1978 Honda CB400T - "Controlled" - First Build

I guess I should introduce myself; I'm Mark, 31 years old and the only experience I've had with motorcycles is my dad's old 1987 Honda Shadow. I basically helped with tools and cleaning things, he occasionally let me fill fluids or bleed the brakes. I wasn't old enough to really appreciate that time. This isn't an homage to him though, he ended up being a bit of an ass. This is my own thing.

Purchased on 8/3/2013 for $400
21000+ miles, doesn't spark, motor turns, gears work but sloppy.

First goal is to replace the things I can; workout the wiring (it's been spliced here and there), get a new battery (recommendations?), spark plugs and wire, take off the carb(s?) and inspect/rebuild, as well as a few other key things. I want to get it to turn over and run before I slim her down for the rebuild.

I've nicknamed this build "Controlled" as I plan to take my time, do things right, and learn a lot along the way. Don't count me out as my passion can carry me a long way but I'll admit I've never welded, I just purchased a grinder for the first time, I have tools and I'm inclined mechanically and electrically. I have a creative mind and I'll be picking the brains of all you awesome people along the way (I hope others learn from me eventually too).

A couple pics included; the one with the cooler was "as bought"; it had a few various external parts in it... I promptly ditched it. Second picture is me being dumb after a stressful drive getting her home.

Comments, suggestions? (What newb welder should I be looking to pick up? light sheet metal fab).

Starting to get a bit of a checklist together now. Aside from when I first bought it, I haven't tried to start it. As I said previously I'm going slow.

I ordered a new battery (YT12C Scorpion - 12v 180 CCA) - $59

I'm looking around for (recommendations?):

• a reasonable carb rebuild kit
• replacement valve shims and replacement tool
• new valve cover gasket.
• feeler gauges

I plan on doing a few checks tonight - remove any loose debris (not cleaning yet), removing the seat, tank (check for leaks, rust, debris etc), possibly remove the carbs. I'll post later tonight with pics here and there.

That looks like a clean start! There is a CB400/CM400 build page around here somewhere. You can see what many others have done with the same/similar bikes.

Check your brakes, cables, and tear into those carbs. If you look through my build you can find a downloadable (free!) factory service manual which will be a huge help. I would suggest keeping your factory airbox unless you plan on upgrading carbs. Another option is to ask Junior Burrell about how to run stock carbs and pods. Check eBay for your gaskets, the manual for valve adjustments, and your local hardware store for feeler gauges. Keep posting pics and good luck.

fresh_c said:

That looks like a clean start! There is a CB400/CM400 build page around here somewhere. You can see what many others have done with the same/similar bikes.

Check your brakes, cables, and tear into those carbs. If you look through my build you can find a downloadable (free!) factory service manual which will be a huge help. I would suggest keeping your factory airbox unless you plan on upgrading carbs. Another option is to ask Junior Burrell about how to run stock carbs and pods. Check eBay for your gaskets, the manual for valve adjustments, and your local hardware store for feeler gauges. Keep posting pics and good luck.

Click to expand...

Thanks! I have the manual downloaded already the Clymer one; I'm all about documentation so I'll see what you have collected. Personally I like having the books in front of me so I'll probably try to purchase them in physical form. I'm not sure if I plan on upgrading the carbs yet or not - I just want to get the thing running first... part of that is tearing into the carbs like you said. Off to check out your build!

So here's the previous owner's story. "I drove it from home to work as much as I could, about 30 miles each way. Then it quit working, there's no spark and I'm no mechanic. I tried a few things but just gave up."

So here I am trying to figure out the wiring job that's left... it's not much and I'm sure patience with the manual will unveil this all but in the mean time, while I'm looking through that, perhaps others will know exactly what I'm looking at here.

Signal-Stat:
I'm assuming this is just a relay for the flashers... in any case the backside has a (ground?) wire disconnected and the connector on the relay has broke off. Unless this is more than just a relay for the flashers then I don't think this is my problem but I'll probably order another one of these soon.



Left side panel of bike:
There were two issues I saw immediately on this side; the connectors on the left... I'm assuming the ones not connected actually connect. The next issue is that floating connection in the center... the plastic is T shaped (female) 3 hole, 2 wire and I didn't see where this connected to anywhere near this area.



Battery Side of the House
Behind the right cover the only issue I had was a dead NAPA battery and the following wires that do NOT appear to hook together... seems unlikely at all. Yellow/Red Stripe and a Green/Red Stripe no other connections near by that were available.



Spark? No Spark?

Could the no spark be coming from here?!?! (I think other wiring needs to be addressed too though...



So that's where I'm at. I removed the seat and took off the gas tank, the fuel line was cut as it was completely stuck to the carb side. I have that sitting over a bucket now seeing if there are any leaks. I checked the spark plugs, they were okay a little black but okay... but it troubled me - they were finger tight and when I removed them I used a flashlight to see inside the cylinder and it's very brown and dirt-like in there. I'm afraid I'm gonna have to tear apart everything. I just want to get a spark first before I get to that point.

If I get time tomorrow I'll take off the carbs to inspect them/tear them down - Note to self - order carb rebuild kit. I have a friend from out of town coming in for a family emergency so I don't know how much time I'll get if any.

Any advice or recommendations thus far?

Thinking about ordering this carb rebuild kit: http://www.outwestmotorcycles.com/catalog/index.php?main_page=product_info&products_id=337 I don't know if there are better options or what else I should pick up. Anyone else have ideas?

Also ordered a harbor freight compression tester and feeler gauges. Still looking through wiring diagrams as this is all new to me and the problems in my previous post are something I want to address before I move forward.

looks like a nice bike to start. wouldn't worry about the finger tight plugs, the guy you bought it from probably had them out and just finger tightened em back in before you bought it.. do you have a charger hooked up when kicking it over? I would probably hold off on any further tear down until the new battery comes in, or you get a charger on the current one. have you tried putting a charger to it and turning the key on? do lights come on? turn over? good pickup though on a compression tester. just keep the basic rule of thumb, if you have spark, compression and fuel you have a running anything.. tuning it and making it run nicely will be a whole other can of worms.. ill jump on board and follow along.

MJPriceisright said:

looks like a nice bike to start. wouldn't worry about the finger tight plugs, the guy you bought it from probably had them out and just finger tightened em back in before you bought it.. do you have a charger hooked up when kicking it over? I would probably hold off on any further tear down until the new battery comes in, or you get a charger on the current one. have you tried putting a charger to it and turning the key on? do lights come on? turn over? good pickup though on a compression tester. just keep the basic rule of thumb, if you have spark, compression and fuel you have a running anything.. tuning it and making it run nicely will be a whole other can of worms.. ill jump on board and follow along.

Click to expand...

Thanks for the reply, I'm thinking the brown is just varnish from sitting gas too long. I don't have a charger yet but the battery should be in tomorrow. I don't plan on tearing off the carbs until I can find the right kit to rebuild it - even if I have to buy all individual gaskets here and there. I hope to pop in the battery and see what happens. I'm looking for a decent bike charger on CL and might just Harbor Freight one with my other order. I'm just more curious about the wiring right now - I checked the fuses; they're intact and so are the 2 spares but disconnected wires and connections that don't have a match bother me.

not sure about the disconnected wires.. I could definitely be wrong, but its possible that they don't have a purpose, or maybe your bike didn't have a specific option that maybe a different model bike did have.. so its the same harness, and they are just there domant with no use. I would for sure wait for the battery to come.. the brownish chocolate color I don't think needs any attention either. do your compression test first. once you know you have good equal compression on the cylinders, move onto the spark issue your having. if the new battery is hooked up and you don't have spark, id check the coils first. make sure they have power running to them while the key is on. if they do have power, then I would check to see if you have power to the plugs. if you have no spark at the plugs, youtube "how to check a motorcycle coil" and it will give you some good videos on the step by step process. that will also require an ohm meter.

MJPriceisright said:

not sure about the disconnected wires.. I could definitely be wrong, but its possible that they don't have a purpose, or maybe your bike didn't have a specific option that maybe a different model bike did have.. so its the same harness, and they are just there domant with no use. I would for sure wait for the battery to come.. the brownish chocolate color I don't think needs any attention either. do your compression test first. once you know you have good equal compression on the cylinders, move onto the spark issue your having. if the new battery is hooked up and you don't have spark, id check the coils first. make sure they have power running to them while the key is on. if they do have power, then I would check to see if you have power to the plugs. if you have no spark at the plugs, youtube "how to check a motorcycle coil" and it will give you some good videos on the step by step process. that will also require an ohm meter.

Click to expand...

Will do man, thanks for the tips. I'll repost after I do the compression test and receive the battery. Looking over your build thread now... I've got several pages to read lol.

lol try not to get lost in the nonsense shit talking, plenty of pages filled with trash talk.

So I noticed with the media blasting in the beginning hahaha. oh well.

shavoc said:

Will do man, thanks for the tips. I'll repost after I do the compression test and receive the battery. Looking over your build thread now... I've got several pages to read lol.

Click to expand...

Start with a wiring diagram, a few beers, and trace every wire. Some of those looms were used on more than one bike model, some have accessory wires built in.
But also start with new plugs.

If you are looking to rebuild the carbs check out partsnmore.com for the rebuild kits:

http://www.partsnmore.com/parts/honda/cb400t/?filters[fitting]=custom

moetrout said:

If you are looking to rebuild the carbs check out partsnmore.com for the rebuild kits:

http://www.partsnmore.com/parts/honda/cb400t/?filters[fitting]=custom

Click to expand...

Thanks for the link!

now the thread is moving along. so many guys (and gals) on here with great insight on anything you need and desire.

MJPriceisright said:

now the thread is moving along. so many guys (and gals) on here with great insight on anything you need and desire.

Click to expand...

Now that I've got a clear direction and a jumping off point... yes! Been reading thread after thread of builds for awhile now... just wish I didn't have a day job hahaha.

So off my stator I see this... 3 yellow to rectifier white with red stripe and black off to a sealed black box with 9 wires out of it... Then a blue, green, red, brown? Cable to a connector mounted to the plate with the rectifier... Got new battery... All lights and blinkers work except for the headlight. Still... No... Spark.

Okay, frustrating because I'm staring at this loom like whaaaa? I can't seem to figure out this damn issue. I almost just want to tear apart the bike entirely and figure it out when I put it all back together.

As far as I understand it, when I kick the starter over it rotates and sends a signal by way of carrier pigeon to the CDI box right? Then the cdi box is like hey YO bitch ass ignition coil... how about you spark up dem plugs.

Right? Maybe it's just a shitty stator that needs to be replace... or maybe the cdi is hosed or maybe it's the rectifier? is that even in the chain for starting?

Only way to find out is to sit down with a multimeter and find out what's up. If you can describe exactly what is and isn't working we can help diagnose more accurately.

Have you checked your fuses? :