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cylinderhead overhaul

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andy_c101:
[continuing on from my December thread....... I know I'm a but slow at this game]
[http://www.sohc.co.uk/index.php/topic,4090.0.html]

I did decide to 'live with my slight oil weep' from the head gasket for a while, but now the old girl has taken up smokin'!

Compression test seemed good (?) at around 150-170psi; so I'm thinking it's probably valve stem seals.
& for all I know they may well be 35 years old!
So having followed the 'if it aint broke dont fix it school', it's now broke, so i need to fix it!
This means off with the head, to do valve seals and the gasket/oilways; & generally check it over.
- at least I'm a dab hand at removing carbs (down to 30 minutes after several years of training!); the pipes are off (me thinks I may need to do something with those down pipes too... probably throw money at them).
-rocker cover off, but one of the two camchain sprocket bolts is seized on solid, and the flats are now rounded. Doh! >:(
 I think I'll have to invest in a set of "Irwins bolt removers".

http://www.screwfix.com/p/irwin-5-piece-bolt-grip-nut-remover-set/96028?cm_mmc=GoogleBase-_-Datafeed-_-Automotive-_-Irwin%205%20Piece%20Bolt%20Grip%20Nut%20Remover%20Set

- any tried those?

I let you all know how I get on....

hairygit:
I recall helping a mate do a rebuild on a 550 many years ago, and the camchain was fitted with a spring link, which means you can split the chain and remove the head without romving the cam sprocket. As far as I know a split camchain was standard, as the motor had not been apart from new (all the yellow paint was still intact on the rocker bolts etc) but for a definite answer, Brian J is the man who'll know for sure! ;D

andy_c101:
I resorted to using an "Irwins bolt remover" socket on the camchain sprocket fixing bolt.
It has chewed the bolt head, so it will need replacing for the rebuild;
but the Irwin tool worked a treat.

The next snag I found is with nut/bolts numbers 2,3,&5 (the inner ones that have the rubber sealing cap) and are buried deep inside the narrow access hole in the head casting - (photo).

first my 12mm A/F standard 1/2" sq drive socket o/dia is too large to go down the access hole;
so using my (cheap) small 3/8 sq drive socket, the heads of these nuts rounded off!
- this despite soaking for half a day with 3-in-1 penetrating oil, (& then after the first difficult nut) using the hot air heat gun.

- ahah! I have my Irwins sockets!.....but...... they have a 3/8 sq drive and whacking-greater Hex-A/F; the hex prevents it going deep enough down the bolt hole.

- only one option..... file the flats off the Irwin socket, down to approx 18mm o/dia! (photo - & that was onlyhalf way).
-  eventually the Irwin socket did the trick, three times over it worked.

I shouldn't  be surprised, this is often the challenge (with 30yr+ old bikes) dealing with those siezed/sheared fasteners.

next task is to lift the head ..... and see what lurks inside.....
( I didn't have time tonight, and didnt want to rush that)

Bryanj:
Use only 6 sided sockets when doing the head bolts, if you can find a supplier there is a whitworth socket that is a "Hammer on" fit on a 12 mm hexagon (3/16 or 1/4 but cant remember which!) as to the spring link on the cam chain that was NEVER a fitment from Honda on any of the fours but the 450/500 twin SOFT link is a fit if you want to change the camchain without splitting the crankcases, speaking of which if you do split the crankcases a new primary chain is a must even tho' its expensive.

andy_c101:
The head is off.
My attention first was directed to 4th cylinder, exhaust valve/seal.
I could see into No4 Ex/port, and the port had a trail of oil from the lower valve stem.
Next I removed No4 Ex valve springs, then eased off the valve stem seal.
The stem seal lip has a 'nick' on the lip (at about 10 o'clock in the photo)
but then on wiping away the oil remnants, I see the top of the valve GUIDE is cracked! (3 o'clock & 6 o'clock, in the photo)
No wonder she was burning oil on No4.
- need to take a close look at all the valve guides now.......

Has any one else come across this type of valve guide failure before?

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