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Vroom's 79 Build Thread- scrambler/brat?

Discussion in 'The Garage' started by Vroom4, Dec 8, 2012.

  1. Vroom4

    Vroom4 XS400 Addict

    I used gold engine enamel from the local auto parts shop...:laugh:
  2. Vroom4

    Vroom4 XS400 Addict

    Okay, so I've run into an issue I am having some trouble diagnosing...:mad:

    Symptoms: The bike starts to die once it gets hotter. It won't hold the idle and has even died while in motion:yikes::wtf:
    - I would give it more gas and the revs just wouldn't climb. It just slowly looses power till she stalls out.
    -Once she dies, kick-starting it will barely get it going if at all.

    Here is the odd part. If I let the bike cool off, it starts right up! :confused:

    Here are my thoughts on what it could be thus far:
    - Battery is not holding charge. I've ordered a ballistic battery(been planing on getting it any way) to see if that helps. My current battery is a re-fill-able liquid type, and I've used two different ones and both have the same problem.
    - Charging system is somehow not charging or loosing charge/draining the battery. I've tested the system using a multi-meter and she reads about 12 volts while at idle and climbs while revving in neutral. My understanding is that if the volts climb while revving it, that means the charging system is at least working. Could it be a bad reg?
    - The coils? :shrug: Could they be heating up to the point that they don't work?

    She only started having this problem after the re-build(to the best of my knowledge) so I'm wondering if something could be wired up wrong or maybe the timing on the points isn't accurate enough?:shrug:

    Any ideas would be great.

    Oh, and a new blade-type fuse box is already on it's way:thumbsup:
    - I picked up a six blade block so there is an extra fuse slot for my eventual usb charger:D
  3. Recreateme

    Recreateme XS400 Addict

    I can't imagine this being battery related... Once you're battery drops enough to cut the power off to the bike while in motion its not going to start back up again after waiting a bit. I would rule out battery here.. You could always bring a volt meter to check this theory.

    I read somewhere (here or xs650) of someone having this issue, and i believe it was an issue with the coils heating up to much and shutting down after a while. Maybe run some diagnostics on them?
  4. Yeah, definitely sounds like the coil. Next time it happens, touch the coils and see if they are really hot.
  5. Recreateme

    Recreateme XS400 Addict

    lol - Mechnewb, maybe don't touch them in case they are really hot... but hover over them, like a campfire see if they radiate a lot of heat.
  6. xschris

    xschris XS400 Guru Top Contributor

    An IR temp gun would work the best. It's very handy when tuning also.
  7. Vroom4

    Vroom4 XS400 Addict

    Thanks guys:thumbsup:

    I'll have to do a little bit of testing to find out. Have not looked at how to test the coils yet, but I tested the battery and it is getting extra juice while it revs.

    It makes sense that the coils could be over heating and stopping. Though, I didn't have the problem prior to the rebuild... that's just annoying:banghead:

    Anyone know a simple explanation on how to test the coils?

    My only other theory would the valve clearances...? Could tight valves cause this symptom :confused:
  8. xschris

    xschris XS400 Guru Top Contributor

    How to test coils is in the manual witch is in the tech section on here. If you haven't set the lash on your valve it's always a good idea to do it. It would be one more thing to eliminate.:wink2:
  9. MrStubb

    MrStubb XS400 Addict

    I rebuilt my first 350 and had similar issues. It turned out that my Cam was a little out of time. On our bikes I don't know if this is possible but you may want to look into it. On GM small blocks you can get off set keys for the cam gear. I had to use a degree wheel and a drop indicator to get it right but MAN did it pick up the ponies and got great mileage to boot.
  10. Vroom4

    Vroom4 XS400 Addict

    Had a chance to snap some pics before she started giving me issues...:doh:


    The other bike belongs to my brother. We picked it up as a runner for dirt cheap as his daily transportation. Of course we had to tear into it right away :thumbsup:

    '85 cb450sc nighthawk
  11. Vroom4

    Vroom4 XS400 Addict

    - Wired in a new blade-type fusebox with 6 blades for extras
    - Re-installed h-pipe intake and and different pods
    - Did valve adjustment(WOW! what a difference that makes:eek:)
    - Adjusted clutch
    - Installed a smaller battery(Ballistic 4cell)

    Put over a 100 miles on her this weekend. Rode down to Miami for the Black Sunday swap meet. Great time and I picked up an awesome little honda tank:D

    Up next:
    - New Seat(im going to try to make one myself and use some spare stock mounts to hook up to the oem location; I want it to be interchangeable to the oem.
    - Wire in a waterproof usb charger that only
    - New solid state regulator(probly an R292 unit) to help with idle charging.
    - A bit more tuning with the mixture(does anyone have a good way to make adjustments with tank on???)
    - Clean up all the rust off the new tank(going to be trying out an electrolysis method!)
  12. Vroom4

    Vroom4 XS400 Addict

    I went a little crazy with ordering stuff on ebay...:doh:
  13. willem

    willem XS400 Guru Top Contributor

    Nice pics :thumbsup: if I hadn't said so already, I'm really diggin the black and gold color scheme. Curious what you got on ebay now though :)
  14. Scorpio1963

    Scorpio1963 XS400 Guru Top Contributor

    Rode down to Miami for the Black Sunday swap meet. Great time and I picked up an awesome little honda tank
    LUcky man to live where its warm all winter.
    WE have a swap meet this weekend at the Gilbrator trade center Im probably going to to go brows around.
    Also you got 2 bikes are his and hers or just yours?
  15. Vroom4

    Vroom4 XS400 Addict


    Scorpio: Not sure what you mean, but the xs400 is mine and the cb450 belongs to my brother.

    Parts arrived!
    - Ninja 250 mc and caliper + new pads
    - r292 solid state regulator

    Will be installing both this weekend and getting started on a new seat. The brakes and seat should be fairly straight forward. My only concern is the new Reg. I'd like to wire it into the old plugs, but i'm not sure which wire is which on the new reg. Any ideas?
  16. xschris

    xschris XS400 Guru Top Contributor

    Are those RFY shocks on your brothers bike?
  17. Vroom4

    Vroom4 XS400 Addict

    I don't think so... we got them off ebay from china:laugh:
    I guess they look the part tho :thumbsup:
  18. Vroom4

    Vroom4 XS400 Addict

    So last weekend we found an awesome park with about 21 miles of trails and camping paths here in south FL. We couldn't believe we found a good place to test out the 50/50 tires so close!

    Rode for about 5 hours and only lost two bolts! :laugh:


    Should have some free time to work on the new seat this weekend... I hope:doh:
  19. Scorpio1963

    Scorpio1963 XS400 Guru Top Contributor

    I think the bike is realy great looking just the way it is,what are wanting to do with the seat?
  20. Vroom4

    Vroom4 XS400 Addict

    Good news and bad news...:doh:

    Got the ninja250 brake mc on. Soooo much more feel on the brakes! Couldn't be happier with the result. Still have to rewire in the light switch though

    Here's a shot of how I wired up the fuses. It was working great till today:wtf:

    I decided it was time to do the r292 reg swap. My idea is that this would help with charging of the battery while idling. Shouldve been a direct swap.

    Mounted it on the side of the battery for easier access in the future. I followed Drewcifer's reg conversion thread and wired it as...
    Orange & Yellow - Brown
    Black - Black

    Shot with the Ballistic Battery and tool kit relocated into the oem battery box

    The bike is running great, with one exception...

    I tried to wire in a usb charger, and tried to create an extra fuse spot for it by doubling the headlight fuse input over to another fuse. Not only did it not work, but now my headlight and gauge lights don't work:yikes:

    I removed the usb charger and tried putting everything back to the way it was, but no-go. All the fuses are fine and the main fuse line and ignition fuse line draw power. The bike turns over on the starter and idles fine. I checked the wiring into the headlight fuse and nothing... no power is even going to the fuse now:mad:

    I'm checked and rechecked all the lines and fuses.

    Everything looks right but there is no power to the headlight fuse and I'm at a loss...

    Any ideas??? :shrug: I Need Help!!!

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