Author Topic: Gold flash vibration  (Read 502 times)

Offline Spayne

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Gold flash vibration
« on: 27.01. 2015 08:32 »
I wonder if anybody has any ideas why my a10 engine has so much vibration.I have checked all the usual things head steady engine bolts timing etc.The engine runs very well no knocks or rattles I've had a few twins but this one vibrates the most just to add 1959 swing arm

Offline cyclobutch

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Re: Gold flash vibration
« Reply #1 on: 27.01. 2015 10:05 »
Welcome, and all that. I’m presuming that this bike is new to you and has always been like this in your care? I can offer up that my iron head is fine up into the 50s and easily tolerable up to 70 (talking mph). That’s on a std tuned engine with about 3k miles on it – and no particular attention having been paid to crank balance. I guess if you don’t know the provenance then you may yet have to dig a little deeper.

Others will soon kick in here with myriad suggestions to work through I am sure …
Various, including ...
'58 Iron Head Flash Bitza


Online RichardL

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Re: Gold flash vibration
« Reply #2 on: 27.01. 2015 14:04 »
Hello and welcome. It would be great to see some photos and hear a bit about the life of the bike.

If this is your first vintage bike, and you are used to riding modern bikes, there my be nothing unusual at all in the vibration from this solidly mounted parallel twin. If anything is awry, crank/rod/piston imbalance seems the most likely cause. If you can find a shop or friend with A10 experience to help with a frame of reference, that would be a good thing.

Richard L.
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Online Ted_Flash

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Re: Gold flash vibration
« Reply #3 on: 27.01. 2015 15:47 »
I don't know if your bike is a plunger - but if so, some years back I started getting ridiculous amounts of vibration.  It turned out to be the bolt loose that secures the rear sub-frame (the big one at the back of the petrol tank).  Of course there is another one that secures the sub-frame under the engine, plus all the other engine mounting bolts to check - 3 to the gearbox, front engine plates, as well as the head steady.
Ted Wilkinson, Ramsbottom, Lancashire
1950 Golden Flash

Online muskrat

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Re: Gold flash vibration
« Reply #4 on: 27.01. 2015 19:24 »
G'day Spayne  *welcome*.
I agree with Richard, you need to compare it with another, even a Trihard or Notrun twin will do.
Vibration is a harmonics thing where a certain RPM might vibe the tank and another RPM the handlebars (adding or subtracting weight there might help). Other things to consider are wheel balance and trueness *????*, suspension (both sides the same), primary & rear chain condition and tightness.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7