Anyone conversant with BSA A50/65 pre-1970.

Or a model that has similar yoke (front fork) arrangement.

I have recently acquired one but have noticed that there is some degree of front fork mis-alignment (twist). Attempts to re-set have so far been unsuccessful. Careful checks on front-rear wheel alignment seems ok. Looking for suggestions on what could be wrong.

Hi know nothing of BSA's but an Mz 250 I had once had, had been used (Abused) with a sidecar attached and it had bent the Fork stanchions into a pronounced banana shape (only obvious when stripped down + rolled on a flat surface)...the the lower sliders were fine + when it was all assembled every "looked" Normal.....BUT NOT SAFE TO RIDE!.....

Yes, one of the tubes could be slightly bent. The forks will re-set to parallel by the usual methods, but when the yoke clamp bolts are tightened they revert back to the mis-alignment.

Slightly loosen the yokes and then bounce the forks to settle them and then retighten yes?

Places to check - stanchions for straigthness - roll on some plate glass to look for flatness.

Check that the triple clamps are not bent as well, had that before.

Also make sure that the headstock bearings are sat properly and they are not worn - I had a Triumph once with the top race that was shot and it took me ages to figure out what was going on - the race causes the clamp to move and that translated into a fork misalignment.

Obelix- I have to go out now, I'll answer you when I return.

---------- Post added 25-02-2017 at 21:49 ----------

Obelix- I have to go out now, I'll answer you when I return.

On a routine check of the rear/front wheel alignment, I noticed that the handlebars (and top yoke) were set slightly to one side, confirmed with taping long straight edges across the lower fork legs and top yolk, I then removed F.wheel and slid a long bar though axle. With everything slackened off (inc. guard stays) it could be twisted straight, but as soon as either lower yolk clamp-bolt was tightened, it was back to square one. So, it could be bent tube. The races seem ok, no play. Ironically it was only MOT tested a few days ago before I had the bike delivered. I have not ridden it yet, In fact I have to insure it etc. I am going to contact the seller tomorrow

This problem can be caused by simply re-tightening the bolts in the wrong order.Firstly slacken all fork retaining bolts,then bounce the bike to ensure the fork legs are fully in their top yoke sockets.Next align the forks,I always do this by holding the front wheel between my legs and twisting the handlebars,then re-tighten each fork leg top nut.Next tighten the centre nut which clamps the top yoke to the bottom yoke,this needs to be really tight.Recheck the alignment and finally re-tighten the bottom yoke clamp bolts.Hopefully this will have solved your problem.

This problem can be caused by simply re-tightening the bolts in the wrong order.Firstly slacken all fork retaining bolts,then bounce the bike to ensure the fork legs are fully in their top yoke sockets.Next align the forks,I always do this by holding the front wheel between my legs and twisting the handlebars,then re-tighten each fork leg top nut.Next tighten the centre nut which clamps the top yoke to the bottom yoke,this needs to be really tight.Recheck the alignment and finally re-tighten the bottom yoke clamp bolts.Hopefully this will have solved your problem.

On these forks, the tubes are a taper fit into the top yoke. I've tried your method but it makes no difference- it takes a fair effort on the bars to square the top yoke to parallel the axle at the same time holding that position whilst tightening the bolts, but on release it springs back. When not under tension, the bars and top yoke are around 5 degrees out of parallel with the axle line. I suspect a slightly twisted yoke.

---------- Post added 02-03-2017 at 22:56 ----------

Problem found, bottom yolk is mis-aligned (distorted), no doubt to some spill in the past.