of anything after two full turns, but I am a complete novice to this and would appreciate any advice. Thanks.

    BTW, when did the site drop the GSXR support?
    Tags: None
    #2
    Suspect it's not the carbs - I put the same brand new set on 3 very different motors ( 1127 K model lump, 82 GS1100 and 99 1200 bandit) to prove the motors before tearing down the bike ...... anyway - straight out of the box with No adjustment all 3 fired,ticked over and cleanly revved (as my neighbours will attest) - mixture was close (if slightly lean) on all 3 too.
    doesnt help but I'd check elsewhere - ignition or valve timing overly advanced ???
    78 GS1000C- Now sporting 1100E suspension and numerous goodies
    82 GS750E/82 1100E/ GSXR Frankenstein bike completed
    83 1100E "rescue bike" saved from the barn
    2008 Bking - Torque Torque Torque
    Next project slowly coalescing

    Comment

      #3
      Check the float height, the mixture screws (fuel) and the idle adjuster screw.

      Float height could be way off from factory, should be set at 17mm.
      Mixture, shey should at least run at 3/4 (but could be lean or rich depending on temperature and humidity) out from lightly seated (only use your fingers to adjust these or you could snap the points off).
      Needle position only comes in to play later but start in the middle groove.
      Adjust the acc pump to where it is as close to disengaged you can go to begin with and adjust later. They should run fine even with acc. pump disengaged completely.
      Bench sync them using the "drill bit method" for a decent starting point (google will help)
      Start the idle adjuster at 1mm (could be a bit high but adjust down after) showing under the slide from the engine side (also measured with the back end of a 1mm drill bit)

      Now she should be running if everything else with the motor and fuel delivery is good.

      Comment

        #4
        You did dial the cams in ? To what lobe centers ?

        Comment

          #5
          Yeah, I think a carb pull is in order. I can get it to run by holding the throttle open, but it dies as soon as I let it close. Choke doesn't let it idle either. I thought maybe my timing has slipped and I had some valve/piston interaction, but I put a camera down the sparkplug hole and saw nothing out of of sorts. It's my own fauly for rushing the install I suppose, since the weather is closing in and I wanted to sample the goods before putting it away for the winter. The valve timing is set to the lines on the cam sprockets, nothing more.

          Comment

            #6
            Not the carbs. Exhaust cam was retarded, allowing the valves to contact the pistons. Just hard enough to burnish the reliefs. Don't know how this happened, I had everything timed right, but the exhaust cam was out of time when I stripped it down today. I guess I timed it with the tensioner out or something. Dammit! I was fearful of a lot more damage actually, 8 new exhaust valves should set me right, but it's too late for this year sadly.

            Comment

              #7
              Originally posted by Roger P. View Post
              Not the carbs. Exhaust cam was retarded, allowing the valves to contact the pistons. Just hard enough to burnish the reliefs. Don't know how this happened, I had everything timed right, but the exhaust cam was out of time when I stripped it down today. I guess I timed it with the tensioner out or something. Dammit! I was fearful of a lot more damage actually, 8 new exhaust valves should set me right, but it's too late for this year sadly.
              I was thinking had to be the fuel OR spark before, But I did have a weedwhacker once that had a wasp nest thing covering the exhaust hole. Took a minute.

              I was reading The RS usually comes adjusted to atleast run...Any links where to get rebuild/parts for the RS???

              Going to replace O-rings and gaskets soon. Can't find the other stuff , on (several) quick searches from time to time.
              Thanks in advance for any info. , Sounds like an awesome project by the way.

              Comment

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