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  1. #1

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    Default Lost the clutch on the '37 80" flathead

    I lost the clutch in the ratchet top 4 speed the other day. I was riding around and then on my way home had no clutch whatsoever. All was fine and then out of nowhere I had absolutely zero clutch. What is the likely culprit? Hoping I can fix whatever it is just by pulling the kicker cover. Don't want to do a full rebuild and I don't think it needs it. But I ain't scared if that's what it ends up needing.

    https://www.youtube.com/watch?v=y34qkNwE9aw

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    Your heading in the right direction by pulling the kicker cover. I've had the same symptoms and it was a bad throw out bearing. I've also seen the adjustment screw on the clutch pack side shear, but that was an aftermarket taiwan ted one and the only time I've seen it happen. I'd start by pulling the kicker cover.

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    Before pulling the kicker I would pull the derby cover and check the adjustment, I like the easy solution if I can, lol.

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    Dang primary chain looks to be ......



    I'd pull the clutch pressure plate off and see what the clutch pushrod is doing is doing, or not doing ...

    Hoping your clutch has been up-graded from the og 2 plate clutch ..
    Those was very wimpy in design straight from the Mo-Co back in that day ..

    Last edited by Dragstews; 04-17-2022 at 10:47 AM.

  5. #5
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    Quote Originally Posted by Dragstews View Post


    Dang primary chain looks to be dry as a Popcorn fart ..
    Indeed. Good point, D. I even see some rust in the links now that you have pointed it out.

    C, it is extremely dangerous to run a primary chain with no cover. Plus, if the chain were being oiled as it should be, it is also extremely messy. Rusty chains do break, and a broken chain can DISMEMBER YOU.

    For the clutch issue, first pull the pushrod adjusting screw as has been suggested above, and check it for wear, which would indicate that the release bearing is dragging. The release finger in the four speeds almost never fail (unlike the ones in the early five speeds). I have never seen one in a four speed broken. But the release bearings do wear out or get rough and cause wear on the pushrod and adjusting screw.

    I would do the inspection and readjust the clutch and see if function is restored before pulling the kick cover.

    And for your own safety, get the primary chain oiling working and get a cover on that chain!

    Jim

  6. #6

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    Quote Originally Posted by montuckymatt View Post
    Your heading in the right direction by pulling the kicker cover. I've had the same symptoms and it was a bad throw out bearing. I've also seen the adjustment screw on the clutch pack side shear, but that was an aftermarket taiwan ted one and the only time I've seen it happen. I'd start by pulling the kicker cover.
    Thanks Matt. I suspected the throw out bearing.

    Quote Originally Posted by DoomBuggy View Post
    Before pulling the kicker I would pull the derby cover and check the adjustment, I like the easy solution if I can, lol.
    Well I'm one step into that process already! LOL!

    Quote Originally Posted by Dragstews View Post


    Dang primary chain looks to be ......



    I'd pull the clutch pressure plate off and see what the clutch pushrod is doing is doing, or not doing ...

    Hoping your clutch has been up-graded from the og 2 plate clutch ..
    Those was very wimpy in design straight from the Mo-Co back in that day ..

    Yep, I've been running Maxima chain wax on it. Seems to keep it lubed without throwing shit everywhere? Yeah it has multiple clutch plates in it so it must be. I didn't know they were only 2 packs back in the day.


    Quote Originally Posted by JBinNC View Post
    Indeed. Good point, D. I even see some rust in the links now that you have pointed it out.

    C, it is extremely dangerous to run a primary chain with no cover. Plus, if the chain were being oiled as it should be, it is also extremely messy. Rusty chains do break, and a broken chain can DISMEMBER YOU.

    For the clutch issue, first pull the pushrod adjusting screw as has been suggested above, and check it for wear, which would indicate that the release bearing is dragging. The release finger in the four speeds almost never fail (unlike the ones in the early five speeds). I have never seen one in a four speed broken. But the release bearings do wear out or get rough and cause wear on the pushrod and adjusting screw.

    I would do the inspection and readjust the clutch and see if function is restored before pulling the kick cover.

    And for your own safety, get the primary chain oiling working and get a cover on that chain!

    Jim
    Ok. I was kinda of waffling between putting the primary cover back on, or getting a belt drive. There is like an elbow or something that screw onto the left side engine case which directs oil onto the chain right? I don't have that piece. I need to figure out what piece I need there in order to direct oil onto the primary chain.

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    Click image for larger version. 

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    These are also made for the Gen cases too ..





    Can be had without fins ...





    Will work with 1.5 or smaller belt drive systems or open chain ...

    This product has been approved by the "Ten Fingers" safety board ...
    Last edited by Dragstews; 04-18-2022 at 6:32 AM.

  8. #8

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    DS, I love the look of that finned cover. If I ever run a cover other than a stock tin, that would be the one. Ten Fingers safety board LOL!!!!



    Matt, IIRC you have a stock style primary tin on your flatty, are you running a belt or chain in there??



    I'm trying to make up my mind between running this chain with a cover, or, switching to a belt drive, which could safely be run with or without a cover. I already have the primary tin here, just need to put it back on.

    I have the safety locking ring which has the tabs that bend down over the three bolts which screw into the left side motor case in order to mount the primary cover, but I have misplaced the bolts. WHAT THREAD PITCH ARE THESE????? Something common from the hardware store or some oddball thread that HD used decades ago??? They look like 1/4-20 bolts from the pictures I see for the Colony mounting hardware kit $7811-14

    Also, what is the correct part# I'm looking for which is the fitting that screws into the primary chain oiling hole on the left side of the case. Bonus, what thread pitch is that hole?




    I removed the clutches and steels (5 clutch plates) and cleaned them and reinstalled them. The end of the clutch pushrod looked fine and as soon as I readjusted the clutch, I have what feels like correct tension on the clutch release arm again. So, hoping it was just that simple......

    Now, I need to really hone in on dialing in this mousetrap....... Fairly complex adjustment to a layman such as myself. Thankfully Pacific Mike has a great video on the process:

    https://www.youtube.com/watch?v=L8sLjkwnJ60
    Last edited by CDeeZ; 04-18-2022 at 3:09 PM.

  9. #9

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    Just stuck a 5/16-18 bolt in the primary cover mounting holes on the engine case. That's what size they are.

  10. #10
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    I've been running a belt in my primaries since 1997. Chains vibrate and require too much maintenance. I hated always screwing with primary chains on my 45 flatties. I run a bdl kit (1.5) enclosed. Set it and forget it.....a huge upgrade in my opinion and with the enclosed primary....looks stock.

  11. #11

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    Matt,

    I have been heavily considering switching this bike to a belt. You just convinced me. I can't seem to find the correct BDL kit for a 37 big twin flatty online? Which one do I need????


    -EDIT-

    I see BDL 4731TK1 showing up on JPCycles as a fit. 11mm 1-1/2". Looks like this is the one I need.

    Stupid question, but if the 1-1/2" refers to belt width, what does the 11mm pertain to???
    Last edited by CDeeZ; 04-19-2022 at 7:07 PM.

  12. #12

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    After talking with Matt, and doing some thinking on it, I ordered a BDL 1.5" 8mm kit. It arrived yesterday.

    The front pulley and insert has 3 bolts, and 3 roll pins which are included in the kit. All I can find is info for this 3" belt drive setup, but I'm assuming it's the same. The installation supplement states to use both the roll pins and the bolts. Is this right?

    http://beltdrives.com/wp-content/upl.../12supp3in.pdf

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    Quote Originally Posted by CDeeZ View Post
    After talking with Matt, and doing some thinking on it, I ordered a BDL 1.5" 8mm kit. It arrived yesterday.

    The front pulley and insert has 3 bolts, and 3 roll pins which are included in the kit. All I can find is info for this 3" belt drive setup, but I'm assuming it's the same. The installation supplement states to use both the roll pins and the bolts. Is this right?

    http://beltdrives.com/wp-content/upl.../12supp3in.pdf
    Yes, the roll pins prevent the two parts from fretting together and possibly loosening the screws.

    Jim

  14. #14

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    Thanks Jim.

    Haven't decided if I'm gonna run it open or put the primary cover back on it. I've read that sometimes enclosing a belt drive primary causes heat issues and will waste a belt. Any truth to this?

    I can't seem to find a definitive answer from BDL regarding this question either P/N# ( 6239TK1 )

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    Heat kills belts. The tin primaries are not as bad as the aluminum ones in that respect because there is a big opening behind the clutch.

    Jim

  16. #16

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    Matt was right. TOB bit the dust. To my surprise, it's the later and weaker unit, not the witch hat setup.... I have ordered the witchhat conversion kit and waiting on it to arrive.




















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    Going to need a new finger that's made for the witch-hat bearing ..

    Don't think it will come along with the kit ??
    Last edited by Dragstews; 05-25-2022 at 4:35 PM.

  18. #18
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    You will at the very least remove the trans top and douch out the case REALLY good, won't you? I'd pour a gallon of denatured alcohol, or something like that through it. There are a lot of particles inside the gear case that don't need to be there.

  19. #19

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    Well, I wasn't planning on it. But I'm sure you're right. There's bound to be some junk in there from the TOB shitting the bed.

    Honestly though, I'm tempted to just reassemble the thing with the new bearing and do a drain and fill several times to try to flush it out that way.

    I'm not familiar with these 4 speeds as of yet. But compared to some other automotive trannys that I have worked on/rebuilt these ratchet top 4 speeds seem very simple, very forgiving and quite tough. I feel confident I could just reassemble this one with the new TOB and be OK. But you do make a point.... Guess I'll have to think about it.

    I wonder if it's possible to remove the top with it still in the frame??? But it's what, 5 bolts holding it in the frame?

  20. #20
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    Less than 15 bucks ....

    https://www.tjsmotorcycleparts.com/p...ic-drain-plug/

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