Alternate Discussion Board for Vision Riders. XZ550RJ XZ550RK Yamaha Vision

    Weber Carb Conversion or Fuel Injection?


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    Join date : 2010-03-15

    Weber Carb Conversion or Fuel Injection? Empty Weber Carb Conversion or Fuel Injection?

    Post  jacobryttergaard on Mon Mar 15, 2010 12:18 pm

    Hi Everyone

    I am new here and found the forum when searching for carb trix for my '82 XZ550 (64HP version).

    I am practically ready to throw my carbs over the shoulder and install other carbs or perhaps a fuel injection system (mega squirt??). If anyone have experience with retrofitting injection systems on bikes please speak up. Previously I have retrofittet a turbocharged Alfa Romeo with a MAP-sensor type fuel injection system but I have no experience doing it on bike. I guess the space restrictions is the biggest challenge?

    After reading the topic 'side draught carb' I got in touch with Glyn and got more info on his Weber conversion, which seems to be a more appropriate solution in my case (low cost and less work than an injection system, I guess).

    With Glyns permission here are the details for inspiration to others and to share experience on the subject. I hope the pictures he sent me make their way also but my forum skills are limited:

    Hi Jacob

    Nice to hear from you. I will help anyway I can.

    The main problem with the standard carb is that the venturi is a bit too large, so when you crack the throttle open the vacumn is not sufficient to draw up the fuel. The dreaded XZ lag or bog. Also the Mikuni is made out of rubbish alloy that corroded and blocks up the jets that are really hard to get to. I also tried very hard to get the standard carb to run well and just could not.

    I chose the IDF Weber because size and design wise it is very similar to the Mikuni. The jets are very easy to change with the carb and venturi's in situ and the alloy is good quality. I think there are 2 sizes (but may be more). Mine is an IDF 40, I think there is an IDF 36 but are less common. The original IDF was made in Italy and copies were made in Mexico/South America I think. I think mine is a copy but works OK.

    My carb came off a Mazda RX7 Rotary car. It was jetted all wrong and the venturi's were huge. I did alot of reading around to come up with jet sizes. The carb now runs well and does not foul the plugs and acceleration is good. I have not put it on a dyno jet, nor will I since I've heard dyno's are very bad for old engines.

    There are alot of things you can change on the carb. Below are the setiings I have;
    1. Venturi size - 32mm
    2. Emulsion tube type - F3
    3. Main jet - 125
    4. Idle jet - 50
    5. Air jet - 180
    6.Pump jet - 50

    I started out with a larger main jet but it oiled up the plugs. My settings are probably not exactly spot on. The F3 emulsion tubes were in the carb when I got it. Another tube may work better. I know there carbs have been put onto Honda Goldwings and Harleys, so you may try to find out what emulsion tubes they use.

    The std XZ550 comes out with non changeable 34mm venturi's (choke size). I originally tried 28mm ones but were too small and the motor ran badly. It would be best to buy 32mmm ones, but I ended up taking the 28 ones and increasing the inner diam on my lathe.
    Do not go larger than 32mm.no matter what anyone says. The accelerator pump rod I set to mid setting.

    The hardest part of the whole conversion was making the alloy manifold. I first made a steel one which worked but leaked and looked terrible. Depending on how much you want to spend you could get an engineer to design one on a CAD and get it made, or cast in alloy.

    I (not having much money) like to do things myself. I found an old Leyland Mini manifold on E bay which looked like I could adapt.
    I wanted to keep the original rubber connectors at the engine side to ensure no leaks etc. Take out the old carb and hang/support the IDF carb between the frame rails, with the air cleaner attached (mine has an old VW K&N filter on). The position vertically will be limited by your space under the tank. My set up still has about 5cms between the top of the air filter and the tank.
    The position of the carb horizontally is to some extend dependend on if the carb is totching the frame rails or the rear engine mount.
    The fit is VERY tight, but it will do in, even with the throttle cable attchement fitted. I have mine with the fuel inlet right next to the left frame rail. I had to compress the frame rail slightly with a small vice (and a nut in the jaws to create a nice dent). Just sufficient for the carb to clear. I also had to take some metal off the rear top engine mount.

    Once you have found the right height and position (I suggest you copy mine), then you know how height the manifold must be etc.

    I took the mini manifold, sawed off the bits I did not need and created plates and tubes out of alloy on my lathe. They were made to tight tolerances so all slid together to make the welding easier. I have pleny of pictues etc in you need them.

    The standard fuel pump is used, connected to a small stainless bracket (see picture).

    I really is worth spending the time to do this, it transformed my bike.

    Please let me know if you need further detail at this stage.

    Good luck and speak soon.



    Glyns Webers came from a Mazda RX7. I searched the web and it seems they are often used here in Europe to upgrade VW Bettles and I also believe they were std. on Alfa Romeo Sud or 33.

    Hope the above was usefull to others and that more people will share their experience.

    Thanks again Glyn.

    Best Regards

    Weber Carb Conversion or Fuel Injection?  Weber Carb Conversion or Fuel Injection?
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    Weber Carb Conversion or Fuel Injection? Empty alternate site location

    Post  akvision on Thu Apr 01, 2010 9:21 pm

    go to the ROV site... www.ridersofvision.net
    that is where most Visionaries reside..
    this is the alternate site.
    Re post there and you will get a response.
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    Site Admin

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    Weber Carb Conversion or Fuel Injection? Empty Re: Weber Carb Conversion or Fuel Injection?

    Post  Site Admin on Thu Apr 01, 2010 10:42 pm

    Hi Jacob and thanks for joining and posting the message from Glyn.
    I set this site up as an alternate for the actual Riders of Vision site. www.ridersofvision.net We have some well established discussion forums over there and lots of talk about getting theOEM carbs working well.

    I look forward to seeing you there.


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