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  1. #1
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    Default Shovelhead w/ Super E Hanging Idle After Rev

    Hi all, I've spent some time trying to diagnose this problem and I'm looking for some second opinions. Bike is a freshly rebuilt 1973 Shovelhead chopper with Super E carb, kick only, belt drive, ratchet top, fresh plugs, new coil. I have the carb set per the starting specs on the S&S youtube setup video. I have had it running several times since the rebuild working through heat cycles and a few short rides, now I am trying to dial it in. I pulled the plugs after a ride the other day and noticed the plugs were pretty much white, and that the bike is harder to start, so I think my issue is mixture related but I'm not sure what is going wrong. The acc. pump squirts as it should with throttle and you can see gas in the carb body when it's running and when you kick it over.

    What happens is when the bike is running and you give it even just a little throttle (maybe like 3000 rpm ish) and then let off, the idle hangs in that rpm range and takes a while to come back down. It is not affected by pulling in the clutch. I know this problem is typical with intake leaks, and I just tried to identify any leaks using my propane torch but I didn't really hear a change in RPM with that test moving it around the manifold, carb body, etc. I should also say that the o-rings and aircraft style clamps are almost new and in great shape, and just the other day I took the manifold off and re attached it all as sturdy and even as I could, with my carb support bracket.

    I have read that the Super E's can sometimes leak through the throttle shaft. I have had this carb opened up last summer and went through it to clean it out. I bought it used but from a guy who said he had it on his evo something or other for just a few weeks then switched carbs and it sat after that. Like I said I tried the propane torch test and found no change in RPM holding it up around the throttle connection on the carb either.

    People also say in other threads to check advance weights/springs. I have not checked this since getting the motor back from rebuild, but I know the advance unit and weights/springs are new as well as the points.

    Any help or ideas on what to check next would be appreciated, thanks!

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    Try using carb cleaner for checking intake leaks and make a dog cone for the carb so it doesn't suck in any of the carb cleaner mist. An old amazon box works. Pressure testing the manifold with 5 psi is better than either propane or carb cleaner. Make sure to spray the throttle bushings, the enrichener, mixture screw, the carb to manifold area to check the o-ring seals there and then the spigot o-ring clamps. Did you rebuild the carb with a re-build kit when you had it open? The accelerator pump has check balls and o-rings along with the accelerator pump to upper throttle body. The mixture screw has a o-ring on it make sure its there. Even new advance springs can be trash.

    Are you using the carb to body phenolic spacer for preventing the carb from heating up?
    You said the carb came off a EVO does the super E have a VOES port? Is it sealed?
    What is your idle rpm set to?

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    Assuming you have stock points ignition - Check your advance mechanism - worn advance mechanism can hang at full advance and cause these symptoms.

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    Thanks Abbandon. I'll try the test with carb cleaner next. I can't remember exactly but when I rebuild the carb I only replaced a couple pieces because it was clean and in pretty good shape, and I'm pretty sure I was careful about getting it all right with the check balls and o-rings. My mixture screw is what looks to be the early style one, no o-ring. I am using the carb spacer. It does not have a VOES port. I don't know the exact idle because I don't have a tachometer on the bike but it is a healthy idle, not too low not too high.

    I pulled the plugs again today after running it and now the front plug is sooty and black and the rear plug is light tan. Could this mean an intake leak would make more sense in the rear jug/manifold o-ring?

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    Quote Originally Posted by 69Glide View Post
    Assuming you have stock points ignition - Check your advance mechanism - worn advance mechanism can hang at full advance and cause these symptoms.
    Yes stock point ignition, everything recently replaced when motor was rebuilt but I will look anyways.

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    And, just for the hell of it, lube your cable(s). Can't hurt.

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    Quote Originally Posted by MOTher View Post
    And, just for the hell of it, lube your cable(s). Can't hurt.
    LOL I was just going to say that.......

    Great minds??????

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    Truth! Cables hang easily and when the rev hangs you can check by pressing the throttle shut at the carb with a long screwdriver. That's the first check I make.

    I have had this carb opened up last summer and went through it to clean it out.
    If the last time it was apart was last summer I'd have it apart again to inspect and soak (spray cleaner is for rinsing off carb parts) in undiluted Pine-Sol (not generic pine oil) or Simple Green but at least I'd remove and inspect the jets. Lean mixture is THE standard result of sitting.

    Your bowl gasket will probably be fine and the O-rings may be but instead of kits I buy Viton and Buna (those materials matter, no unknown mystery rings!) rings dirt cheap by the bag via Ebay.
    http://www.chopcult.com/forum/showthread.php?t=52256

    This is a very good time to make yourself a tool or two to easily remove your carb-to-manifold bolts with as little extra work a possible since swift carb removals pay off for life. It's raining and I don't fell like walking to the shop to take pics but the recipe is simple and you'll figure it out.

    3/8" drive allen bits are often too large for convenient clearance so I cut off a section of hex key (use good quality hex keys) and place it in a 1/4" drive (six point preferred) socket. (I braze or silver solder mine with a torch to keep the hex key section from falling out but that ain't strictly necessary.)

    S&S bolts take 5/16" hex keys
    . The best bit style for odd angle attack is a ball end hex key but standard keys work. I start out with a long hex key length then shorten (cut off with cutting disk, even a Dremel will do) to place the 1/4" drive socket in the most convenient spot to use with a universal joint and a long extension. I don't hesitate to make a tool for every common job since it takes less time to make a tool than fight shit forever because I wanted to save time and not make the tool.

    The most useful hex key sizes for HD use are 3/16", 1/4" and 5/16" so instead of buying more sets I buy more of my most used keys. standard, ball end, square drive and T-handle all have their places. I keep a basic "jack knife" set in each riding jacket.
    Last edited by farmall; 04-19-2020 at 10:06 PM.

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    I guess I should have mentioned early on that the throttle cable was one of my first checks each time I run it and it’s not causing the issue. It’s a new cable and I make sure I am press it closed all the way when it is idling (it closes fine itself with a little free play in the cable). I have the carb off and will open it up today and take a look. I cleaned it last summer but the bike didn’t get ridden much since because I pulled the motor to have it rebuilt but of course I know sitting gas/residue can cause all sorts of problems.

    In the meantime I pulled the manifold off again and checked my o-ring seals and clamps, reinstalling as even as I could get it. They look to be in good shape but anything could happen.

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    Just a thought. This happened to me once. The cable was nice and loose and would only hang open the throttle when the bars were turned to the left. Foot clutch and no front brake so i would always turn them a little left when I came to a stop, so if I lost my balance I wouldn't pop the clutch putting my foot down. Every time I came to a stop the engine would idle way fast. Sounds stupid but I was trying too hard to find the problem and it was right there. If there's anything I've learned working on bikes is that it's really easy to overlook simple solutions and start tearing into things. Probably not the issue but I thought I'd mention it.

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    Quote Originally Posted by gorgeous View Post
    Just a thought. This happened to me once. The cable was nice and loose and would only hang open the throttle when the bars were turned to the left. Foot clutch and no front brake so i would always turn them a little left when I came to a stop, so if I lost my balance I wouldn't pop the clutch putting my foot down. Every time I came to a stop the engine would idle way fast. Sounds stupid but I was trying too hard to find the problem and it was right there. If there's anything I've learned working on bikes is that it's really easy to overlook simple solutions and start tearing into things. Probably not the issue but I thought I'd mention it.
    Totally makes sense, and I hear you on the simple solutions thing. It's a hard lesson learned sometimes. I don't think it's the cable because I am able to physically look into the mouth of the carb with the air cleaner off when this is happening and make sure the throttle closes all the way to the idle screw.

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    Quote Originally Posted by HogsRear View Post
    Totally makes sense, and I hear you on the simple solutions thing. It's a hard lesson learned sometimes. I don't think it's the cable because I am able to physically look into the mouth of the carb with the air cleaner off when this is happening and make sure the throttle closes all the way to the idle screw.
    Fresh motor, heat cycles
    Did you re-torque the head bolts yet?
    Re-adjust the pushrods after?

    When checking for intake leaks, spray around the spark plugs and the head gaskets too.
    Careful some of that carb cleaner (chlorine-based) flashes into mustard gas on a hot engine!

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    Did you move onto a stroker for the rebuild? Either way, it might be worthwhile to try the heavier advance springs. If you are using the black springs now you could try the silver ones.

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    check your throttleplate bushings, I had a E that had that problem worn throttle shaft

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    Quote Originally Posted by Sky View Post
    Fresh motor, heat cycles
    Did you re-torque the head bolts yet?
    Re-adjust the pushrods after?

    When checking for intake leaks, spray around the spark plugs and the head gaskets too.
    Careful some of that carb cleaner (chlorine-based) flashes into mustard gas on a hot engine!
    Haven't adjusted pushrods or re-torqued heads yet.

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    Quote Originally Posted by heyyodho View Post
    Did you move onto a stroker for the rebuild? Either way, it might be worthwhile to try the heavier advance springs. If you are using the black springs now you could try the silver ones.
    Nope, stock bore just refreshed. If it ends up not being an intake leak (a friend pointed out the clamps I have aren't that good of quality) I will check the springs again but I took a look the other day and everything looks solid in the advance/points.

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    Quote Originally Posted by Davestune View Post
    check your throttleplate bushings, I had a E that had that problem worn throttle shaft
    I have the carb apart right now but the throttle shaft is still in place. Do I pull it out to check the bushings?

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    Quote Originally Posted by HogsRear View Post
    I have the carb apart right now but the throttle shaft is still in place. Do I pull it out to check the bushings?

    Yes. Remove the springs and throttle plate and jiggle the shaft. The shaft should not wiggle in the throttle bushings.

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    Quote Originally Posted by AbbandonZK View Post
    Yes. Remove the springs and throttle plate and jiggle the shaft. The shaft should not wiggle in the throttle bushings.
    I'm able to wiggle it a tiny bit, and there's no resistance sliding it in and out of the carb body. You think that could be it?

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    Quote Originally Posted by HogsRear View Post
    I'm able to wiggle it a tiny bit, and there's no resistance sliding it in and out of the carb body. You think that could be it?
    Yes that could be it. Does the throttle shaft have excessive wear where it rides on the bushing?

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