The XT550 Thread: Info, Stories and Mods Inside!

Discussion in 'Thumpers' started by XTwarrior, Feb 16, 2010.

  1. XTwarrior

    XTwarrior My bike is older than me

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    Ya, I have it geared high for commuting MPG. The bike hasn't seen a trail in 3 years unfortunately, but that is also why I'm making it more of a road bike.
    #41
  2. XTwarrior

    XTwarrior My bike is older than me

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    And yet another snowstorm to further delay working on the XT :puke1
    #42
  3. byron555

    byron555 Lame Duck Adventurer

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    here is a picture of my bro-in-laws bike with a 2001 yzf 250 fork and a yz465 rear shock. To install the forks the original stem needs to be pressed into the yzf tripple, and a collar needs to be installed in the upper triple stem hole to fill in the extra space.

    Attached Files:

    #43
  4. G600

    G600 Been here awhile

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    My 1983 XT550 won’t run now. The CDI box is shot (I’m 99% sure).



    Does anyone know for sure if the “HYPERPAK” unit for the XT550 has a rev limiter??



    If so, at what RPM’s??
    [FONT=&quot][/FONT]
    #44
  5. netjustin

    netjustin b00b

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    Not to speak of. I ran my Hyperpak XT550 at sears point to a very high RPM -- well beyond peak torque with my 266-x4 megacycle top end. Probably about 8500 RPM. Never hit a hard limit on the ignition side, just a subtle release in arm stretching surge that told me it was time to shift; way higher than the 7K RPM redline on my stock XT600.
    #45
  6. XTwarrior

    XTwarrior My bike is older than me

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    I've never gone past my 'red line' where I can feel it drop off drastically. I want to say it falls on it's face anywhere after 6,500 RPM so I haven't pushed it. I'd go try it out if I could but.....I don't think the blizzard outside approves :lol3
    #46
  7. Bart

    Bart Constant Lurker

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    I think the reason he is trying to ask is because he wants a rev limiter. Nothing will shorten a 4 stroke motor life quicker than over revving, especially a single!
    #47
  8. Zecatfish

    Zecatfish XTique Rider

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    Stock timing curve on the 550 retards about 6500 so you will not want to rev it bast redline.
    From 6500->7000 it goes from 36* timing to 5*, that is why it fall flat on top.
    From what I've read the Hyperpak cures that, and will rev till it blows up I guess.

    Webcams: I read someplace where a fellow changed out to the Mid-Range cam and the the power increase was great, but then he had clutch issues and was going to R&R the clutch discs. Last I seen him post on it. So nothing more is available and I hadn't seen anymore reviews in the power change.
    #48
  9. XTwarrior

    XTwarrior My bike is older than me

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    I believe I read about the clutch slipping problems too on a T-talk thread as well. Granted the XT was never meant to be a hotrod :rofl

    Cleaned up and painted my XZ550 shock. Now I have to draw up the plans for the mount.
    #49
  10. netjustin

    netjustin b00b

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    I agree, but unless the top end is modified (or oil feed is plugged :huh) it should take some effort to over rev this particular one.

    If he does want a rev limiter and can spend a bit more, the MSD looks extremely trick and might be a good piece to try!

    http://www.msdpowersports.com/single_cylinder.html


    I am curious about webcamshafts too. The megacycle has a violent closing ramp that makes me think I will be doing a valve job when I replace my rings.
    #50
  11. XTwarrior

    XTwarrior My bike is older than me

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    She lives!

    [​IMG]




    Needs a good cleaning, but besides a stumble that went away and a random shut off (wasn't taking fuel for some reason) it ran like a champ! I can do 80+ in 4th gear :evil

    What does YDLS stand for?

    [​IMG]
    #51
  12. spacewalker

    spacewalker Adventurer

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    "yamaha dual intake system" i believe
    #52
  13. netjustin

    netjustin b00b

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    you do look suavé
    #53
  14. Bart

    Bart Constant Lurker

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    Valve floating would be an issue. Also connecting rods in those days were not designed to take the loads of such high revs............ for very long.

    Just my 2 cents
    #54
  15. XTwarrior

    XTwarrior My bike is older than me

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    Well here's a question:

    What should I get for a budget minded carb rebuild?

    I looked around for a bit and found a pathetic excuse for a rebuild kit in Canada. I've never rebuilt a carb but I'm sure mine needs it. If the gas is on, it slowly drips gas onto the case. it could be a float setting but it also does it at random, so not sure. Either way it's been about 15 years since it was last rebuilt :lol3

    Also, are DP Sintered brake shoes going to be my best bet for stopping power in the front?
    #55
  16. G600

    G600 Been here awhile

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    XTwarrior, if the float height is correct and the needle looks ok, you could try to polish the float valve seat with some fine steel wool. My 550 had a random carb leak problem. Everything looked fine including the valve needle, and the seat looked clean. But after some polishing (seat, not needle) the leak stopped.

    Yours must be missing, but there is supposed to be a tube that runs from the carb’s overflow down below the engine. No need to let the gas drip onto the engine…
    #56
  17. XTwarrior

    XTwarrior My bike is older than me

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    Ya, it looks like it is missing. I'll have to pull the carbs I guess. I'm going on vacation Friday so I won't be able to do it for a bit but if I could stop the random gas leak my bike would seem 25% less trashy :D

    I need to torch the frame and find the proper tools to 'blow' the dent out with air in my gas tank.
    #57
  18. G600

    G600 Been here awhile

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    Thanks guys, for the info regarding the CDI's.

    After doing all the measurements, I still was not 100% convinced my problem was the CDI box. I have worked on burned stators that measured within specs.

    So I decided to build myself a cheap/simple CDI to be absolutely sure before buying a new one. New CDI’s are not cheap. Besides, I like messing with stuff..

    A guy has done a lot of research and development regarding the CDI’s on the older XT’s, and he has generously put his findings on the web. Really nice of him!!!
    http://www.transmic.net/en/home.htm

    So I decided to build the simple analog CDI. To be honest I wasn’t sure it would work…

    I have not messed with PCB (printed circuit boards) since in school many years ago. But no problem, the cost is low, so no big deal if the thing would not work.

    The build:

    Board blueprints

    [​IMG]


    The board in solvent!!

    [​IMG]

    [​IMG]


    Board and components…

    [​IMG]


    Board, long legs on the components, as I planned to re-solder the board.…

    [​IMG]


    Board again…

    [​IMG]


    Notice the professional wiring…

    [​IMG]

    [​IMG]


    So – I took out the plug to see if I would get some sparks. Kicked the bike… BLUE nice sparks…. YYYeeeess… So the original CDI was the problem, no doubt.

    Screwed the plug back in, didn’t really expect the bike to start…. But it did…. And idled just fine. Gave it some gas…. Reved up fine…. And returned to idle and sat there purring.. Wow. Didn’t expect that.

    Maybe I can test-ride the bike next week. It will be an interesting ride, the spokes are loose and the swingarm has play, the bike will be wobbling all over the place. Still I am kind of excided to test it, I’ll never grow up I guess…

    I’m sure the engine will run kind of silly with this DIY CDI, with the timing advance of 12 deg jumping to 36 deg in one step. But I will keep the CDI as a spare part, since it works. Just need a waterproof box to house it in…

    Now for the big question… to buy a decent CDI or build my own programmable one …. Hmmmm…
    #58
  19. hobie1dog

    hobie1dog Not a Sheeple

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    G600.....you made that look SOOO easy. You da man.:clap
    #59
  20. netjustin

    netjustin b00b

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    Call me crazy, but I think valve float should never be an issue if your springs are properly spec'd and still doing their job. Then again you probably know more about this motor than I do. Wouldn't take much. :)
    #60