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My 68 CB450 vibrates and it's worse at 5 - 6k RPM range, so much that after 20 minutes of highway riding at 60mph my ass feels painfully numb, my commute to work on highway is 40 minutes so I'm pretty much crying halfway. Are these bikes like this? Anything I can do to lessen the severe vibration?
 

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I changed the front sprocket on my CB500T to a 17 tooth. I can cruise at 60mph all day long at just over 3K RPM, very comfortable.
 

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JayC said:
My 68 CB450 vibrates and it's worse at 5 - 6k RPM range, so much that after 20 minutes of highway riding at 60mph my ass feels painfully numb, my commute to work on highway is 40 minutes so I'm pretty much crying halfway. Are these bikes like this? Anything I can do to lessen the severe vibration?

mine seems to be worst at 4-5k and then smooths out. these things are kinda buzzy by nature, but you might try checking on if your carbs are opening at the same rate and adjusting your throttle linkage accordingly.


probably not your best option but, rearsets and gel gloves did wonders for my situation
 

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Back in The Day (not so much anymore), some guys used to remove the top engine/frame mounts.
They claimed it made a substantial difference, but I never had the hair to try it....

Increasing the size of your counter sprocket will absolutely help. A 450 has plenty of gruntage to deal with the change.

And if you "broke in" on modern bikes, these old bikes will always seem not as smooth.
 

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One of the bug bears of the 450 is the ignition timing which when the points heel wares you will get the timing correct a idle but the timing will be out, and often very far out, at full advance. This is the most likely cause and should be looked at first. You will need a timing light to check the advance at over 3000 RPM. There are ways of reshaping the heels but this is only a stop-gap fix, new pionts are the only real way. On the original Honda points backing plate the only make of points I have found to work correctly are the Diichi.
 

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Hi Rod, I'm in Adelaide. Allan
 

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tbpmusic said:
Back in The Day (not so much anymore), some guys used to remove the top engine/frame mounts.
They claimed it made a substantial difference, but I never had the hair to try it....

Increasing the size of your counter sprocket will absolutely help. A 450 has plenty of gruntage to deal with the change.

And if you "broke in" on modern bikes, these old bikes will always seem not as smooth.
I removed the top engine steady on my 500T over 1,000 miles ago with only sighs of relief. Less vibration in the handelbars, and in the saddle is an understatement. The bike feels less rigid, yet still handles well enough for back roads.
If I were racing the bike, I would never do that, but normal street riding hasn't been a problem. I live in Cincinnati, so you can be sure it's been over more than it's fair share of pot holes, HWY expansion joints, and just plain rough roads, and nothing has vibrated loose or fallen off.
 

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I have had vibration issues.

Things to check, make sure all engine mounting bolts including the large main bolts are tight, “the big bolts on mine had worked loose or I had forgot to completely tighten them on install ", this was a big part of my problem along with wheel balance. Make sure your tires/wheels are balanced, check that your carbs are perfectly synced, this also can be a very noticeable vibration causing factor. These were the main causes of the vibration I had. I had already replaced my handle bar rubber so that was not an issue. It was recommended by others that bar weights would reduce some vibration, I have not yet done that and most likely well not as I don't have the major vibration issue any more. I think you will always have some vibration that is just inherent to the twins.
 
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