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Tx750 madness.

Discussion in 'The Garage' started by ShaggyMech, Mar 30, 2021.

  1. ShaggyMech

    ShaggyMech Socal Mechanic.

    Wouldn't you know it! Georgia registered it! Now that the safety inspection is done. Time for some real work. The new sprag is on the way. Full seal kit in hand. I have a vendor we use at work trying to locate a balancer chain using all the dimensions from here. Carbs have been rebuilt but I find a little on the rich side, so they will be getting a rework and modified for better flow and response. Tytronics cam position sensors to replace the points are ordered. I can make my own ignition box or use a box from dyna or zeeltronics to control spark. Getting the elephant foot valve adjuster mod, as well as hopefully a reworked head. It's going to be a fun project.
    gggGary, jetmechmarty, Grimly and 4 others like this.
  2. azman857

    azman857 '80 XS 650SG Rider XS650.com Supporter Top Contributor

    ROCK ON! Please take lots of pics and post often with your progress.
    gggGary and ShaggyMech like this.
  3. jonesey

    jonesey Dyed in the wool 650 nut

    Gday ShaggyMech and all
    I'm also a TX 750 owner and am rebuilding one now and have been for a while. Very interesting stuff you've posted so far. Well this evening (here in SA) I was on the TX forum and found that Speedandsportinc.com up to July last year had 30 Nos TX 750 Tsubaki balancer chains in stock. Now i found this reference in the New member section so You might of missed it. Also there's a reference to an article in a "94" Classic Bike Magazine about a replacement with a DID O6B-1 which size wise is the same as the starter chain which is just slightly wider (0.5 mm). I failed to find this article. also on that DID number I'm not sure if the first digit is a O or a zero. Ho Hum.
    Again I remember in the fuzzy depths of something a Kawasaki chain being used but its probably the DID chain used by Kawasaki. Hope this is of some help. Cheers Mate.
    gggGary, ShaggyMech and arcticXS like this.
  4. ShaggyMech

    ShaggyMech Socal Mechanic.

    Hello there jonesey, I saw the article involving the DID chain, but someone had mentioned that the side plates were thinner so they were worried the chain would stretch sooner than later. I have a 74 model with the adjustable tensioner so it would only mean sooner intervals of pulling the pan and checking the backlash of the counter weights. Not terrible, but I intend on having this be a pretty reliable rider, and also something that I can do repairs on easily if needed. The Speedandsportinc has the chains, but i am hoping to find a relatively cheap alternative that could be used by those that can't afford or get NOS parts. I am also trying to create a log of alternatives or better parts. Such as the electronics, and hard parts trying to increase the lifespan and durability, without sacrificing at least a semblance or originality,
    gggGary and arcticXS like this.
  5. ShaggyMech

    ShaggyMech Socal Mechanic.

    Perhaps you can give me some insight here until my service manual gets here. My TX is one incredibly stubborn mule and only starts when it wants to. Kick the crap out of it and still maybe starts 1 out of 100 times. Backfires alot, get fuel but just no bang. I even installed one of those old school ARC boxes that helps the points fire and keeps the plugs clean (as advertised) but still i have set the timing multiple times, cleaned plugs checked tank etc, just one hell of a pain to get fired up. any suggestions?
    gggGary likes this.
  6. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Justa oldschool trick.
    Pull the plug caps just enuff to create a 1/8" gap between the sparkplug post and the cap's inner contact, forcing the spark to jump a 1/8" gap, inside the cap. Usually works when dealing with fuel/oil fouling, quickie fix during a race.

    When it fires up, push the cap down onto the plug.

    Can also temporarily close plug gaps down to about 0.015".

    If it doesn't fire, there's more serious problems...
    gggGary likes this.
  7. 5twins

    5twins XS650 Guru Top Contributor

    If this is cold starts, maybe you missed getting the choke jets clear in the carb bowls. If plugged, the chokes won't work and cold starts will be very difficult.


    Paul Sutton, Rasputin and gggGary like this.
  8. gggGary

    gggGary When a whole one is just too much. XS650.com Supporter Top Contributor

    You are tough Shaggy!
    Full disclosure; I've had 4 or 5 TX750's over the years but NEVER one that ran.
    I do know of several hoarders with small collections of them.
    One I got came with about 20 (oily, used one time) plugs. A gonzo box iggy would be one thought. or if there's room, a tyronics stuffed in there? I wouldn't be surprised if oil control (rings) is part of the starting answer.
    Great to follow along, love your approach, dedication.
    ShaggyMech and Paul Sutton like this.
  9. Rasputin

    Rasputin XS650 Addict XS650.com Supporter Top Contributor

    AB4B9F36-826E-49A8-B420-19C444C92929.jpeg TX750 balancer chain.
    This is my old chain I took out. Notice the thickness of the inner plates.
    5.2 mm between the inner plates.
    It’s quite worn, the difference between compressed, ie pushed together all links and pulled out is nearly 6mm.
    Paul Sutton and gggGary like this.
  10. 5twins

    5twins XS650 Guru Top Contributor

    So much for those thicker links helping much, lol.
    Rasputin and Paul Sutton like this.
  11. Rasputin

    Rasputin XS650 Addict XS650.com Supporter Top Contributor

    28829367-50CF-4AC5-8EB9-E15873F22032.jpeg The balancer chain has to cope with throwing two very out of balance weights round, putting inertia into the weights and taking out the inertia, the whole system makes the parallel twin feel smooth but at what cost, vibes got to go somewhere.
    The crank sprocket and balance weight sprockets are 5mm wide.
    Also the chain “as they found out” needs to have minimal play, hence the latter eccentric spindle.
    gggGary likes this.
  12. arcticXS

    arcticXS XS650 Guru Top Contributor

    Pretty sure the balance weights are not the cause of fluctuating chain load. I'd say the 360 degree crankshaft is the main culprit, as both pistons and both rods have to come to a complete stop simultaneously at TDC and BDC. Which in turn causes the crankshaft to have a fluctuating angular velocity, aka rpm (momentary)
    The balance chain would have just the same operational loads if it was driving a perfectly balanced jackshaft with the same polar moment of inertia.
    What Yamaha SHOULD have done, was to take a page out of Phil Irving's book, and built a 270 degree crankshaft with perfect primary balance, and used balancers to take out the rocking couple.
  13. ShaggyMech

    ShaggyMech Socal Mechanic.

    If I had unlimited money I would personally remove the counterbalance weights and have a custom made crank at 270゚ so that it would just be a really angry rephase motor. I actually install a Ignition Box module just to see if it would help and did but I didn't replace the plugs at the same time. I am switching to iridium's right now to see if that helps. If it is any consolation I have a 48 Jeep and a 51 Jeep as well that are all original so I am very used to keeping ornery angry old Mechanics alive as it is my job as a maintenance technician at a steel factory Built-in 68. Gary is not necessarily the rings but I think it is actually the valve seals that may have gone bad my right cylinder continues to fill with oil I assume from the Cam cavity so I will be taking the motor out and resealing the entire motor top to bottom after I get a few other kinks worked out. I am trying to get my hands on another large starter sprocket but the only eBay one is nearly $300 that is a bit too much to scratch right now. Personally if I had 300 laying around I would probably spend it on my XS considering I am setting up a hydraulic clutch and I still have many items I need to address before I consider it even remotely finished.
    gggGary likes this.
  14. ShaggyMech

    ShaggyMech Socal Mechanic.

    Well, apparently iridium plugs are this things best friend. Started 1/2 kick, no choke. I think I need to step back the pilot jet. 1 turn out on the air/fuel screw and it's real rich

    Attached Files:

    TwoManyXS1Bs likes this.
  15. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    When Pamco pete was selling his ignitions he posted up a 30 mile test ride, same circuit, time of day environment etc. Using his ignition he started off using standard plugs and coils, then different coils and iridium plugs.He went from around 50 odd miles per gallon to about 60 miles per gallon. same speed etc, meaning with an ultimate coil, iridium plugs and his ignition meant the bike was using the fuel more efficiently. Won't stop oil problems on the plugs, but would help to burn the fuel.

    maybe look at a better coil that burns hotter with a longer duration in conjunction with the new plugs
    ShaggyMech, TwoManyXS1Bs and GLJ like this.
  16. ShaggyMech

    ShaggyMech Socal Mechanic.

    I read about the iridium plugs and after running them in my xs it really kicked that thing into high gear on launch. The Arc box i installed is supposed to jump the primary coil voltage higher so that helps generate a much stronger and hotter spark. If i am able to use that in conjunction with a Tytronics cam position sensor than i will use a dyna ignition coil to create the hottest spark possible just short of designing my own CDI ignition (which i already have plans to do). The oil is just a matter of going through all the factory service bulletins and correcting any oil seeping and leakage problems. There is many TX owners in Australia that physically do the work, and i will also throw my own 2 cents into the basket after I do a complete tear down and rebuild with Viton valve stem seals, as many NOS or modern day equivalents to many of the problem areas as i can find. My main focus will be on oil pressure, ability to properly scavenge the oil back to the tank, and even distribution to the head and the transmission. The first gear trans bearings, and the intentionally light oil pressure and blow off valve at 2500 are the main cultprits to a poor oiled and soon to be grenaded engine. after bumping the pressure up to say 60-70 psi or even higher and opening the gallery's to the head mainly the valve stem seals, and a windage/oil collection and distribution tray above the transmission will hopefully cure a lot of the poor oiling. As well as a widened scavenge pump to facilitate the return of the oil. If i can build a roller rocker for the XS i don't see why i couldn't for the TX also. And taking the exhaust cross over and either blocking the center or physically cutting the center out will also alleviate the added heat that can easily burn up a set of valves.
    arcticXS likes this.

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