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Need Help with Tuning Frustrations

Discussion in 'The Garage' started by JCE, Dec 15, 2018.

  1. JCE

    JCE XS650 Enthusiast

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    I picked up a 1980 hardtail project bike (my first XS650) earlier this summer that was mostly complete but ran rough. The previous owner really didn’t know anything about the bike or its history but It was a good deal so I rolled the dice.

    The Bike (initial configuration as purchased):
    1980
    BS34 jetting: 45 pilot, stock/fixed needle,145 main, mix screws 3 out, floats L/R @ 23/24.5mm respectively
    Stock TCI w/ battery
    Barebones wiring & kickstart
    New plugs gapped @ .028”
    Pod air filters
    2-into-1 open exhaust.

    Problem: The bike starts and idles great (I'm in California, ~400' USL) but severely stumbles 0-1/4 throttle, then above about 2k rpm bike’s midrange hits good and pulls hard through top end. My first thought was a lean idle circuit and possibly needle circuit so I focused my energy there first.

    Things I’ve done to initially correct/inspect:
    Fully cleaned & serviced carbs and ensured all passage ways (especially pilot circuits) are clean/clear, diaphragms are intact, pods aren’t covering intake port jets, replaced float valve and seat oring, inspected mixture screw oring, and reset floats to 27mm (I’ve got the brass floats).

    After re-installing carbs, syncing carbs, test riding, and not getting noticeable improvements (even tried dialing the mixture screw in ¼ turns from 2-3.5 out with no avail) I decided to go back and establish a baseline on everything since this bike’s history is an entire unknown.

    Good compression in both cylinders, check
    Good fuel flow, check (gas cap venting properly & inline filter working)
    Cam chain adjustment, check
    Valve adjustment done (intake .003”, exhaust .006”)
    Good battery voltage, check (static voltage 12.9V)
    Good spark, check (kicked over with spark plug grounded to head)
    Coil voltage good (0.15V drop from battery to coil)
    Coil continuity/resistance good (primary= 2.5 Ω, secondary= 12.9k Ω, plug wire to coil core=∞ )
    Alternator pick up resistance good (blk-gry=719 Ω, blk-org=764 Ω, gry-gry=1.48k Ω )
    Active/live pick-up signal test, good (used LED lights plugged into blk&org pick-up leads to confirm)
    Regulator/rectifier tested good (A/C measurements wht-wht = 10.6-10.9VAC for all 3 combos @ idle)
    Charging voltage is good (measured 14.72V @ ~3k rpm)
    All connections checked & cleaned for corrosion


    After confirming I’ve got both good fuel, spark, and charging system I tested for air leaks around the known culprits (boots, throttle shaft, etc.) since I still felt a lean condition was a strong possibility. Also double checked the pods aren’t blocking jets (good there too). I tested and re-tested about a half dozen times, each time pulling, cleaning and rechecking my work. Yes lots of beer and cursing!

    I then decided to try the Canadian needles and emulsion tubes (as a set) on various clip positions (from 2-4 from top, 3 is middle position) with no real improvement. Also tried going up on the pilot jet from 45 to 47.5, then back down to 42.5 all without any real improvement from 0-1/4 throttle (taking off from a dead stop).

    At this point I have done everything I can think of with carb tuning within ranges of settings that are known to work good and feel like I’ve narrowed this problem down to a single ‘untestable’ component, the Ignition Unit. Or at least that’s my uneducated hunch unless I’ve overlooked some things.

    When I used my advance timing light (set to 0) to check the timing of my TCI ignition, I get a steady strobe with idle timing retarded by ~1-2° (just to the right of the F mark). But when I try to slowly rev engine it begins to stumble as usual AND my timing light begins to misfire in conjunction with the stumble. Once I get the rpm’s above about 2,000 rpm the engine smooths out (as well as the timing light) and I can accurately make out the advance timing mark as it approaches the fully advanced position. This further leads me to believe the stock Ignition Unit has something to do with the low rpm stumble, not a carb issue.

    If you’ve read this far then you are a true gear head and for that I thank you. If you see anything that I’ve missed and/or have some input to help get my tuning woes off high-center, I would very much appreciate the input. I’ve ‘read til I bled’ in hopes to solve by search but I am left with the reality that I need some real-time help on this one. Thanks in advance!
     
    Wulfbyte, Mailman and Jim like this.
  2. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    The only way to know for sure is to swap out the TCI box... but yeah, with the timing light jumping around like that, I suspect you're right. There's two pickups (hall effects) on the stator. One for full retard and one for full advance. The TCI box uses those two signals to build an advance curve based on rpm. Sounds like it's confused in that range.
     
    TwoManyXS1Bs, JCE and gggGary like this.
  3. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    Wow you are a THOROUGH fellow. Good on you!
    Sure looks like it's pointing at the TCI
    couple maybes and a possible help idea.
    #1 Pull the voltage regulator plug, test ride, see if it changes how it runs. Weak pickup magnet issue?
    #2 try a different air filter? the forum collective.
    [​IMG]
    reports severe slide flutter issues when small pleated air filters are used.
    Try a different TCI, I might be able to help with that.
     
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  4. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    That wouldn't account for the timing light goin' wonky... but yeah, worth a shot. Just take the filters off and run it down the road without 'em. See what happens.
     
    TwoManyXS1Bs, JCE and gggGary like this.
  5. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    145 main is huge on a BS34. 132.5 is stock....
    Just a story here.
    stripping down a set of PO molested BS34's found 45 pjs and 145 mains evidence showed they had been used after the jets were installed but not a lot.
    The light bulb came on when I dug a bit deeper.
    both looked like this. Can't imagine it ever ran decent.
    OK story over, :rolleyes: back to your off idle stumbles.
     

    Attached Files:

    JCE likes this.
  6. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    riffing; a severe mis-carburation could cause short term spark plug fuel fouling, misfires?
    Do actual float bowl fuel level checks with a sight tube? I think I may have seen over full float bowls dump fuel into the intake when the slide opens.
     
    Last edited: Dec 15, 2018
    Jim likes this.
  7. JCE

    JCE XS650 Enthusiast

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    Heh...heh, Thank you sir!
    Ive read up on several comments regarding hit & miss pods and have experimented with 80s wrist sweatbands over the pods to evoke a change, even if bad. Nada!

    W.r.t. #1, never tried this one. Didnt know the bike would even run with the R/R disconnected but will definitely try.

    If you are willing to help on the ignition unit swap/test I would be very grateful. If nothing else it would confirm the hunch. If confirmed then Id try and source a cheap used unit or just go with a pamco & advanece at that point. Ill pm you on that point.
     
    Jim and gggGary like this.
  8. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    Just got a couple TCI boxes in, need to ride test them, maybe tomorrow, got the ice chipped off the driveway....
     
    peanut, JCE and Jim like this.
  9. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Another thought..... along with an rpm specific problem (yours) is the possibility it's vibration specific. As in that particular vibration frequency and amplitude causes an electrical connection to... well, not connect. Vibes could be causing a poor connection to start opening on the coil, TCI box, pickups... hell, even the kill switch. Something to try is to take a pair of needle nose and just twist the male pins slightly to get a better connection. Warning: if you're not sure what I mean by that, don't try it. :rolleyes:
     
    Last edited: Dec 15, 2018
    peanut, delagem, TwoManyXS1Bs and 2 others like this.
  10. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    this_thread_is_worthless_without_pi.gif
    Always helps to see a couple pics of the bike!
     
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  11. JCE

    JCE XS650 Enthusiast

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    Definitely played with this several times, once on the bench to dial in the clear tube fuel level. Then re-checked, with carbs on the bike to ensure I was getting level at or just below (within 1mm) bowl flange. These brass floats are not square and are finicky to boot so the clear tube was necessary.
     
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  12. JCE

    JCE XS650 Enthusiast

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    I appreciate this sentiment 100% and have gone through my connections thrice over. I never underestimate connetion integrity. Good advice!
     
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  13. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    And just to echo what Gary said.... good on ya for coming up here prepared. :)
     
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  14. JCE

    JCE XS650 Enthusiast

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    Lol! Yeah, we're all photo junkies me included. Need to see what Im working with here. I have big plans for after I get the tuning resolved. Weld in some rear axle drop outs for an HD axle and spoked wheel, fine tune a slim fender, possibly a springer front end, few other custom touches, and a fun crazy paint job.
     
    Last edited: Apr 18, 2019
    gggGary, Skip and Jim like this.
  15. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    You should start a build thread. That way you have a journal to reference back to... and we get to go along for the ride.:D
     
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  16. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    At'sa purdy one! Guess I better fire up the basement wood stove and see if I can get "Milwaukee iron" barely roadable this morning, then do some parts testing.
    Do you have a 6 or an 8 wire plug on your TCI?
    Have you looked VERY carefully at the pick up wires where they pass through the sprocket area? Damaged or intermittent wires there are rather common.
     
    Last edited: Dec 16, 2018
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  17. JCE

    JCE XS650 Enthusiast

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    This is a 6 wire TCI on this bike. Just the other night I did see your post with pictures where you ran into that problem but have yet to get a line of sight on that short section of wire running down past the chain. Ill check that out this morning as well.

    UPDATE: Checked those wires very carefully and they are in great shape. Wires and sheaths look like new and the harness anchor points are doing a good job of keeping the wire bundle tucked safely away.
     
    Last edited: Dec 16, 2018
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  18. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    Milwaukee iron just fired on a "spare" 6 wire TCI. Going to get gear on and roll it out for a "road test" right now. Upper 30's,F barely enough parts hung on it to get'r done.
     
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  19. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    Sure occifer it's all street legal n titled licensed, why'd you ask?
    DSCN3405.JPG

    Ran up and down the road great on both the original TCI and the spare, up and down through all 5 gears several times.
    Youse guys running rear brakes only are insane!
     
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  20. 5twins

    5twins XS650 Guru Top Contributor

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    Especially drum rears, lol. In combination with the front, they do add a little to the overall braking effect, but not much. I've never had one on any bike that did a whole lot on it's own, especially at high speeds.
     
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