All that glitters aint gold mate , some bits I am not so happy with but cannot find a replacement . Should have it all together this weekend , but struggling with the wiring at the moment . Just going over each wire and its connections and tracing them on the loom to see see why I`m only getting the magic smoke
Paintwork and the engine have been done , now the build begins
- Thread starter hinksy
- Start date
So close now , just have to figure out the technodigicals . Am I right in guessing the US starter cuts out the headlight when you press it ? I am converting it to aussie spec with headlight/park lights and we only have a two wire starter . This has a three and by the wiring diagram Black red stripe is headlight power and that is not in the starter in aussie spec , so should I join it into that circuit ? Makes sense to me , but hey I`m not that great with the technodigicals . Also may have to redo the front master as when I bled it , it doesnt seem to return and sort of sticks halfway , then very slowly returns to its position . I rebuilt them nearly two years ago and I think I am paying the price for just leaving them on the shelf . They had good spring pressure when I did them , so a new rebuild kit may help
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Chose to disconnect the headlight circuit from the starter and after blowing the main fuse 3 times I found out the starter relay was stuck and it became unstuck as I went through the harness testing each main power circuit . Musnt have liked sitting for 30 yrs ha ha . Still cant get the flashers working right but may have narrowed it down to the relay ( again ! ) At the moment all I get is the rear flashers , flashing like hazard lights . The bike is fitted with a 2 pin but I am being told it needs a 3 pin unit and as it has a 3 wire plug I would agree . And the buzzer is not connected , so I might join that circuit and see how it floats . On another note , I still havent been able to get the front brakes to work . It is sort of bleeding but the lever does not fully return and seems to stick halway out . So I will be stripping it again and see whats going on . Fully stripped , cleaned and rebuilt it 2 years ago but they had just sat on the shelf till now , so somethings not right . At least I can see the light at the end of the tunnel and it wont be too long till I get her on the road and I go for a ride
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Dime
CB750 Member
Awesome build!
Stripped the front master today and all I could find was the piston is somehow jamming . Cylinder bore is clean and clear with no scoring . Seals and rubbers all fitted properly and the two ports were clean and clear , bit of a head scratcher that one . Also think the sliding caliper bolts are way too tight and maybe are stopping the caliper from moving properly . But found it , the piston seal/bore clearance was just too tight . So a bit of cleaning it up and polishing , it now seems to move freely . The seal that fits over the piston was just too tight . I was fitting it greased up and it would seem OK untill the grease wore off , then it would just grip the sides of the bore and jam . So used an emery cloth and hand machined a bit off of the piston shaft under were the seal sits , so the seal could compress more and didnt jam on the bore surface and all seems good now . But the grease hasnt worn off yet
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![IMG_20240930_160147[1].jpg](/data/attachments/15/15570-da27e1753556ac2283e9dfd4ce47413c.jpg)
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Had a breakthrough on the technodigicals . It seems if you follow these diagrams , you will be led astray as they show that everything has an earth connected to it . WRONG ! They ground to were they are mounted . I had been trying to get everything connected and earthed and use what wires came with the bike . It just wouldnt add up and I was connecting the wrong plugs up as nothing seemed to match . So when the penny dropped , I now have headlight on/off and park with the running light and have sorted out the flashers and everything turns on in the instruments and at the blinkers themselves . Have noticed that my clutch cable is way too long as I have low bars , so will have to source a shorter cable . But that isnt stopping much , so hopefully the front brakes bleed up properly and the master works as it should , then I`ll do a once over and check that everything is torqued and buttoned up , a bit of oil and a prime , some fuel and hopefully broom , broom by this weekend
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YEAH NAH ! Looks like the rubber of the seal has just hardened up so much after sitting dry for two years that it wont give . Once the grease wears off the piston just jams as the seal wont compress enough to allow it to move against the spring pressure . So new kit ordered and hopefully problem solved . Thats basically all I need to get it registered now , so then I can do some miles on it , run it in and enjoy my build
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booroobin
CB750 Member
Hey John here from Australia - the paint looks incredible! Great stuff. Question I notice you have the bike on its side - is this a good way to get the engine in and out of the frame without a hoist? Ive been looking on the web and along tome ago I pulled one out by hand...
booroobin
CB750 Member
Where in Oz are you from? I have a K3 motor that was flooded - just wondering to start again or pull it apart? Ar the bottom ends solid?
Also can you substitute K engines? wiring/mounts the same?
Yes it is john . I just put the motor onto a milk crate and lowered the frame over it , then stood it up . Very easy to do by yourself . I pulled my original F2 by myself in the 70`s and did it the hard way .
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booroobin
CB750 Member
Excellent. Do different K motors have the same mounts etc/ wiring - just in case the bottom end on this one is stuffed.
Im in townsville nth qld . When you say flooded do you mean water ? Have you flushed out the motor and reoiled it ? If not you might have some internal rust . You can take off the oil pan on the bottom of the motor and see the middle of the crank . Take off the clutch housing and even the alternator cover , so that would be a start . If it was good before and you had taken those precautions and it wasnt full of crap , it should be good . You can swap motors , the only real difference is 77 on has a different final drive and the sprockets are 630 not 530 . There are also internal differences , but they all use the same oil lines and mounts ish . I think the later ones have the removable side mount . Wiring changed from model to model but is basically the same overall . I just converted mine from US spec to aussie by changing the right side switch and rewiring that and the blinkers ( dropped the running lights ) and put in a front running light in the headlight with the aussie lens
booroobin
CB750 Member
I bought it from a fellow that just left it unfortunately - I will drop the sump and take a look - maybe its "new motor" time? Theres a rebuilt one in SA for 4500...bit expensive. I was thinking if the bottom end is fine I can put a big bore kit on it and go from there. I also have a santee frame chopper. Both have coffin tanks. Crazy stuff. What do pay for one that just turns over?
Do you know of this page on bookface ? Lots of guys on there that can help . It is Honda CB750 Four 69-78 Australia https://www.facebook.com/groups/cb750AU/
booroobin
CB750 Member
Who do you buy your gaskets/inlet manifold rubbers etc from please? Sorry to nag with all these questions
Puds four parts in yarram vic.
Fired her up this week , primed it with a few runs on the starter , didnt take to long to have the oil light cut out . No choke and broom fired almost right away and idled for a while . Revved quite smoothly but not as good as I was hoping for off idle . So now just need to fine tune the carbs ( I hope ) and I should be able to have a ride . While waiting for the new master cylinder kit I had another go at reducing the piston width to try and use the kit I have . And this time it worked . I now have front brakes and best of all no leaks . After pulling the piston this time you could see the dry area on the rubber of the seal that was jamming in the piston bore . It still was way too tight and was not able to move without friction and drying out , then seizing . You can see on the original piston , which I have highlighted < that there is a milled surface that the o-ring sits on . After comparing the original and the kit , I could see the kit`s seal was 1-2 mm bigger in diameter . So something people should be aware of when they do their brakes . And no , I am not going to use this untill I get the new one fitted and checked out
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Low and behold , I have finally figured out some of the technodigicals on this site . So here are two vids , one is when I picked up the motor and andrew test ran it in an engine stand . The second one is after I had primed the oil system and turned on the ignition and fuel for the first time . Broom broom , fired right up ! Have to tune it yet and the idle wasnt set high enough , but it does sound good with the delkevic
Brake master kit has arrived , so now I have to strip the bike again as I dont want to get any brake fluid on it . Not happy with the front brake hose routeing anyway , so I will look at redoing them . Funny how you order a part and you get sent something totally different . Another thing people should do when building their bikes and ordering parts , is check the fitment when you get them . No matter how long it will be before you are going to use it . None of the braided lines I recieved matched what came off of it . None of my std hoses had bends in any of the banjoes and this was even after I spoke with the supplier as he wanted to make sure he was sending the right ones . So two years later , I have to make do , they will fit , but I just have to configure it correctly and I think I need to reverse the top hose or flip the banjo on the junction so the top one sits better , but that looks like the hose will hit the tacho . Oh well , dont you love first world problems
