cb400 project 'hmm...'

J

joeybaggadonuts

comin in hot, hit em wit it
Hey there! here is my first ever motorcycle project, <del>nicknamed 'old blue'</del>, for completely non-obvious reasons....... anyway!, it is a 1978 honda cb400t, super clean in my opinion, and it doesn't run! picked it up for $250 and figured i couldnt go wrong. lets find out! the first big problem is the reason the last guy sold it, he didnt feel like fixing it, (he was a honda scooter kinda guy, and wasnt really into the old cb's) the new plugs get no sparks. i have a couple ideas in my head of where the problem is located, but most of you peoples knowledge and wisdom far surpass mine! i was first going to check wires, i already checked fuses, all good, and i next want to see if electricity is getting to and coming out of the ignition coil. another possible problem is the 'off run off' switch next to the throttle grip. the switch is gone and there is just wires taped together, and one wire just hanging out. i think whoever was playing with it taped the wires in the 'run' position, and thats why the battery was dead. new battery and plugs by the way. so, i'll upload some pics of the bike, i'll share some plans for what i want it to be, and i would love some criticism, ideas, and help from all you DTT builders! Thanks! ;D 8)

AZ6niJMCEAAAPzijpglarge.jpg


AZ6pPnACIAAws16jpglarge.jpg


bikee.jpg
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Re: cb400 project 'old blue'

gotta love the "custom" wiring fixes lol. ;D Looks like a good base. I like the color scheme. I think it would look good if you left that paint job on after you cafe it.
 
Re: cb400 project 'old blue'

I just went through the same problem of getting no spark. Two coils and a new cdi later, I'm in business.

If you got a place near by that will test coils, I'd do that first. You should also test the stator. It's really easy to do with a multimeter. If everything checks out; new cdi time. From what I've been told, these cdi units fried a lot. Search cdimagician on eBay. Good stuff.

Looks like a great a starting platform!

Also check out this thread.
http://www.dotheton.com/forum/index.php?topic=26184.0
 
Re: cb400 project 'old blue'

thanks yayuppp, same bike same problem? i'll look around to see if anywhere nearby can test coils, most likely there will be somewhere. tomorrow i will hopefully be testing whatever i can with multimeter. had to charge up the battery first. I'll definitely check out cdimagician
 
Re: cb400 project 'old blue'

jk333 said:
gotta love the "custom" wiring fixes lol. ;D Looks like a good base. I like the color scheme. I think it would look good if you left that paint job on after you cafe it.
Click to expand...

the wiring on this bike is wonderful.. :o I love the color and the tank is pretty clean so I plan on using it
 
Re: cb400 project 'old blue'

i believe on this bike the off/on/off switch only connects wires in the off position. all it does is closes a ground loop for the cdi the kill the ignition. i am pretty sure in the on stage though there is no connection of any wires. these old honda 400 twins don't require a battery to run as well. first thing i would do is unplug the black with white stripe wire plug coming out of the cdi box(that is the ground kill switch from both the key and the off/on/off switch) and kick that bad boy over!!! who knows you might get lucky.
 
Re: cb400 project 'old blue'

the black and white wire was unplugged... but where is the cdi box? could i actually not even have one which is the reason it wont spark? i looked everywhere for something that looked like what i imagined a cdi box to be but couldnt find it, where wouldi t be? i couldnt tell where the black and white wire had come from, but it was already unplugged. there is wires with a plug end coming out of the ignition coil that isn't plugged into anything too. here are pics of the situation at hand. currently when i kick it there is no spark.


offrunoff.jpg

the blue tape blob you see is whats taping two wires together.

ignitioncoil.jpg

and here's the picture of the ignition coil with random unplugged plug?
f.y.i. it is a green and a black wire
 
Re: cb400 project 'old blue'

The cdi should be on the opposite side of the frame of the ignition coil. It plugs into that random coupler.
 
Re: cb400 project 'old blue'

99.9% positive. There should be 2 10mm hex bolts there, and like an indenting in the frame between them. I think I see them in the picture; is there a wire grounded there?
 
Re: cb400 project 'old blue'

yep, the 2 bolts are there with a small indentation in between them. there is a green grounded wire on one of the bolts.
i have not found a cdi box anywhere else

lolcdi.jpg
 
Re: cb400 project 'old blue'

Well, that's where it was on mine. I'll snap some pics when I get home from work.
 
Re: cb400 project 'old blue'

i got the same bike same problem, thats where the cdi should be. on my bike the black white strip wire is from the wire harnes to the cdi box if u disconnect the black white strip wire and kick start it it will work? im gonna go out side and try it
 
Re: cb400 project 'old blue'

when i kicked mine it still didnt start, probably because i dont even have a cdi. im hoping thats the only problem ;D . not to be pessimistic, but... its never THAT easy! but getting a cdi will be a good start. im going to check my local junkyard and hope they have it. otherwise ebay here i come!
 
Re: cb400 project 'old blue'

yep that's where the CDI goes. I have one I can test and part with. I need the money for barber trip. Pm me if interested. I have been saving one but I am selling the bike too so no point in saving it anymore. Oh and the bike won't run without the CDI, it tells the coil when to fire from the rotation of the Stator.

Cheers,

Maritime
 
Re: cb400 project 'old blue'

joeybaggadonuts said:
when i kicked mine it still didnt start, probably because i dont even have a cdi. im hoping thats the only problem ;D . not to be pessimistic, but... its never THAT easy! but getting a cdi will be a good start. im going to check my local junkyard and hope they have it. otherwise ebay here i come!
Click to expand...

I'm sure I don't have to tell you, first check all the obvious simple things like switches and connections and fuses, etc. Then (I've been told) work from the source of the problem, outwards. Plug->coil->cdi->stator...

But, ya, if you have no CDI, then no spark. The electrical system on this bike is pretty simple. I've been observing my room mate with his quest of spark on his '77 cb750. I'm glad these have CDI systems.

8451dc5f.jpg

In the upper left is where the CDI is, on the frame. Then if you follow the harness that is hanging low by the stator, is where the CDI connects. The blue and white wires via bullet connectors and then the 4 pin/large spade connector. Also, the one going into the coil, that you can't see in the picture.
 
Re: cb400 project 'old blue'

Maritime said:
yep that's where the CDI goes. I have one I can test and part with. I need the money for barber trip. Pm me if interested. I have been saving one but I am selling the bike too so no point in saving it anymore. Oh and the bike won't run without the CDI, it tells the coil when to fire from the rotation of the Stator.

Cheers,

Maritime
Click to expand...

pm'd

yayuppp said:
I'm sure I don't have to tell you, first check all the obvious simple things like switches and connections and fuses, etc. Then (I've been told) work from the source of the problem, outwards. Plug->coil->cdi->stator...
Click to expand...

thanks, i'm hoping it'll spark with the cdi. crossing my fingers! ;D
 
Re: cb400 project 'old blue'

10/3 update: I didn't get a CDI yet, but I hooked up a new battery, and used a volt meter to check wiring around the bike. So far, everything has power that I've checked.

Here's a question that may be dumb, but what's the difference between a cb400t Hawk I and a cb400t Hawk II? For the 1978 model that is. The wiring diagrams are slightly different and I didn't know if that made a difference or not. I'm currently going off of the Hawk I diagram.
 
Re: cb400 project 'old blue'

From what I understand; the difference is the Hawk2 had the comstars with a front disc(disk?) brake.
 
Re: cb400 project 'old blue'

Does the hawk1 have a starter? i think that may be another difference. i have a front disc brake so im going to assume its a hawk2.


anyway, i was looking into air filters and i'm liking k&n style the best. anyone else have some secret awesome filter that i've overlooked? opinions are nice!


i've also been working on making a slim harness. i have the wiring diagram and its treatin me pretty good, not too harsh. i know i'm supposed to make sure i don't break any circuits by removing certain particular wires or whatnot, but have any pointers?


also any clues to where to get a newer, slimmer and better regulator/rectifier? haven't look into them much yet, but thats also on the list


thanks guys! 8) (and girls ;) )
 
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