Topic: 1975 Honda CB400F Build

[inv3ctiv3]

My fuse box looks like that, but it spans the width of 3 fuses. I like your solution, looks clean and gets rid of the glass fuses.

Yea it's super easy to do, just make sure you remember which wires go where and solder them up, cost me like $15 in parts too! I'll be redoing the connections on my rectifier too, I'll post pics asap.

[inv3ctiv3]

Parts are starting to roll in!

Dyna S Ignition
Various bolts/washers
Speedo Cable
Tach Cable
Clutch Cable
Timing cover gasket
OEM Honda Petcock

Awaiting on a throttle cable, carb rebuild kits and a couple of other little things can't wait to have a garage weekend soon!

[inv3ctiv3]

Started to do a lot of work on my bike this weekend and ran into more problems than fixing things

First off I decided to take off the alternator cover because some of the screws looked really iffy and wow were they ever....All the phillips were already stripped and I had to use an impact driver to get the cover off and ended up cracking it....Not a huge deal because it was already cracked from the PO laying it down (luckily that was at very low speed an no real damage) so I need to get a new alternator cover. I JB welded this one as a temp fix but may just get a new one before I ride the bike again:







Next big thing is there is a huge hole in my frame!!!! I don't know how I didn't see this before but it looks like it maybe had rust and someone cut the frame to get rid of it I don't know what to do about this, what do you guys think? I had no intentions of taking this down to the frame but now I feel like I have to in order to fix this and at that point I might as well powder coat the frame...Can this be fixed? Is it worth fixing?





I fixed the melted connectors on the battery rectifier as well:

[kiwikk]

Jeez man! 
If I was you I'd rejig my priority list pronto moving the frame work up to number 1
And I'm off down into my garage with a mirror right now to check my own '75 CB400F. I haven't got that low and dirty on it yet.
Pleased to see you got your RPM's up. I've not had mine long and I haven't got it above 7000RPM yet. (Got a whole bunch of checks to run through and I'll add fuses and electrics to the list.)
I must have had a bunch of crap bikes in the past 'cos I'm already impressed with what it can do with 7000RPM. Roll on 10000RPM 
I'd +1 on everyone else's suggestion that you keep it stock as its already considered by most to be a work of art (there's one of our '75 ruby red's in an art gallery in Auckland NZ with 3km on the clock) but then if you are keeping the original stuff, change away... subtly though eh. Just like I did on my last project bike even though it'd never be considered a classic   

[MoMo]

The frame rot at that spot is VERY COMMON(and, yes, I meant to shout that out), it was where the sidestand had been attached.  It seems that water collects there and the frame rots from the inside out, I remember a couple cases when the stand tore loose while the bike was on it and then let go causing the bike to land on its left side. I have had two successfully repaired by a competent welder(that would not be me). On one I had a spare, untitled donor frame on which the area was cut out and then transferred to the titled frame.  The other was repaired with a metal plate welded to the back.  Yours is missing the side stand tab,  so you could have a new section welded in and have a tab made,  or you could use centerstand only,  or leave it as is. Afterall, the area is between  the front and rear motor mounting points and should have little to no stress other than when the stand is down.  Of course, the latter course is not recommended...Larry

[Nerdos]

The exact same thing happened to my CB400Four.  It was probably exacerbated by me sitting on it when on the side-stand, smoking Marlboro and looking cool (in my head at any rate.)   Originally when this happened I had it welded back together but the tab soon ripped out again.  The next fix used  a spare frame which I had lying about that had a twisted headstock, cut the section out of that and took it to someone with a welder.  £15 fix.  I don't sit on the bike while it's on its stand any more but the welding fix has stood the test of time for 10 years now.  I'm not looking for concours so I quite like the battle scars on my 54,000 mile '75 400Four.

[inv3ctiv3]

Hmmm well I could take it in to get a plate welded in, I don't care about the side stand at all I was worried this was a big problem.....If I take it in to get welded I need to strip the bike down completely and basically do a frame off restoration which I didn't plan on doing with this bike as I just wanted this one to be my DD/runner. It has 25k and is in pretty good condition but didn't want to make this a concourse bike either....

[MoMo]

You could get by with just pulling the motor and taking the rolling chassis to a welder, that is what I did with one of my bad ones...Larry

[nvr2old]

Just as important and nice as it is to have a center stand for adjusting and lubing the chain, a side stand comes into play way more often then you might think.. There are sometimes when a center stand by itself, just won't work, especially in anything loose or un-level.  I would definitely consider putting one on, whether it's the stock one or an aftermarket one after the frame has been repaired.

[inv3ctiv3]

I have never needed the side stand honestly, I just ride around my small town and to and from work. I can't decide if I should just leave it for now or start stripping it down

[Trad]

I would just pull the motor out. You could have it back together in a day; Then you have a solid repair right.

[thirsty 1]

Can you butterfly a small piece of pipe into that cut out and weld it in? And Then put a patch over that to make it flush? (With a little grinder action).  Weld the side stand back in and be set ?

[kyre]

That happened to mine too. Don't leave it like that, you need to get that fixed and you'll be glad you did.  Taking the motor out isn't as hard as it sounds and you may as well do that now. 

[inv3ctiv3]

BIG UPDATE:

So I decided I needed to take care of this frame problem before anything else so I took the bike to my buddies out and took the motor out and welded on some 4130 chromoly tubing to fix the hole. I am not going to strip the whole bike down to the frame and powdercoat it right now, I rather just ride the bike so my plan is to clean the motor and frame and re-do the cables and put on all the parts I already have.

Anyone have any tips to cleaning the engine while it's out?

Some sludge:



Seems the clutch cable cover just keeps water in....



Got the carbs and airbox out (found out some of the boots were not even tight around the carbs...)



I was surprised but the exhaust studs gave me NO problems and were super easy to take off (I also took off the left side studs to make engine removal a little easier:



And it's out!!! I found taking the exhaust studs off made it easier, removed the bottom drain bolt as it was getting caught on the bottom of the frame and just make sure your spark plug wires are out of the way and do not get pinched.



We cut a piece of 1" 4130 chromoly tubing and clamped and bent it to fit snuggly around the frame (the hole is on the bottom side):









Back in my garage:



Me welding:

[NobleHops]

Good decision on the frame repair, well done.

Put the motor on a double or triple layer of cardboard before you start - it will cushion it a bit and absorb the spooge.

Get some wooden carpenter's shims or just shingles, snap off a half inch at a time and use them to dig out the chain spooge. Remove the sprocket first. WD40 or even kerosene is a good solvent for loosening up that stuff without doing any harm.

A good stiff bristle brush and some kerosene for scrubbing the greasy areas, get 90% of the heavy stuff off, then on to medium solvents like diluted simple green, but don't leave it to soak on the aluminum, and rinse it well, and blast dry with compressed air.

Many of those engine surfaces are painted, so be careful or plan to repaint.

[NobleHops]

P.S. Don't leave that conventional lead/acid battery tipped over like that! The electrolyte can run out of the drain at the side and it is corrosive sulphuric acid, will destroy the finish on everything it touches. Go get some distilled water and carefully top it off once it's level.

[inv3ctiv3]

P.S. Don't leave that conventional lead/acid battery tipped over like that! The electrolyte can run out of the drain at the side and it is corrosive sulphuric acid, will destroy the finish on everything it touches. Go get some distilled water and carefully top it off once it's level.

It was only like that for a minute it's upright in my garage now!

[NobleHops]

Dude, one more thing.

Do me a huge favor while your tank and sidecovers are off and photograph and post all the wiring bits please as clearly as you can? I need reference for how it runs along the frame, how it sits under the left and right sidecovers, how the brackets around the horn attach, the rear wiring to the taillight, all of it. Get as much light onto it as you can please so I can make out the details of the black-on-black. And thanks a bunch in advance.

And PM me your email address and I will return the favor with something useful for you.

[inv3ctiv3]

Dude, one more thing.

Do me a huge favor while your tank and sidecovers are off and photograph and post all the wiring bits please as clearly as you can? I need reference for how it runs along the frame, how it sits under the left and right sidecovers, how the brackets around the horn attach, the rear wiring to the taillight, all of it. Get as much light onto it as you can please so I can make out the details of the balck-on-black. And thanks a bunch in advance.

And PM me your email address and I will return the favor with something useful for you.

Yea I can do that this week! Also, in order to paint the engine do I need to tear it down? I don't want to do a frame off restoration on this thing right now, I want to make it ride better, be safer and look better but not be showroom condition.

[NobleHops]

P.S. Don't leave that conventional lead/acid battery tipped over like that! The electrolyte can run out of the drain at the side and it is corrosive sulphuric acid, will destroy the finish on everything it touches. Go get some distilled water and carefully top it off once it's level.

It was only like that for a minute it's upright in my garage now!

OK good. Check all the electrolyte levels just for fun, make sure they are all topped up to the same level. You'll find markings on the side of the battery to indicate proper level. Distilled water only.

[NobleHops]

Dude, one more thing.

Do me a huge favor while your tank and sidecovers are off and photograph and post all the wiring bits please as clearly as you can? I need reference for how it runs along the frame, how it sits under the left and right sidecovers, how the brackets around the horn attach, the rear wiring to the taillight, all of it. Get as much light onto it as you can please so I can make out the details of the balck-on-black. And thanks a bunch in advance.

And PM me your email address and I will return the favor with something useful for you.

Yea I can do that this week! Also, in order to paint the engine do I need to tear it down? I don't want to do a frame off restoration on this thing right now, I want to make it ride better, be safer and look better but not be showroom condition.

Very cool, would really appreciate it, I am in the middle of that now and those pics would be super valuable to me.

I did not tear mine down. It's a little cheesy to do it that way, and it's still a big job. You have to plug every hole, remove the sidecovers, mask all the chrome bolts and other bolt heads and unpainted areas, get it spotlessly clean, maybe soda blast it to etch the surface, degrease it one last time with something like acetone, paint it with etching primer, sand it lightly, then topcoat it, and then bake it with heat lamps or at your powdercoater.  Sidecovers do not get painted. It's a tedious, fiddly, multi-step project and if  you do any of it wrong the paint will not stick and it will break your heart. You must heat cure the paint. This is all detailed in my build thread.

Not trying to discourage you, but that is very much the slippery slope. Your bike seems like a nice rider, not a garage queen like mine. I would not spend the time if I were in your shoes.

[NobleHops]

OK your photos already told me a lot of what I needed to know, which is nice.

As you're cleaning that area under the cover, go check out my thread and see the bit that thirsty 1 taught me about the salt/vinegar cleaning for your electrical contacts. Now on your bike there are 5 bullet connectors from the alternator up through that grommet and to that big wide white plug. Those are going to be dirty, and that's a big point of failure. Take those connections apart, mix up a batch of those two solutions, and dunk and clean all the electrical connectors in that area, blast them dry and give them a light smear of dielectric grease on the male connectors when you reassemble. You can get a little tube of that at any autoparts store.

[inv3ctiv3]

OK your photos already told me a lot of what I needed to know, which is nice.

As you're cleaning that area under the cover, go check out my thread and see the bit that thirsty 1 taught me about the salt/vinegar cleaning for your electrical contacts. Now on your bike there are 5 bullet connectors from the alternator up through that grommet and to that big wide white plug. Those are going to be dirty, and that's a big point of failure. Take those connections apart, mix up a batch of those two solutions, and dunk and clean all the electrical connectors in that area, blast them dry and give them a light smear of dielectric grease on the male connectors when you reassemble. You can get a little tube of that at any autoparts store.

Yea I'll do that for sure, I'm going to spend the next couple of weekends just cleaning stuff (mainly those connectors and the engine) and I agree I don't need to paint the engine I just need to get it really clean. I think it's leaking from the oil pan gasket so I may replace that while the engine is out....

[inv3ctiv3]

Just made another order to 4into1 (they're going to take all my money....) for an OEM breather tube, breather cover gasket, oil pan gasket and throttle cables....I just want to get it back on the road ASAP so I can be riding again.


My plan is to completely re-do the front end and wheels in a couple of months but do it all at once which would include:
New spokes front and rear
New wheel bearings front and rear
New brake pads front and rear
Brake fluid flush
New lower brake lines (have a SS upper hose)
New steering stem bearings
Paint triple tree
Paint caliper

[inv3ctiv3]

Finally had some time to work on her and got the motor back in! I replaced the oil pan gasket while the motor was out and found a bolt just rolling around in the bottom of the pan....Unreal, I don't know where it could have come from and how long it's been there.....

I also got the carbs back in but the funny thing is the airbox tubes don't reach the carbs, I'd have to stretch them to make it work and my hose clamps don't clamp down hard enough to keep them on there....Isn't that strange? I thought people always say how hard it is to get the carbs in and out?







Honestly the whole airbox seems loose and like it doesn't seal up very well, I'm considering using RTV or something on the boots to make sure they seal but that seems kinda hack job.....