1972 CB450 Engine Knock/Rattle - Video

B

blakews

New Member
So the bike has been running really well the last few months and then in the last few kms of a 200km ride it developed this rattle.

It sounds like it is coming from the top end but I can't be sure.

I have adjusted the valves to the specified clearances and also adjusted the cam chain and points for good measure.

Bike starts fine and idles well, the noise has me worried though.

Any ideas gents? Thanks

See youtube link for video

https://www.youtube.com/watch?v=2baXt8HldgM
 
sounds like cam chain tensioner noise or the rubber rings have gone

maybe this will help

http://www.hondatwins.net/forums/55-engine-discussion/7223-help-cam-chain-sprocket-i-could-have-big-problem.html#p63135


http://www.hondatwins.net/forums/55-engine-discussion/14405-450-cam-chain-noise-cam-guides-rubbers-research.html
 
There are so many idlers and wheels in the cam chain system I would suspect one of them. You can pull the main tensioner off and make sure it is doing its job as they like to get stuck once in a while. The idler with the metal cogs in it which is attached to the under side of the head will have its bearings die or the rubber that inside them for cushioning wear out and fall out.

Check the oil fitler and see if you are getting any more metal or rubber particles. If the chain is loose it will slap the cases and wear off aluminum. If the rubber idlers are wearing out or shot you will see a lot of rubber particles.

The rubber rings on the cams are just there to dampen the chain noise, racers take them off just because they can fall off even when new and get stuck. Bill Lane, guy that builds them still has said several times on HT that they are not needed for proper running of the bike, there will just be a little more "chain noise" or singing so to say.
 
Thanks for the responses guys, I have dropped the oil and there was no o-ring pieces or anything in it. The oil filter showed some a very small amount of aluminium particles as you said.

I have taken the cam chain tensioner off and it seems to be in perfect working order. Removing the cylinder head covers there is no noticeable o-rings like in linked post, the flat plastic on each side of the cam sprockets is in great condition and not chipped in any place.

Any ideas? Because I'm all out and a bit over my head haha
 
If there is something that kusploded inside, it would most likely end up inside the right-side crank cover. It won't show up in the oil slinger because there is a screen and it usually wouldn't wash out with the oil.

That's all I got. Lots of reasons for a chain to make noise on these considering all of the cam chain components. When Honda engineered it, they didn't make things easy. Just did whatever it took to accomplish the end-result. Very primitive in that sense. Look at Kawasaki's first DOHC for comparison.
 
Okay so I took apart the cam chain tensioner, lubed it up and re installed as per service manual and the noise is gone. For now. I took her for a half hour ride after work and she didn't miss a beat. Am I being too optimistic in hoping that this was all the issue was?

Thanks again for the knowledge
 
Could have binded, causing it to not take up slack when you did the regular adjustment procedure. Just be sure to check it for leaks now and if it's dry, enjoy.
 
Not an uncommon issue with them. Been recommended to me by other owners to just pull them every time you set the cam chain and make sure they aren't suck. Then push the wheel clear in and lock it in place. Install it, loosen the lock bolt, listen for a nice thunk when the wheel pops forward. Lock the bolt down and call it good.
 
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