OK, how many years later am I?
Does $7 mailed (in the USA) sound fair for this kit? These are all the O-rings that don't come in any CB750 gasket sets.
This will let me turn $1 of each one sold back into the forums' Donations.
I'll take 5 of the kits Mark
BTW, the neutral switch O-ring 3x18, are they actually 3mm? I bought one from Honda a couple weeks ago that came 3.4mm and wouldn't fit the neutral switch back in the hole..... The O-ring was listed as 3mm.
Yeah, I've been thru that, too. It's been Honda's doing, but I think I know how it's happened, knowing other things about them (more about that in a minute...).
The Oring for both the Neutral Switch and the Case Main Oil Port (between the upper and lower halves) is actually 3.0x18mm, despite having been variously listed as 3.1x18, 3.2x18, and 3.3x17.8 at various times in the Honda Parts Fiche system(s) over the last 30 years or so. You'll find similar confusion with the Orings for the intake manifolds of the CB500/550 and the valve caps that fit all these SOHC4 bikes.
(...the more:) In the Old Days, when dirt was young and I used to walk my dinosaur on his leash in the summer evenings before that big asteroid hit Yucatan and killed him, Honda specified their Orings as the 'minimum acceptable size', which was the same way they ordered their parts from their vendors. With Orings they have (or HAD, before ISO came along) an implied tolerance in JIS terms, which was -0%/+8% (some say it was +10%, but I disagree...) give or take. So, if spec'd an Oring that was, say, 3x20mm (and specified the material separately) then this meant they would accept O-rings of 3x20 minimum up to 3.2x21.6 maximum in production buys of parts - and they had LOTS of Honda people measuring incoming parts in those days to ensure quality was #1 there (Suzy/Yamy/Kawi, not so much...). This let their vendors calculate the wear factor for their molds in real numbers so they could tell what their tooling costs would be, and then they could negotiate block purchases for millions of Orings at a firm cost.
This easy-to-understand system was all destroyed when JIS was halted suddenly in 1996 as the world (mostly driven by EU, via Belgium and their endless regulations) decided to kill most all industrial communications and go to ISO, which still wasn't yet defined for these sorts of things. After all, what the f#$k is a BUREAUCRAT doing defining Engineering terms when he/she/it doesn't even understand what mechanical tolerances ARE? ...but, I digress...
So, if you are lucky enough to have [paper] copies of the old Honda parts fiche from the early 1980s era (some which, I am that lucky) you can look thru all of the Orings in all of the bikes and soon you'll see this built-in pattern showing up.
Then came the 'new kids' to Engineering Support (worldwide) in the late 1990s. Since they didn't understand ANY of the history of JIS nor the bikes (nor Japanese cars, etc.) they would go out and tear down an engine to get a measurement for a part if it wasn't available via their burgeoning (but woefully incomplete) photocopies of old manuals and engineering notes. We see some of these 'notes' when we find stamped letters and numbers inside these engines, which told us sometimes WHO, or HOW, or WHICH TOOL SET, or WHICH MOLD was involved with the build of the part(s). This practice in Honda was being phased out with the advent of the 'new era' of bikes in the CX500 V-Twin and the GL1000, when Honda's Engineering groups were split into 3 parts: Vintage Support (that was our guys), Recreation Vehicles (bikes and ATVs, boats, etc.), and Honda Automobile. Some of their 'new' practices then appeared in the bikes, starting for example with the 750F1 and the CB550K3: the last of these bikes designed the "old way" was the CB350F. That's why the post-1976 SOHC4 bikes look and 'feel' so different when you're working on them: they were transition products between what Honda WAS, and what Honda BECAME, i.e., that we know now. Everything in their Engineering became codified, specified on a per-part basis (like Americans have since 1965 or so) and tracked with long chains of people and paper - until microfiche came along, and later computerized listings. Each of these latter 2 changes lost more of the lore of the pre-1976 bikes, to the point now that Honda doesn't even display any parts fiche for them anymore.
This particular Oring on the Neutral Switch started out as 3.1x18. It became 3.2x18 in the early K1 parts fiche, and the Neutral Switch became almost impossible to install, while mating the upper and lower case halves with the 3.2 thick O-ring resulted in the outer edges of the rubber getting pinched into a thin film around the Oring (seen when the cases get opened nowadays) and sometimes a damaged (cracked) Oring, causing mysterious loss of oil PSI when the engines were hot. This was seen as 60 PSI when cold, 30-35 PSI at hiway speeds, and a flickering OIL light when sitting at a freeway offramp on a hot day after riding at speed for a while. Normally these numbers should be 60+ PSI cold, 40-60 PSI at hiway speeds, and 5-12 PSI at that same stop (no OIL light flicker). So, now you know why that mysterious 'legend' got started...and Honda had to address it with a "...don't worry if the light flickers..." message beginning in the 1972 750K2 Owner's Manuals. Dang it, you'd BETTER worry about it, as the loss of pressure was REAL...but, that's more digression...
This same sort of situation has led to the many differently-sized Orings we see in carb rebuild kits today. An example: the intra-carb fuel tees in the 750 roundtop carbs started out as 1.9x7.8mm in the K0 bikes, and one on each tee end. Well, the material was also spec'd as Buna 70 when our gasolines didn't attack Buna, but as lead began to disappear, starting in 1971, the Buna started shrinking a bit when it dried out during a winter park-in. Then the tees weeped gas in the Spring startup until it swelled a bit, presuming the same gasoline was being used. If not, they could continue to weep. So, Honda added another Oring on each end of the fuel tees and re-spec'd the size as 1.9x7.9mm instead, starting in the summer-of-1971 Parts Listings. So, if you buy a carb kit today that is listed as being specifically for the K0 bikes (hard to find now) you can get undersized Orings (and not enough in some cases) for those tees if they are 'faithful to spec', (but won't work well now). I got 4 of these about 4-5 years ago, which were the rubber-only kits first sold at PartsNmore. Those kits vanished, and now only the later ones with 4 Orings per tee are used, and they are usually 1.9x7.9 to 2.0x8.0 in size. The latter, thicker ones will not ever leak with the modern fuels attacking them in the future, but can take a bit more effort to assemble: lube them with silicone of grease during a rebuild to prevent breaking off the fuel hose's spigot because they don't rotate easily at first, either.
The latest manifestation of the errors caused by the loss of the man-to-man information exchange for these parts is: leaking shifter shaft seals on the CB500/550 bikes, and weird fork seals in 'kits' for these bikes. If you buy most seal kits today, they have been 'generalized' using "reduction of inventory" rules to become the most-commonly-available, closest-fit standard part that a lazy designer/engineer/clerk can't be bothered to research further to see if it actually works, so, in this example, it becomes:
1. Shifter shaft seal: the ID was 14mm on the CB500K0 bike's earliest offerings. The bike made a puddle of oil when parked hot in Cycle Magazine's parking lot and Honda traced it to the shifter shaft: when the bike leans over, parked, with hot oil, the cooling shaft sucks oil past the seal's lips. So, the embarrassed Honda changed it to a custom-made seal with a 13.8mm ID hole by the time the HONDA logo plate on the 500 alternator cover also stopped falling off by itself (i.e., by the first month of production), NOT an industry-standard part. Today you will likely get a 14mm ID hole in your generic seal kit, and a puddle of oil by the kickstand from a rebuilt, parked, hot engine. Finding the 13.8mm ID seal will fix it, every time.
2. Fork seals: in the late 1970s and into the 1980s Honda changed the fork seals for the CB750 5 times in their parts fiche. The original seals lasted as long as the forks (and the CB750 bikes) were thought to be living, i.e., about 20k miles. When riders everywhere were quadrupling this mileage by 1975 with their K0/1/2 bikes and suffering oily riding boots, Honda was supremely embarrassed and changed the seal from its first design of 2 inner lips (the upper one for dust removal) to first 3 lips (not a standard seal), to 4 lips, and then 5 lips (also not a standard seal) , the latter which almost locked the forks in position unless you hit a curb, or something almost that big! They then changed back to a 3-lip seal with Teflon coating, which were seals to die for, copied from a Suzuki bike design circa 1976. So, until about 1995 we got these fine seals from Honda for these bikes. They were discontinued in 1997 but picked up aftermarket for about 10 years, now gone again, too bad. They were not a standard part, so today we just find 2-lip standard Parker-style seals, since they are the world's seal giant. While there are some tricks to make the front end work better (see my book), those tricks are lost to today's computerized Parts Clerks.
The list of these little things goes on and on, but they make the difference between these bikes working right, or working OK (or not so much) after a rebuild. Lots of us have become those 'gurus' (to steal a 1960s dubbing) just to make them the fine machines they have long been, again.
