400F valve guides in a 350F

[Trigger]

I found this interesting as, it would save some of my customers paying out for OEM ones.
Had a good measure up this morning on oem 350F and 400F and it is doable but, on the Yamiya ones it depends on how much meat they give you to ream out. And the OD of the Yamiya guide. If the OD is bigger then, a quick turn in a lathe to bring it to spec 

[royhall]

Am going to order a set tonight. Will see how they look, I can always sell them on eBay and the 400 is a very popular bike. Trig, did you manage to find OEM exhaust guides with a seal?

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[AshimotoK0]

In this parts book in my Dropbox links it shows exhaust guides for 350F as 12203-333-325 and 12203-333-335 . My 400/4 book shows  12203-333-315 Wonder what the difference is? I suspect the -335 is the guide that can take a seal

https://www.dropbox.com/s/7pieydvznvy7nhp/CB350_F_F1%20Full.pdf?dl=0

https://www.ebay.co.uk/itm/NOS-New-Honda-CB350-CB400-Exhaust-Valve-Guide-12203-333-335-/202135858908

Yamiya also have the same Genuine Part with that -335 number quoted

[Orcade-Ian]

Hi Ash,
As I said in an earlier post, the 400 head I took the two valves from to measure for Roy had no seal on the exhaust guide, or provision for it (tapered a bit like the nose in the chamber)  The two 400’s and the 350 I have all have seals on both inlet and exhaust.  Perhaps this spare head I have with no exhaust seals is very early?

Ian

[AshimotoK0]

Hi Ash,
As I said in an earlier post, the 400 head I took the two valves from to measure for Roy had no seal on the exhaust guide, or provision for it (tapered a bit like the nose in the chamber)  The two 400’s and the 350 I have all have seals on both inlet and exhaust.  Perhaps this spare head I have with no exhaust seals is very early?

Ian

Interesting ... I have two pdf manuals, different versions  for the 400/4 One shows -315 part and the other the -335 part  Could it be -315 no seal, -335 has seal and  early 400/4 had no seal.

https://www.dropbox.com/s/u51uf0p1dv6m29q/Honda%20CB400%20F%20Parts%20Manual.pdf?dl=0

1975 Manual below

https://www.dropbox.com/s/j0hysqub5jsfg46/400-4%20Part%20List%201975%20searcheable.pdf?dl=0

[Orcade-Ian]

My 1977 Honda parts list shows this:

[ Guests cannot view attachments ]


Only 4 seals listed and only shown on inlet in illustration

Ian

[AshimotoK0]

My 1977 Honda parts list shows this:

(Attachment Link)


Only 4 seals listed and only shown on inlet in illustration

Ian

Agreed Ian .. I still reckon the -335 part is the one with the seal though .. but I last stripped a 400/4 engine in 1986 and I can't honestly remember if seals were fitted or not  I wonder if there were any Service Bulletins for the 350/400F ?

[Trigger]

Early 400's don't, late 400's do 

This info is written on a scrap bit of paper in my draw 

[Orcade-Ian]

Hm,
Mysterious!  My US spec 400 is 1975 and only 500 ish in from the start on engine number.  Although I have now had the thing completely to bits there really was no evidence of anyone having been in there before but I suppose they could have been ultra Trig in the carefulness and used gen stuff back in the day but mine has seals on all valves.  A US thing? Dunno.  Also weird that the apparently none seal number is numerically later.
Ian

[Nurse Julie]

My friend in Tennessee who is rebuilding his early USA spec CB400/4 found valve stem seals on both sides. His engine has never been apart prior to this rebuild. My late UK 400/4 also has them on both sides.

[rosco]

Just to throw this one in  Just stripped my 1978 400/4 head for cleaning It only has seals on the inlet.  Has someone else been in there before me and left them off??

[Bryanj]

Rosco Yes and a numptie

[royhall]

They haven't been left off, the non seal guide is not capable of taking a seal they are completely different.

[Orcade-Ian]

You could well be correct Bryan with your reply to Rosco,
However what Roy and I have said is that there are guides which definitely have NO provision for an exhaust seal and I have heads with both types.  I suppose it’s possible that Honda R&D specially shaped the spring end of the early guides to prevent oil finding its way in.  Presumably, either it wasn’t worth the effort of two machining setups or it just simply didn’t work.
Roger Etcell, who occasionally still writes for Old Bike Mart may remember what actually happened - all a bit academic now, Roy just wants his bike to quit smoking (have you tried patches Roy 🙈)

Ian

[royhall]

I may try hypnotism.

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