Continued CB750 questions

Gentlemen (and ladies),

I noticed a little while ago that when the motorcycle is tipped more
than 20 degrees or so, there's a clacking noise I can feel in the base
of the engine. I didn't notice since the motorcycle was, until now, on
its center stand.

Googling seems to tell me it's a cam chain, and that this can be
resolved by adjusting the tensioner.

Is this correct? If so, would adjusting the tensioner be acceptable on
a '75 model? Could this be a contributing factor to the idling issues
mentioned previously?

In a worst-case scenario can I replace the chain without first removing
the engine? The service manual says no, anonymous Internet posters say yes.

If not, what else might cause this sort of noise, and what's a sensible
fix for a guy who's too broke to pay for professional service of any kind?

As always, thanks to everyone for their help, especially since said help
has saved me quite a bit of money so far.

Sergeant Tibbs

 

More likely to be the primary chains, actually. The CB750 has two, both
conventional roller chains, and they tend to clatter at idle, especially
once a bit worn. The noise is harmless. If they clatter at all revs,
then they're shot.

See above. And the primary chains aren't adjustable anyway. Camchain:
set engine to TDC on (IIRC) the No.1 and No.4 cylinders, undo locknut,
loosen tensioner bolt, retighten tensioner bolt (carefully! It strips
easily), retighten locknut (equally carefully).

No. A slack camchain can, though.

Camchain: yes, it *is* possible using a soft link attached to the old
camchain, but the problem is that you can't even get the rocker cover
off the SOHC CB750 without removing the engine. If you remove the engine
mounts etc to drop the engine down in the frame fractionally, I think
there's clearance. But the noise, like I said, probably isn't the
camchain anyway.

Ignore it and ride it till something breaks.

 

Sergeant Tibbs

 

Apologies for the empty post! The real one's below.

Would the primary chains make a randomly-occurring clack-tap noise?
There's no real pattern but it's more like
taptaptap------tap---tap-taptap---tap-... and so forth.

If it's the primary chain, how intelligent would I be if I were to find
a same-width chain with a master link and then knock it down to length
so I didn't have to take the engine apart to replace it? Would the
speed and torque placed on the chain wreck it?

Heh, that's the method my parents used. I remember a lot of wailing and
gnashing of teeth whenever something on the vehicles died.

Sergeant Tibbs

 

See above

You don't understand. The primary chains run from the middle of the
crank. There is no way to replace tham apart from ripping down the
engine.

You *might* be able to access them through the sump, but using a master
link on a primary chain probably isn't a good idea.