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Vibrations on a 3VC engine

Started by Bozo, September 18, 2023, 07:38:09 AM

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Bozo

My 89 3Cv Fj1200 has some harsher than normal vibration at the usual 3000 to 3800rpm. My engine is not standard (cams, pistons exhaust etc), my standard 89 FJ has a milder form of vibration so is not that much of a problem.
I was thinking of adapting a similar down tube and mounts from a 1991 Fj. (I like my 89 so trading it in for a smoother 91 is not an option), I also know the back mounts are different but I believe its the front that is causing the vibration.
My question is, has anyone done something similar?

Before you ask eliminate -
New chain and sprockets
Shims and carbies checked
New plugs
All mounts are tensioned
All rubber mounts in good condition.
When holding revs at around 3500rpm in neutral you can feel the engine vibrating
First major bike in my life was a Mach III widow maker.
My Second permanent bike 1978 Z1R (owned since Dec 1977)
My Third permanent bike is the 89 FJ12 - nice and fast
Forth bike 89 FJ12 my totally standard workhorse
81 GPZ1100 hybrid - what a bike, built to sell but I can't part with it