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Timing nuances

Discussion in 'The Garage' started by NorazDad, Jun 30, 2018.

  1. Hey guys, it's been a while but I have a timing question. I have an 81H with HHB PMA, Pamco with E Adv. new pistons, rings, head, timing chain and guides and ss valves and oil seals. The new top end was due to an exhaust valve that broke and dropped into the piston chamber. Not the issue.
    This is my second Pamco. The first one was faulty. I had to cut the mounting bracket in order to get it to advance correctly and then due to all the futzing about, the solder on the board failed and that was that. I bought a new one and it fit and timed pretty much right up.
    I used a timing light to set the timing. It idles perfectly. My issue is that around 3200 rpm I get a little hesitation and then it smoothens out at 3500. My question is. To get that advance exactly right, would I move the plate toward advance or retard a bit. I hate to screw it up but I would like some opinions.
    I know some will ask about TDC and I am confident that I have the timing mark extremely close, but with the PMA and no woodruf key, there may have been some slippage where I made my mark.
    Anyway, what can I do to rid myself of that pesky 3200 rpm vibration? Or is it just what happens in that range?
    Thanks for the input.
    Here's what it looks like now. 31961121_2391005354246809_7723937338220347392_o.jpg
     
    robinc likes this.
  2. Paul Sutton

    Paul Sutton Buckhorn Gang Member Top Contributor

    I would retard it a bit and if the hesitation still takes place then I'd check out the carburetor and get jetting advice. Because I am lazy at times, actually most of the time, I would not bother with the retard. I would empty the tank and put in a couple of liters of higher octane fuel and see if the problem resolves itself. Adding higher octane will translate across as retarding the timing.

    Also, does it happen if you open the throttle fully at about 2500 rpm and let the bike accelerate up past 3500 rpm. This will dump the fuel through and let you know if there is a jetting issue - do this in 5th gear.
     
    NorazDad and robinc like this.
  3. Paul Sutton

    Paul Sutton Buckhorn Gang Member Top Contributor

    I just noticed your air filters. Someone will advise on these because they do/sometimes cause problems compared to Unipods. I am not sure if the hesitation is related to this issue i.e. turbulence versus laminar flow.
     
    Last edited: Jun 30, 2018
    NorazDad, robinc and Jim like this.
  4. I will check both issues. I think I will look into the unipods. I think jetting is good as there is adequate acceleration all through five gears. It's just when I'm sitting at 3200 that there is a little balking. I get 55mph at 3500 and 60mph around 4000. No balking at these speeds.
    Thanks for the advice.
     
  5. Paul Sutton

    Paul Sutton Buckhorn Gang Member Top Contributor

    You may wish to read the following thread:
    http://www.xs650.com/threads/airbox-to-cones.8/
    Interesting comments about Unipods by it may be a bit out dated now. Someone will give you good advice perhaps tonight or tomorrow. There are several who know the ins and outs of using alternative air filters. I use the stock setup so know F-all on this subject of interest to you.
     
    NorazDad likes this.
  6. timbeck

    timbeck XS650 Junkie XS650.com Supporter

    To check and see if the Banshee rotor [with no woodruf key] has walked it is simple to put a dab of white paint on the PMA rotor and a corresponding dab on the crank end. One look will let you know if it has walked or not.
    tim
     
  7. 5twins

    5twins XS650 Guru Top Contributor

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    Advance and idle timing are directly related. Whatever you do to the idle timing (advance or retard it) will happen to the advance timing by about the same amount. You mentioned the TDC mark. I hope you're not setting your idle timing at that TDC mark because that would be wrong. Idle timing is 15° before TDC. If you are set at the TDC mark now then your timing is way retarded (15°) at both idle and advance, and that could very well account for the hesitation you're experiencing.
     
    Paul Sutton likes this.
  8. No, I'm setting the timing at the firing mark and at the advance mark at 3200. I am only talking a tweak as you know the Pamco only needs a mm or so to make a difference. I'm just asking which direction I should go to clean up the advance end. I suppose advance...duh! I ordered the Uni filters and a good carb clean is probably in order. I hate to mess with jetting when it runs so smoothly. It's just at 3200+/- a 1000rpm that I get a balk. Just asking for input and I appreciate all I get.
     
    Paul Sutton likes this.
  9. XSLeo

    XSLeo XS650 Guru Top Contributor

    I think your problem is your air filters. I had a set similar to the ones you have, spent weeks trying to tune out that flat spot just off idle and the hesitation at most any steady cruising speed.
    I put on a set of the Uni-Filter foam pods and instantly cured all the carb issues.
    Those pleated element filters cause too much air flow turbulence through the carbs. The stock carbs being a CV type carb lift the slide with vacuum. This turbulent air flow disrupts the vacuum signal that lifts the slide.
    The foam pods don't cause this air flow turbulence. Letting the carbs work as they should.
    Leo
     
    Paul Sutton and NorazDad like this.
  10. Thanks Leo. It's been a while since you've shared you sage advice with me. I ordered a set of Uni Pods and will test them shortly. I will let you all know how they work out.
    Grace and Peace, Bro.
     
  11. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    USA Spec BS34's with stock jets also respond wonderfully to the one washer needle raise mod. Those needles are set quite lean stock.
     
    Paul Sutton likes this.
  12. 5twins

    5twins XS650 Guru Top Contributor

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    I was going to suggest Gary's needle shim mod. The BS34s are so lean from the factory that any little change you make might disrupt their state of tune. You might also benefit from bumping the mains up one size to a 135.
     
    NorazDad, gggGary and Paul Sutton like this.
  13. I might need a tutorial on the needle shim mod. We will see how they respond to the uni pods first.
     
  14. 5twins

    5twins XS650 Guru Top Contributor

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    Yes, the purpose here is to raise the needle slightly which will make it richer. To do so correctly, the added shim washer must be placed just below the needle's e-clip, between it and the thick plastic spacer ring. You can just see the added shim washer in Gary's pic if you look closely .....

    [​IMG]
     
    Last edited: Jul 5, 2018
    gggGary likes this.
  15. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    A hair dryer NOT a heat gun! makes it easy to slide the plastic pill off and on to add the washer you won't lose the e clip if you don't remove it :cussing:..........
     
    NorazDad and robinc like this.
  16. Hey I know it's been a while, but I did the gggGary mod
    It's raining today which made it great to work on the carbs, but not to test ride.
    I did not change the jets yet. One step at a time.
    I will follow up and thanks
     
    gggGary likes this.
  17. pamcopete

    pamcopete Ride.Enjoy.Life is Simple

    I would suggest that you temporarily reinstall the stock alternator rotor to provide a reliable timing mark for both idle and full advance. When you reinstall the PMA rotor, you will know that the timing is correct and you can mark the position of the PMA rotor with white paint on the crank and rotor as timbeck in post #6 has suggested.
    Charge up the battery fully and do a test ride while the stock rotor is installed to eliminate the PMA / regulator as a possible cause of your problem.
     
    Last edited: Sep 8, 2018
  18. Well, that will probably be the next step after this test ride. I know how RG and many on this forum dislike and distrust the PMA, but with the right regulator/rectifier all should be fine. Time and many experiments will tell.
     
    gggGary likes this.
  19. Hey Guys, this issue is resolved. gggGary's needle mod and 135 mains. Will check into pilot jets and air jets as well co continue the carb process. The rest of the story is at Breaking up @4500 and other thread which is really the continuation of this one. Thanks for input.
     
    TwoManyXS1Bs and gggGary like this.

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