New Member with fork trouble

Britain's largest and most successful motorcycle manufacturer was BSA (Birmingham Small Arms Company).

New Member with fork trouble

Postby AltaLightning » Fri Aug 09, 2013 7:46 pm

Hello,

I just joined the forum and am hoping someone can shed some light on my current problem. I am a relatively new owner of a beautiful 68 Lightning. I have only driven a few hundred miles so just getting to know the bike. The forks are leaking and they topped out with a bit of a clunk recently after going over a rise. I assumed they were low on oil, and that the seals and stanchions may be suspect. Upon dismantling I found that the forks did not contain the damper tube, rod and valve assembly I was expecting. After driving the local part supplier in Alberta a bit crazy, I am beginning to suspect that I have forks from older era that did not have damper tubes. We initially thought these forks may have been the shuttle valve style, as there is a restrictor in the bottom of the legs. I was sent a new set of seals, lower bushings and shuttle valve assembly, however they will not fit in my setup. Also, there is no "through bolt" to fasten a new style (1969) restrictor, or for that matter a damper tube from the 68 variety. My fork legs, as noted above, contain a restrictor cone that is considerably larger than the 1969 variety and appears to be integral with the fork leg (not fastened in with a bolt). I assume that there should be no restrictor in a damper tube setup. I understand that the 1965 Lightning Rocket had forks similar to mine, without the damper tube. I am wondering if a member might be able to confirm if the fork legs on that model contained a restrictor. I am a bit suspicious of the stanchion tubes also, as mine have a set of holes in the bottom that are all at the same level. This may be correct, however I suspect the holes should be separated vertically. The top cap bolts are threaded to accept the nonexistent damper rod. If I can confirm my current suspicion that I have an older setup, I could stop looking for missing parts and perhaps search out the correct style for my 1968 year.
If someone with the 65 era fork tubes can confirm that the legs have restictor cones, I would greatly appreciate it.
AltaLightning
 
Posts: 3
Joined: Fri Aug 09, 2013 6:14 pm

Re: New Member with fork trouble

Postby Paul in NZ » Sun Aug 11, 2013 8:14 pm

The easy way is to get the parts books for the specific years and compare the drawings....

By 68 I would expect they were using the group forks which dont have a damper rod. If its topping out a lot check it has the right springs. Sidecar springs were fitted to my TR6C from new and are waaay to strong for normal use.
Paul in NZ
 
Posts: 82
Joined: Sun Mar 25, 2012 10:56 pm

Re: New Member with fork trouble

Postby AltaLightning » Mon Aug 12, 2013 6:51 am

Thanks Paul,
The 68 Lightning is supposed to have a damper rod and tube. In 1969, (and perhaps late 68) they went to the shuttle valve method for dampers.
Mine appears to have neither, although it is a 68. The 1966 model did not have a damper rod, but from what I have seen from that year's parts book, the lower fork legs appear to have a different arrangement for fastening the front fender, I have not been able to find a 67 parts book, but I am guessing it had damper rods.

At this point I am assuming I have forks from an earlier year. I am just not sure what model they came from, but they do accommodate the double leading shoe front brake.
From the outside, the forks look correct for 1668.

I decided to put them back together as is and put Valvoline MAX Life Def ATF in them. The only clunk I got was when crossing some railway tracks. Other than that, they are improved considerably.

I am still curious as to what I have, but at least I have found out some years not to much earlier than 68, they had reduced damping. I have the bike back on the road, which is the main thing!

Wayne
AltaLightning
 
Posts: 3
Joined: Fri Aug 09, 2013 6:14 pm

Re: New Member with fork trouble

Postby Paul in NZ » Mon Aug 12, 2013 7:55 pm

Well I guess if its not topping out so much now either you put on a bunch of weight or the oil helped whatever damping mechanisim it has got work better...

Old british bikes - Ya just got to love em...

I guess forks are one of the most often damaged parts so its probable some accident damage was repaired along the way?
Paul in NZ
 
Posts: 82
Joined: Sun Mar 25, 2012 10:56 pm


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