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'79 XS650 Special Low-Effort Resto

Discussion in 'The Garage' started by BSAKat, Aug 23, 2020.

  1. BSAKat

    BSAKat XS650 Member

    Hey there! Back in the before times (last year) I picked up a long-abandoned '78 SE model that was in pretty sad shape. Here it is the day I brought it home.

    [​IMG]

    I finally dug into it this weekend and the carbs are a disaster. Carb #2 is completely seized up, packed full of filth and dried out varnish. Carb #1's float bowl has about a half-inch of ancient gas that turned into tar-like varnish and gummed everything up. It's pretty gross in there.

    I'm not new to working on old motorcycles (or even old Yamahas, I've had an XS850 for 20 years), but I am new to XS650s. When sourcing carb parts for this thing, what should I watch out for? Any obscure variations between model years I should be aware of?

    Also, if you're curious, my plan for this thing is to get it running, add it to my fleet, and ride it until I find an early-70s 650 (which is what I really want). Gonna leave it stock and just ride it as a survivor.
     
    lakeview, Mailman and gggGary like this.
  2. grizld1

    grizld1 Grumpy old man Top Contributor

    First off, welcome to the madhouse; we're always glad to see another inmate!

    After maintaining that triple for so long, I'm sure you already know to beware of generic rebuild kits with bits that may or may not be correct for your application, and Chiwanese jets, floats, etc. that may or may not be well made. You'll be ahead on time and money if you use genuine Mikuni parts; Niche Cycle Supply has most of the needful stuff at a reasonable price.

    Re. variations, 1978 and 1979 used redesigned BS38 carburetors. These vent through two holes leading from the upper rear corners of the float chamber in the carb body to the intake bell, rather than through a standpipe in the float bowl. You'll find quite a bit of detail the old XS650 Garage USA Carb Guide: go to the Tech section and click on the link. There are also links in the Tech section to free downloads of factory service and parts manuals.

    Enjoy!
     
    gggGary, timbeck and Boog like this.
  3. BSAKat

    BSAKat XS650 Member

    Thanks! Yeah, I buy OEM parts when possible. I do like K&L for carb rebuild kits, though.

    So, I may need to actually buy a whole new #2 carb. I got it nearly apart and discovered that both the slide and the throttle shaft/butterfly are frozen solid. After a thorough soaking down with PB blaster and a long wait, all I got was angry and a bent butterfly. The slide absolutely refuses to move and I got the throttle shaft to move a little, but I ham-handed it despite knowing better. It's what I get for working hangry.
     
    gggGary and grizld1 like this.
  4. 5twins

    5twins XS650 Guru Top Contributor

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    Mild heat (hair dryer) would help, but it sounds like it may be too late. Be careful with those butterfly plates. They were never offered for sale as a separate part. Scrounging is the only way to get one.
     
    gggGary and timbeck like this.
  5. BSAKat

    BSAKat XS650 Member

    I ended up just grabbing a pair of carbs of eBay. I reckon between the four of them I should be able to build a set that works. Does anyone have a line on manifolds/carb holders? The three sets that MikesXS sells don't fit the stock '78 carbs, they're not available from Yamaha anymore, and there are a lot of cheap, no-name sets out there that I'm leery of.
     
    grizld1 and gggGary like this.
  6. grizld1

    grizld1 Grumpy old man Top Contributor

    ARS is the original equipment manufacturer, and they still produce the boots. They are sold under the Tour Max label, and you can find them online or order them through any shop that has a K&L catalogue. I don't know what Mike's XS is selling now, but the Chinese boots they used to sell were worthless. Re. fitment, any boots from 1974 to 1978 will work with your carburetors, although 74-77 boots don't have vacuum barbs. There are several workarounds to convert vacuum petcocks to manual function, including simply running on "Prime."
     
  7. BSAKat

    BSAKat XS650 Member

    They will? Huh. I thought the '78 and '79 carbs were bigger, for some reason. All the places I've looked have boots for bikes up to '77, then boots for '80 and up, but nothing for '78 and '79 models. I'll broaden my search, then. Oh, I forgot to ask, does it matter than mine's an SE/Special model?
     
    Last edited: Aug 24, 2020
  8. grizld1

    grizld1 Grumpy old man Top Contributor

    In 1980 Yamaha switched to BS34 carbs, which require smaller boots. Prior to that BS38s were used. The only difference between 78-79 boots and 74-77 boots is the presence of vacuum barbs in the 78-79 version, and you can live without that feature. Standard or Special makes no difference.
     
    gggGary and lakeview like this.
  9. BSAKat

    BSAKat XS650 Member

    Ah, okay. Right on. I was reading the information completely wrong. I wanted to rebuild the stock petcocks on this one, but they're so screwed up it's not worth it. I have a set of non-vacuum petcocks I pulled off an XS750 that fit perfectly, so I'll just use those and the older-style boots. Thanks for all your help so far, I really appreciate it.
     
  10. Machine

    Machine Race the wind Top Contributor

    20200822_100435.jpg
    There are these extra 77 intake boots in my stash. With gaskets.
    PM me if you do not find a set conveniently.
    -R Vancouver WA
     
  11. 5twins

    5twins XS650 Guru Top Contributor

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    The vac nipples on the manifolds are handy to have for another purpose, syncing the carbs. They give you a place to attach vacuum gauges or a manometer. But on your carbs, there's a work-around. There are actually vacuum ports on the carb bodies plugged by a big flat head screw. Remove the screws, temporarily install hose nipple fittings, and you can attach the gauges there .....

    [​IMG]

    [​IMG]

    The screws are a standard M6 x 1 thread.
     
    gggGary and timbeck like this.
  12. BSAKat

    BSAKat XS650 Member

    Oh HO! I wondered what those screws were for.
     
  13. BSAKat

    BSAKat XS650 Member

    So, parts are rolling in. Along with a new set of carbs I snagged of eBay, I grabbed a new fuse block, both oil filters, carb rebuild kits, carb boots, and assorted bits of rubber and general tune-up parts from MikesXS. If the good lord's willing and the creeks don't rise, this thing'll run and idle by Sunday for the first time since 1987. Stay tuned for pics and videos.
     
  14. BSAKat

    BSAKat XS650 Member

    Okay! So, I posted this on the Facebook group so a lot of you may have seen this already. Here's the '79 (It's a '79, I guess. March 1979 build date but it has what looks like a '78 VIN) running for the first time since 1987.

    Ta-dah!

    To get it running I slapped on a new (to me) set of eBay carbs that I rebuilt with K&L rebuild kits along with new points, new carb holder boots, new airbox boots, a new rubber crossover for the airbox, and fresh plugs. Once it cooled off I did the valves (the exhausts were hilariously tight), cam chain, and readjusted the points. Now that it actually runs and idles I'm going to change the oil and both filters and I ordered new brake lines, new cables, exhaust gaskets (I have a wicked exhaust leak on cylinder 2), rebuild kits for both master cylinders and both calipers, new O-rings for the tappet covers, and new rubber isolators for the handlebar risers (mine are trash).

    The ultimate goal for this thing is to get it safe, reliable, and ridable (which is gonna require a chain, pipes, tires, a new speedo, and some electrical work) with a couple mild modern upgrades (a modern reg/rec and maybe LED bulbs), get a title for it, and flip it. I just can't keep this one and I need money for my BSA project. Besides, as much as I want an XS650 this isn't the model I want. I really want a '74 or '75 standard.
     
    Smuggy and grizld1 like this.
  15. 5twins

    5twins XS650 Guru Top Contributor

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    If the key from that 750 ignition physically fits into the 650 one (just won't turn it), you can "re-key" it so it does.
     
  16. BSAKat

    BSAKat XS650 Member

    It doesn't, sadly. I'm just gonna grab one off eBay. I tried to get keys made for it, but the only key code I could find is the one on the fuel tank. That key fits the fuel tank and the seat latch just fine, but won't even go in the ignition barrel.
     
  17. 5twins

    5twins XS650 Guru Top Contributor

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    Sounds like some locks have been changed, probably the ignition one. From the factory, all the locks matched and used the same key (tank, seat/helmet lock, ignition switch). There should be a 4 number "code" stamped on the lock face .....

    [​IMG]

    Then using this chart, you can determine which Yamaha key blank it takes. The one above would use a #1214 blank .....

    [​IMG]

    But Yamaha blanks are outrageously expensive now, like $12 each, so here's a cross reference chart I made up showing what the aftermarket blanks match up to. Aftermarket blanks can be had for not much more than a dollar or 2 apiece .....

    [​IMG]

    You might get lucky on eBay. There are some sellers with an assortment of cut keys. They list the numbers they have and maybe you can find a match.
     
  18. BSAKat

    BSAKat XS650 Member

    Oh yeah, I did that already to get the seat/gas cap key. I figured that they'd all be the same (I had to do the same song and dance for the XS850) but alas...
     
  19. 5twins

    5twins XS650 Guru Top Contributor

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    Well, eventually, around 1980 or '81, Yamaha did remove the code numbers from the lock faces, I guess in a half hearted attempt to make the locks more secure, lol. But, in '79 I'm pretty sure they all still had the numbers stamped on them. But, it's possible the ignition switch on there is from an '80 or later model. You may find the code number on a sticker on the bottom of the housing .....

    [​IMG]

    But as you can see, the codes are different, a letter and 5 numbers. There was a change to the locks and key blanks used around 1980. The old 4 number locks used keys with two different depth notch cuts (.75mm, 1.5mm). The new letter code locks switched to 3 different notch cuts (.5, 1.0, and 1.5mm). The key blanks were pretty much the same as far as the grooving down the sides but were just a little longer. But, even if you found a blank to fit all the locks, you couldn't match the cuts so that all 3 locks would work with the same key.
     
  20. BSAKat

    BSAKat XS650 Member

    Ugh. Goddammit Yamaha. I've been saying that a lot lately...
     

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