Triumphrat

Snakeoil

I did my homework and ran several searches here on various terms including "thackery" to find the various posts on the subject.

Most are posts for later model, OIF or post '69 big twins. My question is for a '66 T120R.

I found the post below from Mr. Pete, whose experience and knowledge I have come to regard highly.

So,how have you got the shims and thackeray washers installed?
Drilled rocker arms have the thackeray up against the arm,and the thrust washer against the rocker box casting.
Undrilled rocker arms should have the thrust washer against the arm,and the thackeray against the rocker box.
This is often done wrong,and was for many years.It affects lubrication of the rockers,valve-tips etc.

My parts manual, which is for 650 twins after DU 24875 and has a publishing date of 9/65 (if I can believe the cover goes with the contents as this is a repop manual) shows the washers up against the casting and outboard of the thackery washers. Thackery washers are against the rocker arms. That's agrees with Mr. Pete's quote above.

The service manual, which is for '63-'70 650 twins shows the washers inboard of the thackery washers with the thackery washers against the rockerbox casting.That is opposite of what Mr. Pete says in his post.

My spindles are drilled and my rocker arms are drilled so the oil from the spindle is fed to the pushrod ball. There are no notches on the sides of the rocker arms. The thrust washers are 1 each 3/8 washer and 3 each 1/2" washers, which agrees with my parts manual.

I then looked at a 1970 parts book that is on-line and it shows the washers inboard of the thackery washers, which matches my service manual. Spindles and rocker arms are the same part numbers as mine. Only the balls are different. Could be they are undrilled. Brit Only shows mine are for '68 and before and the others '69 on. But since my service manual covers all the way to 1970, it could have the later config.

Trying to understand the purpose behind the design, I would think that plain thrust washers go against the rocker arms to maintain oil pressure which forces the oil thru the rocker arm passage to the ball. But I'm also hesitant to question Mr. Pete's experience.

Mr. Pete or someone with more experience on these, can you please confirm the correct order for these parts on this engine?

Anyone out there have an original '66 Service manual they can check for me, please?

Thanks,
Rob

Morris the Cat

Hi Rob,
Not sure if this will help with your year, but here is a link from my reference archive:

http://www.britbike.com/forums/ubbth...760#Post455760

More info:

http://www.britbike.com/forums/ubbth...654#Post303654

__________________

Morris of Main Street

Mr.Pete

Your plain thrust washers go against the aluminium casting,with the thackeray against the rocker arm.

The later arrangement with different rocker arms was shown incorrectly in the maintenance manual,and not updated.The different arrangement of washers is recorded as a design change in 1969 ,from engine number JD24961,but wasn't even done on the factory floor until about 10 years later (communiction breakdown).The parts manual shows it differently to the maintenance manual.

Snakeoil

Thanks Morris. I was snapping pictures for my resto thread and when I lined up the rockerbox parts, the light went on regarding the assembly.

The 3/8" washer is the key. It cannot go between the thackeray washer and rockerarm because of the step in the shaft. So, it has to go on the outboard side of the thackeray washer.

Here is the picture that made it clear for me.



Then I read the posts you linked in your reply. One created a bit more confusion at first, but a re-read cleared that up.

Bottom line is what Mr. Pete said in the post I quoted is the ONLY way they will fit because of that 3/8" washer and the step on the spindle. That point is actually mentioned in one of the threads you included in your reply.

The issue of limited oil to the rockers and pushrod balls in those threads was interesting. I'm going to look over my parts to see if there are other ways to improve the oil flow thru the rocker arm/spindles.

I'll be assembling the rocker boxes tomorrow.

Thanks,
Rob