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'79 xs400 rough>reliable>cafe 'Scarlett'

Discussion in 'The Garage' started by jthiessen, Nov 4, 2013.

  1. I set my air mixture screws to 2 turns out, now I am experiencing a lingering idle? Other than that I haven't noticed any difference in how the bike ran.
  2. xschris

    xschris a lifestyle not a trend Top Contributor

    I would go up in 1/4 turn increments. Have you synced them in a while? Still stock jets right? A 3-4 k bog is the needle jet and needle. Make sure the emulsion tubes are clean and the needles are set to the correct clip. Also the needles can develop wear spots in them making uneven fuel metering at certain rpm's.
  3. 3 parter today:

    1 . I check my plugs again today after driving with my air mixture screws set to 2.5 turns out.



    Looks like my left plug is getting close! ...right?
    I am planning on doing a carb sync. But also maybe thinking about pulling them apart and giving them a clean...?

    2. I noticed an oil drop forming behind the clutch cover so pulled it off. There were to places that looked could be the culprit.
    Inside it looked a lot like rich grease rather than oil. I've heard a lot about clutch push rods? Could that be the problem? Is that a difficult fix?

    3. To further eliminate carb issues and a potential lingering idle, I sprayed my carbs with carb cleaner with the bike idling to listen for vacuum leaks. There MAY be one around the circle thing on the outside of my left carb. The thing that rotates with the throttle. Would that be the butterfly valve? And maybe an o-ring?

    Any suggestions with where to go next are appreciated!!
  4. xschris

    xschris a lifestyle not a trend Top Contributor

    That is where the butterfly shaft seal is. There is one on the other side of the carb too. If you have not done it in a while re-sync the carbs.
  5. Did a re-sync on my carbs. Thinking I may have to adjust my Needle Jet to sort out the bogging issues between 3500-4500 RPM.

    And where can I buy butterfly seals? I haven't been able to track them down!

    One unexpected turn was having a wad of silicone fall off my tank during removal. I guess the PO tried to repair a leak around the mounting tab first with something that looks like JB weld, then with a good layer of silicon.
    Well, I guess neither held. That could be why my bike has been smelling like gas for a few weeks.

    My friend is a welder so I guess I'll employ him. But I might just plaster some more silicon on to get me through the season first.
  6. lemonhead

    lemonhead Budget Biker

    Gas will turn silicone into sludge. Search around, there are a few companies that make gas tank specific sealants, repair putty, patch kits, liners, etc.
  7. Rambo814

    Rambo814 XS400 Addict

    Mikes XS sells butterfly seals for like $5/pair.
  8. BBS360

    BBS360 XS400 Guru Top Contributor

    Also available on xs650direct.
    Ordered a pair myself but they don't even fill the space between the shaft and carb bodies.
    Apparently better stock ones are still available through Yamaha dealers.
  9. Rambo814

    Rambo814 XS400 Addict

    Good to know. I was actually thinking about buying some.
  10. xschris

    xschris a lifestyle not a trend Top Contributor

    Remember each carb take one on each side of the body. So you need four to do both carbs.
  11. I got half a can of Red Kote from a buddy, I guess I will start with that. But again, I want to wait until I am not riding to work everyday...

    So you would not recommend the seals from XS650direct?
  12. BBS360

    BBS360 XS400 Guru Top Contributor

    Their shipping price went from $3~ to $18 when I selected shipping to Canada. :(

    Mine seem to be ok but i did pack them with grease and that could be masking the issue.
    Supposedly the rings are designed to expand when the vacuum sucks on them but it seems like a pretty big gap and I've read other negative reviews.
    With the Yamaha rings readily available I'd recommend them instead.
  13. So after a carb sync, not a lot has changed.


    There is also popping/backfires with engine braking.

    Is it common for the plugs to be so different?

    I've tried tuning using only the air mixture screws (currently left is 2.5 turns out and right is 2.25) but I think I need to look at jetting for the first time. Where should I start?
    I also want to redo my butterfly seals, is that tricky?
  14. Nwayne

    Nwayne XS400 New Member

    Excuse me if I missed it, but what battery are you using?
  15. kshansen

    kshansen XS400 Addict

  16. xschris

    xschris a lifestyle not a trend Top Contributor

    I think when I got them they shipped them in separate packages. :confused: Also when I bought them they where on sale I think I only paid $20 for all four shipped.

  17. I am using a generic battery I bought or $60 from a guy in town, not sure of the name. It was the smallest he had that could turn E-Start, only a tad smaller that the stock battery.

  18. I ended up getting 4 from the local Yamaha dealer. Came to just over $20 which isn't cheap, but with the Canadian Dollar where it is I think it was the cheapest option!
  19. xschris

    xschris a lifestyle not a trend Top Contributor

    Remember that they will most likely last another 30 years. Just try to avoid ethanol gas:wink2:.

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