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'69 Lightning Fork Issues

Posted By: koncretekid

'69 Lightning Fork Issues - 12/10/11 12:44 pm

I'm in the process of restoring a basket case Lightning which is supposed to be 1969. However, the frame is '67, motor is '65, and front end is either '69 or '70. Assembling the forks to the frame, I found that there was no way to install the front wheel without compressing one of the forks slightly - - one appeared to be about 1/8" longer that the other. Upon dis-assembly, I found that the machining of the bottom of the fork tubes to be grossly different. (note:there is a posting on the Triumph Forum under (Front wheel - Fork alignment issue) which shows the same problem.)

The difference is about 1/8" of an inch. Also, the axle slot was out of square with the tube by about 1/4" in 10".

Was BSA really this bad at quality control? Or is one of these from a different model? I searched thru about 50 sets of used BSA fork tubes at British Cycle Supply, and actually found one exactly like the longer one shown here, including the dimple next to the axle slot, but I couldn't find the mate to it. I picked up a good useable one (on the left) but of course it would have to be powder coated. So I decided to machine them. First I squared up the slot on the shorter one, then I milled about an 1/8" off the longer one and deepened the slot.

the last photo shows the end result.

I will have to get another end cap powder coated, but that can be add at any time.
Can anybody shed light on the small dimples shown on both the fork leg and the cap? Are Triumph, '69 and '70, the same?

Posted By: Bola

Re: '69 Lightning Fork Issues - 12/10/11 1:05 pm

My problem exactly.

You've got missed-matched parts there. Fortunately for me, I found a NOS right slider, and a used left that was a perfect match.

Things to look for... the threads that meet the seal holders should be the same on both legs (of equal length). The sliders themselves should be the same length - making all aspects equal on both sliders. (if lengths differ, the front wheel will fit cock-eyed on the axle) The dimples are only a cosmetic alignment indicator and not an issue. Some tubes had them, some didn't. The axle caps don't have to be the same width but are perhaps better to have the fat ones.

There seems to be quite a variety of fork sliders out there for the same year/s. I'm not sure why. It doesn't make sense. One thing to watch out for - be sure that the knobs that holds the front fender in place are located in exactly the same spot. Machining the fork 1/8" shorter may produce other issues.(eg. compromised thread depth in the bottom of the slider, and a difference in placement for the front fender)

The front fork assembly in both manuals are the same for 69/70 as far as I can tell.

Good luck with this konkrete. It can be maddening!
Posted By: Stuart

Re: '69 Lightning Fork Issues - 12/11/11 1:03 am

Hi Tom,

Various threads on this subject have aired on both the Triumph and BSA Boards in the last few months; while all the definitive answers haven't emerged, this much has:-

. '68, '69 and '70 BSA twin forks incorporate some of the contemporary Triumph bits, but some are peculiar to the Beezas. The BSA top yoke is the same pre-'68 one, and the Triumph tls brakes from each year are used complete, including the shorter axle in '68; most differences are in the sliders, which are not only unique to the Beeza twins but different in each of the three seasons. cry

. In '69 and '70, the Beeza twins used the same stanchions as the B25 singles, which are the same as the Triumph T25 singles. They aren't the same as the stanchions used on the Triumph twins or Trident and Rocket 3 triples. However, because all '69 and '70 stanchions and sliders are different lengths, the stanchions used on BSA twins are also unique to each year. cry


Posted By: EWebster

Re: '69 Lightning Fork Issues - 12/11/11 6:54 am

The dimples are only a cosmetic alignment indicator and not an issue.

You sound quite confident of this! The photo with the tri square.....why not put a protractor head on it and measure the angle?
Posted By: koncretekid

Re: '69 Lightning Fork Issues - 12/11/11 1:20 pm

Tri-square to measure the angle would have been interesting, especially if I could have complained to my local BSA dealer and insisted on warranty! In my case, I only needed to know that it was not square and needed to be fixed.
Posted By: EWebster

Re: '69 Lightning Fork Issues - 12/11/11 4:39 pm

You are assuming the angle is not intentional.
Posted By: Ed V

Re: '69 Lightning Fork Issues - 12/13/11 1:03 am

When we run across this which is quite common we grab a Triumph lower leg and use it in place of the longer BSA one problem cured
Posted By: koncretekid

Re: '69 Lightning Fork Issues - 12/13/11 11:51 am

I guess I should have looked thru British Cycle's box of used Triumph fork legs but I didn't think of that. In any case, the hole being bored out of square had to be corrected, so I solved the problem.
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