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  1. #1
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    Default Super E tuning help

    Well crap, the Desert Rose is giving me problems. Once fully warmed up if I roll on the throttle slowly it revs right up to around 4k with no issues, she feels like she will wind up even higher if I try, but it is a fresh top end on there so I am taking it easy. However, if say at 1k I give her full throttle she revs up to 3k and then starts breaking up, always right at 3k. If I roll the throttle back she is fine again.

    I am running an early Super E with the fixed air bleed. I am running a .295 intermediate jet and a 72 main jet. Fuel line is 1/4 copper from the tank to the carb.

    Since I last had her running I've added a Sifton -Crusader cam and Jesse worked out the heads ( including oversize intake valves ).

    Here are the plugs after a 20 minute ride.
    Click image for larger version. 

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    I have attempted to readjust the idle circuit a few times and went from a .70 to the .72 on the main jet.

    I am wondering next if my coil could be marginal, plug & point gap are correct, timing should be right, but I can recheck that as well. I read 6.8 ohms across the +/- terminals.

    Any thoughts out there, this one has me stumped.
    Last edited by DoomBuggy; 05-09-2022 at 12:51 PM.

  2. #2
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    You are probably fat on your main jet and/ or the main air bleed needs to be larger to separate the intermediate and main jets.

    As always, check the float level using the S&S instructions exactly. For tuning, turn the accelerator pump off.

    As an experiment, go down to a 66 main jet and see if your acceleration cleans up. If so, a larger main air bleed and a 68 or 70 main jet will probably be your final tune.

    The above ASSUMES that the ignition is spot-on, and you know about assumptions.

    Jim

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    Thanks for the quick reply!

    This is an old enough carb that it has the fixed air bleed. I will try your other suggestions, but of course the smallest jets I have is a 70, lol. Amazon here I come.

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    If you have small drills, you can always solder up a jet and redrill.

    Jim

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    Is the air cleaner restrictive ??


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    LOL, there is a picture of the plugs!

    I thought about the restriction, so I went back to the original "Ham Can" air cleaner & a new filter.

    Click image for larger version. 

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  7. #7

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    Fatten the main up until the motor 'blubbers' under acceleration.
    This is a rich indication, then start leaning it out to find the power.
    If you think you are a super tuner then drill and tap the the air bleed out for mikuni jets.
    Then you can tune the air bleed.
    Check out Thunder Jet instructions as that is part of the install.

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    Cool set of directions on the Thunderjet! I really am just looking to get the bike running correctly, not trying to wring out every last pony. Next owner can do that, lol.

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    Quote Originally Posted by DoomBuggy View Post
    Cool set of directions on the Thunderjet! I really am just looking to get the bike running correctly, not trying to wring out every last pony. Next owner can do that, lol.
    Could be the pump. try fiddling with the acell pump, & even consider taking a
    look at the pump diaphragm, a make sure it is not compromised. (dried out
    or compressed, cracked, etc. )

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    Thanks, I rebuilt the carb a couple of years ago, but I will check the pump just to be sure.

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    Might be worth a look at the fuel flow .. Pull the line at the carb and turn on the gas at the petcock ..

    Should see a nice stream of gas ...
    If not ... Oh Boy .. !!

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    Thanks, tried that also,seems to flow well.

    Does anyone know the minimum flow rate per minute on an old panhead?

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    Doom... Is the 1/4" fuel line all new, or have You run it before on that bike?

    The copper tubing may be 1/4" i.d. But the fittings are likely to have a
    smaller i.d. & could be restricting flow.
    I know it's a hassle, But if different main jets don't correct the issue, & the pump
    looks good........try rigging up
    a 5/16" fuel line & see if that does it.
    personally, I never run anything under 5/16" fuel line on a big twin.

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    Thanks for the input. The tanks have the old style shutoff on the top of the tank and the fitting is for 1/4". I am with you on the larger size, but the line that came with the tanks were even smaller than the 1/4" I've got on there.

    And to answer your question, yes this is the first time I am running a 1/4" hard line on this bike. The new jets got here today, hopefully it will cool off later and I will mess with those. ( It went from 50s to near 100 overnight, these weather patterns are nuts this year. )

    More to come.

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    God this is fun....not!

    Ok, closed the accelerator pump, went down to a .066 main and it cleaned it up quite a bit. If I go full throttle from right off idle, she pulls hard but then still stumbles transitioning from the intermediate to the main jet ( right at 3000 rpm, but clears up by 3300 rpm. I know I have a .295 intermediate in there and as soon as she cools off a little, I will change that to a smaller one next to see if a combo of reducing the intermediate and adding a little accelerator will do the trick.

    So damn close! ! ! ( I would kill for a dyno right about now. )

    Edit: .280 intermediate is getting me real close, now I have a slight bog when it hits 3000 rpm. Just a bit more and I should be there.
    Last edited by DoomBuggy; 05-12-2022 at 11:55 AM.

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    Well damn, I thought hey I've got it this close, I bet someone with a dyno and experience could dial it right in. Called two Harley dealers who I know have dynos, and a local "speed shop". No one wants to work on an old bike. Guess if they can't plug in the computer it is too hard.

    I even offered to do the work, just needed their air/fuel monitor and a few runs on the dyno.

    Buncha schmucks!

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    .. And ..

    Last edited by Dragstews; 05-12-2022 at 1:01 PM.

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    It didn't dawn on me that the change in pipes could be an issue. More to come tomorrow.

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    Quote Originally Posted by DoomBuggy View Post
    It didn't dawn on me that the change in pipes could be an issue. More to come tomorrow.
    Got a dumpster close to ya .. ??

    Last edited by Dragstews; 05-12-2022 at 5:09 PM.

  20. #20
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    Looks like you need to make the main air bleed larger (often the case with the drag pipes).

    Rather than drill & tap for a replaceable jet, you can just enlarge the existing hole. You can even do that on the bike. Good to have a number drill set for this. And a pin vise to hold the drill bit. Because it is an air jet, the steps need to be big. Stock size for a Super E is .040 or .042 (reports vary). You will probably want to go to .050 or so as a first step. You may end up around .060 or so as the final size.

    And remember what I said in my first post: that .066 main is a matter of experiment and may be too lean as your final main jet size.

    Note: heads with a fresh valve job and a good set of rings give you a good sealing cylinder, and that means you will probably be leaning the carb out, compared to the way the motor ran when it was all leaky and shit.

    Jim

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