Topic: CB500/4 Lifter Rod Dimensions?

[sammermpc]

Hello,

I know there has been much discussion of CB500 lifter rods, but I've recently realized that mine snapped in two (seems to be a very common issue -- http://forums.sohc4.net/index.php?topic=105659.0).

A number of people have pointed to Ebay, for expensive NOS -- and there are a couple -- but I was wondering if folks had found other reasonable solutions. Seems like a number of people have had good luck fabricating their own, but there are differing opinions of the appropriate dimensions.

From http://forums.sohc4.net/index.php?topic=14273.0, we have:

Measurements for a Honda OEM pushrod are:

10 1/8 inches or 25.7 cm long
3/8 inch in diameter or 9.5 mm

You can easily fashion a push rod from
3/8" steel rod found at any hardware store.
The shifter side end should be ground flat and square,
and the brake side end should be neatly rounded in a semi-sphere
to mate with the clutch basket. If you err, err on the side of a bit too
long since this will allow you to keep the lifter mechanism low and avoid cracking.
May also be a good idea to quench harden the ends.

But from http://forums.sohc4.net/index.php?topic=84249.0:

FYI: 3/8 is not the correct size, in order for this to work, the rod needs to be 8mm diameter (maybe 5/16)

Any final word on this?

[Deltarider]

Just read on the German site the complete rod is 256 mm in length.

[Bailgang]

I can't remember the exact length but I took 2 pushrods from a collection of spare Pontiac parts I have which turned out to be only .002" larger in dia than the old clutch pushrod. 1 pushrod wasn't long enough so I had to take 2 of them and cut them in 2 and cut 2 pieces so the overall length would be correct once joined together. To keep the 2 pieces concentric with each other I inserted a short steel pin that fit snugly into the hollow pushrods then welded the 2 together. The steel pin served 2 purposes, 1 was to keep the 2 halves concentric and the other was to serve as a backing so I could insure a full penetration of the weld,  once welded I put it in my lathe and machined the weld down to the dia of the pushrod. To keep it as much the same as the original I left one end rounded but took the other rounded end that would go into the clutch actuator itself, built it up with weld and machined it so it was flat like the original and making sure my overall length was what I wanted it to be when done.

I'm horrible at explaining things so the above may seem confusion but it was actually very easy but having my own welder and lathe made it easy and it worked perfectly when done and installed in the bike.

[sammermpc]

I measured the diameter of my broken pushrod -- it's 8mm for my 1972 CB500f. Lined up, it's a few mm shorter  than the 256/257mm I've seen thrown around, so it looks like I've lost some material in there.

Does the pushrod pass through a sleeve or something in the crankcase? What's keeping it together in there? Can you lose those bits right into the transmission? I assume not.

[Bailgang]

Here's a link to another thread regarding making your own clutch pushrod.
http://forums.sohc4.net/index.php?topic=84249.0

[Honda-Rog]

8mm is right, I too experienced disbelief at 9.5mm. I blagged a couple of rods cut to length from a local supplier, FOC!

 My clutch is now smoother, if no lighter.

[Bailgang]

Ooops, I didn't look closely enough on you original post and noticed you spotted the link I provided already. On the 500 I had the 8mm dia was correct and I used the 257mm length. The Pontiac pushrods I used were 5/16 in dia which makes them .002" smaller in dia not bigger as I stated before than 8mm.

[Killer Canary]

I can't remember the exact length but I took 2 pushrods from a collection of spare Pontiac parts I have which turned out to be only .002" larger in dia than the old clutch pushrod. 1 pushrod wasn't long enough so I had to take 2 of them and cut them in 2 and cut 2 pieces so the overall length would be correct once joined together. To keep the 2 pieces concentric with each other I inserted a short steel pin that fit snugly into the hollow pushrods then welded the 2 together. The steel pin served 2 purposes, 1 was to keep the 2 halves concentric and the other was to serve as a backing so I could insure a full penetration of the weld,  once welded I put it in my lathe and machined the weld down to the dia of the pushrod. To keep it as much the same as the original I left one end rounded but took the other rounded end that would go into the clutch actuator itself, built it up with weld and machined it so it was flat like the original and making sure my overall length was what I wanted it to be when done.
I'm horrible at explaining things so the above may seem confusion but it was actually very easy but having my own welder and lathe made it easy and it worked perfectly when done and installed in the bike.

Exactly what I would have done. Lathe and welder; almost as important as breathable oxygen.
Invest, folks!