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  1. #1
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    Default Shovelhead Chopper Transmission/Clutch Issue

    Howdy all, I recently got my 1973 Shovelhead put back together after being taken from more or less a stock swingarm bike to hard tail chopper and upon getting it started for the first time this year I'm having an issue with the transmission/clutch.

    Some background info. It is the stock four speed ratchet top tranny original to the bike, which was functioning fine before it was torn down for all the work and remained untouched over the last few months. I was able to ride and shift through all the gears no problem. Since getting the frame hard tailed, I took the opportunity to replace the entire clutch hub, plates, springs, tranny support bracket, new 1.5" BDL belt (it had a different belt on before) and converted to foot clutch. The hardtail is a panhead replica from V Twin.

    We got the bike fired up in a few kicks and after running for a few seconds it started to pull slightly in neutral as if it was somehow slipping into gear. The pressure would be relieved when the foot clutch was engaged. It wasn't enough to actually have the bike take off but it was enough to want to stall the motor out. Eventually something burned out and smoked a bit from behind the inner primary cover and the foot clutch dropped out completely. Tried to adjust it again and it drops out. I know we fucked something up but I'm not sure what, and how badly. Before running it I also noticed the front sprocket couldn't be turned by hand while in neutral but I assumed it would clear up when it was re assembled on the bike.

    Before and after pictures attached for reference just because. Any help is appreciated, thanks!
    Attached Thumbnails Attached Thumbnails shovelhead_ba.jpg  

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    On the big twin 4 speed, the main drive gear (upon which the transmission sprocket is mounted) has a bushing through which the mainshaft (upon which the clutch is mounted) passes. If this bushing is binding on the mainshaft, the bike will try to creep while in neutral. This sounds like what is happening with yours.

    First, is there oil in the transmission?

    Second, since the transmission was running before, a possible cause of the binding could be the mainshaft support bearing that is added when an open belt drive is installed.

    Third, another cause for this drag is belt or chain way too tight, or the transmission misaligned with the motor, badly.

    That should give you some things to check, but you are probably going to have to go through the transmission and fix any damage as you diagnose what is going on.

    Jim

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    "Couldn't turn the sprocket in neutral " That was your first clue that something was amiss. That sort of thing usually does not "clear up."

    Jim

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    Default

    Thanks Jim, all of this sounds pretty accurate. From what you're saying, I'm guessing that bushing is what got smoked as the bike was running. We did put fresh transmission oil in before starting it. The bike had an aftermarket primary belt on it when I got it but stock primary so maybe the addition of the main shaft support caused some weird pressure. Belt and chain were in spec, and motor and tranny were aligned during the hard tail process so I think we can rule that out.

    Transmission will be pulled out tomorrow. Thank you!

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