Topic: Keep telling yourself - a restored 750 K2 is an investment

[CrisPDuk]

Aren't bench grinders great?

Not a great deal of activity to report over the past few days - real life (and work) kinda got in the way.  Still, one or two more jobs have been completed in readiness for the big push over the weekend.

First up, the swingarm has new bushes fitted (glad I got someone else to do that) and the steering stem has been fitted with tapered roller bearings.  Other small stuff like replacing a busted reflector happened when yet another envelope from Silver's arrived.  Just in time, too.

Next, some general 'tidying' of bits and pieces.  Like these exhaust flanges(?) . . .



The one on the left is how all four started out.  After some work on the wire wheel, they cleaned up quite nicely.

And then the shocks.  I gotta say, I don't think they're savageable - they looked scruffy as hell and I've kinda budgeted for new ones.  But since I can't start putting bits back onto the frame just yet (at least, not 'till the engine's in), I thought I'd see what I could do with 'em.



Again, the one on the left is how they started out.  I've taken the paint off the strut on the left, and as we speak I'm waiting for new paint to dry.  I've also had a go at polishing the brightwork with some success - and fortunately the springs are in very good shape.  Anyways, I'm not holding out a great deal of hope, but we'll see what they're like when they've cured overnight.  The paint's heatproof, so I might stick 'em in the oven for a bit.

Thanks for the suggestions about the engine cases.  I'll clean up the mating faces (if that's the right expression) with wet and dry before reassembly.  Hush - I'm hoping it'll be a reasonably high quality resto, but I'm certainly not gonna chop or cafe.  This one's safe buddy.

It's gonna be a l-o-n-g weekend.

Neil

i scanned the thread so forgive me if I am wrong or if this has been addressed already.....

If those are stock shocks, then the plastic sleeve should go between the body and spring, not the shaft and spring.
also, that thing looks great! nice job

Those are Hagon shocks, in near enough the same condition as mine were in. The plastic sleeve is intended to protect the damper shaft from damage, I left mine out because my shocks have the hard chromed shafts and i dont intond using the bike on the salty winter roads

The bodies are easily brought back to 'as new' with a can of black Hammerite, the aluminium spring seats polish up really well, and new springs are readily available from Hagon in black or chrome, to any rating you like for £32 +vat 

[CrisPDuk]

PS The bike's looking great Chauffeur 

What paint did you use on the engine casings?

[kghost]

Shame I just sold a set of crash bars on Ebay.....

If you need a center stand I will send you one.

[HondaMan]

Frame number: I thought so: midrange K2. The last of the K2 no longer had the cast-aluminum gauge mount in between the instruments, like yours. These were K0/K1 parts that Honda used until the stamped-steel parts replaced them (cheaper). Your engine is all K2, and may have the 1-row final drive bearing (good for almost 1 HP!), the spark advancer with smaller diameter springs, the taller (and unsealed) intake valve guides, 657B carbs with 100 mainjets and 18T/48T gearing, original chrome headlight ears. You might just find that a 17T front sprocket does a lot for the in-town ride! 

[burmashave]

Hey Chauffeur, the bike is transmorgifying right before our eyes, and quite nicely, too. Reading this thread makes me feel really slow at how quickly I get jobs done on my bike.

[the-chauffeur]

What ho, chaps.

First things first.  The engine case paint is a combination of PJ1 and A.N.Other brand whose name I can't now recall.  Stick with PJ1 if you can - it's good stuff.  I only changed 'cos I ran out on the second coat.  That said, I made sure everything got a dusting with the second brand to keep the shades consistent.

Thanks for the pointers on the shocks.  I've no idea how/if they work, or how much longer they'll last, but they look OK right now - at least, from a distance and with a squint.  I'll almost certainly send some business Hagon's way once I've recovered from the rest of the bills.

HM - thanks for the information.  That'll prove invaluable; if not now, some time in the future.  I've had a couple of other bikes that Honda changed bits for halfway through the production run and it's infuriating when the bits you order don't match the holes the old bits came out of.  It also explains why David Silvers stock 2 different front mudguards for the K2 - an 'early model' one and a later.

My turn for questions now - and to kick off, we're back to the ill-fitting side panel.  And here it is (with apologies for the image quality - garage space is at a premium right now) . . .



So how does that work?  The upper lugs are located, but as you can see, the lower one is some way short.  At the same time, the curved cut-out that should fit around the airbox comes into contact with the box plastics (that may be right - remember, the panels that came with the bike were just outright wierd and I've got no idea what Honda's fit 'n' finish standards were like in '72).  I s'pose the obvious question is what are my options?  I really don't want to bin the panel, so it looks like a bodge of some sort is in order.  My initial thoughts are to take one of the old panels I've got, cut one of the lugs off, form some sort of short extension in black plastic and weld (read melt with a soldering iron) the extension to the rear of the panel and the lug onto the extension.  So long as it looks OK externally, I'm not too bothered about the internals.  But it's a headache I could do without.

Secondly, where do these live?



10mm nuts with green wires attached.  The fiche seems to suggest that they go inside the headlight attaching to the L&R indicator stems.  This seems to make perfect sense 'cos the indicators themselves only have one wire exiting from the bodies.  But if that's the case, why can't I find similar bits for the rear indicators?  Or do the rears use the frame as earth (and so only need one wire each)?

Burma - thanks for your comments.  It's only now that I'm finding some bits need to be changed/swapped/reversed and so on.  It'll take a while yet to get it going, but I'll keep at it.

 

[andy750]

10mm nuts with green wires attached.  The fiche seems to suggest that they go inside the headlight attaching to the L&R indicator stems.  This seems to make perfect sense 'cos the indicators themselves only have one wire exiting from the bodies.  But if that's the case, why can't I find similar bits for the rear indicators?  Or do the rears use the frame as earth (and so only need one wire each)?
 

Correct - they fit inside the headlight shell and attach (from the inside) the K2 indicator stems.  There is a green multi-connector in the headlight shell for them to hook into.

Side-panel - hard to tell from the photo (need to see whole side panel  ) - but it should look like this....



or as seen on this K2...



cheers
Andy

[the-chauffeur]

Thanks Andy

My panel is the same as the one in the lower of your two photos - the badges are the giveaway.  Had another look at mine last night and it looks as though a small piece has snapped off the bottom and then been painted over without having been repaired or built up again.  Hmmm - I'll have to find some flat black rigid-but-flexible plastic and see if I can make a small extension to mount the lug on.

In the meantime, anyone got any cable and hose routing diagrams?  I'm trying to figure out where the breather hoses from the rocker cover and crankcase should go.  I'm guessing it's to the rear of the oil tank, but I can't find any pictures.

Neil

[andy750]

No worries. DSS has replacement covers - just need to be painted and they are stronger than the original (I have one). The breather hose clips to the top tube of the frame and goes over the airbox and down the side of the oil tank (to come out next to the brake pedal) or you could have it coming out on the other side - same difference. Still has to go over the airbox.

cheers
Andy

[the-chauffeur]

Cool.

I'm still struggling to understand what the breather tubes on the back of the oil tank are for.

And now to fit the retaining spring for the rear brake pedal that I forgot to fit first time (yes, yes . . . I know, I know . . .)

[andy750]

The K2 only one at the bottom of the oil tank  and this one hooks up to the lower half of the engine - you will see a nipple just under the tab where the overflow tubes from the carbs are supposed to go....the top one is the overflow tube - comes out the top and runs down to the brake pedal side (so the cam cover tube goes to the other side!)

see diagram here....

http://www.cmsnl.com/honda-cb750k2-four-usa_model14362/partslist/F15.html


cheers
Andy
 

[HondaMan]

10mm nuts with green wires attached.  The fiche seems to suggest that they go inside the headlight attaching to the L&R indicator stems.  This seems to make perfect sense 'cos the indicators themselves only have one wire exiting from the bodies.  But if that's the case, why can't I find similar bits for the rear indicators?  Or do the rears use the frame as earth (and so only need one wire each)?
 

Hmm...both of my K2s have simple bolts holding those 10mm nuts on the headlight assembly together, and the turn signals go into theeir holes a little further back on the (chrome) headlight mounting ears, much like the the K1, but in chrome.

Do your headlight ears only have 1 hole in them? 

[754]

On K2 chrome light ears there is only 1 hole, the cleanest looking set they made.IMO..

I was sure those shocks were KONI, but you can read the name on the rings.. HoweverI suspect they are the same, and can be adjusted internally for damping siffness.. more on that when you get it running.

Here is what I think happened to the sidecover... the welding stress pulled up the lower edge and shortened it.. but it probably went in but hard.. and eventually broke..

[the-chauffeur]

Yup K2 ears, everyone.  One hole only.

Bloody electrics are driving me up the wall.  Sadly, it's no one thing - I'm plagued by a cobination of gremlins.  COnsidering just how simple the electrics are, it shouldn't be this hard (he says) . . .

First off, crass stupidity on my part.  Can't really call it anything else.  After looking round for instructions (obviously in all the wrong places), I was struggling to work out why I wasn't getting any sparks generated by the aftermarket starter unit (Newtronic).  For anyone who's not seen one of these things before, there are three captive wires (into a connector block) and one other with a ring connector on the end - suggesting one of two things.  Yup - it's either earth or live.  And guess how I found out it wasn't live?



I'm sure you don't need me to point out the ahem, repair to the broken connecting strip.  I'm praying that the broken connector was the only damage.  I certainly can't see anything obvious burned out elsewhere on the board, and it looks as though the connector is the earliest point on the board the current would've come into contact with.  Here's the topside:



Any words of consolation/commiseration/comfort?

Next up, the switchgear - the right hand side to be specific.  When I pulled it apart, I had to re-solder a couple of connections.  After much scratching of head and handfulls of blown fuses, it occured to me that some of those connections weren't sufficiently insulated and were grounding out.  At the same time, the headlight was playing up - there was clearly a dodgy connection in there somewhere.  So I opened them up and cleaned up the previous work.  Refitted all the bits (only to find that a previous owner had used different coloured wires) and finally got the lighting circuit to work - in a manner of speaking.  Turns out that the front bulb needs replacing, too.  Moving swiftly on, I still can't work out the indicator circuits.  That's a whole other story which I can't be bothered to repeat right now.

In the meantime, I started work on the side panel.  Yes, it would be easier to buy an OEM one - although I have no idea what colour the panels are, so matching might be a problem - but I thought I'd have a go at fixing it anyway.  Nothing to lose, huh?  Found a small triangle of black plastic, which I welded (soldered) onto the back of the panel.  Attached a fixing lug to the back in the same way.  I then overlayed some fibreglass mat and resin and left it to dry, before applying some filler to the front.  It's nowhere near finished, but here's about as far as I've gotten so far.

From the inside



Side on



Front view



And yes, I made sure it fits without ripping the new lug out.  I reckon I'll get it flattened off and then paint the filled section black.  Trying to colour match right now would just be too much work that I really don't need, and black against a black frame will look more or less invisible.  Perhaps when I've recovered from the rebuild bills I'll consider a new one.

Finally, the tricky subject of crash protection.  I'm really keen on having crash bars on the sides of this bike before it rolls out of the garage for its first trip.  Not that I'm wanting to tempt fate, but my Hayabusa fell over on me the other day at less than half a mile an hour.  Fortunately, the R&G mushrooms saved the fairings and I (well, the bike) got away with the tiniest amount of grazing - and not a mark on the exhaust.  I've also had the ST1100 do the same thing - slower than walking pace tilt, but because it's soooo well designed, you can hardly tell once the tip-over cover is replaced (all of about $20).  Stupid, I know, but over the years it happens. 

What worries me about the CB750 is the pipes.  I'm terrified of the consequences of even the slowest speed tumble and the damage it'll do to the pipes.  Knowing how much they cost to replace, I'd rather look for other options.  I've got my eye on some NOS engine bars right now, so the front should be OK.  But has anyone had any adverse experience of tip-overs and what did they do to the exhausts?  And what (if anything) have you guys done to try and mitigate the possible effects?  I'm seriously considering replacing the rear footpegs with mushrooms for everyday riding and swapping them back for shows (assuming I go to any on it).  Using a piece of wood I've rudimentally calculated that if the bike goes over, mushrooms instead of the pegs and the engine bars would provide enough clearance for the pipes without putting too much stress on the chassis.  But any advice would be very welcome.

And to cap it all, I'm labouring under a heavy cold.  Knickers.

[HondaMan]

About the pipes: if you have the rear footpegs in place, they take the blows in the back, don't ask me how I know that....and the alternator case or the points cover takes the blow in the front. We won't talk about that either...

Is that Newtronics unit like an electronic ignition for the points, or does it have a pickup trigger device? Or, is it supposed to replace something else? If it was connected wrong electrically, it's probably toasted. Looks like the components could be replaced, though. Usually the IC is first to go with reverse polarity, next would most likely be the 3-leg "F"-pack device, as a regulator. It appears that the two smaller transistors TR1 and TR1A switch the larger TO3 devices, which makes me think this looks like a transistorized sparker. The other components would then be biasing devices for the smaller transistors. The biggest issue with using 4093 ICs on a device like this is: if it was oddly connected, but managed to survive today, it will fail in the near future. That's just my 40 year's experience with electronics speaking, though... 

[the-chauffeur]

Thanks for the notes on the falling over thing.  The ignition system I've got seems to replace the points completely - insofar as there are very few (if any) of the points parts remaining. 

You may very well be right about having cremated the board.  I'm just wondering if there's any way I can test it, rather than sticking my hand straight into my pocket for a new one.  And knowing that the company that made the unit liquidated and is now under different ownership, I don't hold out too much hope of finding another.

Today was a mixed bag.  I've finally gotten all of the lights to work.  Yup, all of 'em.  And the starter turns the engine over.  Hooray.  But in doing so I've managed to bugger up one of the throttle cables and get generally more and more frustrated.

Stopping now before I break something else.

[the-chauffeur]

HM

Can you tell me what I need to test for with a multimeter on the board?  I've been having a ferret around and checking continuity and can get readings from accross just about everything.  Whether that's a good thing or not, I don't know.  Certainly all of the connections on the rear check out - even my bodge.  As do most of the resistors and smaller bits you mentioned.  The only anomolies I've found so far are - C1 has continuity; C2 doesn't.  And D4 seems non-responsive.  All of the others that connect to the broken track check out. 

Here's the instructions if they're of any use - http://www.newtronic.co.uk/new/support/newtro/AK-HO4FittingInstructions.pdf

Unfortunately, I've got two issues with this thing.  Firstly, the original kit contained a replacement points unit thing, so very little of the original points remain (so I've got no failsafe/fallback system).  More awkwardly, I've just found out that these things are now obsolete.  So if I can't get it going, I'm stuffed.

Thanks again

Neil

[HondaMan]

HM

Can you tell me what I need to test for with a multimeter on the board?  I've been having a ferret around and checking continuity and can get readings from accross just about everything.  Whether that's a good thing or not, I don't know.  Certainly all of the connections on the rear check out - even my bodge.  As do most of the resistors and smaller bits you mentioned.  The only anomolies I've found so far are - C1 has continuity; C2 doesn't.  And D4 seems non-responsive.  All of the others that connect to the broken track check out. 

Here's the instructions if they're of any use - http://www.newtronic.co.uk/new/support/newtro/AK-HO4FittingInstructions.pdf

Unfortunately, I've got two issues with this thing.  Firstly, the original kit contained a replacement points unit thing, so very little of the original points remain (so I've got no failsafe/fallback system).  More awkwardly, I've just found out that these things are now obsolete.  So if I can't get it going, I'm stuffed.

Thanks again

Neil

Now I understand why there is CMOS circuitry and a voltage regulator: it's for those optical triggers. They have to be voltage-limited, probably to about 2.2 volts or so. Hmm...

You should be able to repair the board: there's not that much there. Check the 3-legged power-transistor-looking device first: I think that's the regulator, and probably took the brunt of the reversed polarity. The heatsink tab should be the same as the center lead: check from here to the board's GROUND: look for shorts (also check across the outer 2 leads of this device: it should not be shorted). Try to use a VOM, or at least a digital meter with a diode-checker selection for this part. All diodes on the board can be checked for forward-conduct, reverse-is-much-higher-ohms type readings. A shorted diode will read almost identically in both directions. I think that IC on there looks to be a 4093 Schmidt Trigger: these cost about $0.50 USD to replace. Most CMOS chips are cheap: be sure to handle them away from places where static electricity can potentially hit them, or they will fail before you can install them!

The circuit probably looks like this: the collector of the phototransistor(s) gets it's voltage from the 3-legged voltage regulator circuit, through a resistor, and that wire goes to the points plate. On the PC board again, this circuit goes to one of those little (TR1-TR1A) transistors, which boosts the signal to drive the big TO-3 case units. Pretty simple, really.

[the-chauffeur]

Two forward, three back.

Had another look at the board and most of the components seem to test OK (he says, being a klutz when it comes to multimeters).  Replaced the C1 and C2 components, which seem to be the major culprits.

The three legged monster seems to check out, which, having followed the tracks, seems to make sense.  It doesn't connect directly to the track that popped, whereas both C1 and C2 do.  I'd've thought if one/both of them went, the current wouldn't've got as far as the transistor thingie.

A helpful component strore clerk confirmed that if I get continuity readings from TR1 and TR2, they're probably OK - which I can.  They either work, or they don't - right?  He also checked some of the resistors and reported that they were OK too.

I guess I'll try to fire it up again . . . nope . . .that doesn't work either.  Damn it.

Question:  When the kill switch is in the OFF position on the CB750, what happens when you press the starter button?  On my ST1100, the starter motor turns over but the engine won't fire (I'm assuming no spark).  On my Suzuki, nothing happens - the electrics come on, but the not even the starter turns.

On the CB as it stands, it does the same thing as the Pan.  But I'm now beginning to wonder if that's right.  It's not likely to be that, is it?

[the-chauffeur]

Seems like I might have caught myself a break . . .

 . . . I e-mailed the new owners of the outfit that produced the ignition unit to ask if they did repairs.  The answer was basically no, but it turns out they've got a couple of the old units kicking around.  I've gone back to them to ask how to order (would've been helpful if they'd included that information, but hey . . .) and keeping everything crossed, I should be able to get my hands on one v-e-r-y soon.  It may not be the most cost effective solution, but it'll certainly save me a lot of sodding around.

Here's hoping.

[HondaMan]

Two forward, three back.

Had another look at the board and most of the components seem to test OK (he says, being a klutz when it comes to multimeters).  Replaced the C1 and C2 components, which seem to be the major culprits.

The three legged monster seems to check out, which, having followed the tracks, seems to make sense.  It doesn't connect directly to the track that popped, whereas both C1 and C2 do.  I'd've thought if one/both of them went, the current wouldn't've got as far as the transistor thingie.

A helpful component strore clerk confirmed that if I get continuity readings from TR1 and TR2, they're probably OK - which I can.  They either work, or they don't - right?  He also checked some of the resistors and reported that they were OK too.

I guess I'll try to fire it up again . . . nope . . .that doesn't work either.  Damn it.

Question:  When the kill switch is in the OFF position on the CB750, what happens when you press the starter button?  On my ST1100, the starter motor turns over but the engine won't fire (I'm assuming no spark).  On my Suzuki, nothing happens - the electrics come on, but the not even the starter turns.

On the CB as it stands, it does the same thing as the Pan.  But I'm now beginning to wonder if that's right.  It's not likely to be that, is it?

Make sure the KILL switch is in the middle ON position. The starter will still spin over, just no sparks, if at OFF. In this case, ON refers to the engine run position, which later Honda renamed to RUN.

When this is all over, if you'd like, I could take a look at the burned-up Newtronics unit for you. You'd have to pay for the parts and shipping, but then you'd have a spare, if it's worth the $$ overall.

[the-chauffeur]

Thanks HM.

Looks like my excitement over the replacement board was premature.  Actually, no, that's not strictly true - I think I was lied to.  After being told last week that the place that makes them had spares in stock, I rang back this week to ask what was taking so long with my order - only to be told that they had sold the remaining bits last week (?!?) and that it would probably be another four weeks or so before they had any new ones.  To say that I'm not happy is something of an understatement.

So I've ordered a points kit from Honda and will have a go at putting the bike back to standard.  Frankly, I can't wait another four weeks to get this road on the show, and would guess that the new points will be reliable for a good few thousand miles.  In the meantime, I've replaced the carb gaskets and throttle cables - and found myself a centre stand - so it really should be ready to run when I get the points.  He says.

Ho with a capital hum.

[HondaMan]

Well, if you put in those points, you can always add one of my ignitions! (Plug...) 
If you decide to spend the $$ to ship that gizmo over here for a crack at a repair, let me know. I may be slow, since I've got lots of things going before the Colorado winter sets in, but that one would be a good wintertime project.

My K2 is still one of the best transportation/fun/economy moves I ever made. It's outlasted 20+ cars!

[the-chauffeur]

That's a bit obtuse for me . . . tell me more about your points (or stick a link in - please).

Very interested . . .

[HondaMan]

That's a bit obtuse for me . . . tell me more about your points (or stick a link in - please).

Very interested . . .

I went looking, but I guess it expired. Sometimes I put a post in the "For Sale" section with the ignitions in it. That section expires, I think, after about 6 months or so, and the pictures go away.
So, here's a picture or two. You can ask others here about their performance: I've never had to 'sell' them, as they do exactly what these bikes have always needed. The basics are: you install the points, per normal operation, then install this box. The box uses the points as switches, letting transistors inside do all the hard work of running the coils. It also tunes the coils a bit, to improve the idle and bolster the hi-RPM spark, so it runs better thru the whole RPM range (and then some, all are tested to over 10,000 RPM). I call them the Transistorized Ignition: others call it the Hondaman Ignition.