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I have a A65. I was under the impression it was a 65 but after looking at the cylinder studs ( I think I read the studs and crankshaft are different between 65 and later ) and rechecking the numbers I think it might be 66 ? A65T 95xx ?
Would this number be suitable for a 66 and the later crank and cylinder ? Thanks

My understanding is the A65T would have first been available in 1966; prior to that the letter following A65_ did not tend to match the model designation.

Does the speedo cable come out of the trans case bottom?

It didn’t have the correct speedo . It was turned into a chopper. There is a pic of it somewhere on this site under A65 and C15.
I am trying to put it back somewhat like it was but it’s not going to be totally correct .

It’s strange because if you Google it you can come up with a lot of pictures of 65 thunderbolts

That’s a good question.I’ll have to look

I'd have to check the parts books for differences in cylinder studs, but A50s and A65s had a ball bearing for the drive side main up to 1965, and a roller bearing from 1966 on.

The A65T model prefix in the engine stamping was first used in 1966. 1967-8 had a year suffix (A for 1967, B for 1968), then a month and year suffix.


If you go to the top of the page, there is a "Serial Numbers" drop-down menu, which should help.

CBS, and probably some of the other site sponsors has the parts books available for download.
It would be worth grabbing the 1965 and 1966 books to help figure out which parts are correct. There were quite a few changes in that 1965 to 1967 period.
Come to think of it, there were changes almost every year.

The bike may have a bunch of past modifications the fenders/head light/wheels/hump seat/T-lite/battery/etc that make using them for ID help is Iffy at best. The motor case can’t be recast, so looking at the bottom of the trans, if you see a place for the speedo drive cable to attach, it’s an indication of 1965. In ‘66 the speedo drive moved to the rear wheel. The wheel may be changed, but the case…. Likely not.

Definitely, certainly post 65’ no two frames had identical features for more than 2 years at most, there was always something different. 67-68 were pretty identical as were 69-70. Prior to that number locations either moved, had different pad shapes, different seat mounting tab locations, different battery support brackets, bracket for ignition key etc etc.

I’m pretty sure the engine and frame are 66. It has a roller bearing on the drive side .

It is however a mongrel with different bits from different years. That’s perfectly ok with me except when things don’t work together.
At present I’m having an issue wit(the fron wheel and forks. They don’t seem to match. I’m not so sure ( after looking at the parts diagrams ) that the forks aren’t Triumph. I’m pretty sure the wheel is correct for a 66 BSA but ? The axle is too large a diameter. The fork has a lug to fit in the brake plate and the wheel has no corresponding slot.

I don’t remember how to post pics

To post pictures to the forum you would need to be under a paid membership level. Though, if you have a photobucket/imagur(or what ever it’s called) or an account with some photo Hosting website you can attach photos that way.

Marc C. is correct. The Thunderbolt first came out in 66 as an A65T. A65TA in 67, A65B in 68 etc. Engine and frame numbers the same after 66. Cylinder base bolts changed to 3/8 " in 70.

I’m fairly sure the front forks I have are from a triumph as they look like the ones on my 66 T120. Caps on the bottoms and brake lug . I wish I hadn’t rebuilt them and painted them prior to contemplating whether they would actually work with what looks like an original 67 lightning front wheel . The lightning wheel doesn’t have a lug and instead uses a stay which attaches to the fork slider with two screws. So, I’ve either got to change out the forks or find a wheel that works. I’m not sure why I missed seeing that prior to . 🙁

BSA used the Triumph forks 68 to 70 to go with the 8" TLS brake. The stanchions have the BSA taper on the top and the Triumph sliders.

So you have 3 choices.

1. Adapt what you have so the brakeplate is joined in some way to the lug on the slider and a custom axle so it can be clamped on the slider ends..

2. Get the correct BSA forks that have the screw in axle type slider ends.

3. Get a Tri/BSA 8" TLS wheel and keep the forks, 69/70 is better than 68 with more direct brake cable route.

.

BSA used the Triumph forks 68 to 70 to go with the 8" TLS brake. The stanchions have the BSA taper on the top and the Triumph sliders.

Slight correction. 69 to 70 had the triumph forks.

68 was one year only forks which were a clamp but with provision for the damper rod. I think this was the same for the B series bikes too.

The correct 8” TLS is 1 year, 1 model only as there is extra meat on the support lug which the triumph variant didn’t have.

After looking at the parts diagrams I think you all are correct.
What I have is the 69/70 front forks and fender set up.

Is your bike A65LA ***** Y (or -Y)

Also do you have the solid swing arm spindle…

And are the seat brackets on your bike, flat or raised (like go up at 45° and the bend to horizontal)

And one more, are the engine numbers on a raised pad with a fine BSA stamping in the background?

A65T 95xx

Solid

Flat

I’ll have to look

It’s a mix match of parts

I wonder if the axles are the same between the triumph and bsa 68-70. I just bought a 68-70 tls wheel complete with axle off that auction site .

if there is no letter following the T, then its a 66 bike.

though the solid swin arm spindle is interesting, 69/70 bikes had the solid (bolt) swing arm spindle, this threaded into the "cam" piece on the primary side, everything earlier than that had a hollow spindle and the cam part was part of the hollow tube and a large nut fastens on the timing side.

However the swing arm is different too, the type for the hollow spindle uses the silent block bushes (much like every other model from the begining of using swing arms) but the 69-on bikes used a bronze bush and bobbins (more like a jap bike setup - or kinda like one)

(all these being QD hub types) However from about 67, the rear brake plates were aluminium, these had different drums, which held a different drum bearing and a different pair of spindles (beefier), pre 67, they used the chromed steel or painted steel brake plate which used a different drum bearing, different drum, and slightly different spindles, the threaded end of the long spindle is turned to a smaller size before threading (which it isn't post 67), and the bearing ID and the hole in the brake plate is smaller to accomodate the smaller OD of the dummy spindle, the nut size however is the same at that end and you can use the same wheel (cotton reel hub) for both spindle types.

For your forks, it wouldn't be unkown for the bike to have had a front end collison and had the forks replaced, or the front end be changed so the previous owner could fit a TLS front brake.... (you bike would originally have had a QD half width hub SLS front brake, where by the spindle pushed through from the primary side and screwed into the timing side fork leg.


HTH

There are 3 variations of the Axle, the 68 BSA end clamp rod damper forks have the clamp bolts in a different position to the pre 68 BSA end clamp forks to suit the Triumph axle.



A 69/70 wheel will have the widest axle, it will depend on the Yokes on your bike as to whether is correct or too wide as the Yokes/Triple tree sets the distance the stanchions are apart.

Use the Youtube video to check.

Thank you
My swingarm isn’t solid. (Lost in interpretation ) it’s the hollow tube with plate on .

My newest issue is the sludge trap plug. I bought a new one with Allen head and in screws too far in. Way too far ! Is there a source for a correct one.