Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: royhall on May 19, 2019, 08:46:46 AM
-
Is it okay to use a set of 400F valve guides in a 350F. Are the valves the same diameter stem etc. Am struggling to find 350F exhaust guides that have the stem seal and would like to use this set from Yamiya http://www.yamiya750.com/index.php?main_page=product_info&cPath=179_273_180_186&products_id=3630 (http://www.yamiya750.com/index.php?main_page=product_info&cPath=179_273_180_186&products_id=3630) Alternatively, does anyone know of a source for the stem seal guides. Many thanks again.
-
Anyone got a micrometer and a pair of 400F valves. Can you measure the stems please. Cheers.
-
Hi Roy,
I have a complete 400 head so I will pull a couple of valves, 1 in, 1 ex and measure the unworn bit just below the collet groove with a mic. Might not be until tomorrow though - a few glasses of wine may have put me under the affluence of incahol and I have to walk a straight line out to the workshop.
Ian
-
Thanks Ian your a star. Hope your Mikes in real money not that god awful French crap that needs converting to the real world. Hic Hic
-
I can measure them in imperial, metric or Orkney strides, whichever you wish.
Ian
-
feet and inches please.
-
Hi Roy,
Just sneaked out to the toy cupboard and pulled a couple of valves from this old head.
Measured just above the wear mark near to the collet groove:
Inlet 0.2160”
Exhaust 0.2155”
Looking in my Cycleserve manual that tallies with their table within a few tenths of a thou.
Stems are virtually the same figures where they have been in the guides.
Strange but this spare head has only got seals on the inlet side whereas the heads on both my 400’s and the 350 have seals on all valves. Is there ever enough overlap to warrant a seal on the positive pressure exhaust side? Perhaps the seal on the exhaust side just holds enough oil in there to prevent the valve drying up in the guide?
Ian
-
Thanks Ian, I shall cross check the 350 valves tomorrow. They are the sizes for the 400 valves, thought I had better double check. Cheers Roy.
-
Different size guides ;)
400 Four EX stem is 5.477
IN stem is 5.480
-
Hi Roy,
Yes the sizes I have given are 400 valves.
Trig (and Roy)
Not sure where the Cycleserve info has been culled from (published Sept 1975 with permission from Honda and thanks given)
The valve stems are indeed half a thou different with the exhaust the smaller.
However, the service limit is the same for both at 5.35mm (sorry Roy, 0.2106}
These figures for the 350 are all identical to the 400 in this same manual
[attach=1]
400 info above
[attach=2]
350 info above
Ian
-
If you dont think exhausts need seals try a 750F2 with worn guides!
-
Hi Bryan,
So the mechanism of oil getting from the cam and valve gear top chamber and into the cylinder must be because the cam flings the oil at the side of the valve stem which then runs down onto the head of the exhaust valve when shut and then drops into the cylinder as it opens? Is that what must be going on? I hadn’t realised this was worse on some 750’s having never owned one (apart from a brief dalliance with a 750 FA (DOHC of course)
Ian
-
Measured the 350 valves this morning.
Intake - 0.2160
Exhaust - 0.2152
Looks like using the Yamiya 400F guides would result in a 0.0005" increase in stem to guide clearance on the exhaust side, the inlets are the same. Doesn't sound a lot, will that be a problem in reality. Remember the 350 spec is without a stem seal and the Yamiya items have a stem seal, also it is on the exhaust side where a bit of oil is not as troublesome. I would prefer NOS items but cant even find a part number for the items with the stem seal let alone the actual guides.
I am undecided, are the Yamiya parts a Go or a No. Any views on the subject would be gratefully received.
Ian, thanks for your measuring service.
-
Hi Bryan,
So the mechanism of oil getting from the cam and valve gear top chamber and into the cylinder must be because the cam flings the oil at the side of the valve stem which then runs down onto the head of the exhaust valve when shut and then drops into the cylinder as it opens? Is that what must be going on? I hadn’t realised this was worse on some 750’s having never owned one (apart from a brief dalliance with a 750 FA (DOHC of course)
Ian
F2's have larger valves Ian. To get them in Honda changed the valve gear geometry that puts a side loading on the exhaust valve stems that leads to premature wear. The wear can be quite enormous letting oil run down the stems past the seal. I got Kibblewhite guides and valves for mine from CycleX in the states. They are supposed to mitigate the problem. Cant say it fixes it as that would need another geometry change.
-
As Roy says, the F2 used larger valves. To get them into the combustion chamber without then being too close for the valve seats they pushed them up along the same axis and used piston shape to keep volume in size they needed.
It's not by much but places the top of valve stem higher too, resulting in the tappet geometry starting in more of an arc and producing higher sideways load.
In addition they reduced the oil drain routes in the head, looks like they where trying to elevate the level to control wear. Plus an increase in fin size to cope with more heat. That raised level certainly seems to get them smoking when worn. It all goes to show how the original was just under the critical for wear as this small step really breaches it.
It all indicates that they were struggling with advancing the design by hitting limits imposed by original architecture, probably a major contribution in going toward the 16valve successor to keep up with competitors or jump them.
Back to 350, it looks like guides without seals have tight clearance because they get oil. With sealed guides needing more clearance to avoid problems from having the oil wiped from them.
Is that true from looking at it? In other words the two combinations do the same thing but have to be paired to work as intended.
-
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 ;)
-
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?
Sent from my Pixel 3a XL using Tapatalk
-
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
-
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
-
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
-
My 1977 Honda parts list shows this:
[attach=1]
Only 4 seals listed and only shown on inlet in illustration
Ian
-
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 ?
-
Early 400's don't, late 400's do ;)
This info is written on a scrap bit of paper in my draw :D :D :D
-
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
-
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.
-
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?????
-
Rosco Yes and a numptie
-
They haven't been left off, the non seal guide is not capable of taking a seal they are completely different.
-
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
-
I may try hypnotism.
Sent from my Pixel 3a XL using Tapatalk
-
But Rosco only said no seals were fitted, he didnt say if they could have been BUT as a 400 they should have been unless early 350 guides have been fitted. Either way PO either fitted wrong parts or just didnt fit seals----- either way my comment stands, i was just too tired to explain at length
-
Just checked my heads and both, on the inlet side the guide tops are parallel with a provision to take a seal. Whereas the exhaust guides have a conical top with no provision for a seal. I may be unlucky and both heads may be from an early model Yet looking at parts catalogue it only shows seals on inlet side. Confused??
-
It's not the age it's the market the bike was sold into. My 350 came from Ohio and is a very early number F0 that originally had 8 stem seals.