Forum

[nickbarber]

Hi all. Got a 1971 bullet 350 im restoring. Does anyone know the thread type/size for top of the forks (where the forks meet the casquette)
Thanks all!

[Adrian]

The stanchion outside diameter is 1⅜" or **very** nearly 35mm. The thread is 26 TPI cycle thread. I saw a post on a facebook group recently where someone had managed to fit a set of 35mm Suzuki disk brake forks into an Enfield by cutting a thread on the stanchion tops to match.

[nickbarber]

1 3/8" cycle thread.. awesome thanks heaps. I've got a modern(cheap Indian) fork replacement for the bike but the forks are threadbound before they reach the top of the casquette. So it's either buy a modern casquette which I'm guessing will fix the problem, or to buy a die and extend the thread on the forks. (If you can buy a die that large that is...)

[Mark M]

I think you can get that die from Tracy Tools but it won't be cheap! Another possibility is that the Indian thread is not very accurately cut (quite likely,) and if so you could lap the threads together using fine grinding paste. This will remove more alloy than steel but it's up to you. This assumes the threads are allowing the stanchion to enter some reasonable distance and aren't binding after say, 2 or 3 turns in which case you will need the die! And also probably a die stock as the die will be larger than the normal 1" size usually found on most cycle parts. You could also get someone with a lathe to re-cut them, if you have a willing enthusiast this might be cheapest.

REgards, Mark

[nickbarber]

The thread on the forks seem quite good surprisingly, and the threads seem the same on both the casquette and the forks, I can get about 10 or so turns quite easily before the forks become threadbound, so I'm still tossing up whether to increase the thread by means of using a die (finding a stock shouldn't be an issue as I build lycoming engines for a living) but I suppose it's just a matter of finding the cheapest/least time consuming solution.. if only I could attach photos of the replacement forks versus the original forks it would make it easier to explain!! but anyways, thanks for all your help guys I'll keep you updated!

[Adrian]

If everything has been machined properly and you're fitting threaded fork stanchions into a factory casquette or fork yoke they ought to screw fully home. My current project has a set of early type B5/C5 disc brake forks (leading axle sliders, threaded stanchion tops) which screw quite happily into an original Redditch top yoke.



I suspect some less than perfect machining somewhere if the new forks are pattern items, I assume that's a factory casquette and the original forks were a good fit. Check for consistent depth of thread cut on the new forks (damaged threads could be cleaned up with a 26TPI thread file, though you reckon they're in good condition). Excess hard chrome plating on the stanchions might have reduced the thread clearance. I would also check the casquette for damage to the internal threads. If for any reason you end up ordering a new casquette, be aware that some are machined for the latest plain-end forks.



Do a forum search for picture uploading, it has come up several times recently.



A.

[vince]

Hi, Question, if the thread will not screw home how will extending the thread on the leg help? As Adrian stated the threads probably need checking. Have you tried screwing the legs into the casquette without passing through the lower fork clamp. This maybe misaligned/bent which will stop a correct fit.Vince.

[nickbarber]

Th old forks have about 1 1/2" worth of thread but the new forks only have 1 1/4" worth of thread, and the thread runs out with a quarter inch to go til its home. Could possibly be a manufacturing defect (either that or the machinist just got over it) but as I said the threads on both the forks and the casquette are good, and the old forks screw in just fine (but I'm unable to use them due to damage beyond repair)

[Mark M]

Tracy Tools have that die as £20 for carbon steel (ok for thread cleaning and light cutting) or £60 for proper HSS good for new cutting. I don't think I'd worry about the quality, CS should clean up your stanchion and cut that last 1/4".

REards, Mark

[Nettshubby]

I would definitely try screwing them in without going through the bottom yoke. i recently replaced the gaiters and head races, and had a job getting the tubes to even start in the casquette. They would screw in just fine without going through the bottom yoke. Check them this way before "screwing" around with the threads! Them jiggle the yokes to get them started.