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79 XS650 Carb rebuild, signal install, speedo install, crankcase gaskets, and other stuff

Discussion in 'The Garage' started by VladTheDrumpaler, Apr 15, 2019.

  1. VladTheDrumpaler

    VladTheDrumpaler XS650 Enthusiast

    Hey everybody,

    I just got a 79 XS650 from my friend, Nate, that is moving out of town. I'll be rebuilding and upgrading over the next couple of months. I was hoping to gather as much info on this bike as possible. Sadly, Nate didn't have a lot of information about the history of this bike so it's up to me to get educated on it. What I do know is that the bike originated in Michigan because that is where Nate used to live. The guy that Nate got it from is who did the custom build. Nate barely did anything to it and he never registered it in Georgia. He's been in Georgia for 5 years so that should frame the timeline a little bit for you guys.

    I've been a vintage Honda guy for several years but this is only my second Yamaha. My first was a 1991 XT600 about 8-10 years ago. I'm solid enough with troubleshooting and sourcing parts, but I'm afraid that I know nothing about the XS so I'll be deferring to everybody else on this one.

    The first request I have for everybody is identifying the model of the motor and carbs. I need to start with buying seals/gaskets for the motor and a carb rebuild kit. I've got some minor leaks that are easy enough to sort out mechanically speaking. I'd also love to find a solid source for OEM and aftermarket parts. I normally use Bike Bandit, JP Cycle, and Amazon for parts but I was poking around and found a site called Mike's XS. Is this a solid shop?

    As I said, I'm in Atlanta, GA. I'll have to add a few things to make it legal to tag. I have a bill of sale but no title so I'll have to take it to the State Patrol office to get a VIN inspection done. From what I remember, Georgia needs a Speedo, turn signals, brake lights that function from the front and rear controls, and at least one mirror. This bike has a brake light that functions on the rear brake pedal only, but everything else will have to be added. I'll have to add controls on the bars for the turn signals, the actual signals, blinker relay, speedo plus cable, etc. It'll be a little bit of a task to get the bike legal and mechanically sound.

    I'll search the forum when I have specific questions first so I don't clog it up with a bunch of threads that already exist. If you guys could post links to the other threads until I know my way around the forum, I will be eternally grateful. Anyway... Here's the bike. I'll post pics as I get further along and I welcome any thoughts you have for upgrades. I'm all ears and would love the input from other builders.
     

    Attached Files:

    GLJ likes this.
  2. VladTheDrumpaler

    VladTheDrumpaler XS650 Enthusiast

    From another thread, it looks like the carbs are Mikuni BS38. Can anyone confirm?
     
  3. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    they are BS38's 76 to 79 but we need a shot of the intake to completely ID them.
     
    Last edited: Apr 15, 2019
    VladTheDrumpaler likes this.
  4. VladTheDrumpaler

    VladTheDrumpaler XS650 Enthusiast

    Here are some closer pictures. image1(1).jpeg image2(1).jpeg image3(1).jpeg image4(1).jpeg image5.jpeg image6.jpeg
     
    gggGary likes this.
  5. Downeaster

    Downeaster Everything in XS Top Contributor

    First, Welcome! You have just found the single most authoritative site for the XS650 in the known universe.

    Yes, BS38's Go to the tech section and read the carb thread a few times. TONS of absolutely vital info there. Hopefully that set will have been re-jetted to account for the straight pipes and pod filters. If not, the very least that will happen is that it will run like crap. The worst that can happen is a majorly lean burn and possible damaged pistons. Check the plugs.

    All late (post 1974) XS650 engines use the same gasket set. Go with an Athena set. There are variation in ignitions systems and carbs. Later engines (80 and up if I recall correctly) use TCI ignitions (Transistor Controlled Ignition) and BS34 carbs (trying to meet emission specs).

    The '79 came stock with points ignition. Some folks love them, others upgrade to TCI or a Pamco electronic ignition.

    MikesXS tends to be somewhat variable. Some stuff is perfect, other stuff is less than wonderful. If you have part numbers, you can often find OEM parts via Ebay or a web search.
     
    Last edited: Apr 15, 2019
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  6. LiveSlowDieWhenever

    LiveSlowDieWhenever probably broke down. Just call me greasy.

    Welcome Vlad, sweet ride. Shouldn’t take much to get that hard ass road ready and legal! A good idea here might be to retitle your thread to reflect the work you’ll be doing, and just keep posting here to keep from “clogging up” the forum. Seems to be pretty standard procedure here, and when you post something new it’ll pop up in the new posts section for folks to see. As for your question about mike’s xs, the consensus seems to be that parts are hit or miss, so just check here before ordering. A lot of parts can still be found oem or nos for similar prices and generally much better quality.
     
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  7. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    OK great those are the 78-79 BS38s. Noted as one of the best stock carb sets for the 650
    BS38 float bowl vents.jpg
    The chart shows factory jetting through the years, jetting goes with the carb year not the motor year.
    typically mains and pilots get bumped a size or three for less restrictive intake, exhaust. Your tuning may vary.
    650carbspecsreducedsizeey7.png
     
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  8. VladTheDrumpaler

    VladTheDrumpaler XS650 Enthusiast

    Nate did say that the ignition and charging systems had been upgraded. When I start the tear down, I'll take pictures. He also gave me a box of a few random parts. Ignition parts, brake pads, and a few other odds and ends. I'll post and inventory once I sort through and identify what I have.
     
    gggGary likes this.
  9. VladTheDrumpaler

    VladTheDrumpaler XS650 Enthusiast

    Awesome. Thank you, Sir. As I was pulling the filters, I noticed them completely soaked in fuel. Looks like the bowl vents are spewing fuel even with the fuel valve turned off. Float readjustment, Correct? I'll look through the carb threads once I get the parts that I need for more specific answers.
     
  10. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

  11. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    Yeah do the hot water dip test looking for cracked floats, very common. Then check (strongly suggest new) float valves, seats. New fuel lines, check petcock screens, fuel tank rust all the usual suspects. The carb guide and 100's of carb threads cover everything pretty thoroughly. Throttle shaft wear and replace the throttle shaft seals are two more check offs needed. We're pretty big here on using only genuine Mikuni brass for jetting
     
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  12. VladTheDrumpaler

    VladTheDrumpaler XS650 Enthusiast

  13. VladTheDrumpaler

    VladTheDrumpaler XS650 Enthusiast

    Absolutely. The whole fuel system will get a once over for leaks and cracks.
     
    gggGary likes this.
  14. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    Last edited: Apr 15, 2019
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  15. VladTheDrumpaler

    VladTheDrumpaler XS650 Enthusiast

  16. VladTheDrumpaler

    VladTheDrumpaler XS650 Enthusiast

    I pulled the carbs and the holders will need to be replaced for sure.
     
  17. VladTheDrumpaler

    VladTheDrumpaler XS650 Enthusiast

    gggGary likes this.
  18. VladTheDrumpaler

    VladTheDrumpaler XS650 Enthusiast

    I looked through the carb guide last night. Great resource. I'm gonna call 650central when they open and order up the genuine parts. How are they on shipping and availability? There is a Yamaha dealer in Georgia that is pretty good but their prices are insane. Is it worth it to get everything from 650central?
     
  19. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    Mike's a good guy. He'll tell you more than you may want to hear. Have pencil paper, take notes........
     
  20. XSLeo

    XSLeo XS650 Guru Top Contributor

    Welcome to the wonderful world of the XS650.
    On your carbs, rebuild kits are seldom needed. A kit has some gaskets that work, some have float valves that work. If they come with any other parts, those seldom work.
    Better to tear down, clean inspect before you buy anything. The stock gaskets are fairly robust and can be reused. The brass parts can be cleaned and used.
    Often cheaper to buy just the parts you need rather than the kits.
    On the ID, check the engine, on the front kinda behind the front engine mount on the upper case half. Is a number.
    From the factory that number matched the number stamped into the steering neck. If it does fine, If it doesn't that's fine too.
    There are charts that you use those numbers to determine the year and model of your bike. Most states will use the frame number for title and registration.
    Up near the top of the Page you will find a black bar, Click on the TECH. This takes you to a list of categories. Under each category there will be more specific listings. Search the tech section and you will find answers to most of your questions.
    For those that you can't find answers too then ask here.
    The places you found for parts, most are pretty good, Mike's is a so-so place. Some good parts, others not so much.
    There are many threads talking about Mike's quality issues.
    Leo
     

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