SOHC.co.uk Forums > CB500/550

cylinderhead overhaul

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Bryanj:
Cracked guide is usualy due to valve stem getting bent when re-assembling the rocker cover to head and not reading the book!!

andy_c101:
Bryan,
yes I see what you mean (- & I have found the specific note in the manuals about tappet alignent on rebuild).

I'm finding a few little signs that 'someone has been here before'!
actually that particular valve does not want to fall cleanly through the guide (suggest one or both are not 'true'; it also looks 'newer' than others (ie less carbon buildup on it)
- one cylinder stud is definitely newer (shinier) than others;
- some of the rocker cover bolts are black-bolt capscrews (unusual for Honda?)
- and a couple of 'dinks' on the rocker gasket faces, indicates carelessness by someone in the past.

I guess that's often the case with an old bike with big gaps in its history.

andy_c101:
continuing the tear-down....
it just got expensive!
I find 7 out of 8 valve guides have hairine cracks, and the valve stems have a tight spot too! (indicating a slight bend inthe stem; sure enough once removed the bent stems were confirmed.

BryanJ was right, someone (previous owner/monkey!) has fouled the rocker arm and valve stems on assembly; there's even a slight 'dink' one on the top edge of the valve stem.
- anyone ever heard of this so bad before?

So its new valves & guides required; but No4 Ex/valve (the worst offender) has obviously been putting high contact load on the rocker/cam lobe, that cam lobe is now right on bottom limit.  >:(

I guess my best bet is David Silvers or CMSNL for parts?

Q1: Anyone know where I can obtain the 5.5mm guide driver tool?
Q2: When i get new valves & guides, I DONT have to ream the new guides do I?
Q3: Can I just lap the valve seats into the head or do they need 'properly re-cutting'? If so any suggestions for cutting tools?
Q4: if anyone has a half decent camshaft.... ??

On the plus side the cylinder bores look good & measure up A-OK, as do piston ring fit/clearances.

At least I found the problem...
i better start saving the pennies.

UK Pete:
Hi Andy have a read of this  http://www.sohc.co.uk/index.php/topic,4330.msg19487.html#msg19487
pete

Bryanj:
The drift is easy to make; yes you DO have to ream the new guides; yes you DO have to cut the seats. Put some pictures up of the cam and relevant follower to let us see how bad they are.

And your cheapest repair is a used complete head, dont forget all the 500 and 550 SOHC fours use the same head

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