Topic: How did this happen?

[Gregory Groth]

I have a 1978 CB550 that was given to me in non-running condition.  For a number of reasons, I decided to tear down the entire engine.  My plan was to paint the cases, throw in a set of rings, lap the valves & replace the primary & cam chains, and put it all back together.  The odometer has 23K on it.  Tonight I started to clean the head, and pulled the valve guide seals off for the first time, and this is what I found.  I'm assuming that this occured due to someone not keeping the valves adjusted? 

The valves themselves all appear straight, and the valve seats look ok to me.  Not sure what I should do next though.  Toss the head and pick up a used one from Ebay, or replace the valve guides and get a valve job?  If I opt for a valve job, does anyone have any reccomendations of a machine shop in chicago?  If I go the Ebay route, what heads are acceptable replacements?  I've read that the carb changes in '77&'78 were due to emissions regulations, were there differences in the heads as well?  The original carbs were gone when I got the bike, and the PO installed a set from '76 or before.  It also came with pod filters, which I plan on replacing with a stock airbox, if I can get my hands on one.

Everything else  in the engine looks pretty good.  The cylinder walls don't show much sign of wear, as I couldn't detect any ridges on the top or bottom of the cylinders.  The oil pan seemed pretty clean, and the trans didn't have any signs of abnormal wear and tear, so I'm hoping that the negligence was limited to valve adjustment (if that indeed was the cause).

GregG

[tlbranth]

g, I'd replace the guides and have the valves and seats ground. Buy a used head and you'll probably have a lot more trouble than you're having now.

[bryanj]

That damage occurs when the correct procedure for replacing the cam cover is not followed, i suspect that the valves in those positions are bent as it don't take much to break the guides.

ANY 500/550 head from 1971 through to 1978 will fit----it was the top cover that was modified and a used head will probably cost less than buying 2 guides and valves plus the cost of fitting/reaming the guides and cutting the seats

[Gregory Groth]

Thanks for the replies.  I should have mentioned that I only posted 2 pictures as a sample.  Out of the 8 valve guides, 3 were missing chunks, 4 were visibly cracked, and only 1 appeared normal.  If I were to use the existing head, I'd replace all 8 valve guides, plus a valve job.  If there is suspiscion that the valves could be bent, I'd replace those as well.  All of this would add up to some serious money on an engine I still have yet to hear run.  I was looking at complete heads on Ebay for under $100 with shipping, considering all that I still have yet to buy for the bike (tires, seat cover, etc), I'll cross my fingers and gamble.  Thanks again.

GregG

[Hannibal Smith]

With Honda parts being so inexpensive (not for much longer) I would get a "new" everything. That head is jinxed, and the repair will be expensive.

[Gregory Groth]

Picked up a complete head off of Ebay from a '75 CB550 for $85 (+ $20 shipping).  Was supposed to have come off a running bike, and didn't appear to have an overabundance of carbon, and no signs of rust.  Should be here in 2-5 days, keeping my fingers crossed.

GregG

[DJ_AX]

Nice score. I recently took a chance on some forks via ebay ... turned out to be very nice on the inside too. :-)

With Honda parts being so inexpensive (not for much longer) ...

what did I miss?

[Fritz]

Yes, it's a typical damage caused by wrong installation of the cam cover.
I had the same problem. Bought a used head from a commercial ebay vendor (about $100) which had broken guides too. The vendor was kind enough to send me a good head without extra charge.
So this is a common problem and you gotta be lucky to get a head without damage and exessive exhaust valve guide wear.
You should examine the 'new' head carefully and measure the valve stem clearance following the workshop manual. Worn guides will result in increased oil consumption.
Having the head rebuilt is definetly much more expensive but will prevent the blue smoke from coming out of the exhaust

[TwoTired]

Damage caused by ignorance and inappropriate use of force.