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Author Topic: Broken Cam Chain Sprocket and Camshaft???  (Read 2975 times)

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DGoody

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Broken Cam Chain Sprocket and Camshaft???
« on: July 23, 2005, 02:40:47 PM »
Hey all.....I'm a newbie, please bear with me. I did a top end rebuild on my wife's 1975 CB400F this week. I started it up and it idled for about 10 minutes, then it just stopped dead. Thinking that the cam chain sounded loud, I pulled the heads back off and noticed that the cam chain sprocket and camshaft mounting flange had broken completely off. The sprocket bolts had come out, but didn't break, and were sitting right near one of the valves. But, at one of the sprocket mounting points, both the sprocket and camshaft flange (where the bolt threads) had broken. I think I got all the pieces out of the tunnel, and it looks like I need a new sprocket and camshaft. When I manually turn the crankshaft, it seems to move a little less free than before, but still rotates okay.

Anybody have any ideas why the hell this happened? My wife is going to kill me now!
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DGoody

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Re: Broken Cam Chain Sprocket and Camshaft???
« Reply #1 on: July 23, 2005, 07:57:23 PM »
Well as it turns out, I think the culprit was the rear slipper arm. I had installed it backwards.....in other words, the guide side was facing the rear, and the chain must have been hitting the back of the slipper arm, putting undue tension somewhere and causing the breakage.

I guess I just rushed through the reassembly.........makes sense that this would cau
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Offline Terry in Australia

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Re: Broken Cam Chain Sprocket and Camshaft???
« Reply #2 on: July 24, 2005, 12:42:28 AM »
Well I guess your wife killed you halfway through that last sentence mate, or maybe you've faked your own death and are reading this in an internet cafe in Argentina?

Anyway, I'm leaning toward supey's suggestion that you've done some damage in the top end, so you might want to whip the head off for a closer inspection before you just sling in another cam mate, I'd be very surprised if you haven't? Cheers, Terry. ;D 
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Offline Harry

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Re: Broken Cam Chain Sprocket and Camshaft???
« Reply #3 on: July 24, 2005, 01:47:37 AM »
Quote from: supersport_CB400F on July 24, 2005, 01:36:15 AM
Mrs DGoody after the sudden death of your husband, I suppose this is not a good time to talk about your petrol tank  ;)


;D
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Harry Teicher, member #3,  Denmark....no, NOT the capital of Sweden.

Offline Sam Green Racing

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Re: Broken Cam Chain Sprocket and Camshaft???
« Reply #4 on: July 25, 2005, 08:56:20 PM »
Typical Scouser! LOL ;D
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C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Offline Sam Green Racing

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Re: Broken Cam Chain Sprocket and Camshaft???
« Reply #5 on: July 26, 2005, 12:27:52 PM »
Dave , can you not wait till after the funeral?
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C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Ben

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Re: Broken Cam Chain Sprocket and Camshaft???
« Reply #6 on: July 26, 2005, 04:20:53 PM »
Sounds like you may have put the cam sprocket bolts in the wrong holes? I think one is 'stepped' and the other a straight thread. If you put the stepped one into the straight thread hole it will split the mounting flange............ Just an idea.


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Offline Sam Green Racing

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Re: Broken Cam Chain Sprocket and Camshaft???
« Reply #7 on: July 26, 2005, 05:19:08 PM »
Hey Dave, when are we going to get together for a drink?
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C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike
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