Author Topic: stripped fork top nut  (Read 329 times)

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Offline Paulflor

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stripped fork top nut
« on: January 09, 2019, 04:43:26 am »
Hi All,
I have really been enjoying this forum, and i appreciate the wealth of information from all of you fine gents.
I took the forks to change the oil seals but now as the title says the top fork nut on my c12 is stripped.  Any ideas as to how to remove it?
I got it in half way as i was putting the fork back and now it just spins.

I got the bike about three weeks ago in San Diego.  I am in the process of making it road worthy.  Any insight will be appreciated.

Thank you,

Online Owen

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Re: stripped fork top nut
« Reply #1 on: January 09, 2019, 06:41:59 am »
File off the hex flats so the leg can be removed and deal with it on the bench
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Offline timsdad

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Re: stripped fork top nut
« Reply #2 on: January 09, 2019, 07:02:48 am »
As it's only halfway in, Paul, I'd think it would be quite straightforward to grip the hex with Molegrips so you could pull and twist out at the same time.

It's the sort of job I've had to do many times over the years on customers' vehicles and you just have to do what you've got to do. If this didn't work I'd weld something on the top to get a decent grip on, block of wood on the top yoke for leverage while turning and pulling, turn, pull and tap underneath with a hammer   .   .   .

Usually, the thread will get a bit of a hold, likely crossed. once it starts to grip and it will screw out.


Ray
Just a motorcyclist.

Offline Paulflor

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Re: stripped fork top nut
« Reply #3 on: January 09, 2019, 04:10:33 pm »
Thank you guys. I got it out!
Now, i need to rethread the tube.  Anyone know what the specs on the thread size may be?
 
I think the nut is 1 1/32" diameter with a 20 TPI thread. I need to order the right tap.




Offline camman3

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Re: stripped fork top nut
« Reply #4 on: January 09, 2019, 04:20:25 pm »
I don't think there is any such tap :-\ .....and you will probably need to either clean the thread up with an internal chaser if it is not too bad, or weld fill the damaged thread and re cut it in lathe. :(
Graham
1957 C12
In sunny (sometimes) Christchurch, Dorset, UK

Online hampshirebiker

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Re: stripped fork top nut
« Reply #5 on: January 09, 2019, 04:30:24 pm »
I don't disbelieve you Graham, but I thought Cadetchris said he'd managed to get one (tap). Relying on memory though.
Postal - Liphook Hants - But just into West Sussex.

Offline timsdad

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Re: stripped fork top nut
« Reply #6 on: January 09, 2019, 04:45:45 pm »
A good way to clean up a damaged internal thread is to sacrifice another good nut. If you file a flat along one side, sort of wedge shaped so it tapers from the bottom of the threads up to about halfway to the hex head, and carefully use this to dress up the damaged internal threads. Once you get a straight start then backwards and forwards, 1/4 turn at a time, should clean it up as good as a proper tap.

It's best to clean up the edges of the nut's threads with a thread file, if you've got one with 26 tpi on, or carefully with a small hacksaw blade or whatever, and try to leave a sharp leading edge. A bit of greasy rag tied on a length of string stuffed down the stanchion first should save stripping the fork out again. When the thread is cleaned up, I'd poke around with a magnet first to get any filings out before I pulled out the greasy rag.

You can attack it with the good nut off the other leg and then you'll just need to get a new pair, Paul. Best of luck!


Ray
Just a motorcyclist.

Offline Paulflor

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Re: stripped fork top nut
« Reply #7 on: January 09, 2019, 05:01:07 pm »
Thanks again for your  wisdom.  I will try to do what Ray described this afternoon.  i'll let you know how it goes.

Paul

Offline Tman

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Re: stripped fork top nut
« Reply #8 on: January 09, 2019, 05:38:41 pm »
And if you do do it like that, use fine grinding paste to lap it to fit.
A backwards and forwards light action, hopefully going a fraction further around each time until you can screw it home by hand.

Offline Paulflor

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Re: stripped fork top nut
« Reply #9 on: January 09, 2019, 08:01:16 pm »
Hi All,
I tried Rays and Tman approach with this issue, and it worked! I used a little wd40 to smooth things out and a little fine valve paste.  I can screw it out by hand now, wow!

Thank you guys.

... next problem, the front wheel axle pin is also stripped. any ideas with this one.  Does anybody know the thread size so i can order a die if needed?

Offline chaterlea25

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Re: stripped fork top nut
« Reply #10 on: January 09, 2019, 11:09:50 pm »
Hi,
The front axle is 9/16in x 20 Left hand thread
This is the same thread as used on old fashioned cycle pedals, a long established cycle shop should have a tap set
for the fork leg
If the axle is damaged I would opt to replace it for safety

John

Offline timsdad

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Re: stripped fork top nut
« Reply #11 on: January 10, 2019, 06:24:35 am »
It would be easy for me because I've got a set of good thread-chasing files and the 20 tpi side would bring back the damaged left-hand thread simply enough.

I'd get myself thread-restoring files if I were you, Paul, because they cover just about everything if you get a set of three - Unified, Old Imperial and Metric. Imperial ones with 26 tpi are hard to find nowadays but an Imperial one, with UNF and UNC on, will do the job. Coarse BSC 20 tpi is as near as dammit to UNC 20 tpi and these ones are readily available.

If you order off e-bay, maybe a tenner or so, you'll get it tomorrow and it'll last you rest of your life. Wonderful things! I've had mine since the early '70s and, used about weekly for most of their lives, will hopefully see me out. I've only ever stroked them forwards, in the upwards direction of travel, on damaged threads and they're stored on a foam rubber mat in a drawer.

They work for me - and cheaper than a new axle!


Ray
Just a motorcyclist.

Offline Paulflor

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Re: stripped fork top nut
« Reply #12 on: January 11, 2019, 05:18:21 am »
I managed to fix the axle pin and the threads on the stanchion using a die and a thread repair kit. 
It got a little dicey but at the end it worked out ok.
I used heli coil kit which I got from a local commercial fastener shop.
The owner explained that heli coil kits are used in aerospace repairs so im confident that the repair is safe.
Thank you guys for all the great insight and information.