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Discussion Starter · #1 ·
Trophy 650 chop 1966, 4 speed box.Accelerates reasonably smoothly to 60mph, goes into severe vibes around 70mph, then smooths to a buzz around 80 onwards. is this normal?- feels like mechanical abuse pushing through the70mph.. its got extended springer forks, and heaps of other odd parts, hardtail etc..so maybe sympathetic resonance, or anyone know how to sort it.

new to old brit bikes, so do htey all do that?
 

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I beg to disagree. Severe vibration (and I suppose that's a judgement call) isn't normal at any speed with a standard 650 in good condition. Given what you've done to the bike, though, normal rules don't apply.
 

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I beg to disagree. Severe vibration (and I suppose that's a judgement call) isn't normal at any speed with a standard 650 in good condition. Given what you've done to the bike, though, normal rules don't apply.
I am going to agree with abmar on this one. Any vibration on
one of these engines will be a steady progression. Not starting
up and then going away. Barring any weird imput from suspension
at speed or an out of balance condition of tires and wheels.

I would look into these, check timing and balance the carburators if
a twin carburator setup.

Pookybear
 

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Does the bike still have the head steady braces on it? They are the 4 small pieces that go from the top of the rocker boxes to brackets on the lower top frame tube.

Just a silly thought: Jim
 

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Jim
Not silly at all! I was going to suggest that he should check all the motor mounts and brackets/stays for loose fasteners and/or cracked or broken brackets. I had a bike years ago (another brand) that would vibrate severely at around 3 thou RPM . Relatively smooth otherwise. Some one much wiser than me suggested I look at the top motor mount. Claimed this bike was notorious for this piece failing. You can guess the result.
After the repair I felt I had traded for a different motorcycle. SMOOOOOOTH.
 

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If the motors smooth up to 80 mph, l would be happy with that. The sudden vibration could be the change to the frame ect, l would be louthed to mess with the engine unless it was in the original or similar frame with engine brace. How often would you run a TR6 past 80mph, after all 90mph is top wack to be honest and cruising is 70-75. Could be opening a can of worms.
 

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Sorry l reread the opener and he said 70mph ,the vib started, so ignore what l said. yeh replace the head steady!. Hey T100R !. my T100c is the smoothest bike l own up to 65+ mph, my German pal rode it to the Isle of Mann classics and was so suprised as he felt it was as smooth as his early BMW,s , cannot get a better compliment than that. Think you need a balance!!.
 

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I decided to leave the bottom end alone when we did the top end last year ... Hopefully, the engine will outlast my ownership ... or at least last until I have the other one built ... which will be sometime after I start working on it... which will be sometime after I amass some more pieces ... which will be sometime after I start having money again ...

Anyway ... yeah ... my T100 is definitely NOT smooth ... maybe if the cases ever get split I'll do it up with the lightening / balancing / etc ...
 
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