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Author Topic: AUXILIADORA 1981 HONDA CB750K BUILD  (Read 5245 times)

Offline PRIMEWORKS

  • Posts: 28
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #40 on: May 06, 2018, 00:23:41 »
Wiring questions for the wiring gurus

So I've come to the point in my wiring where I need some help. Wiring the motogadget was easy enough however incorporating the original components of the wiring harness are leaving my stumped. I'm going to point out everything as best I can and hope that someone can help me out cause at this point I only have the wiring and the tuning to go before this beauty can start!!

1. Regulator/Rectifier

So to break everything down and make it nice and simple the Reg/Rec has essentially 2 parts to it.

PART 1: A set of yellow and black cables (larger connector of the two) that connects to the stock alternator wiring. Easy given that its a direct connection)

PART 2: 1 Green wire, 1 Red wire, and 1 black wire (wires that are originally in the smaller connector.

             Red wire: Goes to my Starter Relay located on my Starter Solenoid ? Not sure how that would connect but that's what I've read on another
                            post

             Green wire: The ground (simple enough)

             Black wire: I need to splice the black wire in to the wire coming from the ignition switch(key), and going into the m-unit ? reason being is
                              that it needs to be connected to a wire that when the key is off reads 0 V to ground, and when the key is on the same wire reads
                              12 V to ground ?

2. Pulse Generator cable, spark units and the ignition coils

For the most part I've just been looking at this wiring diagram as it seems to be decently accurate, colours and all or at least I hope it is



Given I do what i mentioned with respect to the Reg/Rec and follow the wiring diagram I've attached for the Pulse Generator cable, spark units and the ignition coils would that work?? Any opinions would be appreciated!

Also, is there any recommendations for upgrading any components? I know a ton of people recommend upgrading the Reg/Rec given these bikes tend to have recharging issues but what about anything else?

Please remember to go easy on me in the case i ask very stupid questions hahah wiring just isn't my thing

Thanks everyone!

ps... GO JETS GO!!!!!!! WOOOOO





Offline 88SS

  • Posts: 94
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #41 on: May 06, 2018, 08:21:41 »
The three most annoying things on the DOHC is the charging system, the carbs, and the ignition system. Upgrade these three.

Since youíre going with no airbox, I would start with the carbs. Thereís a relay mod for the ignition coils. It basically bypasses the ignition switch. That paired with better coils will get you by for a while.


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Offline PRIMEWORKS

  • Posts: 28
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #42 on: May 26, 2018, 15:23:53 »
Update time!

So since last posting I've gotten the wiring done for the most part. I've tested to make sure that I've done it correctly by testing to make sure the starter turns over and I have a spark and so far so good. The only wire that needs to be connected at this point is the wire for the start button. However, I think I'm going to have to check my connections in my controls for a bad ground as when I touch the start wire from the m button to a wire from a button on my controls the start feature just automatically functions (tries to turn the starter). Hoping I can take a look at that today. Otherwise, all the wiring is loomed up! Ill have a picture once I feel like everything is properly tucked.

Aside from the wiring, I've run the clutch cable and the throttle cables through the frame in preparation for the carbs. As of right now I'm waiting on getting my order of new jets and a fuel filter from fortnine. Went with 98's and 125's for the jets since I'll be running pods and have the 4-1 exhaust.

The last thing to do is get a seat made and the bike will be done for the most part (for now atleast)


Offline PRIMEWORKS

  • Posts: 28
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #43 on: Jun 15, 2018, 13:19:39 »
Update time!

In the process of waiting for the jets I decided to paint the tank and cowl... The cowl is currently still being worked on to get the correct symmetry and curvature because I'm a bit OCD, but as of right now this is where they are at...

Tank & Cowl



As you can see there is a lot of pitting and unevenness with respect to body lines in the cowl



These pictures aren't the best pictures but after a ton of body filler, sanding, more body filler, more sanding, primer, sanding, body filler, and more sanding, etc this is currently how the cowl looks. It still requires a ton of sand, body filler, and primer (as you could have probably guessed) but there is not longer any pitting and I've managed to get the body lines to match pretty well with regards to height and spacing after a ton of measuring and rechecking. Once I'm happy with the shape and symmetry I'll be painting the cowl to match the tank colour.


Tank after paint stripper is applied to get old clear coat off. After this process was done I sanded with multiple grades of sand paper and polished as best I could.



Tank after being polished



End result. I painted the taking using a satin black paint with a satin clear. I was hoping it would come out a little less glossy so I'm still currently undecided on the colour but given my frame is a glossy black it might work. Only time will tell at this point how I feel about it. (The lettering is edited, I just wanted to see how it would look.)


I also installed one of the side plates which covers the electronics



It might be hard to see but the bend in the cover matches the rear frame (I'll get better pictures in the future)



Aside from the tank and cowl I also got my new jets in. Installed them and set the fuel mixture screws to 2.5 turns as per a post recommendation I saw on another forum. I also ended up polishing the tops and bottoms of the carbs


quick before and after

And so this is the point we have all been waiting for. The point at which I install the carbs, put some new oil in, add some gas, and turn this thing on and so that's exactly what I did and believe it or not surprise surprise..... i was met with more work :D (bet you thought I was going to say it ran like a dream and i set off into the sunset)

Problem #1

I turn the key, the motogadget m unit turns on, I test my lights to make sure everything works, and it does. I put the bike into neutral, pull in the clutch, hit the start button..... and nothing. I scratch my head and find that when I press and hold the start button I am getting a spark as you can hear it. However, the starter isn't turning over. At this point 4 things come to mind:

1. The starter needs to be replaced (doubted that was the case because the starter was working perfectly fine before the rebuild, confirmed starter is ok later in this post)

2. The starter solenoid is bad and needs to be replaced (This could be the case however I replaced the old starter solenoid before the rebuild when i was getting the bike a safety and it was working perfectly fine... however it's possible it has gone bad as it was just a replacement off amazon, does anyone know of a way to test these starter solenoids?)

3. The wiring was done wrong (This is one of the more likely cases given i'm new to wiring, however as far as I can see everything is done correctly with the starter.... The starter is in place (there isn't a specific ground wire for the starter as far as I'm aware, it just grounds via its position), the main wire from the starter is connected to the starter solenoid, so the solenoid has the main starter cable and on the other side a cable going to the positive battery terminal. I also have the the red wire from the Reg/Rec connected to the solenoid post that holds the battery cable, and I also have a wire from the start input of the motogadget m unit connected to the post on the solenoid that has the main cable from the starter.. maybe this is my problem? Looking at the following diagram I also don't have a wire coming from the spark units to the starter solenoid which might also be a problem.. Can anyone make a comment on this?



4. The battery is just to weak (really just a guess)

The last problem I'm having is with my throttle push and pull cables. The throttle just doesn't snap back at all and sticks. Part of this could be due to the fact that I need to play with the cable adjustments but it could also be that I need new cables. I'm going to try and make some adjustments and if that doesn't help I'm going to order all to cables.

Even with all these problems however, a friend and myself did manage to get the bike started which was HUGE for me because the engine didn't blow up or make any bad noises  ;D ;D. We did so by jumping the starter (which showed me that the starter is fine). The bike didn't run for long as it didn't have a steady flow of gas going into it and it did rev quite high on it's own randomly but I think that's in part due to the fact that the engine was rebuilt, oil had to be circulated, the carbs need to be tuned/adjusted, and the throttle sticks slightly. But over all I'm happy and can see the light at the end of the tunnel finally.

Here is a video of the bike starting (please don't judge my face at the end panicing ;D the bike is loud as hell and I didn't expect it to rev as high as it did so it freaked me out)





Offline PRIMEWORKS

  • Posts: 28
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #44 on: Jun 16, 2018, 01:14:13 »
Alright so I figured out my starting issue. Turns out I didn't have the cables on the starter solenoid connected properly! so that's huge! Now it's just a matter of getting new cables and tuning the carbs!

Offline 88SS

  • Posts: 94
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #45 on: Jun 16, 2018, 22:56:58 »
Alright so I figured out my starting issue. Turns out I didn't have the cables on the starter solenoid connected properly! so that's huge! Now it's just a matter of getting new cables and tuning the carbs!

I was going to say: doesnít the m unit eliminate the starter solenoid?

Iím probably wrong, and donít have any experience with the m-unit, but I thought that was one of the features

These carbs are a super PITA. Iím following and wishing you all the luck.


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Offline LiamG6

  • Posts: 17
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #46 on: Jun 17, 2018, 01:53:17 »
It only replaces the starter solenoid if the starter motor draws low amperage, less than 30a I think, which these bikes do not, starter solenoid is required.

Offline 88SS

  • Posts: 94
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #47 on: Jun 17, 2018, 12:29:22 »
It only replaces the starter solenoid if the starter motor draws low amperage, less than 30a I think, which these bikes do not, starter solenoid is required.

Wow. Good to know. How many amps do they draw? I personally am not a fan of the solenoid. Main reason being I canít find a decent mounting point. Curious what your doing with yours


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Offline PRIMEWORKS

  • Posts: 28
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #48 on: Jun 17, 2018, 13:00:59 »
It only replaces the starter solenoid if the starter motor draws low amperage, less than 30a I think, which these bikes do not, starter solenoid is required.

^^ Exactly what he said lol. I'm not 100% sure about the amperage but I'd imagine it's a lot bigger then 30.

Wow. Good to know. How many amps do they draw? I personally am not a fan of the solenoid. Main reason being I canít find a decent mounting point. Curious what your doing with yours


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As of right now it's kind of just in my wiring hanging in a random spot lol. If you've noticed I haven't posted a single picture of my wiring because as of right now it's not very neat in my electronics box. Once the bike is up and running properly I'll likely make the wiring a lot neater but for right now my main goal was to just get it to work lol. I'll potentially also make a wiring diagram for the bike but for the most part it would be very similar to the one I've already posted.

Offline 88SS

  • Posts: 94
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #49 on: Jun 17, 2018, 13:05:34 »
^^ Exactly what he said lol. I'm not 100% sure about the amperage but I'd imagine it's a lot bigger then 30.

As of right now it's kind of just in my wiring hanging in a random spot lol. If you've noticed I haven't posted a single picture of my wiring because as of right now it's not very neat in my electronics box. Once the bike is up and running properly I'll likely make the wiring a lot neater but for right now my main goal was to just get it to work lol. I'll potentially also make a wiring diagram for the bike but for the most part it would be very similar to the one I've already posted.

Donít feel bad. Mine is also a dangler LMAO.


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