Topic: Maduncle has FINALLY got himself a CB750K

[maduncle]

Progress!

Yep - its been a very long time between drinks, but then this engine was a slow and methodical build and required a few short breaks between build sessions to chase up those little things you find you need - like new pistons, dowel pins, bearing C clips, etc.

But Mal the engine builder got there in the end. He and I installed the engine in the frame at his place on Friday, then I brought the bike home and spent a few days getting everything else fitted.

All I have left to do before the tuning and synching begins is to complete the wiring. The bike is using a new harness, but I am a little challenged by this red connector - what does it do and what am I missing that plugs into it? Is this reproduction harness fitted with two optional plugs for the stator/neutral gear or something? I have no idea.



The wiring should be relatively simple. I do have aftermarket headlamp, indicators (LED) and gauges, and I am fitting a Motogadget m-lock keyless ignition - hang on, did I say the wiring would be simple?

Anyway - here is how it looks 99.9% together.

[Terry in Australia]

Looking good  Cliff, don't worry about the red plug, it's for the K3 and later models that had a clutch lockout doodad which real CB750's don't need, of course. If you have problems getting it to fire up let me know, I'm using the same harness on Mike's build and had no problems getting it running. Cheers, Terry.

[maduncle]

Looking good  Cliff, don't worry about the red plug, it's for the K3 and later models that had a clutch lockout doodad which real CB750's don't need, of course. If you have problems getting it to fire up let me know, I'm using the same harness on Mike's build and had no problems getting it running. Cheers, Terry.

Thanks Terry - I have been reading up on the forum here and yep, discovered the thing called a "starter motor safety unit" used in later models. I figured that was what plugged into the red plug. Good to know I can just ignore the plug and I don't have to do any wiring bypass stuff.

I pick up two oil galley plugs for the underside of the engine tomorrow night, and I have ordered a Joker Machine oil pressure gauge for the top - so I won't be doing any engine starting until the Joker gear gets here and is installed.

[maduncle]

... and another thing.

The stock throttle cables are way too long for clip on's and I do need to take another look at the routing, but the throttle action is quite stiff and difficult to pull.

I have ordered a pair of CB400F throttle cables as they may help to reduce the amount of unnecessary cable from carbies to wrist - but I need to do something to make the throttle "lighter" to operate.

Any ideas?

[Terry in Australia]

Yeah mate, they do have a pretty strong return Spring on the carbs, so as long as your cable routing isn't contributing to the heavy throttle, just go to an engineering supply store and buy a lighter Spring, but understand that it still needs to be pretty strong to close all 4 slides. Cheers, Terry.

[maduncle]

Wiring.

My LEAST favourite part of any build.

Well, I got the tail light and indicators all hooked up, then sorted out 90% of the "plug and play" stuff under the left side cover.

But - this "multi model" harness has a few leads left that I have not been able to connect yet.



From left to right - red, black, pale grey and green coming off the harness - red and red/white line coming off the short battery to solenoid lead, and heavy duty green coming off the harness. I am guessing heavy duty green needs to go to earth on the frame () the rest I do not know.



From left to right - green with yellow line, black, blue and yellow. All from the harness. Now I am guessing two of these might just go to the (LED) two wire indicator relay?

All advice appreciated - with any luck I may see one of these new harnesses in another bike tomorrow and take some photos, that will be a big help.

(And I haven't even got to the 1,000 connectors in the headlamp yet!)

[Terry in Australia]

Yeah, we'll drag Mike's bike out tomorrow Cliff, I haven't finished all the wiring on his bike yet, but most of the major wires are connected, (the charging system works, woohoo!) so it'll give you an indication of where everything goes. Cheers, Terry.

[maduncle]

Yeah, we'll drag Mike's bike out tomorrow Cliff, I haven't finished all the wiring on his bike yet, but most of the major wires are connected, (the charging system works, woohoo!) so it'll give you an indication of where everything goes. Cheers, Terry.

...was hoping you would say that.

Cheers Terry.

[maduncle]

Green/Yellow is your BRAKE circuit. Probably from the front switch heading to the tail light assembly. The Blue and Yellow ought to be your points to coil leads. The Black is your switched 12v voltage from the key.

In the top picture, the Grey is for the Winker Relay, heavy Green is indeed Earth/Chassis. The slim Green and Black might indeed head to your Winker relay, hard to know from the limited pictures.

Oh yeah - green/yellow and black need to go to the rear brake switch - forgot about that one! Not sure what the blue and the yellow are doing there in the same loom, as blue and yellow seems to only be used from points to coil.

Maybe grey and black for the turn signal relay, I think the green might be for a later model 3 pin relay but I have a 2 pin LED relay as I think the K2's ran 2 pin relays.

That thick red lead with the bullet connector on the end ... ?   Power from the battery to solenoid lead?

[maduncle]

And I learnt this tonight too.

To bypass the "starter motor safety switch" red terminal block, jump the solid green wire to the dark green/red wire.

That's a good nights learning done.

[maduncle]

To bypass the "starter motor safety switch" red terminal block, jump the solid green wire to the dark green/red wire.

That Dark Grn/Red is your Neutral switch wire, is it not? If you do this, do you still have instrument light for NEU?

According to a thread on this forum, yes.

[maduncle]

Cool.

Had a look at one of the bikes in Terry's TARDIS and now I know where all my wires go.

And I had a look at my PAMCO ignition - it has two sets of three wires coming from it, lucky I found the online wiring instructions for it.

Might find some time to get in the workshop after work during the week and finish off that part of the wiring.

[maduncle]

Got the CB400F throttle cables from 4into1 today and fitted them right away.

Wow - what a difference to the throttle movement - so much easier.

These shorter cables really work well on clip ons fitted to a CB750, lesson learned.

[Retro Rocket]

Hmmm, I'm wondering how long you'll last with clipons on a 750...

[maduncle]

Hmmm, I'm wondering how long you'll last with clipons on a 750...

Forever I hope.

I figure if I don't like it then I will just have to build myself another CB750...

... wouldn't mind a chopper - anyone in Aus got a Santee frame kicking about?

[Terry in Australia]

Don't hold your breath Cliff, they were pretty rare in Oz, and you could buy a really good chop frame from Sonic Choppers in Elizabeth Street back then.

Probably half of the hard tail frames that occasionally appear on eBay are actually Sonic frames. There's a hard tailed CB750k4(?) frame on eBay at the moment for 400 bucks.

[Noddy78]

Hi Cliff, bike looks great mate! A couple of questions:

• What did you use to paint your fork lowers?

• What brand/make are the pipes?

Cheers,
Andrew

[maduncle]

Don't hold your breath Cliff, they were pretty rare in Oz, and you could buy a really good chop frame from Sonic Choppers in Elizabeth Street back then.

Probably half of the hard tail frames that occasionally appear on eBay are actually Sonic frames. There's a hard tailed CB750k4(?) frame on eBay at the moment for 400 bucks.

There is???

(Off hunting now ...)

[maduncle]

Hi Cliff, bike looks great mate! A couple of questions:

• What did you use to paint your fork lowers?

• What brand/make are the pipes?

Cheers,
Andrew

Hey Noddy - coming down for two weeks in November, be great to see your projects in the flesh.

I used rattle can flat black on the fork lowers, under a good coat of etch primer. Same on the frame, wheels, etc.

The pipes came from the Mill Park TARDIS supply depot - along with 99% of the bike.

[Noddy78]

Hi mate,

Sounds great, I imagine we'll be knee-deep in renos by then though! Isabel has gone into storage at a mates place (but is still accessible) and Douglas will be is disparate pieces all over the shop by then I reckon, but by all means, let me know when you're planning on heading down and it'd be great to meet up.

Cheers,
Andrew

[maduncle]

Cool Noddy - I will.

Meanwhile, my sump plug arrived today from the UK so now I can make my engine oil tight.

Time to go spend money on oil, I am thinking Penrite 10/40 for the first 100km before oil change.

[Terry in Australia]

Don't waste your money on good oil for breakin Cliff, Supercheap sell a cheap oil ( can't remember the name, but it's in a blue container) for around 14 bucks for 4 litres, it's actually pretty good oil, so run it for a couple of hundred Km and then switch to Penrite. I use their HPR GAS in the FJR1300, as did the previous owner, and it's done 231000Km (over 140,000 miles) and the engine's never been apart. Cheers, Terry.

[maduncle]

Good news - no oil leaks in the static engine! Which bodes well for no leaks when it is up and running.

Meanwhile - I spent a couple of hours sitting in front of the front end of the bike, playing "what happens if you join these two wires together?"

What I learnt:

- aftermarket speedos with built in idiot lights have wiring that actually makes sense  once you realise every coloured wire with a black trace is the earth for the matching coloured wire with no black trace.

- photocopiers distort colours on wiring diagrams. There is no "orange with white trace" in the front end, it is actually brown with white trace".

Closer to completing the wiring now - tell me please:

- do I really plug the wires for the indicator light into the pale blue and brown for left and right indicators?

- do repro wiring harnesses have a whole mess of unused connectors in the headlamp bowl all with white collars on them?

[Terry in Australia]

Don't worry about the unused connectors Cliff, I haven't seen a CB750 yet, with a wiring harness where all the connectors were, er, connected. I'm not sure what you're asking in your first question, but the blinker wires are pale blue and orange, so if you have a light for them on your dash, the wires from the harness to the indicator light will be (drum roll........) pale blue, and orange. Cheers, Terry.

[maduncle]

Don't worry about the unused connectors Cliff, I haven't seen a CB750 yet, with a wiring harness where all the connectors were, er, connected. I'm not sure what you're asking in your first question, but the blinker wires are pale blue and orange, so if you have a light for them on your dash, the wires from the harness to the indicator light will be (drum roll........) pale blue, and orange. Cheers, Terry.

Got that bit Terry - but if I have one pale blue wire and one orange wire for the blinker light, do I connect the pale blue and orange to the same terminals the corresponding blinkers are on?

Just does not make sense to me, as that would seem to be connecting a signal light up to two positive power feeds and no earth.