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How To: Rocker Arm Rebuild

October 8, 2010

Now that the Cannonball is over, Occhiolungo can get back to more workshop stuff and How To articles…  Click on the How To link on the right side of this page to see older articles.


When I bought the boxes of bits that were to be assembled as the 1916 Excelsior motor, there were a few sets of worn out rockers in one box.  In the photo below you can see the pivot holes have been worn oval and the hemispherical surface that receives the pushrod is worn.  Lubrication for both of these wear surfaces was lacking, and over the last 80-odd years the parts were run and run with occasional drops of oil and continuous exposure to dirt, dust and other grit…

The rockers on the right have been cut with a hacksaw.  By moving the socket/pushrod closer to the rocker pivot, the leverage ratio changes and the valves lift slightly further.  It is an old tuning trick that I thought I would try with one set of worn out rockers.  The additional valve lift feeds just a bit more air/fuel mix into the motor for a bit of more power.  The modification is fairly simple; much easier than re-profiling the camshaft to get the same effect.



This view shows two of the rockers after welding.  The socket is now full of new metal (half of the ball & socket joint with the pushrod).



The two rockers on the left have been machined and polished.  A carbide ball end mill was used to cut the spherical socket to the correct size to fit the pushrod end.  At the center there is a very small little hole that is used to drip oil onto the ball/socket joint.  This oil probably goes away within a few minutes of riding, but that is the way that the Excelsior factory made the parts.

On the bottom left rocker there is a new flip top oiler to lubricate the rocker pivot.  These will be used on all the rockers, and judiciously filled with oil before each ride.  I don’t want to be  like the previous riders and wear these parts out!  Reproduction oilers come from Restoration Supply Company, just a few bucks each.  Size 1/4-32.



The next step was to make and install bearing bronze sleeves into the pivot holes.  The rockers had been hardened when new, so I had to cut them using a carbide end mill to take out the oval shape.  Once the holes were round, I made round plugs of bronze, pressed them into the rockers, then machined them to the correct width to fit the rocker pivots on the motor.



Once the bushings were the correct width, it was pretty simple to drill and ream them to fit the new pivot screws that I had made previously.  Here is a photo showing two of the rockers, plus one new pushrod end.  The old pushrod is below.


16 Comments leave one →
  1. Paul Venne permalink
    October 8, 2010 9:36 pm

    Pete, Looks like there is a slight chamfer due on the bottom of the pushrod end to increase contact with the lock nut. I see some valve adjusters backed out on the Cannonball. For now I’m just rotating the pivot shaft for a fresh surface and assembling with high tech oil additives to buy me some time friction wise. Pushrod end should be hardened too, right?
    I’m droolin’ heavy over these bits! My machinist here is making some of the lock nuts and maybe more if I can get my buddy Scott from California to bring samples or discriptions when he comes to Thailand. Tried the high performance rockers yet? Thanks, Paul

    • Pete Young permalink*
      October 9, 2010 4:19 pm

      Good eye Paul! Yes the pushrod ends have a chamfer, and the locknuts have a mating taper. Those were copied directly from my 94 year old parts, as I want them to be identical and interchangeable. Pushrod ends were hardened, see the next article for details.

      I tried the rockers with the additional lift, but the socket wasn’t hard enough on one of them. So the valve clearance kept opening up. I’ve pulled them off and replaced them with standard parts until I can fix ’em.

  2. Anton B permalink
    October 9, 2010 9:20 am

    Do you case harden the sockets and/or ends or the cam following pads? Do you have to polish them, or do you just lube ’em up and let ’em break in?

    • Pete Young permalink*
      October 9, 2010 4:16 pm

      I hardened the sockets, as well as new pushrods and pushrod ends. That will be the next How To article, in a day or three.

  3. Kris Thompson permalink
    October 9, 2010 5:29 pm

    Pete, I was on the Cannonball Kris Thompson (1915 Henderson) Great meeting you in person. By the way, what type of weld did you use to fill the ball cavity? I need to repair one of my Hen rockers as well. Thanks.

    • Pete Young permalink*
      October 9, 2010 6:21 pm

      Hi Kris. It was great to meet you on the Cannonball.
      I don’t have a TIG welder, so I took my rockers to my friend’s shop, Advanced Welding in Mountain View. He was able to get down into the holes and fill them up. I’m not sure exactly what filler rod he used though.

  4. brian b permalink
    October 10, 2010 12:50 pm

    Are we going to get the dyno number to see the HP improvements? (smiley face)
    Great how to.. love when you are able to add video as well.

  5. Richard McKenney permalink
    October 13, 2010 2:57 pm

    G’day Transcontinental Racer Pete

    All good engineering enthrals, but isn’t shortening the rocker going to increase the load on the cams, causing rapid wear? For an extra half pony? Maybe how to make cams next?
    Just an idea that popped into my head at 3 in the morning, whilst I was trying not to dream about cheerleaders; that got me a smack in the ear from the wife. How do they know what you’re dreaming about? How about an occhio lungo Dear Abbey?

    Cheers Richard

    • Pete Young permalink*
      October 14, 2010 8:24 am

      Shortening the rocker increases the lift, which will cause the valve springs to compress a little bit more, which does increase the force on the pushrods down onto the cams. But I think it should be OK. One way to find out… 😉

      Sorry about the wife smacking your ear. Maybe you need to dream more quietly?

  6. Paul Venne permalink
    October 24, 2010 4:49 am

    Ever seen dust covers for these parts? Ace has them on what looks a lot like the preceding 1919 Henderson cylinders. Did Ace get pressure up there? Did any Excelsor cranks fail during the cannonball? Rods? Recasting replacement cylinders for Excelsior might be a cheap way to gain performance. A guy at a swap meet once told me it would only be about $100 per cylinder to do castings from custom patterns using modified originals. Thanks, Paul PS Cheerleaders over here now in my dream.

    • Pete Young permalink*
      October 24, 2010 8:36 pm

      I’ve never seen dust covers put on X rockers, but it could be done I suppose. The X motors on the Cannonball did ok, just Buddy’s trouble with his timing case. I think that all the cranks, rods and cylinders made it ok. Vils had some trouble, I can’t remember if it was the big end. I’ll drink another beer and see if I can remember.

  7. Paul Venne permalink
    October 25, 2010 6:46 am

    Pete, Timing case failure sounds like dried up lubrication caused it.
    Have you ever seen a rating for the stock HP on the 1916 Excelsior? The 60’s Honda Scramblers are rated about 27 hp but won’t break the ton. The Super Hawk street model with basically the same motor supposedly will. I think that kind of speed for the Big X would be rather extreme, but what do I know? It does have three plus times the displacement. Got any camshaft grinders you could call?
    Have you ever tried for top speed on your Excelsior? Is it geared for top or pulling? How does it sound? On pins and needles (and cheerleaders) for the next episode, Paul

    • Pete Young permalink*
      October 25, 2010 8:26 am

      In Victor Page’s books of circa 1914, he shows dynamometer curves for some motors, but not for Excelsiors. Singles top out around 4-5hp and twins around 9hp. But of course things changed a bit between 1913 and 1916… I don’t have speedos fitted on my bikes, but I’d guess that my X goes to around 65mph. It has standard gearing, but a slightly small rear tire. I might get my old Jones speedo working next year and try to find the maximum. Mike Vils knows a cam grinder in LA that he used for his Cannonball X.

  8. November 4, 2014 10:33 am

    I would love it if some one sold these rockers in the modified form for years 1912-24. Do you use oil additives like Duralube? (Team X secret, ssssssssssssh)

    • November 4, 2014 10:36 am

      I don’t add anything to the motor oil or fuel. I figure that modern oils and fuels are so much better than what was available 100 years ago. I do put a little powdered graphite into the gearbox grease/oil mix though.

  9. November 4, 2014 10:35 am

    Right now I’m using 3-IN-ONE oil on the externals of my 1914 Excelsior. Going to upgrade.

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