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  1. #1
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    Default Shovelhead 3/4 to WOT Tuning

    1984 FXSB with dual plugged OEM heads, S&S 80" jugs, Dyna 2000i ignition, Python Pipes, Hydraulic Lifters, Super E and that's all I know about this engine. I do not know unfortunately the inner products in this engine.

    - The timing is set to the very left edge of the window.
    - Primary side plugs are NGK ZGR5C.
    - Carb Side NGK UR5.
    - All plugs gapped .030.
    - 2000i set to Curve 3.
    - No VOES.

    All I know of carb settings at this point is the idle mixture set at 2.5 turns out. I haven't played with it at all yet. Haven't pulled the bowl.

    Engine runs great low-mid. Fires up without a fuss cold and hot. Very responsive. However, once I get up towards 3/4-WOT bike feels "fat". No lean bog, no popping, just fat. Lots of vibes and not much GO if I can describe it best. Fuel mileage doesn't seem that good either. Always been like this as I try not to push it, and riding like a "grandpa" the bike performs just fine. However, it is nice to crack the throttle now and then. Clutch seems to be grabbing OK.

    I'd ASSUME the main jet is a bit fat. Yes, I need to do a plug chop. I have new plugs on the way.

    Here are pics from a bit back when I pulled the plugs for the first time since I bought it. (Short reach plugs are the carb side, orientation is exactly as it would be sitting on bike with the left side plugs in the photo being the front of the motorcycle, yes that rear primary side plug is a bit wet/oily... maybe a leaky valve guide).








    I replaced them, just because, and rode a couple days of regular riding. No WOT plug chops. Bike still seems "fat" up top with no crisp PULL.

    As for the plugs though what do you think? Obviously they had some miles on them.

    When the new plugs come in I will gap them all .030 and do a WOT plug chop and post back.
    ​​​​​​​

  2. #2

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    First, 2 1/2 turns out on a Super E idle mix screw is ridiculous. That setting on the accelerator pump screw on the other hand, would be in the ballpark.

    The idle mixture screw will be 1 1/4 turns out, plus or minus 1/4 turn, IF the intermediate jet is correctly sized.

    Baseline jets are: .0295 - .031 intermediate, maybe .028 in the odd instance.

    Main jets .066 - .072 for an 80cu.in. motor with moderate compression.

    Float level 1/8 - 3/16, CAREFULLY adjusted according to the S&S instructions. Many people get this WRONG. I try to split the difference at 5/32.

    Pipe choice may necessitate a change of the main air bleed size. Later carbs have a replaceable jet.

    Shovels like to be a little on the fat side to run good; the combustion chamber is very inefficient (lazy).

    Jim

  3. #3
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    Quote Originally Posted by JBinNC View Post
    First, 2 1/2 turns out on a Super E idle mix screw is ridiculous. That setting on the accelerator pump screw on the other hand, would be in the ballpark.

    The idle mixture screw will be 1 1/4 turns out, plus or minus 1/4 turn, IF the intermediate jet is correctly sized.

    Baseline jets are: .0295 - .031 intermediate, maybe .028 in the odd instance.

    Main jets .066 - .072 for an 80cu.in. motor with moderate compression.

    Float level 1/8 - 3/16, CAREFULLY adjusted according to the S&S instructions. Many people get this WRONG. I try to split the difference at 5/32.

    Pipe choice may necessitate a change of the main air bleed size. Later carbs have a replaceable jet.

    Shovels like to be a little on the fat side to run good; the combustion chamber is very inefficient (lazy).

    Jim
    Thanks Jim,

    Something to note I forgot to post the closeup pic of that rear plug in my original post. It was BAD! I replaced the plugs since and although that plug still appears more oily than the others, it is no where near as bad as it was here...





    Forgive me, I think the pic of all the plugs in my original post was after I replaced the plugs and ran it for a few hundred miles.

    I continue to monitor that plug since then. Again, that was the plug from when I bought the bike.

    No crazy oil consumption, no noises, no puffing smoke. I DO think I should pull that head this winter.

    I rode the bike from CT to Maine and several trips since changing THAT plug...

    Should I still move forward wit fresh plugs and plug chop test?

  4. #4

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    Well, you have an oily combustion chamber, so reading the plugs might not tell you much (except that you have an oily combustion chamber). I'll bet the valve stem seals are worn out, or one is loose (which turns it into a little oil pump). Or of course the head gasket may be leaking to the oil return.

    The right side plugs look a little better than the lefts, so maybe go up one heat range on the left plugs only.

    Farmall always suggests a quick compression test, I would concur.

    Jim

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    Might wanna do a leak-down test to see how well the ring seal is ... ??

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    Quote Originally Posted by Dragstews View Post
    Might wanna do a leak-down test to see how well the ring seal is ... ??
    Yup just bought a Leak down kit.

  7. #7

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    Leak check will tell you if the rear head gasket is blown to the oil return, by comparison to the front number.

    Jim

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    Waiting on some new plugs. Been monitoring that rear plug... it really hasn't gotten bad (oil fouled) since the replacement. I think that fouling was a previous owner mishap or lack of maintenance. Of course, I will continue to monitor... but I dont want to jump to conclusions as the bike runs great no noises, no noticeable oil consumption, no smoke.... A leak down and compression check to be performed.


    I tinkered with the mixture screw. I got it running better at 2 turns out compared to the 2.5 turns it was at. Intermediate jet is probably still a tad fat but it pulls nice and clean down low. I can confirm the actually jet sizes... just waiting on a float bowl gasket. Bowl needs to come off anyway since every now/then I get some fuel dribble out of the overflow when the bike sits. Probably shit in the needle/seat. I bet the mainjet is fat but I will confirm that with new plugs and a plug chop...
    Last edited by garystaven88; 05-15-2020 at 2:49 PM.

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    That picture belongs in a museum...

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