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Falcon 67 rear suspension

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rear - Falcon 67 rear suspension Empty Falcon 67 rear suspension

Post  marcusrm on Thu Nov 29, 2018 2:20 pm

Does anyone know the length (eye to eye) of the original rear shocks on a 1954 Falcon?
I am aware of the scarcity of originals. When I bought the bike it had fitted already modern suspension units.
The units are about 12.4 inches long. I think that this is too long, making the swing arm crush the rubber bump stop, and when
the bike is on the centre stand the rear wheel still touches the ground.
Although not a proper match I am hoping to get a pair of shorter modern units.


Thanks in anticipation.

Marcus

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rear - Falcon 67 rear suspension Empty Re: Falcon 67 rear suspension

Post  Rex Stewart on Thu Nov 29, 2018 5:16 pm

Marcus I would be interested in which suspension unit you eventually buy, I bought a Falcon in August which has a similar problem and a side stand has also been added at some point. A part from that the bike runs well although could do with a repaint. So any information would be welcome.

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rear - Falcon 67 rear suspension Empty Re: Falcon 67 rear suspension

Post  Jack Clegg on Fri Nov 30, 2018 11:42 am

12.5 inches eye to eye unloaded, 10.5 inches riding, 8.75 closed. So 12.4 is nearly correct. Perhaps your stand is a bit worn?
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rear - Falcon 67 rear suspension Empty Re: Falcon 67 rear suspension

Post  marcusrm on Fri Nov 30, 2018 1:03 pm

Jack, thanks for that. I have taken off one suspension unit of to measure it.
The eye to eye length is indeed 12.5 inches, the unit was slightly compressed when fitted.

What disturbs me is the massive force that I have to use to compress the units to fit, I even had to make
a special tool and it was still a fight. And the compression of two units puts an even bigger pressure, taking in to account the leverage ratio, on the rubber bump stop.
In fact I would say that the bump stop is crushed rather than compressed.

So I am now thinking that the units may have a springs that are too strong.
Your thoughts?

Marcus

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rear - Falcon 67 rear suspension Empty Re: Falcon 67 rear suspension

Post  Jack Clegg on Sat Dec 01, 2018 12:27 pm

Marcus, you shouldn't have needed a spring compressor tool. Sounds like the springs are OTT. I recall struggling to compress my units by hand & using a small lever between the frame & shock-top. It's a weird set-up for sure & the shocks are slimline specials. NJB units I used. TTFN Jack
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rear - Falcon 67 rear suspension Empty suspension units

Post  Bigjim on Sun Dec 02, 2018 6:44 pm

Are these the in-house homemade ones? The ones that can be totally stripped and rebuilt, apart from getting the chrome covers?  As used on James 1955 Captains?rear - Falcon 67 rear suspension 1954_r10
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rear - Falcon 67 rear suspension Empty Re: Falcon 67 rear suspension

Post  Jack Clegg on Mon Dec 03, 2018 12:04 pm

Yes Jim, they're the ones.
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rear - Falcon 67 rear suspension Empty 67 rear springs

Post  keith livingstone on Wed Dec 05, 2018 10:58 pm

Hi guys
I too have a 67 and would appreciate any feedback from your experience.

Rear springs
Your question in the shock absorber centre length hit a chord
I got my 67 back on the road again in 2010 as a rolling restoration project but have been frustrated that despite my best efforts the top chain run continues to wear down on the swinging arm.

I have the original refillable shock absorbers
I've tried to keep the chain adjusted correctly
I've increased the gearbox and rear sprocket to 18 & 50 to raise the chain run
I've attached a steel guide to protect the top of the swinging arm
But the chain wears it out and still wears down on the swinging arm.

Any suggestions?

My last chance is to fit shocks with smaller centres! Maybe 11" instead 12.5"
Hopefully this should raise the wheel centre above the sprocket enough without causing the wheel to rub under the guard when fully compressed.

Best wishes with your's Martin
I'd be interested to see how you get on.
Keith



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rear - Falcon 67 rear suspension Empty chain wear

Post  piston 197 on Thu Dec 06, 2018 5:32 am

Keith replace the steel block with a piece of urethane, the chain will still rub, but will not damage anything.
JH
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rear - Falcon 67 rear suspension Empty Re: Falcon 67 rear suspension

Post  Jack Clegg on Thu Dec 06, 2018 12:01 pm

"They all do that sir." Bad design. As John says, urethane is best.
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rear - Falcon 67 rear suspension Empty Re: Falcon 67 rear suspension

Post  marcusrm on Fri Dec 07, 2018 12:34 pm

Interesting. I have just checked the chain on my 67 and it has about 8mm clearance above the swing arm.
Bike is on its stand and the suspension (12.5" units) fully extended.

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rear - Falcon 67 rear suspension Empty cHAIN CLEARANCE

Post  piston 197 on Fri Dec 07, 2018 12:38 pm

marcusrm wrote:Interesting. I have just checked the chain on my 67 and it has about 8mm clearance above the swing arm.
Bike is on its stand and the suspension (12.5" units) fully extended.

That will all change when you sit on the bike and even more so as you ride up and down a bumpy road, i have never seen one yet where there is not chain witness marks on the swing arm when the standard shocks and sprocket sizes are used
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