Topic: IDK Numero Dos - 1975 Honda CB400F

[minimo]

I caught the bug and it's happening again.
Yesterday, I purchased a 1975 CB400F from goldarrow, who was very helpful toward the end of my last build, a 1977 CB550F. The 400F is a non-op and according to goldarrow, it was pretty much a basket case when he purchased it some years ago, and in an attempt to clear up some of the clutter that is his backyard patio workshop, decided to put the bike together so that it could roll with all the parts. Nevertheless, once in my garage a bit of tear down has already gone underway. Behold, my CB400F totem:

Primary objective for this rebuild is to get the engine to turn over. Meanwhile, I will lighten it up a little (remove the lights to achieve maximum power for turn over). According to goldarrow, he has gone through and cleaned the carbs but just to get familiar, I'm going to take another pass at it, probably purchase a complete carb gasket kit. So in the coming days I will breakdown a parts list to cover the basic criteria to get this engine to turn over: Spark, Fuel and Air/Compression. Then, if I get this going I will begin to peel it back to lighten up the bike a bit. Hopefully, this will not take the four years or so that I took with my 550. My goal is to get this baby up in running quick as possible and I'm looking forward to getting some help along the way :-) And here we go!

[minimo]

Drool...
New Koso TNT-02 tach/speedo (smaller version of the TNT-01)

http://kosonorthamerica.com/shop/motorcycle-mx/tnt-02/

[SOHC4 Cafe Racer Fan]

You kids and your small gauges! I tend to prefer a standard size TNT or Motogadget to keep it easier to read when riding.

[lightsareout]

I really like the gauge, looking forward to see your build

[calj737]

Don complains about small gauges because guys his age can't see crap anymore. And who watches a gauge anyway!?!?

I'll see your TNT-02 and raise you a MotoG Tiny!

[minimo]

calj, that Motogadget Tiny looks cool and the aluminum casing is a nice touch. A couple of design-y things bug me about the MotoG though but I cannot get used to reading that red dot-matrix-like digital readout - very early 2000 Audi-esque and clicking through functions feels annoying and a bit slow due to the scrolling animations of the text, nevertheless in lower-case digital text, ugh. And the price...

SOHC Fan, I hear ya but it's mostly in an effort to minimize/simplify and tuck in the handlebar area; more an aesthetic thing, where function as well as legibility are niceties.

[SOHC4 Cafe Racer Fan]

Don complains about small gauges because guys his age can't see crap anymore.

I resemble that remark!

[SOHC4 Cafe Racer Fan]

CB750, I hear ya but it's mostly in an effort to minimize/simplify and tuck in the handlebar area; more an aesthetic thing, where function as well as legibility are niceties.

Gotcha.  Just making sure you had considered this before plunking down the coin.

[marting100]

Nice! looking forward to see your build.
M

[minimo]

Musical wire cleaning of the emulsion tubes...
Gave a light polish to the top and bowl covers and other rusted parts where I could reach with my bench wheel and Dremel buffing bit. Also rubbed out some crusty varnish on the floats and brass bits. Leaving the float valves and other bits to soak in some Marvels Mystery Oil - love the stuff; such a sweet smell. Buffing other parts around the carb rack... Not/never striving for showroom polish. F that. Life is short - let the ride be long.
75 mains and 40 slow jets which I believe are original. Replacing the top and bowl gaskets and about to button this sucker up tonight.

A bunch of parts I ordered came in too so I'm hoping that this will all move along pretty quick (in spite of the cam tension adjustment screw that's seized and probably needs some extraction).

[minimo]

Dreaming of an ultrasonic cleaning and a vapor blast but for now it's gonna be elbow grease and a spit shine; these carbs are done.
O-rings for the mains, valve seats, bowl drain screws, top cover and bowl gaskets all replaced to a fresh set (thanks, goldarrow for the kind kit). I'm gonna trust that the needle heights havents been meddled with and gonna move on to whatever is next... ⚡️

Gotta stay on target and get the engine to turn over before I go too crazy with the rest of this build, especially with the look and cosmetics...

[strynboen]

nov use a extern tank..and test for overflow.....before put them back on the bike..
..its easy to fix a problem now...and dont ruin engine paint..vhen you have the Black overflow lines on..its not posibel to see the one vho flote ,,so test vitaut lines..
on the Photo i put komp air in the fuel line...so i can hear the presise close/open point so i can adjust the float/ fuel valve(i used a regulator to hold the pressure low)

[minimo]

That's a cool trick, strynboen. But I'm not quite clear on your description and what I'm seeing there. In your pic I see that you have the bowls removed... This is AFTER having the external fuel tank connected to the fuel lines, right? Also, in the upside down position, the floats should be pushing the float valves down so is this why you have the low-pressure air pushing to fine tune the float heights? A video of this process would be fantastic if you can link me to one

[strynboen]

yes it just to adjust the floth height...the air escapes..until the valve get stuck of the flot...and the exatc point is clerly to be heard..and use your messure gerete you get a perfekt adjusting...vitaut any fuel vaste all over the shop....

the fuel tank test is the last thing to be done..just to be 100%shure it not floting  on the bike
on mine 400 i put sone new o rings at the brass main jets they vas komple Loose vith the old ones..but that metal clips hold them right on..

[MoMo]

jet sizes are stock as mentioned.  An ultrasonic cleaner from HF cost me 70-well worth the cost the first time I used it

[minimo]

Gotcha, strynboen. Thanks for the video. I will wrap my head around his for sure and try that out. Appreciate it!
Btw, that's a sweeeeet 400! Well done! I'll have to check out your thread if you have one for that one.

MoMo, if you followed my last build, Harbor Freight is one of my favorite shops and I totally didn't think about them having an ultrasonic cleaner. Thanks for the shout. Will use the next 20% off coupon opportunity to make that purchase! Boom!

[strynboen]

i have both threds in my signature..just klick
..they are gett old..since i Work slovly on more bikes at same time...400 four cbx 1000 and a lot of mopeds..dax puch Yamaha ...

[minimo]

Cool cool, strynboen. We have bikes in common. Cool bikes! Yeah, the 400F does look pretty cool as stock. I just wish my headers were in a lot better shape - they are heavily rusted/pitted.

I like your custom cam chain bolts - may have to inquire about that down the line... I was made aware of the cam chain tensioner adj bolt that seized and snapped off and failed attempts to extract it from my 400 engine. I was told not to worry about it and just try to see if the engine will turn over. We'll see how it goes!


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[strynboen]

its at total rebuild if the bolt is snapped... ..there is a small chance to take the engine aut..and drill the bolt..and free the tensioner up..but it hard to drill vitaut to damage the parts...not possibel in the frame..i did drill the bolt in mine..it gave a small dot mark in the shaft..but im a rutined maskinist,,,so find somone prof to help on that job

but get the bike running.is a good idea
.to thek the transmision and cylenders for Wear..and thek carefull the damp from the breather..a bad seighn/(as you already nov)

i had 2 of this bikes...they are often more vracked then the 550 and 750..its a slow bike..and most got so bored of them,(back then)( now daus they are fine for city riding),so they did not take care..and vreacked them
..but its still the nicest looking..and best running engine..if all bugs is cures....and there is just a lot to fix in this engines..bad oil vear them aut..but still a super Classic,, all Honda fans must ovn one...or 2

[minimo]

Hahaha! Thanks for that, strynboen.
I do like the look of this 400 for sure. I'm working to get this to run but not without some obstacles/distractions to come in the way like...

The hex head on the tappet cover stripped and that opened up a can of worms that ultimately brought out my right angle grinder. Luckily didn't grind into the valve cover or other parts. Thanks for the replacement tappet cover and gaskets, goldarrow!
Other funny distractions like fixing cracks on the headlight bucket

And rebuilding left and right controls. Stripped down the master cylinder and front brake assemblies and about to rebuild those.

But to stay on target, my next step is adjusting the valves, which are a little different from what I'm used to seeing on my 550. On the 400F, there's a 9mm nut that loosens and the adjustment is made by turning a tiny square stud bit

I don't have the correct tool to adjust the tappets but for now, a set of some needle nose pliers are doing just fine, I think. I read about using a roll pin that fits just right and using the split on the pin to catch a corner of the square of the tappet which is enough to turn it securely. Might give that a shot.

Anyway, I figured this might be good enough to report for now. I haven't made a whole lot of progress so I'm riding that proverbial treadmill and I'm enjoying it.

[minimo]

If I'm correct on my measurements, the dimensions here for the Tarozzi fork brace (Tarozzi part # 22-0020; meant for a 1981 Honda CB400N) should adapt to my 400F, right?:

Tube Diameter: 33   
Mounting Diameter: 56   
Center Distance: 172

Anyone actually have a Tarozzi brace they were able to get fitted onto their 1975 400F? I would LOVE to know!

[minimo]

Still no solid news on adaptability with the Tarozzi fork brace... FastFromThePast said that they could not guarantee a correct fit...
Think it might be worth trying? I'll check on their return policy (I nvr feel good about returns, but this could be worth a shot).

Meanwhile, the 400F is getting showered with parts from the darkside...

And I'm still on the fence about going with individual pods on this one. The bike didn't come with the plastic air box manifold so i checked into eBay and got this just in case

I have the air filter ready to fit so I think I'm real close to the point of attempting to turn the engine over. Gonna stick with the old coils and points and condensers and twist some new NGK boots on the old wires to see if that all checks out.

Busy at the daily grind, long hours and some weekends but chipping away at this. Huzzah!

[MoMo]

Unless you don't mind spending hours jetting your carbs stick with the stop set up...  One advantage to pods though is the carbs are much easier to get on and off every time you need to make a change...Larry

[strynboen]

forks is not made for boots..but i have used them on more cb..so it can be done..
use the konnektor box..and put a BIG pod at the back side..then you got the best from both..and it can be set up looking cool...and yes this bikes is hell to get running on pods

[minimo]

Thanks, MoMo. I'll try sticking to stock at the start of this build.

Strynboen, the fork gators are mainly for aesthetic purpose; to cover the shiny silver as I am going all black on this build. I'm not sure what the fit will be like but I'll get them on there somehow.

RE: TENSIONER SETTING BOLT
Honda Part: 90016-286-000

The PO (ehem) had broken the bolt head off and made attempts at extracting the remains of the tensioner bolt threads that might be seized in the lower case... I was wondering if I took a set of needle nose Vise-Grips to clamp down on the remains of the bolt and turned it out from underneath - is the bolt accessible from the underside? Or, shall I continue with the attempt to extract the bolt with my trusty Grabit Pro set to exhume the bolt... Or, I can very carefully try to obliterate the threaded parts by step-drilling out from the bolt's center...
I realize this tensioner bolt is unique so I want to try to preserve the case threads as best as I can.
Any good recommends?