73 Yamaha TX500 "Dual Sport"

Discussion in 'Old's Cool' started by modified1, Mar 27, 2016.

  1. modified1

    modified1 Adventurer

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    Bought this TX500 off craigslist for $600 maybe 6 months ago. Was listed as a running bike, but the right cylinder wasn't firing half the time. Turns out Compression and spark were good. Spark plug came out hard on the right clyinder and pulled the threads. Got those fixed up and put in new plugs. Right cylinder finally fires with some adjustments and with a load, but gets missing at idle. Took it for a short run down the street and got it up to 70mph. Seems to run pretty smooth and shift ok.
    [​IMG]

    My idea is to strip this thing down and turn it into a desert racer/scrambler. I didn't do too much research on the TX before I went to buy it. So of course I didn't read about hard to find parts, cracked heads, and balance shaft chains, ect. Even read one article somewhere about buying old 70's bikes, which specifically mentioned one model you shouldn't buy......TX/XS500's. But that's all the better anyway. The point is to make things work that aren't supposed to. This one has 23,000 miles on it and seems like the engine is ok. I figured if it blows up I can get an old honda twin and jam it in the frame.
    [​IMG]

    Previous owner stated he had cleaned out the carbs, but I think he missed something. Removed the pain in the neck airbox and got the carbs out. I'll put some K&N filers or something right on the carbs to make carb work easier. Then once it's running, I'll ride around a bit before I really start hacking. Decide if I want to continue with the project or just bail on it. Has new tires, but I'll need to switch to some dual sport tread. Probably cut down the fenders, remove turn signals, smaller seat, get rid of the beat up mufflers, skid plate. Good thing is it looks like it's been stored inside all it's life, so there's minimal rust and the chrome rims are nice. It's clean, but also something I won't feel too bad about hacking up. Open to all suggestions and or criticism.
    [​IMG]
    #1
  2. McJamie

    McJamie STROMINATOR

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    Great Dual-Sport, if you like hiking.
    #2
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  3. Andyvh1959

    Andyvh1959 Cheesehead Klompen Supporter

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    Pull the head and check for cracks. The TX500 was a great looking bike and engine. But the engine was known for two major issues: 1. the cam chain routing was long and complicated, requiring very consistent adjustment, 2. the head design had a weak area that could crack if the head got too hot.

    Don't mean to rain on your parade, but like said above, hope you like hiking. Always carry a lot of water to drink.
    #3
  4. modified1

    modified1 Adventurer

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    Aw come on, this is obviously an excellent choice for an off road machine. Maybe if I get it real hot off road and cook the head, I won't have to worry about adjusting the cam chain...... I'll have to do some more research on engines. We're the later years better for the head issue? Maybe I could find something that will drop right into the frame if needed. Otherwise I figured I could just weld up some new mounts to fit something else. For now I guess I'll just see how it runs and go from there. I don't really care much for inline 4 cylinders, any air cooled twin with around 40-50hp would be good.
    #4
  5. sparkingdogg

    sparkingdogg Prisoner In Disguise

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    I am pretty sure that bike has CV carburetors, I had one years ago. Expect it to never run right, if you take the air box off and replace with filters. :deal Might wanna keep the air box. Good luck, looks like a (heavy) fun project. I had a '73 CL350 that would run circles around the TX500 in the woods, it's much lighter. Be interesting to see what you come up with though. Good luck!
    #5
  6. modified1

    modified1 Adventurer

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    Thanks. I've heard some guys switch to mikunis. I was thinking about what to use if I were to switch engines. Maybe an XT550 or 600, stay with the yamaha brand at least. I could probably pick one up pretty cheap not running and without a title. I don't think beat ones bring too much. You'd have slightly less power, but probably a lot less weight and being a single should fit in the frame easy. Pretty much have to stay air cooled or it's going to look too modern.
    #6
  7. Pvanlan

    Pvanlan n00b

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    I'm in the same boat as you, bought an old XS500 because it was $300 bucks and a fun project. And because you dont see many (even if it's for a good reason...).

    Few answers: No, I couldn't get it to run right with pods, however, I had a few other issues too, so that data point might not be valid. And yes, the later heads are 1 piece to reduce cracking issues. Also, later models use slightly different timing for cooler running. Also, the Keihin CV carbs were ditched for Mikunis in the later models.

    Question: I also have a stripped spark plug hole that I just ordered a backtap for. What did you use, and how did it work?
    #7
  8. modified1

    modified1 Adventurer

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    Thanks for the info. Makes me feel at least a little better that I could scrounge parts to keep the same engine if I had too later. I still had some threads left in my plug hole, but they were just chewed up some. I just used a regular tap with some grease on it to keep shavings from falling into the cylinder. I don't remember off hand what size it was. Worked out pretty good as far as I can tell. I put that plug in kind of easy just in case.
    #8
  9. GR0NK

    GR0NK Got some screws loose!

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    Looks like everybody is bustin' your balls over this thing. :cob

    I wouldn't sweat it. Get her going, don't expect too much from her and maybe get a AAA membership. :wink:



    Sean :bmwrider
    #9
  10. sparkingdogg

    sparkingdogg Prisoner In Disguise

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    Lol not trying to bust anyone's balls, have just seen a lot of people put pods on CV carbs then spend the year trying to get the bike to run right. If you really want to run pods on a CV carb, you "might" be able to get away with it if you can use the air box ducts in between the carbs and pods. There's a little oval port on the inlet side, pods interfere with how the port is engineered, and it messes with the air flow. The oval ports are part of what makes the throttle valves move. Hope you post pics as you go, it's always fun to watch a build!
    #10
  11. bajaburro

    bajaburro Ancient Adventurer

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    thats never going to make a dual sport,wrong model for that.street bike yes.
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  12. Garbln

    Garbln Been here awhile

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    I had one in the late 70's early 80's not a bad bike but not a great one ether. Keep the cam and counter balance chains adjusted and they are OK, it shouldn't vibrate much at all for a vert twin and will rev pretty high. The head oil leak on the early years was a problem but in reality it was mainly a cosmetic problem, it made a mess on the front of the engine. Mine had the problem I just learned to live with it, cracks and all. I never actually heard of any major failures because of it, just that it made an ugly oil stain down the front of the engine.
    #12
  13. GR0NK

    GR0NK Got some screws loose!

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    +1

    I would just put the airbox back on and run it like that. This way you have the factory settings to make it run properly.



    Sean :bmwrider
    #13
  14. GR0NK

    GR0NK Got some screws loose!

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    I dunno. It really only looks to be a Scrambler pipe and some knobbies away from being able to run dirt roads and such.
    Cut the back half of the seat off and clean up the subframe so the fender is nice (maybe a small rack) and throw a matching chrome shorty fender on the front. The bars already look to be high enough with good sweep so the riding position should be good.



    Sean :bmwrider
    #14
  15. modified1

    modified1 Adventurer

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    I'll do a little experimenting then with the air box situation before I toss it. I just don't like how tight of a fit it is to remove when you want to get to the carbs. Realistically, you shouldn't have to take the carbs off every five minutes, but that's just the stuff that gets in my head. Maybe I could make some inserts or something if air flow is an issue and stick them in the pod filters. As far as the cylinder head cracking deal, that wouldn't be so bad if it just causes an oil leak and doesn't interfere with running.

    So I did find a little dirt in the carbs, and by the scratches in the tarnish on the inside of the bowls, it looks like the previous owner did try cleaning them out at some point like he said. However...This plug covering the low speed system seems to be missing and I'm pretty sure I didn't lose it. Happens to be on the dead cyl side. Maybe that would explain why that cylinder misses at idle... Anyway, no big deal. I found a billet of aluminum close to the right size, ground it down a bit and hammered it in. Purchased a new battery. Couple of days and we'll have a running machine again.
    [​IMG]
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  16. Pvanlan

    Pvanlan n00b

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    I actually did enjoy that about having pods, although ironically, having pods was part of why I was pulling my carbs so much... haha. And now that I have an airbox, its such a huge pain in the ass to pull carbs. Especially with hard rubber boots now.
    #16
  17. sparkingdogg

    sparkingdogg Prisoner In Disguise

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    If it was easy, Girl Scouts would be working at bike shops. :D
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  18. jimroid

    jimroid Long timer

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    image.jpeg Been there, done that. Worked great.
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  19. modified1

    modified1 Adventurer

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    Cool build! Still a TX frame with different forks and rear arm?
    #19
  20. jimroid

    jimroid Long timer

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    YZ250 rolling gear/arm/brakes. YZ450F muffler.
    #20
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