Hi,
I don't know if it's meant for, but I put the tube coming from the head (on top of the head next to the condenser) in this hole. Seemed logical to me, spraying the chain with oil mist.
Jensen
Mystery Hole
Well, I tied my shoelaces together in anticipation (e3steve's caution), and after spending much of today scouring all the photos I could find on Bill Silver's cd, I will again suggest that the hole is/was for carb overflow tubing.
I didn't think my battery vent tube suggestion was all that much out of line. Under normal circumstances, the battery should only vent water vapor or hydrogen and oxygen gas, no acid to speak of. And I don't really know where I would place a battery vent tube if it did contain acid--anywhere other than a couple of feet behind the rear axle seems bad to me. In searching the "Shop Manual 250-305 1973" file on the Bill Silver cd I did find 5 photos that may shed some light on the mystery. Figures 8, 10, 12, 13 and 15 on pages 46 through 49 appear to me to show a bowl overflow tube running from the carb through this hole and down into the chain case. It seems odd that the end of this tube would spill fuel right close to one or both of the oil seals, but that's what I get from the photos (I think the figures depict a C72). And if you're spilling fuel from the bowl(s), you've got other problems anyway. I am aware of the discussion regarding bowl overflow tubes, but I do believe that's what the brass spiggots were intended for. I base this on my experience with a 1968 CT90 carb which has exactly the same internal and external fitments on the bowl, and an expressly designed channel in the skid plate to accommodate the tube. I also see that the CB77 carbs have an atmospheric vent for the bowl, although it is quite tiny and easily obstructed by dust etc. which may have reduced its reliability and, ultimately, lead to its abandonment? I have yet to run across any pic's of a CB77 showing carb overflow tubes going down that hole. In any case, these are my current guesses...and footwear. Thanks to all for your continuing interest. Wilf
Even though there is not supposed to be tubes on the carb vents I found from experience that fitting them stopped the engine cutting out in certain crosswinds. I used to ride on a regular trip and between some hills in certain winds the bike cut out suggesting fuel starvation on one side, so two short bits of plastic hose from the carbs to under the cover above the gearbox solved the problem. The wind needed to come from nearly right angles to the bike.
Leon. long time rider
Wilf, you slay me! Precautionary action [with the footwear securing devices] indeed!
I can't agree on that point; the gassing from a flooded l/a battery is very corrosive. It's what creates a lot of the terminal-post corrosion on top-vented batteries (notice how little, if any, you'll get on the post[s] of a car battery that is "sealed for life" or "maintenance free"). Down through the box section of the frame spine where it can vent freely around the centrestand fulcrums. Assuming yours has no oil mist there (mine has!), spray the underside area with WD40 and mop away the excess with paper towel or a cloth. I don't polish my exposed areas (oo...err, missus!) but just wipe with a WD40-impregnated cloth and lightly buff off. Coming from the marine sector, I find that method works well on all metals, including stainless. If you do it frequently enough stainless "absorbs" the treatment. Sounds odd, I know, but you can see the effect on a yacht when an untreated stanchion is left; the windward curve suffers surface-changes much more than the leeward side. All metals have different molecular properties [funny, that!] but 316L stainless is almost like a living, breathing element rather than an alloy. A bit like marble, which reacts in an almost-living manner to different environments. Leon, I like the logic behind your viewpoint. I think the reason that Honda/Ed dislike the attachment of 'overflows tubes' to these spigots is because maintenance on the tubes gets overlooked and they have been known to become blocked. That situation, coupled with the easy blockage of the bowl vent hole that you mention, has sometimes resulted in fuel starvation when a vacuum starts to be created within the float chamber. But your anecdote surrounding crosswinds is interesting, which I, for one, shall pay close attention to next time I encounter such. Another compelling topic for those of us who are a bit obsessive!
Hi LM,
The engine number is 1007539, on the wiring loom is 1966 printed. It's sold here in 1967, so it's licensed as a 1967. Why do you need the engine number ? It doesn't have chrome fenders, nor the flipped up seat, but has the powerjet carbs. It does have the dutch / german special air filter cases and turning lights (winkers) standard. It' a original dutch model, not imported. If you need more info, just ask, jensen assembly of Japanese motorcycles requires great peace of mind (Pirsig)
Where can I view pics of your CB72 please? I'm sure you've posted pics / link, but I can only find your CB400f pics. rgds, Steve
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