Hurricane Head teardown

Published - Oct 29, 2012
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Comments - 10

My work Drexel University is closed for the next 2 days because of a hurricane, so I decided now would be a good time to get started on my cb475 supersport build.

Let me recap what I’m doing…
I have a 73 cb450 that I put a 75 cb500t engine into last year. (Hence cb475)
Read about that HERE.

The head gasket leaks… so I’m going to tear the engine apart and rebuild the damn thing into a super hybrid engine. (Hence supersport)

  • I’m going to put a 450 head on the 500t cylinders because it has a smaller combustion area, so it will yield higher compression. I bought a used 450 head on ebay.
  • Also going to put 10.6 high compression pistons in it from Charlie’s Place.
  • And going to also replace the valves, rocker arms and cams… which you’ll see why. Keep reading…

Get the cams out.

In case you didn’t know… The cb450 / 500t have torsion bars instead of valve springs. Ducati can suck it. Honda did it first. So… no valve springs. The torsion bar is a weird concept. It’s wound with a spring, so an arm hits the valve open and then the bar returns the valve closed. Apparently this reduced the risk of valve float which is when, at high rpm, the valve doesn’t close fast enough and the valve never closes. When valve float occurs, you can burn up a valve and/or feel surging at high rpm.

The rocker arms are worn pretty bad. See how they “dish inward”. Bad shit. Read this. Apparently this is common on 450 & 500t engines. The cam hits the rocker arm, and then the rocker arm hits the valve to open it. If it’s worn real shitty like the below picture, you can’t adjust the valves to spec. I’m going to get new ones from M3 racing which are harder. Also, it looks like a piece of the rocker arm broke off and damaged the cams a tiny bit from bouncing around.

Valves are shitty too and where they seat in the head isn’t the best. I found new NOS valves on ebay. Going to buy them, and lap them in. Valves guides seem okay… I think.

Once you get all the shit out, you can access the valve seals right above the guides. Going to be replacing these guys later.

Cams are fucked like I said earlier. They’re scored to the point where I’m going to look for another set of good condition used ones, or buy new high-lift cams from M3 racing. Not sure if I want to get high lift cams though…

All done.

Empty head now.

Time to figure out what I want to order new, and what I want to try and pull from my 500t head and use the best parts from both.

10 Responses to “Hurricane Head teardown”

  1. Brian says:

    “In 1956, Fabio Taglioni, a Ducati engineer, developed a desmodromic valve system for the Ducati 125 Grand Prix, creating the Ducati 125 Desmo.”

    Honda can suck it.

  2. Jason says:

    And another thing. . . a torsion sprung valve closing action is NOT the same as a desmodromic valve action, where both open and close movements are direct (not sprung).

    Honda and Ducati both make motorcycles, which we all are admittedly hooked on. Neither need suck it.

    Jason

  3. ed says:

    @brian
    I’m pretty sure in 1955 Honda made their system… ha. Just kidding.

  4. ed says:

    @jason
    … love em both, i was just kiddin around

  5. Brian says:

    I know you we’re kidding. As was I.

  6. Dan says:

    Ed, I would seriously consider claying the tops of your pistons when installing a smaller CC head and larger domed piston. Accepted MIN valve to piston clearance for most street motors I’ve worked on is .060

  7. ed says:

    @dan
    good input.
    i’ll def look into that.
    thanks.

  8. Adam says:

    Hey Dan. Can you explain what claying the tops of the pistons is/does?

    Side note, I liked your tip at two wheel Tuesday to stash a spare clutch cable in the headlight bucket… I’m gonna use start doing that.

  9. [...] I’m getting ready to order the parts for my cb475 supersport build, I’ve been looking at other cb450′s out [...]

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