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(BS series) Throttle Seals: Who's done 'em, who needs to?

Discussion in 'The Garage' started by DirtyErnie, Sep 7, 2011.

  1. DirtyErnie

    DirtyErnie Renaissance Hick

    Just changed out the throttle shaft seals on my BS34's tonight, it's amazing to finally hear the thing idle properly. I took a bunch of pics of the process (it's not as bad as you think it would be) and I might be able to work up a how-to if anyone so desires or I get bored. I didn't seem to find much by searching, and it was a bit scattered... might be nice to get all the info in one place.

    Anyone have any related tuning horror stories? Words of wisdom? Strong opinions? Trolling?

  2. glennpd

    glennpd 4 bikes, 4 dogs, 1 wife

    Oh yes!

    Please post the pictures and the "how 2"would be very much appreciated.

  3. 5twins

    5twins XS650 Guru Top Contributor

    I got some nice stainless replacement screws for the butterfly plates from McMaster Carr. These are slightly longer than the originals but that allows you to bugger the threads up on the portion that sticks through using needle nose vice grips so the screws won't back out. Yamaha peened the original screw ends but I don't know how, maybe they have a special tool. It's very difficult for the home mechanic to do.

  4. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    Thanks 5T and yes DE do up a pictorial. I have done it a few times, not too bad but the possibility for disaster lurks, Getting the butterflys centered properly seems to be the biggest "trick"
  5. I agree....a good topic for a tech article treatment with pictures. More than likely most of us have leaking throttle shaft seals, probably holes in the CV diaphragms and leaking O-rings on the mixture screws and needle jets as well.

    Anyone have any spec. info on throttle shaft seals and sources alternative to MikesXS. They seem to be perpetually out???

    How does one "peen" the ends of those screws anyway? Blue
  6. 5twins

    5twins XS650 Guru Top Contributor

    The seals are still available from Yamaha for slightly more than Mike's, part #256-14997-00-00. There's also a square sectioned or "quad" o-ring available from McMaster Carr that works .....

  7. DirtyErnie

    DirtyErnie Renaissance Hick

    I just used blue loctite on my screws when I put them back in, squeezed them down fairly hard, too. <-- any concern here? They sure didn't feel like the free ends were peened, came out too easily. Although I did have to smack my screwdriver with a hammer a few times to break them loose. I'll get working on that write up, but I gotta go ride for a while first. :-D
  8. Thanks so much for the two sourcing tips and great info 5 Twins. I usually like Buna-N for enclosed conventional O-ring but Viton could be a far better choice for wear, lubricity and resistance to ethanol (absorption, drying, hardening etc). Blue
    Last edited: Oct 5, 2011
  9. glennpd

    glennpd 4 bikes, 4 dogs, 1 wife

    Smack the screw driver with a hammer against the thin throttle plate shaft could easily lead to disaster. Are there any other less dangerous techniques for loosening those screws?


  10. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    Hand impact wrench is prefered but it still involves a hammer. Best I can offer is
    'judicious use of force". I have put the Mcmaster Carr seals in 3 sets so far all ran well after. If the shaft has up and down wiggle the seals are shot. If the wiggle is more than a very small amount the bodies are junk.
    Last edited: Sep 8, 2011
  11. 5twins

    5twins XS650 Guru Top Contributor

  12. XSLeo

    XSLeo XS650 Guru Top Contributor

    I used a dremel tool with a sanding drum to grind off the screws on the inside of the throttle pates. Hold the throttle plates open. Gringd off the screw to flush with the shaft. They come right out. Replace with new screws, brass would be nice, easier to crimp the end to prevent backing out.
  13. DirtyErnie

    DirtyErnie Renaissance Hick

    Wasn't much of a hammer, medium-sized urethane head, plastic-handle screwdriver, didn't swing too hard either. Didn't have the best of screwdrivers available, things were sticky and needed a little encouragement. Berryman's Chemtool may have softened up the varnish enough to do the job, but after I nearly boogered a screw head I wasn't taking chances.

    Just 'cause I was born in a swamp doesn't mean I use the three-pound hammer on everything... :poke:
    DaveO likes this.
  14. Thanks Leo...I remember you giving us that tip sometime back and I have been doing likewise and find that it works great as you say.
    (ps...tape off those little ports in the throat to keep the crud out when you grind the peened ends off the screws)

    The JIS #1 or #2 screwdrivers or 1/4" drive JIS driver bit fits those OEM JIS cross point screws perfectly and will help greatly. Blue
    Last edited: Sep 22, 2011
    yamamunn likes this.
  15. blackbetty

    blackbetty XS650 Junkie

    This thread has me scratching my head....

    Replacing the throttle seals on my 38's was pretty uneventful :shrug:
  16. glennpd

    glennpd 4 bikes, 4 dogs, 1 wife

    Ok, I ground down the backs of the screws. I set the carburetor over a piece of wood so the force of the blows from the hand impact driver was not braced by the carburetors but by the cut off piece of broomstick placed against the throttle shaft. Two screws were fairly easy to back out. The other two are buggers. So much so even with a hand impact driver I was able to bugger the heads. Now what? How screwed am I ?
  17. retiredgentleman

    retiredgentleman XS650 Guru Top Contributor

    I've bought some from Yamaha with the part # that 5twins listed. They were still used as recently as 2006 XV250V Virago 250, as a stock part. They are somewhat strange, in that the inside diameter of the seal seems to be larger than the throttle shaft, but they work fine. The vacuum must pull the seal lips tight to the shaft.

    I suspect if the screws have been removed by a PO, then that's why some find no difficulty removing i.e. the staking part is no longer there.

    As others mentioned, its absolutely key that the screwdriver fit the heads perfectly. Either buy the correct JIS screwdrivers or grind down the sharp point of a standard phillips. A few sharp hammer blows to seat the screwdriver into the heads is wise.

    I've just used blue locktite in the past, with no attempt at staking, so I hope they stay in place.
  18. retiredgentleman

    retiredgentleman XS650 Guru Top Contributor

    You could try using a drill bit to drill out the damaged screw head, without damaging the shaft itself. Then use a small drill bit to drill the screw shaft, which may very well spin the screw out the back side far enough that you can grip it with a vice grip for removal. New screws needed of course.
  19. weekendrider

    weekendrider Iron Horse cowboy Top Contributor

    S.W. MO
    A bit the size of the screw shaft will take the head off. Then a smaller bit will screw it out the back.
    You can find hex head replacements.
    Remember to center the plates before tightening fully.
    RG I use blue only and haven't had any problems.
  20. retiredgentleman

    retiredgentleman XS650 Guru Top Contributor

    weekendrider...............a good point for sure, the plates need to be centred before tightening the screws.

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