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1966-74 500/650 triumph fork leg question. #698304
06/13/17 6:56 am
06/13/17 6:56 am
Joined: Aug 2001
Posts: 172
england uk.
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billy banger Offline OP
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billy banger  Offline OP
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Posts: 172
england uk.
Hello Everyone, i have just bought a pair of fork legs for a triumph 650 which are the later type with the welded on brackets and anchor peg. the problem with these forks are that the anchor peg is present on the r/h leg but the welded on brackets are not present on either leg nor do they look like they have ever been on. i have some other fork legs that are poor and corroded inside but the welded brackets are good. i plan to have them cut off the bad legs and welded on the new fork legs that i have. i will have to put a reamer down after being welded as some distortion will have taken place. my question is what is the internal diameter of the fork legs. i have a digital caliper which when measured looks to be 1.5 inches but i know they aren't that accurate for measuring internal sizes. i can buy an adjustable reamer that goes to 1.5 inches but if it is more than that, the reamer will not do its job and reamers over 1.5 inches look to be a bit thin on the ground. your input on this is welcome. cheers. billy.

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Re: 1966-74 500/650 triumph fork leg question. [Re: billy banger] #698310
06/13/17 9:21 am
06/13/17 9:21 am
Joined: Dec 2004
Posts: 9,486
Scotland
kommando Offline
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kommando  Offline
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Scotland
I have a 38mm reamer that I send down these fork legs to remove the internal dings you get from too long a bolt being used, its on an MT4 taper and I use it on my lathe which has a hollow spindle large enough to take the slider. The factory ID of the slider is 1.498" to 1.5" or 38.049mm to 38.100mm, trouble I find is that if the slightest piece of swarf gets caught then you end up with a rough surface from the swarf creating grooves so you have to constantly pull the reamer out and clean it.

Re: 1966-74 500/650 triumph fork leg question. [Re: billy banger] #698316
06/13/17 11:15 am
06/13/17 11:15 am
Joined: Jun 2002
Posts: 10,177
Scotland
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Stuart Offline
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Stuart  Offline
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Joined: Jun 2002
Posts: 10,177
Scotland
Hi Billy,

Originally Posted by billy banger
fork legs for a triumph 650 which are the later type with the welded on brackets and anchor peg. the problem with these forks are that the anchor peg is present on the r/h leg

"1966-74" sliders aren't all the same:-

. '69-'74 - brake anchor tab 1/8" wider, Unified threads (I have it in mind the oil seal holder thread is Unified Constant Pitch), land for addition 'O'-ring to prevent oil leaking down seal holder threads, '70-on had studs for the axle caps;

. pre-'69 - brake anchor tab 1/8" narrower, Cycle threads, no land for addition 'O'-ring to prevent oil leaking down seal holder threads.

Hth.

Regards,

Re: 1966-74 500/650 triumph fork leg question. [Re: billy banger] #698404
06/14/17 1:16 am
06/14/17 1:16 am
Joined: Oct 2003
Posts: 11,263
North Georgia, USA
RF Whatley Offline
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RF Whatley  Offline
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North Georgia, USA
The fender mounting posts may be brazed on. Hit them with a torch first and see if they fall off. Brazing would not add nearly the distortion as welding would.


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
Re: 1966-74 500/650 triumph fork leg question. [Re: Stuart] #698422
06/14/17 6:05 am
06/14/17 6:05 am
Joined: Aug 2001
Posts: 172
england uk.
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billy banger Offline OP
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billy banger  Offline OP
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Joined: Aug 2001
Posts: 172
england uk.
Hello Stuart, its good to hear from you and i always value your opinion. the 1966-74 fork leg before it is machined and lugs added is the same one. you can turn a 1966 leg into a 1974 leg by machining it and changing lugs and threads. 1966 was the first year of this style of fork leg. 1966 only did not have the rebate for the O ring in the fork oil seal holders and had cycle threads for the fork caps and fender mounting brackets. you can machine the rebate on the earlier legs and my friend who had a set got a machinist to put the rebate onto them as he is restoring a 1967 TR6C. 1967 and 1968 fork legs have the rebate and are still cycle thread on the threads. things change in 1969 when the threads go to UNF and the 1969 r/h fork leg is a one year only as it still has the old style anchor peg but it is different to the earlier ones as the boss that attaches to the fork leg is deeper to make the peg longer as the fork yokes widened in 1969. in 1970 the peg is changed as are the fender mount brackets which are now all welded on. 1970 had bolts to hold the fork caps on and 1971-74 the 500's which use the same fork leg went to studs. these are interchangeable with each other and the stud is 5/16 24 tpi on both ends. you might be able to throw some light on the bsa versions which look the same but are different. if you are at a swapmeet/auto jumble and picked up a fork leg that looks triumph, say a 1969/70 one and it has a line running round the bottom of the fork leg, then its bsa 250/441/500/650 or triumph 250. some bsa ones have a contersunk in the fork leg and cap which go together as a pair. i have heard of bsa fork legs of this type being different lengths on the same bike. have you heard of this. as always Stuart i welcome your imput as none of us are too old to learn. i work with this stuff everyday of the week and i am still learning and i will be 60 years old later this year, so i am not a kid by any means. cheers and all the very best. billy.

Last edited by billy banger; 06/14/17 6:18 am. Reason: missed out a detail.
Re: 1966-74 500/650 triumph fork leg question. [Re: RF Whatley] #698423
06/14/17 6:15 am
06/14/17 6:15 am
Joined: Aug 2001
Posts: 172
england uk.
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billy banger Offline OP
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billy banger  Offline OP
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Joined: Aug 2001
Posts: 172
england uk.
Hello there, 1970 and on do have welded on brackets but there is nothing to say that you can't braze them on which would help against distortion. i believe that the earlier lugs were soldered on but i could be wrong on that. Velocette silver soldered their fork legs together and they have been known to leak over time. i know a guy who had a pair that leaked at the bottom and he got a plumber to dismantle/clean and re-solder them. job done. i notice that you are selling your 66 t/bird. i have a 66 bottom end from one of these and it is stamped 6TA. i was told the designation is 6T with the A being America. is yours also stamped 6TA. cheers. billy.

Last edited by billy banger; 06/14/17 6:22 am. Reason: spelling mistake.
Re: 1966-74 500/650 triumph fork leg question. [Re: billy banger] #698547
06/15/17 11:48 am
06/15/17 11:48 am
Joined: Oct 2003
Posts: 11,263
North Georgia, USA
RF Whatley Offline
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RF Whatley  Offline
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Posts: 11,263
North Georgia, USA
Originally Posted by billy banger
i notice that you are selling your 66 t/bird. i have a 66 bottom end from one of these and it is stamped 6TA. i was told the designation is 6T with the A being America. is yours also stamped 6TA. cheers. billy.


Are you talking to me ? I have no idea what the difference between 6T and 6TA is, and I worked for over a decade at a dealership ! A = America seems fairly lame to me. Mine is stamped "6T".

bigt


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
Re: 1966-74 500/650 triumph fork leg question. [Re: billy banger] #698553
06/15/17 12:19 pm
06/15/17 12:19 pm
Joined: Jun 2002
Posts: 10,177
Scotland
S
Stuart Offline
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Stuart  Offline
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Scotland
Hi Billy,

No worries; from your first post, I wasn't sure if you were aware of the differences, but obviously you are. grin

Originally Posted by billy banger
1970 had bolts to hold the fork caps on and 1971-74 the 500's which use the same fork leg went to studs.

Mmmm ... the '70 T150 parts book, which went to a 3rd edition published in January 1970, shows the studs - might've been one of the '70 Mid-Season Mods., along with the speedo. 'n' tacho change to black-face, etc.?

Originally Posted by billy banger
you might be able to throw some light on the bsa versions which look the same but are different.

Some are, some aren't:-

. 250, 441 and R3 sliders are the same as Triumph - 97-3921/2 ('70), 97-2294/5 ('69)

. Singles and BSA twins then used the same stanchion ('70 97-3906, '69 97-3637), so I suspect A50/A65 sliders are then a different length because the top yoke didn't change from the earlier BSA forks.

Originally Posted by billy banger
i have heard of bsa fork legs of this type being different lengths on the same bike.

There was a recent thread about this - turned out to be the 'block' on the bottom of each slider tube, that has the axle cut-out, was a different distance between the bottom of the slider tube and the axle cut-out ... facepalm Given what you posted about the Triumph sliders being basically the same all the way from '66 to '74 (just having different threads), it makes sense if - '68-on - both Triumph and BSA tubes are all the same length, just Small Heath attaches the axle 'blocks' and mudguard brackets for the models assembled there? And sometimes the completed sliders were mixed up?

Originally Posted by RF Whatley
Originally Posted by billy banger
66 t/bird. i have a 66 bottom end from one of these and it is stamped 6TA. i was told the designation is 6T with the A being America.

A = America seems fairly lame to me. Mine is stamped "6T"

"6TA" has come up before on the Forum. I wonder if someone at Meriden suddenly felt the need to differentiate pre- and unit 6T's, as was done with late-50's/early-60's 350's and 500's?

Hth.

Regards,

Re: 1966-74 500/650 triumph fork leg question. [Re: billy banger] #698714
06/16/17 6:45 pm
06/16/17 6:45 pm
Joined: Dec 2012
Posts: 249
seattle
T
tiumphdave Offline
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tiumphdave  Offline
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Joined: Dec 2012
Posts: 249
seattle
Stuart, can you link me to that post about slider differences? I can't seem to find it. Thanks, Dave.

Re: 1966-74 500/650 triumph fork leg question. [Re: billy banger] #698717
06/16/17 7:31 pm
06/16/17 7:31 pm
Joined: Jul 2012
Posts: 1,675
UK Berks
A
AngloBike Offline
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UK Berks
There is a 6T AC (rigid ac generator)
And a 6T SA (swingarm)

Re: 1966-74 500/650 triumph fork leg question. [Re: AngloBike] #698728
06/16/17 9:23 pm
06/16/17 9:23 pm
Joined: Mar 2006
Posts: 3,771
Norfolk, UK
L.A.B. Online content
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L.A.B.  Online Content
BritBike Forum member
Joined: Mar 2006
Posts: 3,771
Norfolk, UK
Originally Posted by AngloBike
There is a 6T AC (rigid ac generator)
And a 6T SA (swingarm)



However, I believe the 6TA was '66 only and could have been a US (East Coast?) variant of the 6T.

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=541624


Moderated by  John Healy 


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