cam chain adjuster

[cliff7]

I've recently bought a 1978 CB400F. There is a slight rattle when cold that disappears when warm. I am paranoid about adjuster problems. Is there a way of checking whether the horseshoe and/or tensioner rod are seized? Does sump removal help? Also if the threads for locking bolt are damaged is there a way of repair? These questions have probably been answered before but new to site.

[Nurse Julie]

If something is noisy when cold but the noise goes away when warmed up as the metal has expanded, it's usually the tappets that need adjusting. If the noise is still there, it could just be a chipped tappet. If its the cam chain / adjuster the noise will get less noticeable and may disappear completely at higher revs when both hot and cold. It depends where this rattle is from, it could be the standard SOHC/4 clutch rattle.
No, you can't get to the cam chain adjuster horseshoe through the sump, the engine needs to be stripped. Dodgy trying to do a thread repair but not impossible, it's the swarf entering the engine which is to be avoided at all cost as this can wreck the engine completely.
Just try a normal cam chain adjustment to start with. Engine running at 2000 rpm, loosen off adjuster locking nut, loosen off adjuster nut and if the springs are still OK and the horseshoe pivot not seized, it will tension itself automatically being that it is a self adjusting mechanism. Do not screw the adjuster bolt inwards on any accounts. Lock it off with lock nut, job done.

[cliff7]

Thanks for speedy reply. will do as you suggest.

[bobv7]

Would this be the same method for adjusting the CB500 cam chain? The newer? Haynes book seems a bit short on this info!

[Nurse Julie]

Would this be the same method for adjusting the CB500 cam chain? The newer? Haynes book seems a bit short on this info!

No, totally different set up on the CB500/4

[bobv7]

Covered by the official secrets act then, is it? G,wan you can tell me!

[Nurse Julie]

Covered by the official secrets act then, is it? G,wan you can tell me!

If I tell you, I will have to kill you 🤣🤣🤣🤣🤣 It's self adjusting on your bike, you can't do any adjustments at all.

[bobv7]

Awww, that's not fair...an I bought a spanner an everything!

[taysidedragon]

When the tensioner has adjusted itself you have to tighten the bolt then tighten the locknut or the tensioner will keep moving.

[Clem2112]

The self tensioning mechanism was marginal at best on the 400.
The spring loses shove over time.
With care a bit of 'help' from above via that blanked hole usually works.

 

[Nurse Julie]

When the tensioner has adjusted itself you have to tighten the bolt then tighten the locknut or the tensioner will keep moving.

Ah yes, thanks for pulling me up on that. What I was trying to say is don't wind the bolt in, thinking that the further you you go, the more tension you are applying to the cam chain. Yes, needs to be re tightened to lock it off.

[cliff7]

Further to my initial enquiry, I am aware of how the system is supposed to work and the fact that you can't actually remove the horseshoe without stripping the engine, what I was trying to find out was whether there is any way I can see/feel if the slack has been taken up after adjustment or if the horseshoe is seized. Rocker cover off?
P.S. I am an ex (car) mechanic, 40 years, so I know the basics but realise I have much to learn when it comes to this type of engine.

[Nurse Julie]

Further to my initial enquiry, I am aware of how the system is supposed to work and the fact that you can't actually remove the horseshoe without stripping the engine, what I was trying to find out was whether there is any way I can see/feel if the slack has been taken up after adjustment or if the horseshoe is seized. Rocker cover off?
P.S. I am an ex (car) mechanic, 40 years, so I know the basics but realise I have much to learn when it comes to this type of engine.

2 ways... run the engine and have a listen or as you suggest, take rocker cover off and try and lift chain off of the cam sprocket, it should be nice and tight. Unfortunately you won't know for sure even with these two procedures if all is ok, the horseshoe pivot could still be seized and / or, the chain is beyond spec and needs changing along with freeing of the pivot and fitting new guides etc. If it were my bike, at this stage, I would just do the basics and ride the bike and take it from there.
How many miles has the engine done and as far as you are aware, has it been well maintained?.

[cliff7]

Thanks again for info. Not sure of engine history. Last owner hardly rode it but previous owner did lots of work on bike including engine strip. (Don't know why). I will try and contact him. Also I know a guy who was a Honda mechanic in the 70's who might help me. Mileage on clock is about 28k.  Cheers.

[Athame57]

Do you have to split the crankcase to change the guides?