Difference between -59R pushrods & standard pushrods?

[Simon]

Hi everyone, just curious as to the difference between the 17904-59R pushrods and the standard street-going bikes? Were the pre-1960 street pushrods steel or something like that? Did street bikes from 1960 or so onwards start to use the aluminium pushrods, obsoleting the -59R part number?
I have a set of the -59R pushrods (and see a set that have been on ebay for ages) that I'll use on my 61 XLR project, but the set of 1961 pushrods and aluminium covers I just bought look identical - not that I have them in front of me yet to directly compare.

[Simon]

And an answer from Leo: "Physically identical, only difference is weight, 50g Vs 68g for stock." Neat!

[C6AE]

Hi all,
New Member here, as a brief introduction I used to occasionally campaign my 'not stock' '62 Sportster ('coffee racer' w/Cerianis, 4 shoe, Konis etc) at Fremont Ca. in the Early '70's (11.5/135 mph) Then I settled into life as a married man with no motorcycles.

And now, 50 years later this XLR fell in my lap.
I'm slowly assembling/mocking up 62XLR 2069 - a 'Super Basket Case' and finding in the details an interesting learning curve!

So... I have been searching for information which brought me here, because this is mostly a KR!
Perhaps someone will know this bike? As far as I know it came from the Bay Area. Orange rocker boxes, Ceriani gp forks modified to take the a 9HD front brake (missing), rear brake backing plate also has remnants of orange paint, lots of lightening holes...
This thing, which was a race bike, came as parts in many old cardboard boxes, some wrong, some correct and some still unknown. It has suffered a hard life, but I'm confident it can be returned to the land of the living! (I am a machinist) As it progresses I will keep you in the loop, but it will be a slow journey!
(Cases are '58R, casting date 7-60m timing cover has same date code)

This bit is interesting:
I have a set of 4ea. 59R pushrods (still in the original wrappers)

Compared to standard Sportster they look very similar but:
59R pushrods are .440" dia, Sportster is .500"
59R weigh 68.4 G, Sportster is 47.4G

Not exactly what I expected to find!
(It has been suggested these were smaller dia perhaps because of possible pushrod/rocker box interference with a high lift cam, but.. they are heavy! it has been fun speculating on the 'why did they introduce these in '59"?
Any thoughts?
Thank you

[Rubone]

I would suspect to prevent the bending that occurred with standard pushrods and heavy valve springs.

[Simon]

Hmm...maybe I got the weights the wrong way around in my previous post...

Would be keen to see more pics of the rest of the bike!

[C6AE]

The weight and dia of the pushrods sure surprised me... In my misspent youth I ran my Sportster with minus-minus cams at 7k with stock pushrods and no issues. (This engine has Sifton HH cams)

As far as pics, It's all in boxes, and a bit of an embarrassment right now!
It has been sitting (in boxes) gaining a "patina" for probably 30 years.

I'm working my way through the bottom end, I have the flywheels trued up without the rod set (which are 55R and might actually fly!) to check the line bore, set up the flywheel end play, oilpump, cams/tach drive/magneto drive and etc. I have the option of running a ball bearing or bushing on the #2 cam. Which raises a question, The last one of these ball bearing motors I worked on had a ball bearing with a wee oil seal in the timing cover #2 position. I don't understand the need for a seal there, but the shaft has a boss for it. It has been suggested I omit the seal, anyone have thoughts about this?
Thank you