1978 CB400T II project

78HondaHawk

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North Carolina
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Please excuse my garage and lack of proper tools/setup.

So...I'm new to all of this. I am not a mechanic, nor do i know anything about motorcycles other than I've always wanted one.That being said, this is what I've done so far. I know I haven't done anything in the correct order and probably not correctly, but I'm learning.

1. Kinda cleaned the bike to see what I was working with.
2. Replaced battery.
3. Cleaned tank and sealed the inside. (The outside of the tank had grinder swirls and rust so I sanded it some and oiled it so it wouldn't rust while I figured things out.)
4. Changed oil. (There was no washer, I didn't know that at the time, but I do now.)
5. Removed carbs. (Cleaned them and replaced a few parts. If it was bad on one side, I replaced both sides. That is how I found this forum. Attempted to do what I could)
6. Reinstalled carbs. (I've seen how to synch and such, I gave it a shot)
7. Started bike. It only ran for a few seconds and I found that only one cylinder was working. (Choke is not correct, if I tighten the nut holding it in place the choke doesn't move, if I loosen it a bit, the choke will go where I want it to..if I loosen it all the way the know won't stay put in any position)
8. Left bowl is leaking from the overflow.( I need to adjust the float better, I assume)
9. Replaced spark plugs. (Now both cylinders are hot. Choke out to start and in 2/3rds to keep it running. Once choke is fully depressed, engine dies.)
10. Fixed seat, and various odds and ends.

I assume that the floats, throttle cable, choke cable, synch, and overall alignment is off but I consider all of this a win since it didn't start when I got it. (Carbs smelled like turpentine and we're all gummed up, spark plugs were black, I was using the wrong manual and praying YouTube was going to help me)

I'm amazed that I even got it to start. Any suggestions or comments would be greatly appreciated.

Stay safe out there.
 
Fix the overflow before any more running. Possibilities are float level too high or float needle sticking, cracked overflow stand pipe or drain screw not sealing.
 
I believe the float needs adjustments. Drain screw is sealed, stand pipe appeared fine, new float needle, I used aftermarket floats but I still have the originals..they seemed ok too. I'm fairly certain I just screwed up adjusting the floats...I hope. Can't wait to take it all apart again. Sheesh. Ha.
 
ballbearian said:
Sounds like you are doing pretty good. Did you read and use LDR's sticky on VB carb rebuilds?
Click to expand...
I had but I seem to have lost it again. Carbs are back off and I'm debating on using the original floats or the new ones. If anyone has the link to the rebuild, I'd appreciate it. I'm also concerned about the orientation of the floats. The pictures help!
 

How to Rebuild the VB Carburetors

This is dealing with the VB22J carbs in particular but most of it applies to the VB21 and VB24 carbs. As everyone knows that has done these they are problematic to get right the first time at best so hopefully this will help you get there. In this case I'm dealing with VB22J carbs that have had...
www.vintagehondatwins.com www.vintagehondatwins.com

There you go… 👍🏻
 
tomeben said:

How to Rebuild the VB Carburetors

This is dealing with the VB22J carbs in particular but most of it applies to the VB21 and VB24 carbs. As everyone knows that has done these they are problematic to get right the first time at best so hopefully this will help you get there. In this case I'm dealing with VB22J carbs that have had...
www.vintagehondatwins.com www.vintagehondatwins.com

There you go… 👍🏻
Click to expand...
Thank you very much!
 
The overflow fuel tends to be aftermarket float valves, cracked standpipe, and/or bad seal of the drain screw.

What I do is get a mityvac, set to pressure mode, attach it to the drain end and put a rubber stopper on top of the standpipe. Then fill bowl with mineral spirits or alcohol. Pump about 10psi into the bowl. You will see bubbles where the leak is.
 
Update: the bike is registered, insured and running! I did require some help with the floats and the brake master cylinder but she is now road worthy. I've replaced a few other parts and am currently working on my riding skills. She still needs to be cleaned and painted but that is not my main issue. I have been looking for the bushings under the triple tree and I'm having difficulty finding them online. I know I can put a bunch of O rings as a temporary fix but I'd really prefer to have the actual part. If anyone has a suggestion as to where I can find such a thing, I would appreciate it.

Ride safe everyone
 
I may have my verbiage wrong but I was shown directly under the handlebars ( they may wobble a bit) something that looks like black rubber washers that need too be tightened or replaced. I will take a picture after work. Thanks for responding.
 
OK, I think I have it figured out. You're looking for #3 and #4 in this fiche https://www.partzilla.com/catalog/honda/motorcycle/1979/cm400t-a/handlebar-top-bridge #3 is used top and bottom, that's why no #4 is listed.
This also indicates the top bridge has been changed along with the forks. I suspect you have a top fork pinch bolt #8 in the above fiche.
Here's the correct top bridge fiche, solid mount bars, no pinch bolt since the top nut/cap of the forks locks plate 6 in place when torqued.

Honda Motorcycle 1979 OEM Parts Diagram for Handlebar / Top Bridge | Partzilla.com

Buy OEM Parts for Honda Motorcycle 1979 Handlebar / Top Bridge Diagram
www.partzilla.com www.partzilla.com
 
LongDistanceRider said:
OK, I think I have it figured out. You're looking for #3 and #4 in this fiche https://www.partzilla.com/catalog/honda/motorcycle/1979/cm400t-a/handlebar-top-bridge #3 is used top and bottom, that's why no #4 is listed.
This also indicates the top bridge has been changed along with the forks. I suspect you have a top fork pinch bolt #8 in the above fiche.
Here's the correct top bridge fiche, solid mount bars, no pinch bolt since the top nut/cap of the forks locks plate 6 in place when torqued.

Honda Motorcycle 1979 OEM Parts Diagram for Handlebar / Top Bridge | Partzilla.com

Buy OEM Parts for Honda Motorcycle 1979 Handlebar / Top Bridge Diagram
www.partzilla.com www.partzilla.com
Click to expand...
 
Thank you very much for the help! I swear I looked everywhere and couldn't come up with that. Am I to understand that the forks have been replaced at some point? I've been looking at engine parts more than what is original or not. Function over style at the moment. I'm still learning and finding all sorts of quirks. Everytime I look, I find a new screw or wire or part that I haven't seen before. You guys are amazing. Thank you again for your help.

Be safe everyone.
 
78HondaHawk said:
Thank you very much for the help! I swear I looked everywhere and couldn't come up with that. Am I to understand that the forks have been replaced at some point? I've been looking at engine parts more than what is original or not. Function over style at the moment. I'm still learning and finding all sorts of quirks. Everytime I look, I find a new screw or wire or part that I haven't seen before. You guys are amazing. Thank you again for your help.

Be safe everyone.
Click to expand...
Function is way more important than form. You are doing the right things here. Too many people get caught up on cosmetics and don't pursue mechanical excellence first.

EDIT: With the handlebar bushings don't forget the cotter pins. Looks like they are missing in your photo. Part number: 94201-20250. Well there's many part numbers in that fiche, the difference is length. Really, any 2mm cotter pin will work as long as it's long enough. But if you're ordering bushings from the dealer makes sense to pay the $1 at the counter to just get it and be done with it. Get 2.
 
A few additional road worthy things you should consider when you get some time:

  • Grease swingarm bushings. Contrary to forum lore you DO NOT need a special grease gun for this. A regular gun will work. Check the zerk fitting to be sure it is not seized before pushing grease in there. Sometimes they need to come over and cleaned up. If bushings are seized swingarm neesd to come off and needs new seals and bushings. Will cost about $200. Not hard to do, but slightly annoying if needs done. Getting grease in those bushings, fresh grease, makes a huge difference going over bumps like you would not believe and all of these bikes have solid, nasty grease in them.
  • Fork fluid and seals. Another thing with suspension and makes a big difference. Earlier 400 years are annoying to swap the fluid out because there's no drain so front wheel needs to come off and front forks need to come out. Season is almost over, so good time to do it in the winter.
  • Steering bearing tightening. Affects handling. It's not hard to do, but you must have a torque wrench for the large cover bolt on the triple tree. You will have to flip the handle bars out of the way if doing it. Tighten the pin spanner finger tight then back off about 1/8" of a turn if i remember correctly per FSM. I do it a slightly different way that involves a special tool to "square" the bearings into the races and then backing off to spec.
  • Brake fluid flush. Not hard to do, but do it and do it every other year. DOT3/4/Glycol fouls things up quick in these small reservoirs. A better option is to switch it over to DOT5/Silicone, use a vacuum bleeder like a Mityvac to do it and then never look back with brake fluid fouling up the system ever again. If you go the DOT5 route just pop the piston and seal out, clean everything up (you should do this anyways if you haven't already), then just flush. It'll be fine. I have a guide here on VHT if you want more info on how to do it. But either way, pop that piston out, get the seal out, take a brass wire wheel in the seal area to clean it up, clean the caliper then reassemble.
  • Grease rear brake cam and pivots on the rear pads. Requires rear wheel to come off.
There's more I'm probably forgetting, but these will make a difference in ride quality and braking.
 
Maraakate said:
Function is way more important than form. You are doing the right things here. Too many people get caught up on cosmetics and don't pursue mechanical excellence first.

EDIT: With the handlebar bushings don't forget the cotter pins. Looks like they are missing in your photo. Part number: 94201-20250. Well there's many part numbers in that fiche, the difference is length. Really, any 2mm cotter pin will work as long as it's long enough. But if you're ordering bushings from the dealer makes sense to pay the $1 at the counter to just get it and be done with it. Get 2.
Click to expand...
Good eyes and great catch. I have just ordered the bushings AND pins. Thank you for your input and I'll be sure to do as you suggest.

Stay safe.
 
Maraakate said:
A few additional road worthy things you should consider when you get some time:

  • Grease swingarm bushings. Contrary to forum lore you DO NOT need a special grease gun for this. A regular gun will work. Check the zerk fitting to be sure it is not seized before pushing grease in there. Sometimes they need to come over and cleaned up. If bushings are seized swingarm neesd to come off and needs new seals and bushings. Will cost about $200. Not hard to do, but slightly annoying if needs done. Getting grease in those bushings, fresh grease, makes a huge difference going over bumps like you would not believe and all of these bikes have solid, nasty grease in them.
  • Fork fluid and seals. Another thing with suspension and makes a big difference. Earlier 400 years are annoying to swap the fluid out because there's no drain so front wheel needs to come off and front forks need to come out. Season is almost over, so good time to do it in the winter.
  • Steering bearing tightening. Affects handling. It's not hard to do, but you must have a torque wrench for the large cover bolt on the triple tree. You will have to flip the handle bars out of the way if doing it. Tighten the pin spanner finger tight then back off about 1/8" of a turn if i remember correctly per FSM. I do it a slightly different way that involves a special tool to "square" the bearings into the races and then backing off to spec.
  • Brake fluid flush. Not hard to do, but do it and do it every other year. DOT3/4/Glycol fouls things up quick in these small reservoirs. A better option is to switch it over to DOT5/Silicone, use a vacuum bleeder like a Mityvac to do it and then never look back with brake fluid fouling up the system ever again. If you go the DOT5 route just pop the piston and seal out, clean everything up (you should do this anyways if you haven't already), then just flush. It'll be fine. I have a guide here on VHT if you want more info on how to do it. But either way, pop that piston out, get the seal out, take a brass wire wheel in the seal area to clean it up, clean the caliper then reassemble.
  • Grease rear brake cam and pivots on the rear pads. Requires rear wheel to come off.
There's more I'm probably forgetting, but these will make a difference in ride quality and braking.
Click to expand...
Awesome suggestions! I was curious about the greasing. New master brake cylinder has been installed so I think I'm good there for now. I will need to do some homework on grease, fittings, and gun. I will be sure to check all of these points. Thank you very much for your suggestions.


Ride safe.
 
78HondaHawk said:
Awesome suggestions! I was curious about the greasing. New master brake cylinder has been installed so I think I'm good there for now. I will need to do some homework on grease, fittings, and gun. I will be sure to check all of these points. Thank you very much for your suggestions.


Ride safe.
Click to expand...
Not just the master cylinder, referring to the piston and seal in the caliper. Grease gun and type I've done that homework in the past.. there's a cheap gun for $20 that works just fine. Just get some Lucas Red N Tacky with it and you're good to go.

 
Maraakate said:
Not just the master cylinder, referring to the piston and seal in the caliper. Grease gun and type I've done that homework in the past.. there's a cheap gun for $20 that works just fine. Just get some Lucas Red N Tacky with it and you're good to go.

Click to expand...
I've greased everything that I could find...thank you.

I have also replaced the bushings beneath the handlebar but I still have some flex in it. How much play should this have?

I've also run into 2 different issues:
1. I feel like the gear shift should be moved up slightly to give myself a better foot position to get to it quicker (I see how to do it, but will this change anything in the shift mechanism other than the height?)
2. I've replaced the headlight and seem to be only able to shift it left and right, not up and down. I believe the housing is too close to the speedometer but without lowering the entire housing I feel like I'm missing something on how to adjust it where it lays. The bulb sits in the housing so it should be able to move independently without having to change its location.

Any suggestions would be helpful. I'll get to my engine starting queations soon enough. (It starts but I think some adjustments need to be made)

Thanks....Ride safe everyone.
 
78HondaHawk said:
I've greased everything that I could find...thank you.

I have also replaced the bushings beneath the handlebar but I still have some flex in it. How much play should this have?

I've also run into 2 different issues:
1. I feel like the gear shift should be moved up slightly to give myself a better foot position to get to it quicker (I see how to do it, but will this change anything in the shift mechanism other than the height?)
2. I've replaced the headlight and seem to be only able to shift it left and right, not up and down. I believe the housing is too close to the speedometer but without lowering the entire housing I feel like I'm missing something on how to adjust it where it lays. The bulb sits in the housing so it should be able to move independently without having to change its location.

Any suggestions would be helpful. I'll get to my engine starting questions soon enough. (It starts but I think some adjustments need to be made)

Thanks....Ride safe everyone.
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There will always be a small bit of play which serves to absorb the vibration.
Go ahead and move the shifter up for a better fit, won't do anything to the trans.
The headlight will pivot up/down by loosening the 2 side mounting bolt, clearance is very tight between the headlight and gauges.
 
1.) No, repositioning the shifter lever (via loosening the single clamping bolt on it) will not affect the shifting mechanism (but you don't want to raise it so much that it requires lifting your foot off the peg to shift into 2nd thru 5th). Factory torque tightening force limit for the clamping bolt is 8 ftLbs (or, 8x12 = 96 inchLbs)

2.) Up & down headlight adj is done by loosening the turn signal stalks (however it's done with the aftermarket ears) on your bike

This one has its original ears :
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Thanks. The torque measurement for the gear select is very helpful.

I hate the aftermarket turn signals on the bike. I have 2 but I need 2 more. I'll play with the only screw on the aftermarket ones for now but I'll try to get originals in the future.

You guys rock. Stay safe.
 
Just to add to the headlight adjustment, on mine I found that after 45+ years the wiring harness in the headlight is too stiff to allow the headlight to move down. You may need to manualy flex that harness just a bit for clearance allowing the headlight to move.
 
Thanks for the suggestion. I will give that a shot. Riding at night is no good if you can't see!

Once these 2 things are done, we will move onto the start-up issues. I appreciate all of your help.

Ride safe.
 
esmith250624 said:
Just to add to the headlight adjustment, on mine I found that after 45+ years the wiring harness in the headlight is too stiff to allow the headlight to move down. You may need to manually flex that harness a bit for clearance allowing the headlight to move.
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When I encounter old sheath-insulated wiring, I heat 'em up good with a hairdryer to add flexibility
 
Well..I moved the headlight down and attempted to adjust the hight of the lens but to no avail. Any other suggestions? Also, I have noticed when I downshift, if I shift too fast I have a tendency to stall. I can have the clutch in, or even go down gear by gear and it seems to happen only occasionally. I'm assuming it's user error but I've also read that raising the idle a bit can help that issue. I've always felt that the idle was a touch low ev3n though it is at 1200. Any suggestions? Should I leave it alone or can I make a small adjustment to maybe 1300? Thank you all in advance.

Stay safe.
 
78HondaHawk said:
Well..I moved the headlight down and attempted to adjust the hight of the lens but to no avail. Any other suggestions? Also, I have noticed when I downshift, if I shift too fast I have a tendency to stall. I can have the clutch in, or even go down gear by gear and it seems to happen only occasionally. I'm assuming it's user error but I've also read that raising the idle a bit can help that issue. I've always felt that the idle was a touch low ev3n though it is at 1200. Any suggestions? Should I leave it alone or can I make a small adjustment to maybe 1300? Thank you all in advance.

Stay safe.
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You should use a digital tach to verify the stock tach. Some timing lights have a tach built into them. The stock tach after 50 ears of wear and abuse is probably off and your 1200 is more like 1000.
 
Good day everyone. I hope everyone's projects are going well. If I could ask a quick question...does anyone know a part number for a kickstart seal/washer? I noticed some spray from the arm and i see some splash back behind the arm, running down the right side of the bike.i tried to reach about it in the manual and all I find is "remove the kickstarter". I appreciate everyone reading. Stay safe.
 
Do you mean the kickstarter seal on the cover is leaking? This is very typical and so is the gear shifter seal. Both parts are still available from Honda.
 
You mean the crud in there where it pivots? That's normal. If it bugs you spray some brake or carb cleaner in there and use a few paper towels. Then use any of the following: Blue 3-in-1 oil (i.e. SAE20 or so), gear oil, white lithium grease (dislike this as it always stains), cable lube, etc. Don't use penetrating fluid that just evaporates quickly.

EDIT: I should have mentioned you need to relube that and work it back and forth because there is a spring-loaded ball bearing in there to help it snap into place. Cleaning that out every so often and then working some lube in there will help keep the action smooth.
 
That is wonderful information. I don't think I had noticed the spray before. Is that a common thing? Is there a seal behind the shaft? It isn't leaving a puddle or anything just seems new to me. Granted, I'm new at all of this and the bike is finally running well enough to take long rides. Is it more common with long trips vs short ones or it just accumulates over time and work it's way out?
 
Capture.PNG
You're talking about this circled area, yes? If yes, then there is no seal behind this. You can actually remove the whole lever with the bolt near by. Behind that flathead screw on the right side of this lever is the spring-loaded ball bearing. Simply put because of the oil/grease needed for the ball bearing this area can collect road dirt from time to time and needs cleaned.
 
Yes. That is what I'm talking about. When you mentioned cleaning it and greasing it, is that all done from the outside? No need to remove the kickstart or mess with the spring and bearings?
 
And the questions keep on coming...

I'm replacing the front and rear turn signals...I managed to figure out the rear signal wiring and it basically had 2 wires per side, power and ground. They work correctly.

However, the front turn signals currently have 3 wires a piece. I assume power, ground and the extra seems to be a link between the 2 sides that both go to another bundle of wires that appear to go towards the rear of the bike.
The real issue is that my front turn signals only have 2 wires a piece....any suggestions would be helpful.

Index and pinky are power and ground
Middle finger grey wire - down the bike
Ring finger orange and black -down the bike

1000014956.jpg



Sorry for the odd picture. Would I splice the "down the bike wires" into something else?

Thanks
 
Here is the wiring diagram straight out of my book. Easier to read than the old crappy PDF thats floating around:

20250220_143411.jpg20250220_143418.jpg20250220_143422.jpg

Here is the wire and cable routing and how the rats nest goes back into the headlamp assembly:
20250220_143438.jpg20250220_143443.jpg

It appears Orange leads to the turn signal switch and is labelled PL which I believe means Power Left.
That Gray is actually Light Blue, it's just incredibly faded. This is Power Right.
Green is ground. It should be a matter of the male bullet connectors going into the solid coloured females to the switch. Black off the turn signals should go to Green for ground.

EDIT: There should be another Light Blue and Orange female bullet connector leading of another terminal connector. These ones lead into an 8 pin terminal connector under the bucket. Not sure which one it will be. Should be the colours you're look for and a female bullet connector will be crimped to it as well.

So yes, you'll have split it out off the turn signals. However, maybe not. Give a try and see.
 
Second post to my EDIT (yeah!) I believe the other bullet connectors that go to the 8-pin are for the turn signal dash indicator bulb. Front and Rear lead to this eventually.
 
I'm sorry. I'm not understanding. I get that the green and black wires are ground and power but the extra light blue and orange wires go to different connections. They are all currently (3wires a signal) connected to the same bulb. Im guessing that I have to connect the power and orange wire together? And light blue and power together on the other side?
 
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