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Comfortably Numb
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1,151 Posts
Discussion Starter #1
OK, when I hit a bump in the road on my 1993 Heritage Classic I'm getting a banging noise coming from under or somewhere in the bike towards the rear not the engine. It's like something has broken or is loose. I'm aware of pretty much everything it could be but before I start tearing the ass end apart I'd like to hear from someone who has had a similar experience and what they found out it actually was.
 

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Comfortably Numb
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1,151 Posts
Discussion Starter #3
Nope, nothing like that under there. Went around and under tapping with a rubber mallet and nothing was loose or broken.
 

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weird member
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1,935 Posts
Man, the same thing happens to me on the FXSTC that I had before and on this one (three Evo softails, two different riders). Let me know if you find it.

It's only when I hit a bump just right and just hard enough, almost always uphill or like, a rattly bump, definitely not bottoming out and all fasteners tight (transmission to transmission mount plate, mount plate to frame, engine to frame, inner primary to everything, oil tank, etc etc etc). Mainly it happens when the road is flat, then there's like, a steep angle, amost like a ramp, say like an intersection where approaching, road is kind of downhill but the cross road is up and it's a sharp V where it crosses, if that makes sense?

And I hit some bumps hard before where I almost did bottom out (or would have had I not kept my suspension adjusted tight enough for 2-up) and it not make that "thunk" sound. Almost sounds like it's coming from within the primary, my suspicion is maybe the primary chain either smacking the inner primary (even though it's properly adjusted). There's absolutely no marks where maybe the shocks might have hit the transmission mount bolts, nothing on the swingarm.

The only place I have seen any scraping on mine is on the inner primary, just below and slightly forward of the clutch basket (and a chain that's too loose on this kind of primary is going to smack at the top where that cover mounting boss is right before the comp sprocket). And my chain is definitely not loose. I roll the tire cold and find the tightest spot on the upper strand and adjust it to the tightest (≈ 5/8" to 11/16"; maximum is 7/8" cold), because I got that 28 tooth comp sprocket for the Baker DD6 so if it's adjusted to 7/8" cold, chain smacks like crazy when cold.

Anyway, next time you're in your primary, let me know if the inner is scraped below the clutch basket.

I even checked the final drive belt guard for looseness or the belt smacking and nothing.

EDIT:
Here's a pic of what I mean by the primary chain smacking the inner...

IMG_20190827_032850762.jpg
 

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weird member
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I got to thinking about it today and I wonder of it's not the jiffy stand? I mean, mine is properly adjusted and the spring is good but, it's not hard to bounce it in its up-most position.
 

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Lost the bumper on mine twice. Clanked against frame. Glued the third one on. Had another sound coming from rear. Sounded like something sliding while in curve on two lane roads with some gentle bumps in the curve. 50-60 mph. Found the inner plastic splash shield just forward of rear wheel loose. One small screw secures it at bottom. Snaps on to frame at the top. It was off at that point. Popped it back on, no more noise. Quite a few electronics behind it.
 

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You might want to check the rubber bushing in the bracket(s) that support the pipe(s) at the furthest point down stream - that was my problem and I had a heck of a time describing it or reproducing it. The keen ear of my HD tech guy crushed it.
 
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