73 Yamaha TX500 "Dual Sport"

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

  1. MacMcMacmac

    MacMcMacmac Been here awhile

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    Apparently you can get some pods to run right if they have an internal velocity stack. i.e, they have a rubber tube inside the filter itself. Those cheap hipster special conical bird strainers are not the ones. You need some vacuum generation before the throttle plate to get the slides to open properly. With no/low restriction, the diaphragm will not get the signal strength required to reliably lift the slide and needle. This is one reason many jet kits require drilling the signal hole in the slide. I remember the giant hole in the powerband I got when I removed the lid off the airbox on my GS1100.
    #21
  2. modified1

    modified1 Adventurer

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    Makes sense, I noticed the opening at the top of the air box is pretty small. I got the carbs back together now, but didn't get them back on yet.

    I was looking under the engine to see how I would make a skid plate. Kick stand bracket sticks down a little low, but the fancy cooling fins also stick down below the frame tubes a bit. Maybe space a skid plate down a bit and it would end up about level with the bottom of the kickstand bracket anyway. I'd like to move the exhaust pipes up out of the way eventually. Probably put them both on one side.
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    Couple of chunks already knocked out of the fins. You wouldn't think that much stuff would kick up on the road. I figured if I made a skid plate, keep it vented pretty good up front so air can still flow under the engine. I think I have some aluminum road signs floating around. If I want to get too complicated, I'll have to use steel because I don't have anything to weld aluminum. I don't think I'll be scrubbing the bottom too much, probably a stone guard to stop things that kick up would be good enough.
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    #22
  3. modified1

    modified1 Adventurer

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    Finally got it running and ran around a little. Replaced the giant grips that were on it with something I could actually get my hand around.
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    Left the air box out and messed around with various combinations of junk wired in front of the carb throats. I finally got it to run best with some plastic tubes clamped onto the carbs and rags over the end of the tube. They do seem to be pretty touchy. I have some filters ordered. I was reading on a TX500 forum how people tried different stuff. One guy put pod filters on and then wrapped them with gauze and a sock. Some people take out the spring over the slide, which I tried also, but the slide on the right carb gets stuck open sometimes without the spring. Seems like it's close though.
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    #23
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  4. k-moe

    k-moe Long timer

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    Airbox :deal
    #24
  5. modified1

    modified1 Adventurer

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    Never!!!!!!!! Actually, I messed around with stuffing some old foam into the area where the air box was, partially restricting my plastic tubes. It almost runs 100%, but you've gotta be somewhat easy on the throttle and work your way up. I'm pretty confident with the pods on there I can get it to run ok. In the upper mid range there is a somewhat dead spot. Then if you hold it wide open, it will get through that rough spot and pull pretty good. Ran good enough that I went for a short ride today and it wasn't so annoying that I didn't want to ride any more.
    #25
  6. k-moe

    k-moe Long timer

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    That's as good as you're going to get with pods.
    #26
  7. modified1

    modified1 Adventurer

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    Well we'll see. But if that's the case I'll just buy some brand new mikuni round slides.
    #27
  8. modified1

    modified1 Adventurer

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    Unexpected good news! My super cheapo budget filters came in the mail. First I found out they are slightly shorter than advertised, which was good because they clear the frame tubes no problem. Oiled them up and stuck them on. Then I decided to go down the street and see if the thing would run any worse or better than the plastic bottles I had clamped on the carbs.........
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    As it turns out, it seems to run perfect. I didn't have a chance to go too far today, just down the street and back, but the dead spots are gone. I tried getting on it kinda quick and it seemed to take the gas, so I think we're good to roll. Now I just have to change the oil and this weekend I'll see if I can go break down somewhere. I'll see if I can get some video footage.
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    #28
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  9. McJamie

    McJamie STROMINATOR

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    Wasn't one of the ( many )factory updates an extended sump? Or was that just the 750?
    #29
  10. modified1

    modified1 Adventurer

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    I really don't know much about them. You mean you think this is a deeper sump than the original or not?
    #30
  11. MacMcMacmac

    MacMcMacmac Been here awhile

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    I still think these are funky-cool looking and would love to pick up a blue one as a book end for my 650.
    #31
  12. modified1

    modified1 Adventurer

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    I was thinking of painting the gas tank yellow with the black band like the 70's yamaha dirt bikes. Ordered a set of super budget Shinko SR 241 tires. Looked at some larger block treads, but most are around $90-120, figured I could give these a try anyway. I was gonna get some on board footage of some off road testing with the street tires this weekend, but the weather is supposed to be rain/snow here. The carnage will have to wait.
    #32
  13. modified1

    modified1 Adventurer

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    Tires came in the mail.
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    #33
  14. modified1

    modified1 Adventurer

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    #34
  15. Steve in OC

    Steve in OC Been here awhile

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    Sounds like it isn't running right. A TX500 should pull very strong when it's properly tuned, and that one sounds like it is running on half power. Of course, you won't really know if it's running well unless you accelerate hard on pavement; riding it on that dirt trail can't tell you much.

    If those are EMGO filters, they partially block the ports on the carb mouth, causing poor throttle response. It may also be running too lean in midrange (or at any rpm above idle), due to the pods/missing airbox.

    Ditch those pods, they have very poor filtration and your motor will be destroyed by grit, especially if you ride off road.

    I wanted pods too, so I put on some aluminum tubes to provide still air, similar to the stock airbox:

    [​IMG][/URL][/IMG][​IMG]

    For your offroad use, I recommend putting the airbox back on. After you put the airbox back on, compare the performance to your pod setup, accelerating 0-60 mph. I think you'll see that you're missing a lot of power by not using the airbox.




    Note: It is possible to tune a TX500 to run well with pods. But it takes a lot of work. Start with decent quality pods, of course, not EMGOs. First, make sure the carbs are clean, and the butterflys are in synch. Then, do a plug chop at 2000 rpm, with the bike parked on the centerstand. If the plugs look lean, go up one size on the slow fuel jet. Do another plug chop at 2000 rpm. Keep repeating the plug chops and trying different slow fuel jets until you get a nice looking tan plug color at 2000 rpm. Then take the bike out on the road and do plug chops at 4000 rpm and 6000 rpm. If the plugs look too lean at 4000 rpm, you may need to lower the needles. If you get a stumble at the transition from idle to midrange, you may need to raise the needles. If raising or lowering the needles doesn't optimize performance, you may need to drill out the vacuum port on the dashpot cap. You won't likely need to change the air jets or main jets. Careful tuning will get your power back, and then some.
    #35
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  16. modified1

    modified1 Adventurer

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    Thanks for the info. I would try it with the airbox back on, but I don't even have a filter for it. Someone in the past had put a K&N filter in there with nothing to really keep the filter tight against the box to seal it. I could probably jam some cardboard or something behind it just for checking purposes. I know it's not 100% where it should be with that sort of raspy sound. I had some issues the other day with one cylinder cutting out, not sure if one side is way rich and the plug fouls up on that side or what. Didn't get a chance to pull the plugs out. As I may or may not have said before, there was an o-ring around the main jet in the right carb that fit back in pretty loose. Fuel could be getting around it and making it too rich on that side. A couple times it has accelerated pretty smooth without any raspy sound, seems to come and go a bit. I figured I would order some carb kits and clean them out again while I have them apart to put those o-rings in.
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    Hit a couple of off road spots with the street tires still on. It's not nearly as tough to ride off road as I thought it would be. Not that it's super easy either, but I'm getting a feel for it. Had my camera just a bit lower than it should have been, but oh well.
    #36
  17. jussumguy

    jussumguy psuedo intelectual

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    Awesome video, I felt like I was standing on the seat behind you!
    : )
    #37
  18. modified1

    modified1 Adventurer

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    Thanks, once I get everything patched back together again I'm gonna make a video where you can actually see the bike in action. Working on painting the tank, exhaust, and putting the new tires on. Tank has a very slow leak in near the seat underneath. Last guy apparently tried to glue it up with some silicone. I'll clean it off good and seal it up with some better stuff for now, maybe find a different tank later if needed. Doesn't drip, just seeps out. Guy coated the inside of the tank too, so it's pretty much junk anyway.
    #38
  19. modified1

    modified1 Adventurer

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    Pulled the back wheel off and removed the exhaust. Also removed the chain guard. Got the street tire off and tightened up some spokes. As far as I got with that.
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    Under side of the gas tank where the leak is. Cleaned off all the silicone that was around that bracket. I think there's a pin hole either under or near the edge of it.
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    #39
  20. modified1

    modified1 Adventurer

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    Rear tire back on. I didn't realize the exhaust pipes are double wall. Actual pipe is almost 1/4" smaller than the outside pipe. I cut one of the pipes off ride after the flange so I can start my own pipes from there.
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    #40