Author Topic: Honda cb175k6, 1972 re-build  (Read 32807 times)

Offline Terrotmt1

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Re: Honda cb175k6, 1972 re-build
« Reply #30 on: September 22, 2020, 10:32:59 PM »
Some big moves forwards on the bike for a change.
Collecting the chrome on Tuesday :shock:

The materials to make myself some side panel badges arrived, silicon mould chemicals and casting resin to make the parts. I was sceptical about this approach, be easier to buy some rattly originals in the USA, but that would be easy, and 90 each.

I have one stripped original which after cleaning I used as a piece to be moulded. Bought a kit off ebay for 23 and made a tight fitting casting box.
Mixed the silicon and gently poured it into the casting box slowly so allowing any trapped air to leak out. The badge is quite detailed, and most people do this work with a vaccume chamber which of course I don't have.
Mould cured in 24 hours and removed the original part. The detail in the mould looked very sharp from the bits I could see, so while it was super clean I mixed the cast resin and poured the first slug into the mould. The mix sure gets HOT, but after cooling and removal the part had two voids where air was trapped, but the detail on the casting was superb!

Encouraged, cast another with a slope on the flimsy mould and dribbled the resin mix in to the point the mould was flooded and waited.

It came out perfect! Really good, so cast some more to the same effect, I'm in production almost!

Made the reflector 'jewels' from trailer reflectors which will be glued onto the painted badges soon as the chrome paint arrives, Flat white and flat satin black applied with a fine sable brush will finish them off.

Result! :drunken: Cost 26 and I have spares to keep or sell.

Also cleaned and trial fitted the twin exhaust systems which fit like a glove. They came with the bike and have saved me about 450.

The chrome arriving will march to bike on hugely.




Offline murdo

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Re: Honda cb175k6, 1972 re-build
« Reply #31 on: September 23, 2020, 08:21:36 AM »
Nice work. I have often thought of doing something similar but never got to do it.

Offline Mark M

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Re: Honda cb175k6, 1972 re-build
« Reply #32 on: September 23, 2020, 09:08:28 AM »
Very good work, congratulations. Out of curiosity, was it necessary to make the silicone mould box so complete, ie with such high sides? Or is that because you had to fully immerse the original and then cut it out?
REgards, Mark

Offline Terrotmt1

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Re: Honda cb175k6, 1972 re-build
« Reply #33 on: September 23, 2020, 12:51:57 PM »
The sides are high as I wanted the mould to be reasonably ridged as you have to get it out of the casting box and then it is remarkably flexible, this is why the mould is floated level to the side walls.
Inverted to cast, the face is flat on the bench so keeps the part shape true to the original.

I had to cut the 'triangular' hole to get the original out and of coarse, the cast part.

The mould is fragile, I doubt I could cast more than 10 items before tears would ruin it, but I've never done anything like this before, so a bit of a leap of faith.
These badges are rare, even rarer than the side panels, and it is just too easy to buy something from the States for around 100 each which are prob damaged, esp the right side (kick-start bashing).

Plan is to shape the reverse sides of the castings to fit the side panels then silver/chrome spray, hand detail the character colours and clear coat for robustness.
The original came from the USA for 28, the casting kit from ebay for about 26 but I have 7 badges.

I will keep the original as reference  and prep 2 castings for use.
This is not a 100 point restoration, just a nice usable Twin.

Offline Mark M

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Re: Honda cb175k6, 1972 re-build
« Reply #34 on: September 23, 2020, 01:22:04 PM »
Thanks for that explanation, I'm not planning anything similar but all restoration tips are useful!
Looking forward to the finished result,
REgards, Mark

Offline Terrotmt1

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Re: Honda cb175k6, 1972 re-build
« Reply #35 on: September 24, 2020, 05:44:17 PM »
An hour or so with Humbrol paints and a fine brush has the badges all done.

I have come to the conclusion there is NO chrome paint that works, so having found out the hard way that Humbrol paint reacts with 'chrome' paint I reverted to my trusty UPOL paints.
Etch primered the 4 cast badges and sprayed them Wheel Silver, a can I had in in 'stock'.

After a few hours and a flu jab later the silver paint was cured, and I have two coats of Humbrol matt white and satin black in place.

These look ok about 12" away, but no closer! However, will do a treat on this re-build bike.
Will adhere them to the side panels with clear silicon once I find some and they are all done.

Still puzzled over the wiring of this little simple bike, conflicting opinions on the voltage regulator and routing of the loom by the tank. the Haynes manual diagram does not show a voltage reg at all..

Tank now has a nos Honda dual outlet petcock at a huge 40, but will be leak-free,
Can't wait to get the chrome back as so much will happen with those parts to hand.


Offline Rex

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Re: Honda cb175k6, 1972 re-build
« Reply #36 on: September 24, 2020, 07:23:31 PM »
Some of the smaller Honda never had regs at all...CD200 etc. The alt output was matched to the electrical load so no spare juice to be regulated.
I had three cheap 6V batteries over the course of about 12-15 years on my daily driver CD200, so clearly the system worked OK.

Offline Terrotmt1

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Re: Honda cb175k6, 1972 re-build
« Reply #37 on: September 24, 2020, 09:01:07 PM »
This cab is a 12 colter, but I think there is some tweet which boosts the system when the lights come on, an extra coil in the generator, but I'm hoping there will be some wires spare that will match up with the voltage reg.
The 1976 cb175 I did had the rectifier, but I don't remember fitting a voltage regulator and can't see one on the pics I took along the way as I restored it.
The circuit diagram does not show the volt reg.

The cb has an electric start if that has any bearing on it.

Offline Mark M

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Re: Honda cb175k6, 1972 re-build
« Reply #38 on: September 25, 2020, 10:44:04 AM »
That sounds like late 6 volt Lucas systems fitted to British bikes with alternators. The alternator can only produce alternating current (AC) by design and batteries must have direct current (DC) to charge so the designers make the alternator feed all the rest of the electrical system via a rectifier which turns AC into DC. The variation in output as alternator speed rises isn't very great on a 6v system so the bulbs and horn can cope with the small potential over-voltage. This is doubled in a 12 v system so more likely to blow bulbs and boil batteries, therefore the need for a regulator to prevent over charging. Designers could use a CVC (Compensated voltage control) box as on cars of the era but these were better suited to dynamo systems as well as expensive and don't really like being in the hostile environment of a motorcycle! Semiconductor electronics had yet to arrive of course. So they did it on the cheap by balancing load to supply and losing the excess current as heat via the battery and bulbs.
Warning! Some parts of this explanation have been simplified!
REgards, Mark

Offline Terrotmt1

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Re: Honda cb175k6, 1972 re-build
« Reply #39 on: September 25, 2020, 12:42:02 PM »
Thanks Mark. On the loom there are no terminals to take the wires from the regulator, all sockets are together and the only loose wires are right at the back for all the lights, or a lot up front for the headlamp/indicators etc
Again, the diagram in the Haynes manual does not show for the CB 175 UK.

Maybe when I finish all the light connections there will be 4 wires over....

Spent 2 hours this morning getting the loom fitted right over the frame/underside of the tank. The loom is brand new, bought by the prev owner from David Silver, but it seems not quite right. Many wires are simply too short, and by 50mm in places.

Offline Mark M

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Re: Honda cb175k6, 1972 re-build
« Reply #40 on: September 26, 2020, 04:37:10 PM »
Some manufacturers produced 'generic' wiring looms to cover several different models or different market variations. I've come across redundant wiring on Honda, Suzuki and Moto Guzzi for instance. I can't explain the short wiring, is it an original Honda part or a copy?
REgards, Mark

Offline Terrotmt1

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Re: Honda cb175k6, 1972 re-build
« Reply #41 on: September 26, 2020, 05:15:31 PM »
Copy, but from respected Honda classic specialist David Silver, so should be good, they don't sell tat, BUT, all these specialists rely on supplier QA control..
I think it is all in and tied/clamped down and the tank on now, so hope I don't need to move it!

Utterly scuppered until the chrome is collected on Tuesday, then I can get going again.

Since learnt that it was the USA bikes that had a voltage regulator, the UK bikes did not have one.
There is a modern rectifier that has a voltage reg in it which switches the generator to high output mode every time it runs.
Tempted!
« Last Edit: September 26, 2020, 05:17:31 PM by Terrotmt1 »

Offline Terrotmt1

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Re: Honda cb175k6, 1972 re-build
« Reply #42 on: September 29, 2020, 04:53:46 PM »
Chrome back, and a trial fit of the home made badges:






Offline murdo

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Re: Honda cb175k6, 1972 re-build
« Reply #43 on: September 29, 2020, 09:55:22 PM »
Looking good.

Offline Terrotmt1

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Re: Honda cb175k6, 1972 re-build
« Reply #44 on: October 03, 2020, 05:10:05 PM »
Thanks!

Needing a bit of relief from the 'Garage saga' and my ill Skoda Superb, and with the rain, it was the perfect day to do a bit now the chrome was here, no excuses.

Pictures hopefully say more than my clumsy words, but started with a 'mojo' lift and got the chrome on the rear first.

All went well, the indicator mounts are a bit special but with many parts now NLA had to improvise and get the same result. These Hondas vibrate so many parts are rubber insulated, so important to try and do the same.
Rear done (wheel etc on tomorrow) the front forks came next which is a bit delicate with all the paintwork and chrome, but again, all went well. Instruments on the brackets all tight and damper fork oil in. Had a leak, so fixed that and all together. The front fender was a bit tedious as it was not made for this bike, originals NLA years ago.

Made a school-boy error on the forks, wrong way round... so took it all apart and did it again...

Hope to get all tomorrow on the bike again tomorrow, plan is to mount both wheels, run the cables and stare at the wires again that somehow fit in the headlamp, goodness knows where they all go.
Finally, fit the emblems to the side panels for good.
Looking like a bike!