Topic: 400F valve guide o-rings

[Killer Canary]

Hello sohc hive mind,
I restored my 400 a couple of winters ago with new rings and a honed standard bore.
I replaced the 4 intake valve seals but the exhaust guides of course don't take any seals.
She smokes heavily on startup which fades away as the engine warms.
I noticed in a blow up diagram that there is an o-ring under the flange of each guide on the rocker side of the head.
I'm suspecting bad o-rings to be the source of the oil that's seeping into the combustion chamber while parked yet searches of the subject haven't turned up a thing.
I'm assuming that Honda knew what they were doing when they decided that the exhaust guides didn't require seals so I'm asking: hasn't anyone replaced the underside o-rings
as the source of smoke on startup?
Looking forward to learning more about this.

[MRieck]

 Valve guides without seals are bad. You need to replace the guides basically. The symptoms you described are exhaust guide related. Replace all of them with OEM intake guides. Kibblewhite 5.5mm guide seals are better then OEM. And you will need the 8 guide orings and a valve job after guide replacement.

[Killer Canary]

I appreciate the response Mike!
 "Valve guides without seals are bad."
Did 400Fs smoke on start up when brand new?
Or begin to when wear developed between the stem and guide on the sealless (exhaust) guides?
This discussion led me to believe that intake and exhaust guides are not interchangeable:
sohc4.net/index.php?topic=93998.0
Please let me know what the truth to all of this is; I want to learn.

[MRieck]

I appreciate the response Mike!
 "Valve guides without seals are bad."
Did 400Fs smoke on start up when brand new?
Or begin to when wear developed between the stem and guide on the sealless (exhaust) guides?
This discussion led me to believe that intake and exhaust guides are not interchangeable:
sohc4.net/index.php?topic=93998.0
Please let me know what the truth to all of this is; I want to learn.

When the engine was new they didn't burn because the stem OD in guide bore were tight. Unfortunately it doesn't remain that way. I have used the intake guides on about 6, 400F heads no problems....the lengths are different. That's it. You can use CB550 guides too but the length has to be cut down quite a bit.
 I actually have a 400F head sitting in my shop that I ported and went through. It has the intake guides on both sides. If you PM me your cell # I'll send you some pics of what it looks like.
 PS....that link didn't work for me.

[Killer Canary]

PM sent:-)
http://forums.sohc4.net/index.php?topic=93998.0

[The Lone Builder]

PM sent:-)
http://forums.sohc4.net/index.php?topic=93998.0

I followed the link; very interesting.

This is not relevant to the 400F, but interesting ...

After reading the post I decided to - for no particular reason - decided to check out the situation on the 750K2. Interestingly, and complete news to me, CMS show that after engine number 1014995 only inlet valve seals are required. DSS don’t seem to register that at all.

When I rebuilt my engine 231*** a couple of years ago, I put in 8 seals, so since my engine is a K4 engine – it’s the one that came with the bike, or at least was with the bike when I got it in ‘78 – I checked on a 750K4 (USA) parts fiche. This says:

“K0” up to 1014995 has 8 seals - as per CMS; exhaust valve guide P/N is 12027-300-310
“K0” & K1 1014996 to 2000000 have 4 seals; exhaust valve guide P/N is 12027-300-320
K2, K3 & K4 after that are back to 8 seals; exhaust valve guide P/N is 12027-300-330

Inlet valve guide stays the same throughout; 12025-300-00.

Of academic interest to most I suppose, but the message is clearly, make sure you are using the right parts fiche and check P/N against the engine number.

[Killer Canary]

All kinds of goofiness!
The first motorcycle that I encountered with no guide seals was an early 70s CB350 twin.
I thought that was odd.
It didn't even smoke!