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Discussion Starter #1
Rather than update the many posts in which I've participated I thought it would be simpler to summarize my experience in a new one.

The symptom: vibration and noise, specifically at 30mph. Severe enough to feel it in my legs and through the foot pegs. Wife gets on the back and the noise would disappear! I could not replicate the problem on the stand. I found about 6 other riders here with the same symptoms, but none were available to share their solution, or perhaps were never solved.

I've been at this for almost a year and have changed every bearing (wheel, steering, swingarm), the universal, fork bushings & seals, rear wheel flange, and tires. I ruled out the speedo housing, fuel tank, headlight bucket, tire inflation, brake rotors, calipers or pads, and heat shields. Basically, I have a new bike.

Solution: a few years ago I had replaced my OEM 1300 SHOWA shocks with used ones from an 1800. The 1800 shocks are just a half inch longer, slightly changing the drive angle. I replaced these with Progressive 412 4234C heavy duty 12" shocks and I am pleased to report that the vibration and noise has completely disappeared.:pepper1:
 

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Pete---congrats on eliminating your issue.
Longer 1800 shocks caused your problem.
Did you actually have a higher ride height with the 1800 shocks?
Wondering if it was the drive line angle or some resonance.
 

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Discussion Starter #3 (Edited)
Thank you Hans, I never felt like I was riding higher but I believe so. I had my son measure the shock length with me on the bike, and then again when my wife sat on the back. The difference came to roughly 1/2 inch more compression with the additional rider. I had thought about switching to Progressives anyway, so since I no longer had my original 1300 shocks, we decided it would be worth the additional $240 investment if it could possibly solve the problem. And it did!

I also thought of the possibility that our final drives might have some minor vibration at that speed, and that some shocks absorbers could act as an amplifier. I'm not sure how we could make a positive conclusion whether it was the length affecting drive angle, or a resonance. One local Honda dealer tech did say that when they installed snow blowers on the front of a Honda tractor (or ATV?) that it would change the drive train angle just a bit and "wreak havoc" on the universal.
 

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And here I was expecting to see that explanation that the blowing wind and whining problem was from the passenger...once they got off it stopped and couldn't replicate the issue.:p
 

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I'm glad you got it figured out, Pete.. That is a lesson for all of us.. Any modifications from OE can and mostly will have side effects.. Some we may notice, and some we may not.. Nice work!
 

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Congrats on your fix, I had what sounds like the same vibration & noise when slowing down and Progressive shocks fixed my problem also.
 

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Thanks for sharing Pete. Good lesson for the rest of us. BTW were your shock bushings still good when u pulled the longer shocks off?
Tony
 

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Actually I believe it was the longer shocks causing the issue. I'm not a motorcycle mechanic but I am a mechanic and have had engineering schooling. The same issue can present itself in autos and trucks as well. What happens is when elongate (raise) the rear ride height it changes the geometry of the bike effectively loading the front shocks and changing the front to rear weight balance. Drag racers do it on purpose to change to traction point of the rear by putting the effective weight just in front of the center of the tire instead of the actual center. So what occurs when your wife climbs on it relieves the front shock loading by moving the center of gravity of the bike back to where it was.
 

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Discussion Starter #10
Congrats on your fix, I had what sounds like the same vibration & noise when slowing down and Progressive shocks fixed my problem also.
Thanks Grizzly, That makes THREE of us with the same problem and same solution. There was one other gent's post that put the thought in my head.
Thanks for sharing Pete. Good lesson for the rest of us. BTW were your shock bushings still good when u pulled the longer shocks off?
Tony
Yes, I had switched them to the green poly bushings. They were brand new. The Progressive shocks contain their own bushings.
 

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Discussion Starter #11 (Edited)
I doubt the shocks were the actual cause of the problem, more likely they are just masking the real issue....like putting weight on the back.
Possibly jetting related, this can be the cause of weird harmonics.
Hi Donnie, I agree with you that the shocks weren't the cause. I believe the increase in length & drive angle was the culprit. Putting additional weight on the back actually quieted the noise. So many of us have switched to the 1800 shocks with no problem, but there are so many moving parts involved - maybe some our bikes just cannot handle that small change. I've never changed the jetting - that's still stock
 

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Discussion Starter #12
I'm glad you got it figured out, Pete.. That is a lesson for all of us.. Any modifications from OE can and mostly will have side effects.. Some we may notice, and some we may not.. Nice work!
You're welcome Starr. I'm so glad it's fixed. I was starting to look at new Harleys! Phew! That was close:laugh:!
 

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Pete, I am happy to hear that you solved your problem after all the hard work that you put into solving the problem!

You sound quite confident that the problem is resolved. Would you say that you are sure this is the final resolution or do you still think there's a chance the noise will return?

Also, where did you order your shocks from?

Max
 

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Discussion Starter #14
Pete, I am happy to hear that you solved your problem after all the hard work that you put into solving the problem!

You sound quite confident that the problem is resolved. Would you say that you are sure this is the final resolution or do you still think there's a chance the noise will return?

Also, where did you order your shocks from?

Max
Hi Max,
I was hopeful once before, after replacing my universal & rear tire that the worst was over, but it was never 100% completely quiet. With the shocks replaced it is now completely quiet. I've ridden it three times since the shock install, and I will be taking it out for a few hours tomorrow for a lunch ride. If it remains absent through tomorrow, I will be comfortable claiming a victory.

I purchased them through Amazon. They had the best price, shipped, at $236.96. This was for the 412 Series Heavy Duty 12in. Shocks - Chrome 412-4234C.

I will post an update tomorrow afternoon.
 

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Discussion Starter #15 (Edited)
Update: Vibration is still GONE

I will post an update tomorrow afternoon.
Hi Max,
Update, as promised...
I put on another 150+ miles today. The bike is running smooth. The Progressive shocks feel great, and it is as though the vibration had never occurred.
 

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Hi Max,
Update, as promised...
I put on another 150+ miles today. The bike is running smooth. The Progressive shocks feel great, and it is as thought the vibration had never occurred.
FANTASTIC!

I also had good results after replacing the Final Drive but the problem does still occur. The problem is not as bad as before the replacement but still not resolved 100%. I may just bite the bullet and replace the shocks. Thank you for sharing your experiences.

Max
 

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Discussion Starter #17 (Edited)
FANTASTIC!

I also had good results after replacing the Final Drive but the problem does still occur. The problem is not as bad as before the replacement but still not resolved 100%. I may just bite the bullet and replace the shocks. Thank you for sharing your experiences.

Max
That's what I experienced when I changed the universal. Partial success. Please do let me know the results if you do decide to go with the Progressives.
 

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Pete,

I was out of town when the shocks were delivered. I took today off to get ready for a trip to see our grandsons but had time to pop the new shocks on and put about 50 miles on. I can't honestly say the noise/vibration is noticeably any different than before the shock replacement. It seems replacing the Final Drive made the biggest difference for me, so far. Maybe I'll have to try the Universals. I am just not looking forward to replacing them though.

The noise is probably no big deal but I am the type that if something isn't "right" I have a hard time ignoring it.

Thanks for documenting and sharing all your experiences, you have been unbelievably helpful.

Take Care and Ride Safe!
Max
 
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