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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! XS650.com Supporter Top Contributor

    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.
     
    zodc likes this.
  2. zodc

    zodc XS650 Enthusiast

    Awesome! Thank you for the link 5twins.
     
  3. zodc

    zodc XS650 Enthusiast

    I'll definitely do this. Looks like I'm rebuilding some carbs in my near future!
     
    gggGary likes this.
  4. zodc

    zodc XS650 Enthusiast

    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

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    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

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

    https://www.ebay.com/itm/Yamaha-XS6...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

    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 .....

    https://www.ebay.com/itm/80-81-Yama...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649
     
    zodc likes this.
  7. zodc

    zodc XS650 Enthusiast

    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.
     
  8. zodc

    zodc XS650 Enthusiast

    Finally an update on this slide situation. Turns out the actual slides are different lengths and the amount of needle hanging out below are very different too.
    The incorrect slide measures 47mm from the diaphragm down and the amount of needle hanging measures 48mm.
    upload_2019-11-24_20-51-20.png upload_2019-11-24_20-51-54.png

    Compared to the correct slide measuring 48.5mm from the diaphragm down and the hanging needle at 45mm.
    upload_2019-11-24_20-55-26.png upload_2019-11-24_20-55-50.png

    I went ahead and took an easy route (Haha I thought) and purchased a completely rebuilt carb setup with new internals. It was a fair price since I'd have to completely buy just about everything to replace the carbs I had anyway. Now I'm troubleshooting the float (flooding gas on one side); but that's another topic. I'm getting really good (and confident) at taking these apart and putting them back together again.
     
    gggGary likes this.
  9. 5twins

    5twins XS650 Guru Top Contributor

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    Yes, if the actual slide lengths differ then I don't think there's any way you could match the flow side to side. The needle amount hanging out could probably be matched, but with the slides not matching, that wouldn't solve the overall mismatch.
     
    zodc likes this.
  10. zodc

    zodc XS650 Enthusiast

    Well, I picked up this rebuilt carb set. I opened them up and checked them out. As far as I can tell, they are super clean, all new "guts", and looking great. I think these are probably '81 or later carbs because the floats are not brass and the bowls have a drain plug - comparing to my '80 which does not have these features. No biggie right? I hope...
    upload_2019-12-7_21-31-16.png
    But, the side marking isn't "MIC MIKUNI KOGYO".
    Instead, it's "Mikuni Corp. Made in Japan".
    Should I be worried? Are these aftermarket carbs or something?
     
  11. azman857

    azman857 '80 XS 650SG Rider Top Contributor

    '81 and later BS34's had these features. Different float, screw drain on the float bowl. Float level is different with the plastic float. Even later BS34's has a pull linkage from the handlebars for the fuel enrichment(Choke).
     
  12. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

  13. zodc

    zodc XS650 Enthusiast

    Got the bike together and took a test ride around the block. Seemed to be great. After getting back home I put the bike on the center stand in the driveway and let it sit at idle. The right side carb started to flood, bog, and gas poured from the intake. I tapped the bowl with a rubber mallet and it seemed to stop flooding for a bit but after a few minutes, still at idle, it began to bog again and flood. I'm assuming it's the float level or float valve. I'll pull them apart and check.

    On a side note, as the bike got hot, I noticed smoke from the right side near the exhaust header. Looked closer and it seems to be oil leaking from above the spark plug. You could see the oil on the fins.
    IMG_5670.JPG IMG_5669.JPG
    Could this be related to the carb overflow?
     
  14. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    Not related, probably cam oil seal, but look in the cover.
    did you remove float valves from carb bodies replace o-rings?

    oil.JPG
     
    TwoManyXS1Bs likes this.
  15. zodc

    zodc XS650 Enthusiast

    7AF627C1-22E3-4C53-A48D-57FF3FFF85BF.jpeg
    If the cam oil seal needs replacing, would that mean that’s not something included in the gasket kit correct?

    FB0B6A94-58EA-47F2-AFEB-8D588BA592B9.jpeg
    Also on closer inspection, that drip you circled is actually a dried up goop on what looks like silicone sealant or something.
     
  16. zodc

    zodc XS650 Enthusiast

    I went ahead and ordered this kit because I have a feeling I’ll be needing it. While ordering I also included their gasket kit. Unfortunately, their gasket kit is not Vesrah even though they use a Vesrah image and product number in the title. Just so you know.
     
    gggGary likes this.
  17. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    Look into cam oil seal there's buzz round about that the factory seal is the way to go and it's fussy setting them in to the right depth. When the old seal is out check the cam is smooth where the seal sits.
     
    Last edited: Dec 13, 2019
    Team Junk likes this.
  18. zodc

    zodc XS650 Enthusiast

    IMG_6506.JPG
    My guess would be it should not look like this. Going to clean it up and reseal.
     
  19. Jim

    Jim Beyond the edge, is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Your leak is inside the housing. That's the seal, not the gasket. Holes are blind, so any gasket leak would be outside the housing, not inside it.
    Also, you're missing the o-ring that fits around the outside of the seal flange
     
    gggGary and zodc like this.
  20. Jim

    Jim Beyond the edge, is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Should look like this...

    138.jpg
     
    gggGary and zodc like this.

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