My CB175K4 / K6

Richard Pitman

Richard Pitman

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Worcester, England
In 2017, I bought a CB175K4, another un UK registered import. Gold paint. I prefer red, so it got rebuilt in that colour.

It was in good shape, nice chrome, engine ran, in fact the engine still hasn't been apart. It needed new silencers and usual tyres, battery, brake linings, chain and sprockets etc. Bent brake pedal and handlebars replaced. Got it MOT'd and registered.
 

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But it still wasn't like my old K6. The K4 frame had damaged steering lock stops and a bodged welded up side stand bracket, plus the K6 side hinged seat doesn't fit the K4 frame etc. So I bought a K6 frame, swapped the Vin plate ( ! ), had it powder coated, then rebuilt the K4 mechanicals into the K6 chassis. I've kept the K4 frame in case there is hassle in the future. I'll never sell the bike, so any problems can be left to my heirs …
 

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My 'new' K6 still isn't exactly to original spec, it has CB200 clocks, pattern front fender etc, but this doesn't bother me, I'm not a rivet counter !

Here's the original.
 

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This bike is running well and used regularly.

When I rebuilt it from a K4 into a K6 frame, I reused the K4 air filters, after rebuilding them using RamAir foam to replace the paper.

Worth pointing out that the K4 air boxes are smaller than the K6 and later ones. Means that K4 side panels won't fit over K6 air boxes, I've been running K6 side panels anyway.

I notice that this bike makes a lot of induction roar, more so than my CL175 K7, which has the larger air boxes, also rebuilt using foam. So I've just fitted some CB200 air filters to my K4>K6. Waiting for the rain to stop before I can road test it.

Some pics attached.
 

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Funny the small things that evolved over the years, stuff you wouldn't have expected would need any modification.
 
I'm assuming that Honda revised the airboxes for good reason. It'd be nice to think that it was to improve performance, but more likely just to meet new noise standards. That certainly happened with other models down the years, exhausts became more muted.

The rebuilt K4 filters won't go to waste, they look as though they'll fit onto my bitsa SL175 without too much trouble, ought to run better than my home made efforts.

Spent ages trying to get that one to start the other day, turned out to be sticky float valves, same problem that I had in the nearside carb on my CL175 quite recently. Engines run much better when the float bowls are full …
 
Richard Pitman said:
Engines run much better when the float bowls are full …
Click to expand...

And I'm guessing when they get run often enough to keep things wet as well. The only problem with having more than a couple bikes... but we can take it, we have broad shoulders :dizzy:
 
I'll never sell the bike, so any problems can be left to my heirs …
Click to expand...

I like the way you’re thinking. Little surprises aren’t bad.

Look forward to updates. Are you doing a restoration of sorts?
 
Experimenting with a photo hosting site.

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Hmmm, I'll return to the above later. All I'm trying to do is to get my photos to appear full size, as Nabs and Snicks photos do.

Anyway, I took my CB175 for a run yesterday, and it does seem to go better, over 70 on the speedo with more to come, sitting upright with a following wind, only 60 into wind. Two trips to get some Koi food, forgot my mandatory face covering on the first trip.

Is it a resto ? Engine is untouched, never been opened. Original excellent chrome on wheels and rear mudguard. Pattern CG125 front mudguard, later K6 bodywork, rattle can paint by me. Later K6 frame, powdercoated. Original header pipes with David Silvers silencers. Rebuilt rear shocks. Obviously new tyres, brakes, cables etc, new wiring harness by me, new reg rec, UK spec handle bars. CB00 clocks and (now) air filters.

In essence, I was trying to recreate the K6 I had back in the day.
 

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So what site is it Richard, if you don't mind saying? I wish our hosted pics showed larger myself, may be the only thing I was spoiled by in that other site's format
 
Richard Pitman said:
Hmmm, I'll return to the above later. All I'm trying to do is to get my photos to appear full size, as Nabs and Snicks photos do
Click to expand...

You can get uploaded images to appear full size too Richard - if you double click one of the attachments you will see there are options to show how they display.

I love your CL and CB by the way! Now I am the proud owner of a CB175 carb perhaps I should get the remaining bits and make a whole bike like you did :)
 
ancientdad said:
So what site is it Richard, if you don't mind saying? I wish our hosted pics showed larger myself, may be the only thing I was spoiled by in that other site's format
Click to expand...

The site is imgur.com

Code is cut and pasted directly into the body of text, the insert image icon isn't used.

Like this ( I hope ! ) "img]https://i.imgur.com/ARQUjcB.jpg[/img" - open and close square brackets omitted.

ARQUjcB.jpg
Click to expand...
 
I just might sign up with Imgur, my Google photos account works well but they end up the size of our uploaded images here. Thanks Richard. Oh, and the Admin must have taken the weekend off from his newly-expanded role at HT, he hasn't been there in over 2 days so he hasn't seen your (and Chris') shenanigans... you did see Chris' efforts, no?
 
As mentioned elsewhere, the CB200 air filter experiment was a failure, clogged elements strangled performance. Fixed by reverting to K4 filters rebuilt with foam.
 
I've now rebuilt the CB200 filters using RamAir foam. The old paper element comes away easily using an electric heat gun to warm the mastic that sticks the air filter assembly together, just doing a bit at a time, scraping it off. The metal parts all come apart in the process, I used JB Weld to stick them back together, then Sikaflex mastic to glue and seal the Ramair foam. Very satisfying process.

Now to refit them to the bike and road test.
 
Are these engine really picky about the air filter density?
My current cb had no filters, so I've fabricated a foam 'wall' between the intake hole and the tube to the carb using the foam I had over from the Gold bike. Planning to leave the intake hole as Honda made them.
 
I never used to think that they were, which is why the episode I've just described puzzled me.

My other 175, the CL175K7, has the later type filters, (same as K6 ) rebuilt with Ram Air foam, and that runs as expected, none of the symptoms that I've just experienced. It must be that the K4 carbs are setup to run with the K4 filters, maybe mixing and matching parts between different K series is not a good idea.

EDIT I then changed the carbs on the CL and opened a can of worms, now resolved.
 
Now that the CL has been put to bed, the CB got a run this afternoon. Seems more 'lively' than the CL, also idles perfectly hot or cold, and revs to red line, a good advert for standard carb settings. I also prefer the handling with the UK spec flat bars, far more connection with the front wheel, if you see what I mean.

Got stuck behind a blue Ferrari on the way home. Mind you, he was also stuck behind other traffic.

Brimmed the fuel tank and put the bike away, will hold off winterising it just yet, might get a few decent days yet.
 
Got the CB175 out of hibernation today. Put the battery back on it and it started and idled first go, after being stood for nearly 4 months.

Pumped the tyres, changed the oil, lubed the chain, then went for a quick spin. I've just got an Apeman A100 ( cheap GoPro clone ) and a helmet mount, so I wanted to test this. Video is excellent, sound is hopeless. My camera angle on the chin bar mount is wrong, good view of my hands and the clocks, none of the scenery. And I must stop jerking my head around, makes it look as though bike is swerving all over the road, it's really not. I'll have a go at posting a clip in a bit, all part of the learning curve.

 
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Richard, the sound isn't that bad compared to some of my videos where the wind noise is horrible. I've gone to an open backed case for my GoPro and it helped a bit. I'm reminded of how much of the rev range the 175 uses to run highway speeds, love to see the tach up in the range. It might be my ears but the tach seems a bit optimistic, like the engine is possibly turning a little less than indicated
 
On my TV, the engine sounds like it has a chronic misfire. As regards the tacho accuracy, I was changing up when the engine cried enough in each gear, around 9.5k on the dial, which I thought matched the claimed peak power at 10K pretty well. Worth noting that I'm running a CB200 tacho on this bike, redline 1K rpm less than the 175s 10.5K.

Back in the day, my brand new CB175 would run the tacho needle deep into the red. Neither of my current pair will do that, either that or I'm more mechanically sympathetic these days.
 
Interesting... on my computer speakers (not tiny little ones like most have, but a decent small sub and two 6" 2 way JBL "bookshelf" speakers for the mid to upper frequencies) it sounds like it's running cleanly all the way up, but the wind noise could be affecting some of what I'm hearing. Though I have abused my ears with loud engines/exhausts, plenty of exposure to open header V-8s at the drag strip, working in mechanical shops for more than half my life and the probably hundreds of concerts I've attended, my hearing is still amazingly intact. I suppose the tone of urgency when the engine nears redline is less emphatic when translated from video on the internet than when hearing it live while riding. I honestly did not pay attention to the lower redline on the CB200 tach but I'm well aware of the 175's stock redline and reached it often on my SL175K0 while a 15 year old, as well as on the CB175 drag bike my Dad built in the early '70s, it went 11,500 for its power peak and would go 12,000 in the lower gears if you weren't quick with the shifter (thinking about it makes me wish we had video with audio of it back then). Love these little engines.
 
Sounds good to me!
Are those mirrors good or actually get in the way, esp the RHS?
Mine seems quite blind and I would only trust a look back over my shoulder before changing position on the road.
 
The sound issue is weird. I was listening to the sound on the original footage through my 'smart' TV, which uses a media server app to play the .mp4 file stored on my Synology NAS box. However, once uploaded to YouTube and then played back through the same TV, via an Amazon Firestick, I get the full fat sound effects.

The living room PC I normally use does not have sound connected, so I did not listen to original footage. PC upstairs is connected to a hifi amp and speakers, will have a listen on that later.

Mirrors - Nice view of my elbows, but usable if I shift about. I couldn't ride without mirrors, lifesavers over shoulder as well, obviously. The CL has wide bars and original CB600 mirrors, brilliant rear view on that one. My CB600 is fitted with Aprilia Tuono mirrors, look 'sportier', but still effective.

As a kid, I was followed by motorcycle cop for several miles, doing 40-50 in a 30 limit. When he pulled me over and booked me, he pointed out that not once did I look in my mirrors while he was following me. Lesson learned ….
 
The other thing that occurs to me is that the engine featured is 51 years old, and has never been opened up or rebuilt, yet still runs to nearly 10k rpm without complaint. If original speedo is to be believed, it has probably done around 8000 miles from new.
 
Richard Pitman said:
The other thing that occurs to me is that the engine featured is 51 years old, and has never been opened up or rebuilt, yet still runs to nearly 10k rpm without complaint. If original speedo is to be believed, it has probably done around 8000 miles from new.
Click to expand...

And that's what I mean about their durability and easy-revving "demeanor", if you will. Obviously it was treated properly in its previous ownership life prior to you, but it's still a testament to solid design and manufacturing when built yet you hear so many complain about that 51 year old design based on being spoiled by modern advancements and making unfair comparisons to modern equipment. As I heard in a TV commercial recently, "do you want modern, or reliable?" and I was amazed that it might finally be sinking in
 
Idle hands strike again. A CB200 ( or CB/CL 175 K7 ) rear grab rail bolts straight on to the K6 frame. I've been meaning to do this for a while, finally got around to it. Makes use of the centre stand so much easier.

KwoAnbH.jpg
 
Avon Streetrunner tyres fitted recently, as well, replaced the (new) Chingshengs that let go on me over on Jubilee drive last year. Avons seem OK, butvery easy to get them leant over onto the rather high shoulders of the tyres, think I prefer the Michelins Street Pilots that I fitted to the SL175 at the same time.
 
Nearly two years since I revisited this thread. Four bikes now, all road legal, I do try to ride each of them in turn.

I have already had several rides on the CB175 this year. Decided to change the oil today. Last change, 300 miles ago, was some Halfords 10/40 semi synth bike oil, quite inexpensive. Possibly my imagination, but engine seemed mechanically noisier on this stuff when fully hot. I've already drained this from the other two 175's, and refilled with Mobil 1 15/50 fully synth bike oil. They seem quite happy on this, so I've done the same on the CB. After only 300 miles, the Halfords oil was thin and black. Oil spinner wiped clean, no hard deposits. Used my new breaker bar to undo the sump plug. It wasn't overtightened, the long bar just gives so much more control, just a gentle push required to undo the plug. Obviously not used to retighten ..

As mentioned before, the CB175 engine seems to have escaped untouched over the years, and still starts and idles well on the original ( ultrasonically cleaned ) carbs, points ignition with new coil, modernised charging system, DS 'silencers', and air filters rebuilt with Ram Air foam.

I had fitted LED indicator ( turn signals ) bulbs and relay, but the 175 vibes have gradually killed off my LED bulbs, replaced both rears with incandescent type this afternoon. You'd think someone could make solid state stuff that could survive being shaken about a bit, guess you get what you pay for.
 
Just been out between rain showers to give it a sound thrashing. Because of the chance of rain I wore my Arai full face, shocked to hear how much engine noise gets through compared with open face Bell, sounds like a right bag of nails. Perhaps I should get some ear plugs, won't feel so guilty about possible mechanical abuse then.
 
Two or three years ago I bought a Caberg Fiber open face off a colleague at work who had sold his bike; I paid £20 for it.

It is very comfortable and VERY quiet. It is quieter than my Shoei flip up with ear plugs!
 
Weather forecast is rain on the way all next week, so thought I'd better make the most of it. CB175 dragged out of hibernation, tyres pumped up, chain oiled and battery refitted. Fuel tank brimmed with E5 dosed with Stabil last Autumn, engine started first go. This engine is unmolested, never been apart in its life, just had normal servicing, leak and smoke free.

Nice 40 mile ride this afternoon, circular route through the villages around Bredon Hill. Stopped here to pinch some pond weed for the new wildlife pond that I'd dug out earlier in the week.

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Just looked at the photo above, history repeating itself !

I got the CB175 out of hibernation yesterday, refitted the charged up battery, inflated the tyres and oiled the chain, gave it a quick wipe over. Tank was full of Esso E5 fuel, with added Stabil, probably dates back to last October, possibly earlier. Carbs drained for winter. Anyway, it started second press on the starter, and idled more or less straight away. As I've said before, this engine has never been apart and carbs are standard apart from foam rebuild of air filters.

Just back from a 35 mile circular run on the lanes around Bredon hill, stopped for a photo in the same place as last time - I'd completely forgotten about that. Bike is happiest at 50 mph, will cruise at 60mph, and we did have quick spurt up to 70mph, just to check that it would still do it. :love:

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Plenty of black and white cottages along that route as well, but it's a bit embarrassing parking outside someone's home and taking photos. Although the tourists do this all the time in some of the Cotswolds honey pots, coach loads of Japanese folks descend on Bourton on the Water. We live on the edge of the Cotswolds on the Worcester / Hereford side, so we have villages full of black and white timber framed cottages on one side of the county, Cotswold stone buildings on the other.
 
Good power on those CB175s. You almost described the power of my RE Hunter 350. Roy is happiest at 55, will cruise at 65 and has popped up to 70 (ish) because the devil made him do it!
 
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