SOHC.co.uk Forums > CB350/400
Yet another clock resto' thread
exvalvesetdabbler:
--- Quote from: Oddjob on May 21, 2025, 11:05:35 AM ---Different makes? One a Nippon Seiki and the other a Nippon Denso?
--- End quote ---
They are all Seiki and I have had the calipers out to be 100% sure. Internals look exactly the same. The only difference is the face plates, the fixing for the lamp shields and breather holes. Even though the UK one has 120 mph as the largest number and the other (US ?) has 130, when overlaid the actual values for a given needle deflection match up.
Things like this bug me until I can find a reasoned explanation!
The UK versions came of a S Reg F2 scrap bike I bought in the mid 80S all original but totally gnarly all round. Think I paid about 90 Quid for it from a dealer that was shutting up shop and retiring. Probably never had a wash in its life either. Cylinders were on max oversize and with a washer embedded in the crown and top ring area of a piston. Bores weren't much better. Fins on the barrels are top notch though. It was probably an ex dispatch bike and had 72K on the clock. I did recover a lot of useable aluminum bits that were free of gouges or butchery together with the yokes and a lot of bracketry, carbs/air box with all of the small bits that people usually toss when they fitted K&Ns or can't remember where they go.
Regards
Dave
Oddjob:
The 350/400 never got the larger type clocks, I was referring to the 500 and 550 mainly. For some reason they differ in size between Seiki and Denso, I thought that maybe there were 2 makes on the 400 and that would explain it but clearly not.
exvalvesetdabbler:
Calibration check.
Time to check the calibration before closing up the cases.
I approached this from two directions,
1). Calculate from shaft speed Speed=60*shaft speed/2240
2). Time to clock up one mile Speed = 3600/time in seconds
Assumptions,
- lathe speed is what it says it is.
- gearing of the odometer is right.
Here's the results
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We are somewhere in the region of 2.2 to 5 mph high at 42.5 mph and 2.7 to 3.6 high at 25 mph.
I will probably strap a GPS on the bike once installed just to calibrate my brain.
Screwdriver bit in the chuck and the cable lashed to the tail stock.
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Foot note: Notice there is no difference in the colour from the main part of the face to the outer edge which would have been shielded from the sun by the inner case. These faces are from a bike that had recorded 72K but haven't seen the light of day since the mid 80S.
Regards
Dave
exvalvesetdabbler:
Closing up the speedometer case.
First thing to do was to fit the ring back on the upper part of the case before fitting the trip reset boot. The boot from cb750faces have a mold line which needs to line up parallel with the case. I just put a bit of flowable oxime based silicone on the inside to keep it in position. Once dry I used a drill bit shank to smear some silicone grease inside the boot.
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I made a tool to get the ring starting to fold over and then used a screwdriver to press the crimp down some more each time going between each fold and folding it over further. Once at the screwdriver stage I found it easier to roll the screwdriver over the crimp while pressing down hard. Probably went around 5-6 times.
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First time around with the screwdriver, if my pension doesn't stretch out enough, maybe I could get a job crimping Cornish pasties.!
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Finished item
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Well that's about it for this project. I set the mileage on this replacement about 100 ml more than the old one on the bike was reading and once they match up I'll swap them over. The old speedo on the bike reads 9 mph high at 40 and has cut bands which is something I can work through without having to chuck it back together in a hurry to get the bike on the road.
Even though I know what the calibration of the old speedo is my brain still won't let me go through a 40 speed camera at 49 and my son who has a modern bike keeps asking why I slow right down for the cameras. I have checked it against a hand held GPS on a straight road and keeping pace with his modern bike, my brain still won't let me.
fear not , those specs of dust are on the outside after wiping off oily finger prints with a tissue and white spirit.
All the best
Dave
Johnny4428:
Very nice job on these clocks, they are looking great and ready to put into use.
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