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'79 xs400 rough>reliable>cafe 'Scarlett'

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


  1. ImageUploadedByTapatalk1428777321.936950.jpg
    Here she is. Not too sure what it should be looking like...
  2. I just gapped my points and set my valves to spec. During this work I pulled the spark plugs (pictures a few posts back). I believe that white indicates they've been running hot. I have never jetted the carbs before.

    Could this be resulting from me installing my uni 2-stage filters with that sticky ass oil? Perhaps it is starving the fuel mixture of oxygen?

    I've tried to rinse out some of the oil. I am a little annoyed at how sticky the stuff really is. I have to use gloves to touch it or else my hands and all my tools get coated.
  3. 16VGTIDave

    16VGTIDave XS400 Guru Top Contributor

    Over oiled filters would act the same as a dirty filter - low power and running rich. The plugs would be black with dry soot - as your are. A weak spark, rich carb settings, or high float levels would all have similar symptoms.

    Gapping the points is a good way to get the bike running so the dwell can be adjusted. It is NOT the final step, despite what some may say. You will need a dwell meter. They are not very popular these days, and most mechanics don't own one never mind know how to use one. Once the dwell is set correctly, you can then adjust the ignition timing.

    Looks like your oil leak is from the tach drive.
    Last edited: Apr 11, 2015
  4. Is there a gasket that I can replace, or something I should tighten up to stop the leak?

    So if I was out all the oil from the filters I might remedy the situation?

    Also, I have stock jetting, but should I also have the air mixture turned out the standard 3 turns?
  5. xschris

    xschris XS400 Guru Top Contributor

    Those plugs don't look bad so I thing filters and jets are ok. There is a seal in the rocker box for the tach drive that you would need to replace for that leak. The manual shows what the ATU looks like. It is your advance for the timing. It is behind the points plate. It needs to be cleaned a lubed from time to time. Agree with dave on the dwell.
    Last edited: Apr 12, 2015
  6. Look on eBay. There's a guy in Vancouver that sells engine seal kits. He ships very quickly and you'll get the kit the same week. The seal took me a little while to get out with picks but it will come. Drive the new one back in with a socket.
  7. A few updates.
    I finally put my Counteract Balance Beads in my tires.
    Then I went to inspect my tach oil leak, as I was exploring I pulled the tach cable right out of the engine. I guess I didn't push the cable in far enough when I installed it the first time. Now hopefully after a good shove and tighten on the locking screw the oil should stay put.

    I also adjusted my idle air mixture screws on my carbs, I previously had them turned out slightly more than the standard 3 turns to work with my paper pod filters. Now that I have oiled foam filters, I figure that they will be restricting the air flow slightly more. I hope that will help balance the mixture.
  8. Strange Air Filter quandaries again...
    Yesterday when I got off work my air filter was hanging down, almost fallen off of my h-pipe. The hose clamp had slipped forward and the top half was off of the filter. Why am I having so much trouble with these things? On the ride home I was constantly looking down making sure I hadn't lost my brand new filter.

    Once I got home I took both filters off and wiped them down real well. I though perhaps some of the oil used on the foam had cause the hose clamp to be lubricated.

    The filters themselves are a touch big for the h-pipe, they go on with a bit of room. Then I tighten them down but if I tighten too much, the H-Pipe will crease under the pressure...So i just tighten enough in hopes that the ridges on the H-Pipe will catch the grooves and hold it tight...

    Any one have any experience with that?
  9. xschris

    xschris XS400 Guru Top Contributor

    I never had. But if you are you could use a bit of pvc pipe in the H-pipe to keep them from collapsing.
  10. I will try to make it to the irrigation shop this weekend. I don't like having to keep an eye on my filters as I go down the highway.

    Would it be alright to rivet any PVC I might find to the H-pipe where the filter would cover?
  11. xschris

    xschris XS400 Guru Top Contributor

    I guess you could but they should stay put after you tighten them up with just the pvc.
  12. I'd try it without making any holes. The less chance for air leaks the better.
  13. I am tired of feeling my rear wheel bottom out on my seat pan whenever I hit a bump, so I am planning on buying some new rear shocks. I was thinking of going with a 13.2" and a quick browse on DCC brought up these:

    13.20" (335mm) "Retro-Slim" Chrome Eye to Eye Shock Absorbers

    13.20" (335mm) Chrome Eye to Eye Shock Absorbers

    Anyone have any experience with these two products?

    Also, I need to replace my sealed beam headlight and want to upgrade to an H4, anyone use this?

    6-1/4" Gloss Black H4 Headlight Assembly
  14. OleDoc

    OleDoc FREEBIRDS MC Central NY

    I am gonna try a 750 Vulcan headlight(I'm a regular on vn750.com as I have one)will put a pic up in my build thread if I use it
  15. I just gapped both my plugs and figured I would take another stab at this whole tuning thing...

    Here is my set up and findings:
    Stock exhaust, Uni 2-stage oiled filters, air mixture 3 turns out.

    I find the bike runs decently except for 3-3.5K RPM where is gets a bit bogged down.



    Any guidance?
  16. Wolfe_11B

    Wolfe_11B XS400 Guru Top Contributor

    Left plug looks too white(lean). Right plug has too much shadow on it to make a good call
  17. xschris

    xschris XS400 Guru Top Contributor

    Right is way too rich, left looks rich also but the tip is white which would mean lean. What are the needles set at and what size mains? The plugs should look something like this.

    Attached Files:

  18. All jets and needles are stock.
    Should I turn my mixture screws in a bit?

    What other variables could there be? Spark wire length? I opened the gap on my right spark plug after the picture was taken (it was tighter than the .711mm feeler I had). Put in high octane fuel for the first time. I would love to be able to sort this out using mixture screws and without re-jetting.
    Last edited: May 13, 2015
  19. xschris

    xschris XS400 Guru Top Contributor

    I set my plugs to .030" But I also use iridium plugs and non-resistor caps. So stock jets ( 42.5 pilot, third clip for the needle and 132.5 main. This is what you have, right. The mix screws set to 3 turns out, right. I would try 2 turns out and go from there. The wires for the 79 xs400 4 ohm coils are non-replaceable so length is not an issue as long as they make it to the plugs.
  20. Just to clarify - to turns out in total, not in addition to my current 3 turns out.
    How is the left plug both rich and lean? :confused:

    Another note: there is some minor pop/gurgle/backfire occurring when I slow down with the engine.

    This weekend I am going to clean my spark plugs off to get a new fresh reading. Set my mixture to 2 turns out and hope for the best...

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