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post #1 of 9 (permalink) Old 12-02-2012, 06:22 AM Thread Starter
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Pre-unit front suspension

The forks I have are from an early pre-unit forks....just post war...late 40's early 50's.
There is too much movement on them for my liking and would like to stiffen them up if possible.
Is there an easy way to do this? I've put in the thickest fork oil I could find, bit it seems to make little difference.
Are stiffer springs available or maybe an additive to the oil I can add to thicken it up?
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post #2 of 9 (permalink) Old 12-02-2012, 06:50 AM
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You'll have to make up your mind what the problem is. If the springs are too soft, you probably just need new springs to original spec. Your springs are probably just old and knackered. Putting heavier than standard springs in, without having tried good standard ones, could be a mistake.

If your problem is insufficient damping, there may not be much you can do, apart from trying thicker oil. SAE50 engine oil is available and is very thick.
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post #3 of 9 (permalink) Old 12-04-2012, 10:40 PM
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Originally Posted by Splittie65 View Post
The forks I have are from an early pre-unit forks....just post war...late 40's early 50's.
There is too much movement on them for my liking and would like to stiffen them up if possible.
Is there an easy way to do this? I've put in the thickest fork oil I could find, bit it seems to make little difference.
Are stiffer springs available or maybe an additive to the oil I can add to thicken it up?
New springs and new internals are available, and may stiffen your suspension up to the point where 20 weight fork oil is more than enough. At least that has been my experience with 1959 forks. Parts came from Ace Classics.

Hope this helps
Cheers,
Neil.
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post #4 of 9 (permalink) Old 12-05-2012, 04:39 AM
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you could do worse than price up hagon replacements
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post #5 of 9 (permalink) Old 12-05-2012, 05:01 AM
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you could do worse than price up hagon replacements
Is that not for the back end, of newer bikes than that?
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post #6 of 9 (permalink) Old 12-05-2012, 06:01 AM
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They do supply fork springs, but I'm not sure how far back the catalogue goes.
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post #7 of 9 (permalink) Old 12-05-2012, 07:07 AM
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Early preunit forks should be plenty stiff enough for an early preunit bike if in reasonable condition. What are they being used on?
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post #8 of 9 (permalink) Old 12-05-2012, 08:12 AM
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I'm not sure how far back the catalogue goes.
Availability of springs never seems to be a big problem. Not dear either.

Maybe because so many are so similar.
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post #9 of 9 (permalink) Old 12-05-2012, 11:46 AM
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I had a similar problem. I tried new springs and all sorts of ideas. What solved it for me was a 3/4 inch spacer at the op of the spring between the spring and the top nut.

You also want to check the length of the bottom tubes they might have been changed out at some stage and may be longer or shorter than the originals.

Note that 3/4 inch was the lenght that worked for me but it could be more or less.

What you can do is assemble the whole shock on the work bench and check if you have play or free space and then make-up a spacer just longer than required between the top nut and spring.

Oil will not solve you problem.
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