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'82 Seca 750 Refresh Project: Now Scooby's Bike

Discussion in 'XJ Technical Chat' started by Nuch, Aug 24, 2019.

  1. XJ550H

    XJ550H Well-Known Member Premium Member

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    if you set to prime air may go back into petcock leaving line full and no air
     
  2. Nuch

    Nuch Well-Known Member

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    Yes, fuel supply issue sorted out. Other issue... not so much.

    Seems like a simple problem with my mixture. At three turns out on the screw and STILL needs choke to keep running? Hmmm.

    I'm going to spin it out even farther and try again. If that doesn't work, maybe the problem is opposite. Maybe it's too rich...
     
  3. Rooster53

    Rooster53 Well-Known Member Premium Member

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    Anytime I have had that bad of popping I have had a fouled plug, and that has occurred before when I was doing some testing and started the bike several times with the choke on and never rode it. Plugs could also foul from a weak spark, so it would be a good idea to do the ignition circuit ohm checks just to be sure, particularly on the secondary side to verify the caps and ignition coils are OK. Plugs can be difficult to clean once fouled, so I would go for new ones if in doubt.
     
  4. Polock

    Polock Well-Known Member

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    can you keep it running with the throttle/idle knob long enough to glance at the sync?
     
  5. Nuch

    Nuch Well-Known Member

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    Yes... If I use the idle knob, I can keep her running, but that's with choke on.

    Each time I give it a new try, I've pulled the plugs and wire brushed them and replaced them. She will start with choke ON immediately. She will run... (No throttle) As she continues to run, and warm, I try to ease the choke off... I get about half way off choke and she starts to stall... I can give her throttle, and she will rev, but as soon as I let off, she starts to stall. If I try to remove all choke and stay on throttle, the popping starts and it sounds terrible... I'm afraid to break something so I give up and shut her down. Wash, rinse, repeat. I know, I know, doing the same thing and expecting different results is the true mark of insanity!

    Today was booked up so I didn't have a chance to pay any attention to her. I can go either way with the mixture screw to see if things change. I plan to make another attempt tomorrow. If I turn the screw IN, I'm going to turn to 2 times from seated as apparently 2.25 was not working.

    Of course I went to the manual. My plugs (All of them) are textbook for a rich condition. I believe the choke is in good order and if anything I have too much air based on the UNI filter.
    carbon-fouling.png

    Though as @k-moe said, sooty could mean either lean OR rich...

    @Rooster53 makes a good point with the weak spark potential and I attempted a ohm check as per directions in the manual...
    coil-test-directions.png primary-coil-check.png secondary-coil-check.png

    Primary coil coil check was giving me numbers that fluctuated between 3.9 and 4.1. I used two different Harbor Freight gauges with similar results. Those numbers seem high against the 2.5 +/- spec.
    When I attempted the secondary coil check, I got absolutely nothing on either coil... but I then did the check on my Maxim 700 (who is extremely happy and healthy I might add) and got nothing either (1 & 4 or 2 & 3) and got the same NOTHING so I'm sure I'm not using this thing correctly.

    Today wasn't a total loss though, The Seca made a fine server this evening...
    seca-steaks.png
    It was tough getting the rib eyes in sync... I heard bacon will help to move away from a "lean condition."
     
    Last edited: Aug 28, 2019
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  6. Rooster53

    Rooster53 Well-Known Member Premium Member

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    The meter is likely set to the lower scale, it should be set to the 200k scale when doing the secondaries.
     
  7. Nuch

    Nuch Well-Known Member

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    Did a check on secondaries... this time with the dial to the correct position... (thank you @Rooster53 ). It’s reading 22.5 ohms. Seems high, no? Both meters displaying the same.

    What position should the meter be set at for the primary check?
     
  8. Polock

    Polock Well-Known Member

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    the chances of both coils going bad at the same time are about the same as winning the lottery.
    "only runs with the choke on" has been on here thousands of times.
    you don't want to hear it, i don't want to say it, but
    your pulling those carbs again
     
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  9. Nuch

    Nuch Well-Known Member

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    Those are some dirty words... heh...

    but I guess a man's gotta do what a man's gotta do.
     
  10. Nuch

    Nuch Well-Known Member

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    Ok, please don't laugh.

    I think that sometimes we need to go through these trials as the necessary part of learning. I'm chalking this up to a rookie mistake... After all, with only about 5 years of XJ ownership, I am still a rookie. With the carbs still on the bike, here's a picture of what I found after removing #4's top assembly.
    incorrect-jet-placement.png
    My mixture problem is consistent across all 4. That being said, what was bothering me was that it was unlikely that the problem was a un-zestfully clean passageway somewhere within a single or even multiple carbs... but all 4?


    Upon disassembly, I drew this diagram... I must have swapped the numbers at that point and then used the wrong info to re assemble all carbs. Here is what I scribbled on the work surface...
    incorrect-jet-placement-diag.png

    I haven't opened the other tops yet, but I'm sure I'll find the same situation.

    I might just fire my XJ mechanic!

    Will update again.
     
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  11. Rooster53

    Rooster53 Well-Known Member Premium Member

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    But aren't those installed correctly, the larger jet (pilot) to the front of carb?

    That is a good reading with the caps on - approx. 11K coils plus two 5K caps for 21K
     
    Last edited: Aug 29, 2019
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  12. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    You have the air jets in the right places. The service manuals have the photo miscaptioned. Below is the correct info (matching what you have).
    [​IMG]
     
  13. Nuch

    Nuch Well-Known Member

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    I want to cry.
     
  14. Polock

    Polock Well-Known Member

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    this worked for me twice, only tried it twice. carbs still on the bike>get a glass jar, perfectly clean, wipe the bottom of the float bowls, drain a bowl into the jar, go to prime and give it a rinse, take it out in the sun and look for anything that wasn't there before. now take the slide out of the carb, take the pilot screw washer o-ring out, lay a paper towel under the carb, get your new can of carb cleaner with red tube, put it in the pilot air jet, eye protection, blast away, look on the paper towel for anything, put it in the pilot screw hole , blast
    away, do that three more times.
    can you tell i don't like to pull carbs? if you see chunks when you drain it maybe just pull them, if not a chunk that could plug a jet could have gone anywhere
     
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  15. Nuch

    Nuch Well-Known Member

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    I can't tell you how much I appreciate your willingness to work with me here on this. I have resigned myself to the fact that I am going to pull the carbs again.

    It's ok.

    I'm going to do it as soon as I hit the "post reply" button. This forum is truly why I love these machines so much. They are just a bunch of really cool (and often shiny) parts that are bolted together in the correct order without this community... At least for me.

    I think I might have a fuel delivery problem. I rolled the bike out to the apron of the garage due to the uneven drop of the drive way. That said, I was able to get the front wheel high enough while the bike was on the center stand to completely level the carbs as if they were on my home made stand.

    I put the fuel tank on PRI, and opened #4 drain screw. Guess what... Not a whole lot came out... And it didn't recover either. Correct me if I'm wrong... but shouldn't the bowl begin to replenish as the fuel level drops? I tried #3. That bowl was only half full and again, as I drained it, it never fully came back to spec.

    flow-of-fuel.png

    I'm sure the floats are dropping... When I was wet setting, I made sure the "full" state of the fuel was at the spec measurement, but I obviously didn't do enough "drain-refill-drain-refill" testing.

    Again, a properly working float/needle/seat should begin to replenish as soon as the fuel drops, correct?

    In any case, I'll pull the pilot screws again and give the passages a blast while the carbs are out.
     
  16. Jetfixer

    Jetfixer Well-Known Member

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    Popping usually indicates synch being off, when I did my carbs I set the floats at 17.5 mm measured with a 6 inch scale measured from the flange without the bowl gasket in place. Never bothered to wet set , I have both the 4 vacuum gauge manifold and the Morgan 4 motion , I had my carbs close with vacuum gauge . I used the Morgan synch and wow what difference I was off on number 2 carb , no popping at idle, no popping on deceleration, no stumbling and plugs are set with colortune plug all 4 uniform in color.
     
  17. Nuch

    Nuch Well-Known Member

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    Well... I thought I had figured out the problem. Indeed I did have a fuel delivery issue. I pulled the carbs again and dropped the bowls. I hooked up the fuel source and let it flow... Only it didn't go anywhere! No bowls, floats hanging... and no fuel was dropping out of the carbs.

    When I pulled the seats, the screens were all blocked up.
    anti-seize.png

    I guess the "touch" of anti seize that I put on the threads was too much. I know, I know, (At least now I know... heh) I shouldn't have put any anti seize in there.... When I initially pulled the carbs apart, they were really stuck in there and I didn't want that happening again...

    I pulled the seats & jets and gave them another blast of carb cleaner. I put everything back together, put the carbs back on the bike and...

    Same Result. :(
    Popping as described previously... The smell of fuel is pretty intense.

    I didn't think to bench sync again when I had the carbs off, so perhaps I should pull them again and start from square 1?

    Also, what are your thoughts on the potential condition of my plugs at this point. I've been giving them a brush off here at there, but it is it possible that I've "ruined" them?

    On the bright side, I'm really good (and fast) at pulling and reinstalling the carbs.

    I might need a @hogfiddles intervention.
     
  18. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Unless you sand-blasted them, or broke the porcelan, or cleaned them enough to require regapping, they will work as intended.
     
  19. XJ550H

    XJ550H Well-Known Member Premium Member

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    only place you would use anti sieze would be a little on mixture screw, drain screw and any external screws not on jets or valve body
     
  20. Polock

    Polock Well-Known Member

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    cut loose for some plugs, you could work on this for a week and then find out it was the plugs all along.
    that would piss of the pope
     
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