Rebuild of my English CB175K6, 1972

Thanks for noticing the missing pin in the arm/cable clevis, I knew it was not in as I'm not sure if the front will have to come apart to sort the fork oil leak on the one side.
The repair looked good, so i kept it as a bit of past history.
There are several places where I've left the 'past' on this and all the others I've done.

In the Haynes Manual, the engine oil stated is the in-period Castrol GTX.
I can't remember what rating that was or it's make up, but what modern oil do people use please? I thought of Castrol Classic Oil for pre 80's machines.

The loss of the cast brake stop is odd..



 
Many of us are using Rotella diesel oil for our bikes as it has higher levels of zinc and is JASO-MA rated so it'll work with our wet clutches. Like you, I used Castrol GTX 20-50 back in the day and bought it again after my almost 20 year bike layoff not realizing the change over that time.
 
Thank you for that, I'm thinking the formulation will have changed in all the current classic oils esp when you consider the wet clutch.
Ill look for that oil to see if we can get it in England.
 
I've been using Silkolene Comp4 10/40 for the last few years, even used it in my Hornet engine last oil change.

Just read the specs for the recently release 10/30 verson of the above, blurb implies that it is ideal for our older engines.


AtUTgH9.jpg
 
That reads well Richard, thanks.
Easy to forget to fill the engine in a re-build like this, so will get some asap.

I think I have the wires all together now, but several connections are male-t0-male so waiting for a kit of connectors to arrive to get them together.
Will test with a battery soon. Hate this stage.
 
Lovely progress Graham, wish I could get to mine I'm sure I'm being steered away from the garage on purpose by SWMBO.

As regards the wiring, before connecting the battery what I did was to connect the live battery lead to earth and then use a multi-meter set to resistance to check each circuit. For instance, remove the headlight bulb and put your meter on, say, the dipped beam to see if it measures continuity when the handle-bar switch is on. It's one step up from a battery and bulb but it worked for me and pre-empted me switching the ignition on and shorting the battery/setting fire to the bike etc. :)
 
Thanks James.
Fortunately, I have a wife of 42 years who likes cars, loves F1, comes with me to every hillclimb we race at and is tolerant of the many hours these projects make! Phew, but her birthday is tomorrow, so no bike!
I was a bit nervous using the battery in the loom, but the new loom that came with the bike seems to have different colours to the original, and I still have 4 wire ends I can't find a home for.
Using the 12 volts (the battery has an isolation switch) I am first following the function along each juncture with the DVM bell and then knowing the circuit is complete running the 12v down it to prove, say, the neutral light is on when the switch by the primary drive is in the right location.
However, the last function I was sorting was the electric starter circuit. Got it all to bell through, but the solenoid would click hard pressing the handle bar button, but 12v would not pass to the motor, duff solenoid, another ordered tonight which will delay progress.

Plan is to tackle the lights next then come back to the starter, horn and ignition.
I want to fill the engine with oil before exercising the engine (plugs out) hence asking about oil above. Going to follow Richard's advice, he's been running these twins for a long time.

The electrics and the carbs took ages to sort last time on the gold bike, looks like my luck has not changed!
 
Have all the circuits working on switch position 1 after a bit of messing about earthing solidly the front indicators, but all ok.
I need some help on position 2, lights.

Is it so that unless the bike is actually running you can't get the headlamp to run but can get the front/ rear side lights ( position lights) to come on?
In pos 2, the engine not running, the rear brake light will not workthough the rear lamp is on at the lower wattage element of the bulb.

I seem to remember my gold cv had this layout, but without a users manual, I need your help gents please to clarify what should work on Postion 2 on the key switch, engine not running.

thanks.
 
If the English version of the CB175K6 electrical is the same as the US version, position 2 on the switch is Park with only the taillight working, for roadside emergencies. Nothing else works on position 2 on the US version, but I can't speak to any differences there may be with the UK version.
 
According to my UK spec wiring diagram, in position2 (PARK) the low taillight filament (5W) and the headlight "position" light (4W) should be illuminated (Both connected to solid Brown wires), and NOTHING else has power beyond the key switch.....
 
Thank you both, I think you are correct, Pos2 is Park only lights.
Engine spins over nicely on the electric start, got all the circuits up in Pos1, big final check tomorrow with fully charged battery and a clear head, then headlamp in.
did a trial fit of the chrome rim today and all the screws fit.
All the loom is in place and all connectors together.

still have 3 wires coming out of the new replacement loom by the battery and nowhere to connect them, maybe the loom is made for other countries too?
got the mass of inline connectors in one place, seem to recall the original bikes had a large sliding sleeve to cover this lot up?

so far, so good.

need to prep to fire the engine and start that mini adventure, the gold cab was really tricky to get both carbs working.

I don't really want to finally fit the tank wile messing with the carbs so thinking of a temporary container to feed the carbs to get things going.

as ever, thank you for everyone's help so far.
 
Those three wires are likely the ones for the voltage regulator, not present on UK bikes.

Black, Green and Yellow.

Ground the Green wire. Black is switched live, useful if you fit a five wire modern reg/rec. Blank off the Yellow wire.
 
The 3 wires are black, female connector, very dark green female, and dark green with a 3 way female connector.

There is now nothing spare in the lamp bowl and no male or female connector items that are not wired in, except the horn which I'm waiting to arrive. The horn wires are a long way from these stray wires.

iirc, the black has 12 volts the others are 'dead' but all this is without the engine running of course.

My pc is waiting a new Sky booster to arrive, so can't take and post a picture until Tuesday.

Going to go though the wires again today as a double check everything is tight and put the headlamp in which will feel to me a bit like installing the engine, a big job done.

will trial fit the tank to be sure the loom route is clear and no chaffing can take place.
 
Pleased to say the bike is electrically complete, headlamp back in and tank back on.

petrol and sparks next...
What can go wrong?
 
I don't have a good track record with motorcycle carbs and sparks, and the gold bike was no exception....Took a lot of patience from several HT forum members to guide me to getting both cylinders firing and to the same temperature as Richard may recall.

Before I delve into the sorcery of Honda cb175 carbs, any tip as to where to set various screws please?

Bike looks great with the lamp in and tank on even though it is quite tightly packed in under and to one side of the tank.

All controls adjusted and the split pin in the front brake clevis. ( just to show I do take notice of advice!)
 
I can't vouch for the veracity or provenance of this document, but it seems pretty authentic to me. I think Simo found it on the web many moons ago.

03kt0eb.jpg
 
Thanks Richard, that will give me a good starting point.
The bikes carbs are in great condition, std jets etc and look as if they have not been messed with before me...
 
Mad and maddening afternoon on the cb today.

Getting ready for the first attempt at starting the engine, decided to get things tidy.
I like to get the cable runs neat so started with them all only to find I had cabled the left lever as the brake and the right lever as the clutch....
Corrected that in a jiffy, but what a pratt.

Decided to re-route the throttle cable too which led to removing the tank and all sorts, but ok now.
Filled the engine with 1.5L of oil to the top dipstick mark and plugs out wound the engine for 20 secs to get the oil pumping (I hope).

Tank off, decided to rig a small petrol vessel at tank level to the carbs and enjoy the access to the carbs. That done, poured some petrol in (99 octane) and the bowls filled.

With some trepidation, put the gapped plugs back in, choke on (all screws out 1.5 turns from tight) and pressed the starter.

Nothing.
Checked for sparks at the plugs, yes, nice stream of sparks, could be fatter, but there. Plugs were dry, but I only gave it a few stabs on the starter.

Then, noticed a slight whetting of the rhs carb's bowl at the body/bowl gasket (O ring) so drained the carb and tomorrow will try to get a seal before probing what is wrong.

I should really replace those bowl gaskets, but they are not easy to get in the UK, all in the USA!

Shades of the gold bike returning..
 
One carb leaks from the bottom bowl gasket, so need to replace the rubber seal that has been compressed for 48 years...


Will do both carbs, kit on order from David Silver of course.


However, it runs. Lovely Honda Twin rumble, vibrations everywhere (seems they are all like that?.


Some tuning to do tomorrow, but a great kick-off to the last match. Soon be off the bench and on it's center stand.
 
Need to study the set-up for the carbs, I seem to remember it can be tricky to get them just right, but both sides get hot equally which the gold bike did not for ages.
From Richard's experiences best to tweek them with the air filters on.

Close to the finish line!
 
Well, maybe not as close as I thought...
Exactly like my gold bike was, poor running.
Taking this from the top:
Set the floats to 21mm, all jets good and clean, body drillings too. Air mix screw @ 1.25 turns out from tight.
Fresh 99 octane fuel.

Pulled one plug lead off to do the rh side first. Full choke (cold engine) and it reluctantly started.
Held on the twist grip until I could get about 3000 rpm and slowed the engine down, choke off, to about 2K.

The rh side now started to give white smoke and smelt rich. Air Adj screw just about does nothing when you turn it and pause. Seems to rev freely. Tickover a bit rough.

Over to the lh side, rh side plug lead off, lh side on, very reluctant start and died. Got it going after a good electric start churn and much twist grip working, buit not good.

Put rh lead on and the bike started well, now on both cylinders.
rh side ran cold, lh side very hot, lh side smoking still. All air screws seem to have little effect.

Took plugs out. Smokey lh side black plug (rich), rh side far far less so and only luke warm to the touch.

So! what am/have I done wrong?

I cant get both sides to run together though they did at the first start-up.
Any help appreciated.
 
Some folks use that (pulling plug wires) as a way to balance carbs on bikes without vacuum ports. Never worked for me.

As posted above, your carbs could require anywhere from 92-98 main jet, That can be a pain to zero in on. I’m in the same boat right now. Also you gotta start with the slides synced via the throttle cables, then try to tweak each idle screw the same, etc.
 
Several steps back today:
One google search said treat each cylinder as a separate item then as a twin.
I have checked the 'cold' side (RH side) valve tappets for 0.002", the inlet was tight, so reset that to 2 thou, ex was 2 thou.

However...
I took the generator cover off to set the engine at TDC to do that tappet re-set and found the inside of the cover with oil on it, BUT forgot to put it back on and on start-up the engine belched a load of oil onto the bench.

I presume the generator runs in a bath of oil?
What a mess, still mopping it up so came here to see if there is any guidance on the carbs.

I can't grasp why one cylinder runs hot and rich and the other as good as no combustion at all.
Going to remove the carbs again and try to find the jet numbers but they look very very original to me from the factory.

Had this kind of issue with the gold cb but can't recall what I was told and did to fix it, but it did all chime in eventually.

iirc, 'SIMO' gave me guidance that worked a treat, but that was on the HT site 5 years or so back. Might try to find the thread and re-read it.

Irritated in England.
 
Just back in from a session in my garage, swapping float valves and floats on my CL175 ( now with CB pipes for ease of access )

When that was only running one cylinder, it was because the float chamber on that side was empty. Sticking float valve was the cause.
 
Float valves can be changed in situ. A dab of LM grease on the moveable part holds it in place while the float is replaced, then petrol flow soon washes the grease away. Unless you use red rubber grease, which doesn't easily dissolve in petrol ….

Another tip I've just discovered, thanks to Allen Millyard, is to use clock cleaning fluid to clean the brass parts of carbs. Smells strongly of ammonia.
 
The carbs are 644A's and all the jet numbers are correct, yet the lh side runs really 'black soot on the plug' rich.
The rh side barely runs at all. How can that be so?

Floats are 20mm with the float 'just' touching the sprung needle. (float hanging by gravity)

Sparks are good on both sides and I presume the timing is good as it runs and revs etc.

Awaiting the gasket kit to arrive, maybe monday so some days respite from the bike.
 
911hillclimber said:
The carbs are 644A's and all the jet numbers are correct, yet the lh side runs really 'black soot on the plug' rich.
The rh side barely runs at all. How can that be so?...I have a few tricks you can try.......

Floats are 20mm with the float 'just' touching the sprung needle. (float hanging by gravity)...Spec is 21 mm not 20 mm

Sparks are good on both sides and I presume the timing is good as it runs and revs etc.

Awaiting the gasket kit to arrive, maybe monday so some days respite from the bike.
Click to expand...

Just for fun, swap the plug wires.....
Also note the air screw (Mixture screw) WILL NOT have any effect once you are off the idle circuit (RPM much over 1300)......
Please verify that the plug wires (coil secondary wires) are NOT contiguous with the coil core.....The secondary should NOT fire at all unless both plug leads can achieve a common connection (usually ground), so firing with one plug wire disconnected usually indicates an internal short to ground in the coil.....Your bike should not run at all with either plug wire removed (and ungrounded)
 
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Thank you, food for thought and some action on Monday when the gaskets arrive for the carbs.
Never thought rpm over 1300 would negate the air adjustment screw.
The spark path is to ground via the engine so I think that ground is good, shopping the leads an excellent idea!
thank you!
Graham.
 
Based on recent experience, I still reckon that fuel levels / lack of fuel are the basis of your problems. Too much fuel on the rich side, too little or none at all on the cold side. Easy to check for too little fuel, drop the float bowl or loosen the drain screw.

You mentioned a leaky float bowl gasket. Was that on the rich side ? That gasket should normally be above the level of fuel in the float bowl, a constant leak there indicates fuel level is too high.
 
Thanks Richard.
yes, the weep was on the Rich lh carb which today also overflowed a touch.
the rhd side is tight.
I have just ordered a new coil, I think I had to change the coil on the gold cb, could be wrong.
They are cheap, so good call for reliability in the future.

Both bowls are full during all this, fuel is from a gravity fill from a small container, the junction to the carbs is at the same level as the petcock would be.

the gold chain would go cold one side and hot other side then swap for no reason that says ignition to me, hence new coil ordered.
I can't find my old cv thread on HT which had the changes I made to get that bike to run cleanly, irritating.

will reset the floats to 21 from 20. Will that really make a difference?
 
will reset the floats to 21 from 20. Will that really make a difference?
Click to expand...

I just wish that I was able to set them that accurately, bending that tang is pretty hit or miss when I'm attempting it !

I wonder if a new set of OEM floats would come ready set at 21mm ?
 
Bet they are like spark plugs, gapped to a random number..
It is a very crude way to set the float, can't imagine the carb factory tweaking that tab to exactly 21mm hence me asking if it is dead critical.
 
911hillclimber said:
Bet they are like spark plugs, gapped to a random number..
It is a very crude way to set the float, can't imagine the carb factory tweaking that tab to exactly 21mm hence me asking if it is dead critical.
Click to expand...
Actually NGK plugs are preset to a specific gap, usually .026" or .028".
Yes, float level is a critical number, it set the fuel level inside the jets and passages so fuel is drawn properly. 20mm float height is raising the actual fuel level so it could create a richer than normal condition. Yes, bending the tab is a PITA. Try to bend both sides of the tab when you do it to keep it parallel to the float pin
 
Must admit, I just fit new NGKs without bothering to check the gap.

Interesting to put a K number to a carb.

My K4 CB175 engine has the 306B carbs, with 98 mains and (IMHO) less restrictive air filters.

My K7 CL175 has, as standard, the 653A carbs, with 92 mains, CL exhaust and later type air filters.

So, Grahams K6 has 644A carbs, 90 mains and later air filters.

None of which has any bearing on issue in question, just interesting ( to me ! ) info.
 
Best bit is the carbs correspond to the data sheet you posted above, so the carbs on the bike are stock.
Both floats are 21 mm to 1/2 micron and the brass tab ready to snap due to flexing a million times.

I'm setting the '21mm' with the float hanging down and 'just' touching the needle without depressing the spring. Hope that's correct (?)
The pilot jets and drillings are all clear inc the fine hole just downstream of the main jet/needle.

Gaskets on Monday so will try it all then. New coil on it's way too and I found a dicky connection from the neutral line as it mates with the rectifier connector.

That stopped the bike dead until I noticed the light was out....
Should be out of the woods end of the week coming.

 
It's getting irritating.
Fresh float gaskets, 21mm float heights, still a dribble every now and then from the overflows.
Brand new coil.

Got it started ok, very hard to get a reliable tick-over, according to the tach best I can get is 1900 or so before it stops.
Air screws do noting, so presume the tacho is reading accurately enough.

Thr rh side that was running cold now runs hot and the left is now luke warm, about 32 deg C, the temperature difference is just touchable at the exhaust tip on the rh side, easy/cold touch on the lh side.
This is exactly how my gold cb was, the hot/cold sides would alternate not during a run on the bench, but between cold starts sometimes.
Bowls are full due to occasional weeping from the overflows.

So, just how do I get these to balance? Any ideas please?
 
^^^Yes, his and LDR's engines look stellar. Sadly, the looks of his isn't helping it run properly... always something.

As to that - 911hillclimber, how is your battery? I'm sure it's already something you're thought about, but a low or degraded battery will cause more idle speed running issues than most would believe. I mention it because of the switching sides description. Also, the idle speed might be why the air screws are non-functional. Cables adjusted so there's enough slack at the slides for them to drop all the way?
 
LOL! 'All Show, No Go' phrase comes to mind...

Battery: I have been using a good size sealed motorsport battery so far, certainly not the youngest battery, but today it had been charged for hours.

However, a nice new one, size to suit the bike arrived with the coil, so can charge that fully (it is a sealed type) and switch to that.

To try to uncover what is wrong here I'll go back to the start, check the timing and points gap, valve clearances etc while the engine is cold tomorrow, after the dentist's appointment...

I had this very same issue with my gold cb too, just can't remember what SIMO told me to do (on HT site 5 years back) but it worked and it was simple too.
Wish I could find the old build thread now.

As to slide drop, I slackened the cables until the slides would drop no more then screwed the top adjuster on the top of the carb to take the slack, but I agree that could be stopping a low tick over, another check for tomorrow incase one is hung up a touch.

Just to add injury, the electric starter chain/wheel/sprag rollers sound awful and getting worse, so i see a strip and replace the sprags etc very soon. Parts just ordered, real Honda parts.

My self imposed deadline of the end of October is now out of the window.
 
Wow!
thank you for those, some bed time reading tonight.
Hope the solution is in there, they were big threads.
 
Useful reminder for me as well !

66Sprint wrote:

[I start with the slides synchronized (cable adjustment), throttle stops backed out, and the mixture screws turned to the center of their specified range......
Hold the throttle slightly open and start the engine..... Back the throttle down until you get an idle ~1200 RPM, HOLD it there, and gently turn in the throttle stops until it starts to rev.....adjust back to 1200.... Once it is again idling at 1200 with both throttle stops set, you are ready to do the actual adjustments......

Pick a carb....adjust its MIXTURE screw throughout its spec'd range to find the point of highest idle RPM, and leave it there at highest revs...adjust that carb's throttle stop back down to 1200 RPM...
Same procedure, other carb......
Repeat on both carbs to verify/fine tune.......Repeat again IF necessary....
Re-verify slide sync...Adjust IF necessary (usually no more than 1/4 turn on the carb top adjuster, often they are still fine)...
If you did this correctly, vacuum , exhaust pressure, and exhaust heat will be the same on both sides (hard to verify last two on the CL)
Engine response to throttle should be "crisp" and smooth throughout entire range..../QUOTE]
Click to expand...
 
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Have printed those instructions off for the next few days.
Went to those 2 old threads, almost forgotten how hard I worked on that gold cb.

First thread, the actual build gets to the carb issue on page 35.
The issue I currently have is exactly as on the gold cb.

The solution seems to come from a clean by boiling water with lemon juice and a good poke through the drillings and then simply using the R66 tuning guide above!

I thought I found or was advised a step I had missed.

Thus, my approach today will be carbs off, full re-clean and poke through inc the float needle seating and focus on the idle circuit.
Back on and re-balance as per instructions and see.
 
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