Hitchcocks Forum

After 40 years on two wheels I finally had a prang yesterday on the RE. It was absolutely and entirely my fault. I changed into the next lane on the motoway heading for the lane after it without noticing that the van in front had stopped. Other than a few bruises and very dented pride i did little damage to myself but I bent the 50's forks on the Bitsa. Amazingly I was able with the tool kit I carry to put the bars around the right way again (their spining in the mount probably saved me broken wrists) and a couple of zip ties held the broken clutch perch on sufficiently for me to drive it home. Sadly though whilst most repairs are simple cosmetics the fork stauchions are going to need to be straightend. Interested to hear if anyone has done this successfully and if it was cold or hot or in a press?

Any creases in the fork tubes? Get new ones...


Otherwise, press cold, and over-press slightly as the tube will spring to some degree. Check for truth by rolling, or if you have a decent lathe use a dial indicator. Try to keep run-out to under 0.010"


Both tubes will probably be bent in the same plan, so mark each leg (L & R and front) and return it to its original place.


That will minimise any errant offset that can otherwise occur when swapping them about if they are not perfectly straight. Any more than 0.010" run-out will be most obvious when you go the screw the tube back in...


Be patient and take your time, allow at least 10 minutes and half a dozen trips on and off the press for each leg. Use an alloy spacer between the press and the leg to prevent any steel-on-steel damage from occuring.


Also, check that the bottom fork yoke has not 'opened' up. (The distance between tube centers) The latter Indian made bottom fork yoke is reinforced across the front of the yoke and stands up better to front end damage. You can tell if the bottom yoke has been bent back as the axle clamps on the sliders will be 'sprung' apart and wont be sitting up against the axle nuts.


Inspect the steering head races for indentations from the balls...

Thanks Tim that sounds like sound advice, it was a relatively low speed prang so so I doubt there is any damage to the head race. As you say both legs seem to have a similar deflection and from a brief inspection that seems to be all the damage other than a scratch on the tool box lid. Ill dissemble this weekend and see what there is to be done.

I had a front end impact on my sm. Wrote my fork legs off. But the lower stanchions were ok. I also bent the lower clamp. It wasnt visible to the naked eye but when i clamped it in a vice and inserted the new tubes it was clearly apparent. You will need to check the front wheel as well to make sure it is still true. Ed

A good careful check of the sliders wouldn't go amiss.

A woman pulled out in front of me whilst I was riding my Honda 750 and I ran into her. The forks were bent a small amount and so a friend that built bull bars for 4 wheel drives straightened them for me.
As Tim said he pressed them cold and over pressed so that they sprang back strait again. He tested for straightness by rolling them on the gasket side (no gasket of course) of a car head that he had sitting in his work shop.
With a light behind he could see if the forks still had any bend. I should imagine that a straight edge would have been better but this was all that he had. I put them back on and I am still riding around
years later with them. I can not detect any difference. He said that they were probably straighter than when they left the factory brand new.

Spent Saturday morning straightening the stauchion tubes. Clocking them with a dti the bend on both was about .085". My mate the musical instument maker made some maple wood blocks with the appropriate size saddle cut into them so we didnt crease or mark the tubes. Used a 20 ton press with a dti to measure the deflection. It is really interesting that the tubes will flex to a certain extent and then give the secret is knowing the give point. At first we tried the .085" plus another .050" but that did nothing. Ended up requiring around .180" deflection to get a useful bend. Got them both back to within .010" so hopefully the Bitsa will be back on the road in no time. Thanks for the help. S:)

Yeh, steel is like that. You have to take it over its elastic limit so it returns to where you want it. There's a black art to bending steel. Thing is, the stuff can take several hours to creep to its final position (hysteresis), so it may be worthwhile measuring the fork legs again before fitting them.

There's also a technique called heat straightening. Applying heat (blowtorch) to the band will push it straight and somewhat surprisingly, it doesn't go all the way back when it cools.

Simon, don't forget to check the bottom yoke as well. The Enfield bottom yoke is very weak and prone to twist in even minor shunts. Try turning the handlebars with the front wheel between your knees and you'll see what I mean. On forks from 1958 onwards there is a strengthening rib added to the casting but it does no good because it doesn't include the stanchion "eyes" which actually transmit the forces. It's pretty easy to fix, the steering stem and eyes are in the same plane so with a stanchion in one eye and the stem clamped in the vice, heat cheery red and twist. Then measure run out between the two stanchions. I've done so many it probably only takes me half an hour. Once the yoke is off the bike!

REgards, Mark