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#853758 07/15/21 12:31 pm
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Hi,

I have recently helped rebuild the top end of a friend’s 1971 Triumph TR6C 650 twin. We replaced the rocker assembly and boxes as they were taken off but, when doing the clearances, I have noticed some play on the left side intake and exhaust arm.

Both left side arms have some lateral movement on the spindle, while the right side arms have none.

I haven’t fired it up yet, only turned it over by hand to adjust the clearances.clearances are good.

Will it sort they themselves out and settle into place once it is running, or has something snagged one side and I need to remove the boxes?

I can’t remember, but pretty sure we installed them with the Thackeray washers against the box and the thrust washer against the arm.

Any help would be greatly appreciated. Thanks!

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With the oval rocker adjustment opening, it should be a fairly easy task to remove the adjustment cover and see what's going on. The springs should center the striking tip of the rocker arm directly over the stem of the valve. The spring allows ample lateral movement when forced, but should slide the arm back into its correct position.

The shafts, washers and springs are not typically a "problem area"... unless re-assembled in the incorrect order. The only reason to dis-assemble the shaft from the box is to renew the o-ring on the larger end, but even then the shaft only needs to be slid over about 1/2".

After 40 years, the Thackeray washers sometimes collapse, but that's the only other issue.


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Hi RF Whatley. Thanks for your reply and apologies for the long wait. I had to put this issue on the back burner, but I have some time again to focus on this issue once more.

I have uploaded a video of the play in the rocker arm as a visual aid. Again, the play is only on the left hand side exhaust and inlet rocker arm. The right side is tight and has no movement.

TR6C rocker arm play

We started the engine and let it run for a couple of minutes, but this did not change the discrepency in the difference in movement between the two arms on each side. What seems to be happening is that the thackeray washers are notdoing their job, but strange both exhaust and inlet arms on the left are the same.

The rocker arms and assembly were removed in order to have the boxes vapour blasted. They were reassembled in the the order they had been installed on the bike at the time of disassembly, which was working normally when inspected, but this order may have been wrong.

Anyway, I am planning on having another look on Friday so any help or advice would be really appreciated. Thanks!

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They should be the same both sides - as RF Whatley says, the spring should allow them to move laterally with a small amount of force. if there is no movement or you can't feel the spring pushing the arm back into place, something has changed during reassembly. I had this happen recently and found a washer was binding on the spindle. You're right something's likely to be snagged.

NB the Manual has the incorrect position for the thrust washers and springs and you should reassemble as per a subsequent service bulletin.



https://www.thebonnevilleshop.com/t...all-end-assembly-order-of-spring-washer/

Last edited by Bikeosaurus; 09/07/21 7:10 pm.

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Originally Posted by Bikeosaurus
I had this happen recently and found a washer was binding on the spindle. You're right something's likely to be snagged.

Thanks for the reply Bikeosaurus. It is looking like I shall lift the boxes off tomorrow whilst the tank is off, and see if the snag can be located.

It was a while ago now that we reassembled the top end, but I do remember having a printed copy of the amendment to the Manual, as I have rebuilt my own T140 engine and had to address the thrust/thackeray position conundrum.

Last edited by Scotto75; 09/09/21 6:49 pm.
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So... on closer inspection it looks like the thrust washer is jammed. It's a '71 650, so we installed the thackeray washers against the box and the thrust washers against the arm. Somehow, there is a gap between the thrust washer and the arm on both the exhaust and inlet on one side. (apologies but it is the right side, and not left as mentioned in previous posts. It actually looks like the thrust washer has been deformed or bent?

Here's a couple of photos taken with my phone camera....

[Linked Image from i.postimg.cc]

[Linked Image from i.postimg.cc]

Anyway, somethings obviously gone wrong, so new washers and gaskets have been ordered and the boxes will be coming off this week.

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In the second picture especially, it looks like the Thackeray washer is already fully compressed (jammed by the spindle against the side of the rocker box). I had a similar problem on reassembly. The Thackeray wasn't quite centered and when drawing the spindle home, it got compressed like that. It should be simple fix unless the thrust washer is bent and needs replacing, but even then shouldn't be too bad.

Hopefully, you can get things sorted out soon!

Noel


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