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  1. #1
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    Default Shovelhead primary belt

    I'm just about finished with my project bike. Its a 78 hard tailed frame with a shovel in it. I have a 2 inch belt drive, but I'd like to swap it for a 1.5". The issue I have is belt tension.

    I use an original inner primary to align the engine+transmission. Both of the belt drives I have are BDL. Using the inner primary leaves the 2" belt pretty loose and the 1.5" belt will barely go on. It's very tight.

    Is there a way I can set these up with regular garage tools?

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    Is there some reason a straight edge wouldn't work?

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    I have trouble keeping the left/right and front/back from moving. Do you do it without the belt on?

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    Quote Originally Posted by Cuddles View Post
    I have trouble keeping the left/right and front/back from moving. Do you do it without the belt on?
    This has been covered before. Very common issue that the belt is too tight or loose and the tranny adjustment wont help Ill see if I cant get the link. You need a bearing idler for tension

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    Your issue isnt really alignment. Even if it was, there isnt much you can do for belts riding too far left or right (as seen from above) on the pulleys, and that shouldnt be your problem

    For some reason, on some builds with front open belt drives, the common available belts sizes are either a little long or short, really no in between, no matter how far front or rear the tranny adjustment is.

    You need a idler bearing, or in some speak, a belt tensioner idler for the looser belt. If the tranny is canted left or right, as I beleive you are saying?, and the belt is too tight or loose, I dont think thats the cause. Its just the belt size (length)

    Im running a 1.5 open belt, and while the belt tracks a liitle outboard (not exactly in the center) and the pulleys are like 2 inches wide or so), it doesnt run off or rub the side of the pulley. And yes, my 1.5 was way too loose even with the tranny all the way to the rear

    Whatever you choose to do, realize most folks run the front belt too tight. It should twist in the middle almost a 1/8 to 1/4 turn when you twist it by hand

    Heres the link http://www.chopcult.com/forum/showthread.php?t=55290

    Good luck, keep us in the know

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    I don't have one, but a guy I watch on the internet tubes has a trans plate with positive adjustment screws built into it. It looks like it should work great?

    It is in two pieces and the top slides via two allens in the rear and you draw the plate back and forth to adjust tension, then lock it down.

    We got one for the Mrs's project, but haven't used it yet. Hers is a VTwin part.

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    PS: It is a black version of this one:

    https://www2.vtwinmfg.com/adjustable...ing-plate.html

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    I have one of those adjusters. They work great and help preserve tranny cases but a HUGE pain to adjust

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    I have a 2" belt, now. It rides in the middle most of the time. Sometimes it rides inward off the edge of the pulley. I have a 1.5" setup I was going to put back on mostly just for the guides on the front pulley, but I think I'll stick with the 2".

    This bike is very close to being finished. I'm running into trouble here and there. I had oil flow issues, before. Got that straightened out, and now, I seem to have a problem with crankcase pressure. Some day, I'll ride this bike outside our neighborhood. maybe.

  10. #10

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    Quote Originally Posted by confab View Post
    PS: It is a black version of this one:

    https://www2.vtwinmfg.com/adjustable...ing-plate.html
    This is not the same as the one i got. This look alot more user friendly . Wish i knew about it before i installed the one i got.

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    It looks like it will work real good!

    Can't speak to it yet, though. Winter time projects.

    If OP is still having trouble after this is over, maybe give one of those a shot?

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    I think I'll stick with the looser belt. I ran a 1.5" before. It was a bear to get on and off and eventually broke. The 2" is loose but not too bad.

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    Really both instances you're having an assembly issue, your 1.5in and 2in belts are the same--ALL BDL belt drives are setup for 12-13/16in center between the motor and trans shafts. The pulley size and combo dictate belt length. So make sure your belt matches the tooth count. If you bought each kit new you won't have this issue.
    When I assemble I get everything where I want it alignment wise, put the belt on. If it's too tight, I keep the motor bolts in loose, keep the trans ear nuts snug to the inner primary, and loosen the trans plate bolts just enough that I have tight movement. Then I hit the trans with a rubber (lead) mallet until belt tension is proper. You also may need to shim between the motor and inner primary.

  14. #14

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    Belt tension is subjective. What I was told long ago, and seems to work, is the belt should be able to be twisted by hand in the middle, a 1/8 turn, or a little more. Folks seem to tend to adjust them too tight

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    Quote Originally Posted by seaking View Post
    ALL BDL belt drives are setup for 12-13/16in center between the motor and trans shafts. The pulley size and combo dictate belt length.
    Is this measurement also good for stock primary setups on the BT Pan, Shovel, Etc? Anyone?
    Last edited by confab; 3 Days Ago at 9:54 PM.

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