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BS34 1980 XS650 Special Carb Mix-Match?

Discussion in 'The Garage' started by zodc, Nov 3, 2019.

  1. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    You need to remove the float valve body and usually it needs a new o-ring, unless recently replaced the o-ring leaks and lets fuel seep AROUND the float valve, not a good thing.
  2. Awesome! Thank you for the link 5twins.
  3. I'll definitely do this. Looks like I'm rebuilding some carbs in my near future!
    gggGary likes this.
  4. upload_2019-11-10_22-3-59.png
    Well, the needle for the odd-ball slide is on the left. Needle from the normal slide on the right.
    They both measure about 53mm from the clip down to the needle tip. However, the needle on the right taken off of the normal slide is slightly shorter.
    I'll be replacing everything! Hahaha
  5. 5twins

    5twins XS650 Guru Top Contributor

    The portion or length of the needle above the clip slots isn't important. It can vary and since it doesn't meter fuel, it doesn't matter. OK, you've established that you have matching needles. Now you need to determine if the same amount of needle hangs out the bottom of the slide in each of your slides. Since they are mismatched slides and mount the needles in different ways, what hangs out the bottom may differ with both needles set in the same clip slot. You may need to set one differently than the other to get the same amount of needle hanging out of the bottom of the slide.
  6. 5twins

    5twins XS650 Guru Top Contributor

    The needles you have there may be from this dyno tune kit .....


    I say that for a couple of reasons. First, I see yours have 6 clip slots. Those kit needles have 6 slots as well. Adjustable Mikuni needles usually have only 5 slots. Second is the length. Those kit needles are supposed to be longer than the stock ones. Yours are longer as well. Stock ones are only 50mm long from the one clip slot to the tip. This kit was developed by Heiden Tuning in Europe and designed for use with a 750 big bore kit and their 2-1 exhaust. Most reports are it doesn't work very well on a stock or near stock 650.

    So, if you're going to replace those needles (you probably should), I'd recommend this kit from eBay seller cruzinimage. It's a rebuild kit but it contains needles. And not one but two different sets. And they are the proper length .....

  7. Thank you again. I really appreciate the information and knowledge. Going with the full replacement route but I will still sort this old carb out to learn more.

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