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REPETE'S 650B Preservation

Discussion in 'The Garage' started by REPETE, Oct 22, 2019.

  1. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    Good Morning all!
    I am forensically putting my 650B back together as I address every mechanical & electrical issue along the way. I say "forensically" b/c the bike was partially disassemble when I obtained it... parts in boxes and ultimately some missing.
    I'm currently focusing on the air boxes.
    The right air box is no doubt original to the bike. matches the diagram and fits.
    The left side is a curiosity to me. It can't possibly be stock. Or, at least not for this model..
    It fits perfectly fine, but it is completely different than the right side... meaning not a "mirror image" and it's made of plastic. The single biggest issue with it is that the crossover connection doesn't match that on the stock right side. So, I sourced a left side replacement that is on its way.
    And this brings me to my question......
    I'm sure these work whereas the engineers that designed them were pretty smart.
    But as I'm studying them, I'm really curious as to how well they allow air flow?
    Naturally, they're not air tight, but they certainly don't have any obvious air flow passages. In fact, the air boxes on my '68 - 72 Enduros are more ventilated.
    Are these known for being a problem related to performance?
    Am I going down the wrong path by even giving this thought?
    Sure would like to hear some fact based opinions.
    Thanks all.

    Pete IMG_4791.jpg IMG_4792.jpg Capture 1A.PNG
     
  2. YamadudeXS650C

    YamadudeXS650C Central New York XS650 XS650.com Supporter Top Contributor

    Pete,
    Many of us use the stock air boxes. They perform well.
    An alternative is to go to foam UNI filters, but in that case you'll probably have to rejet the carbs. We'll give you starting points for the jets.
     
  3. YamadudeXS650C

    YamadudeXS650C Central New York XS650 XS650.com Supporter Top Contributor

    If you decide to stick with your current air boxes, don't throw away those skeletal remains of filters you got there, cuz you can buy sheets of green filter material from UNI and glue sections into your carcasses, making good, inexpensive filters.
     
    59Tebo likes this.
  4. YamadudeXS650C

    YamadudeXS650C Central New York XS650 XS650.com Supporter Top Contributor

    Ignore the foam silencers (part #21), as they are useless.
     
  5. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    Thank you!
    I'm not looking to stray from stock. I was simply pondering the prospects of air flow through what is a basically a sealed up box with the exception of the filter cover.
    As I said... the engineers were smart. I just didn't know if folks were modifying these due to unsatisfactory performance. After all, it was 1975 and the EPA was having their way with vehicle manufacturers
     
  6. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    Understood. In fact, without them I can't even discern where they'd go! That mystery shall remain unresolved! :)
     
  7. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    I have a couple of filters coming from MikesXS, but was planning on "rebuilding" the originals... they'll go into the "to good to throw out pile".
    I knew about the UNI Foam. The challenge for me will be the soft rubber/foam that'll make the seal against the inside wall of the air box. I don't know what to use or where to source. so, it'll go on the back burner for now.
     
    Last edited: Oct 22, 2019
    GLJ likes this.
  8. jetmechmarty

    jetmechmarty XS650 Guru Top Contributor

    The plastic airbox is late model XS650. I think the plastic box began with the 1980 model. For sure, the '81 box is plastic. For '80, it's my assumption. I run with airbox.
     
  9. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    Thank you.
    Concerning my incorrect plastic air box, do you know if it's complete based on the pic? I'm thinking there should be a cover of some sort?
    If it's complete I'll find a new home for it.
    If it's incomplete I'll toss it.
     
  10. YamadudeXS650C

    YamadudeXS650C Central New York XS650 XS650.com Supporter Top Contributor

    if your'e referring to your post #1, the one on the left, its missing the cover.
     
  11. jetmechmarty

    jetmechmarty XS650 Guru Top Contributor

  12. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    Thanks fellas!
    I suspected.
    Your input is appreciated.
    To the garbage it goes.
     
  13. 5twins

    5twins XS650 Guru Top Contributor

    18,880
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    That plastic airbox you have is indeed from another model. It is from an '80 or newer model with the BS34 carbs. It is pretty much useless to you.

    Stock airboxes work OK but I think pods work fine too. The airboxes on my '78 were trashed when I got it so I went with pods from day one. Once the carbs and jetting were sorted, it ran fine, always has. I recently got an '83 and it still had the airboxes. I decided to try them out because many claim they work the best. All I can say is to repeat that they work OK. This bike runs no better than my pod equipped '78. Now I've finally gotten around to installing pods on the '83. This went hand in hand with other mods - an all new freer flowing exhaust and re-jetted carbs. The bike runs great, just as good but probably better than with the airboxes. But keep in mind, this is a combination of mods doing this, not just the pods alone.

    I guess I favor pods for simplicity's sake. They make carb access much easier and don't hog so much space under the side covers. The airboxes are a royal P.I.T.A. to remove and install. Several bouts with them on the '83 had me looking forward to using pods even more.
     
    59Tebo likes this.
  14. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    5T -
    Down the road I'd be interested in the pods (with jetting guidance) if they'll tuck in behind the side covers. And, I can clearly see what you mean about it being a challenge reinstalling the stock boxes. But for now, I'm committed to that plan. I want to get the bike road worthy, dependable and running well prior to dealing with any mods. I know I can rebuild it to stock but I wouldn't be comfortable adding enhancements to the menu at this time.
    I don't have to more to do. Mostly just bolting back on parts I've removed for scrutiny/de-cruding/repair or replacement.
    The "to do" list:
    Reinstall air boxes w/ filters (waiting on left box & filters)
    Need to re-visit/re-clean right side carb... inoperable below (roughly)1800rpm
    Re-build petcocks (waiting on parts) and mount tank
    Reinstall rear wheel (waiting on local shop to change tire) along with sprocket & chain
    Reinstall cleaned exhaust system.
    Add mirrors
    Road test.
    I'm close... so very close.

    Pete
     
    Machine likes this.
  15. 5twins

    5twins XS650 Guru Top Contributor

    18,880
    9,720
    688
    Yes, I feel it's best to get the bike running "as is" or stock, sort the bugs out, then start in on the modding. The typical "pods and pipes" mod is usually done together, you change both at the same time. You want to let more air in because you're flowing more exhaust out. The two mods work together and compliment each other.

    I wouldn't toss that late model airbox just yet, someone may have a need for it. They may have broken their box but still have a good lid for it.
     
  16. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    Understood and thank you!
    Onward!
    I'll drop a post when completed or stumped.
    I appreciate all the input.

    Pete
     
  17. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    Yes 5T... agreed!
    I believe in helping others where & when I can.
    So, that said - LATE MODEL LEFT SIDE AIR BOX (LESS COVER) FREE TO SOMEONE THAT ACTUALLY NEEDS IT.
    Reference picture in 1st posting.
    Please don't ask for it if it's just going to be thrown in a box or resold for monetary gain. I'd like for it be be helpful to somebody.
    Recipient will pay the postage. I'm guessing it'll fit in a USPS mid sized Flat Rate Box ($16 +/-).

    Pete
     
    Last edited: Oct 22, 2019
  18. Gator xs2

    Gator xs2 XS650 Addict

    397
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    FL
    When the EPA crammed everything down manufacturers throats in the late 70s it all went to hell. Yamaha actually vented the crankcase back into the air box. Really??? Are you kidding me?
     
  19. XSLeo

    XSLeo XS650 Guru Top Contributor

    On the stock air filters I found the black weather stripping you buy for weather stripping doors or windows work. Find some about 1/4" thick and a 1/2" wide. On wrapping the green foam from Uni Filters on your old fitter cages, Don't glue them on. Cut them a bit big and tie on with light wire. That way you can take it off to wash it out when dirty.
    On my 81 and 83 I cut it wide enough to be snug fit between the sides and wrap around with some over lap. I install with the over lap towards the inside. It stays in place with out being tied.
    Leo
     
  20. XSLeo

    XSLeo XS650 Guru Top Contributor

    Almost forgot. In your last pic it shows the side of the air box. That slot is the air intake. If flows in there, through the silencer(the foam block with holes in it) to the filter element.
    This air intake seems small but the cylinders run 360 degrees apart, each cylinder draws air in through both filters.
    So it's not as small as it seems.
    Leo
     

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