Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: badger_eng on November 02, 2026, 04:12:21 PM
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Guru's.....
Whats your thoughts??
I've started to strip my US 1977 CB550K engine this weekend and its coming apart quite nicely. Only one chewed bolt so far (Oil filter housing required stiltsons as the head on the securing bolt was already semi round) and I'm almost ready to split the crankcase halves.
When I stripped the valves out of the cylinder head, there was no INNER SEATS for the inner valve springs. The outer seats for the outer springs were present but alas, according to CMSNL,,,,,,, I'm 8 seats short of a full house 8)
Seeing as the inner spring sits on the hardened valve guide, whereas the outer spring would sit directly onto the ally head if it were not for the outer seat, do you think its critical to have these inner seats????
The cylinder head was removed some time ago because the spark plug thread was stripped in cylinder two and the P.O. had a helicoil inserted. I found this out when the bike was delivered... a receipt for the work was in a shoe box with a few parts. Stragely enough, a brand new un-used oil filter was also in the box. Sherlock here reckons thats why the oil filter nut was rounded and the filter never fitted as intended :-). Maybe I'm just too cynical!
Anyway, the inner seats may have got lost during the work on the cylinder head but for sure, they are not there now. The engine has been running without them for duration unknown.
So just to repeat the question and canvassing opinion..... required or not?
Thanks for your input.
Pete
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I also wonder why, mechanically, the inners were needed, they obviously increase the spring load but not by much.
As you, like most of us, are now very unlikely to wring the neck for every last bit of hp now i doubt leaving them out will cause a majour problem.
They do stick to the guides with oil film
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“They do stick to the guides with oil film”
Ha!!!! Don’t I know it….. must have spent an hour getting the last two outer ones to give up their love for stiction!
This did make me question if the inners were actually there but alas, they are not.
Thanks for the feedback Bryan, unless I hear from someone with a pretty strong argument to have them, I’ll save the cash for other items I’ll need 👍
Cheers
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I think Honda fitted them for a reason, personally I would source a set and fit them, especially if I had the cylinder head off.
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I'm with Ted.
Honda wouldn't fit them unless they were needed. Think how many of these bikes Honda built (I know the 400/4 has them fitted as well as the 250RS along other CB's etc). If Honda could save a few yen and increase their profit margins by not fitting them I'm sure they would have done.
Personally I would spend the money and buy eight new ones for peace of mind, no doubt they are reassuringly expensive as well!
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I concur(red)…..
On their way from NL as we speak.
Thanks all
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It does beg the question though on why have them on the inner springs.
I do get the outer shim as the hardened spring sits directly onto the soft aluminium head.
Being all things Japanese with JIT, Kaizen, 7 deadly wastes…. etc.
If the inner seat was to extend the length of the inner spring, why not just grind the spring to the required length?
I can’t see the spring being any harder than the valve guide so is there a need to protect the surface with what is essentially a shim?
And why, if you are a Japanese company obsessed with reducing waste, would you add a shim if it’s possibly not needed? - Cost
Why would you add a shim that takes effort and could be left out by mistake - People time and potential rework cost?
Why should I even care?? 😂
It just seems a strange addition to me