Topic: 1975 CB 400 Newbie

[CTCB]

Opinions, Questions, snarky comments and concerns all welcome!

I picked up a very clean 75 400F last weekend from my Godfather.  I know very little about motorcycles and even less about operating them.  The closest I ever came to riding was when I nearly purchased an orange? cb350 nearly 14 years ago…i couldnt afford it AND a diamond engagement ring.  The love of my life won out and i have no regrets ...but man those orange 350s sure look cool!

Fast forward to last weekend when I saw this bike out in front of my Godfathers house with a for sale sign..I couldn’t let pass the opportunity to pick up this sweetie.  It has just under 24K and is what i would consider very good condition.  My Godfather takes care of all his possessions and his pride in ownership really shows.  I have every receipt, record of every service and repair.  From what I can tell it is 100% original and i have everything that was ever taken off this bike including mirrors, fender brackets, air cleaner, old spark plugs, coil and points. I have articles and catalogues…he documented absolutely everything…the only thing I don’t have is the used motor oil.  Seriously.   So here is what I am thinking and let me know your thoughts. 

1. Fuel tank-  the last time the bike ran was in August 2002.  The last thing that was done to it was that it was “Kreemed.”  Thankfully he kept the directions bc it seems to be failing in places.  A large chunk of the liner came off near the filler neck.  When you feel inside the tank you can tell that its starting to peel in places. There was a small amount of fuel in the tank so i removed it (the tank) from the bike, drained and flushed it with some clean fuel and now its empty.  Im torn between dissolving the liner with acetone as per the instructions or just filling her up and continuing with the project.  Im a fan of the KISS Modus operandi so I’m leaning towards leaving well enough alone and pressing on.

2. Carbs.  This looks a little more technical.  Daaang four carbs really?  I nearly had blew my mind trying to fix the one carb on my log splitter earlier this year.  When I jacked that up beyond all repair i bought one on amazon…two days shipped to my door…I’m thinking in this case that is not an option.  I know for a fact that one float needle (not sure which) is sticking open and leaking fuel.  What do i do with this?  The records show the carbs were cleaned at 23,924…that was 14 miles ago…but it was also in 1996!  my guess is the cleaning messed something up.  So far as i see it my options are 1. Read each of the service manuals carefully and try to figure it out.  2. Buy a case of beer for my buddy that may know more about this than me 3. take it to someone who knows what they are doing 4. combination of 1,2 & 3. 

3. Brakes.  The first headache occurred when trying to wheel it off the trailer…front brake locked. Thanks God I didn’t drop it because I was close a couple times.   I wrestled it into the garage and had to loosen the entire caliper to get the front wheel to turn.  Besides the fact that the caliper is stuck it looks like it needs new pad and possibly a complete rebuild.

4. Exhaust.  This one is a little more straightforward.  the headers look good, just a little worn.  The muffler has been patched but is original.  Ive scoured the internet and can’t find an original muffler. This may be one thing that has to be reproduction. How much does that matter?  not sure, I’m trying to keep it 100% OEM, but not sure that is feasible.

5. Battery, any suggestions? again trying to stay original.

6. Tires.  They had been replaced once in 1981.  They look decent but have a little dry rot…I’m thinking its better safe than sorry and outta be replaced.  What was OEM?

Thats all I can think of for now and covers most of the majors.  Im really pretty excited about making this thing really shine and purr once again.  I honestly don’t know what my intentions are for it other than that. 

[innovativems]

Great score!  Love the 400’s.  On that tank you will want to strip that liner.  Castellated has a new product for removing tank sealer that I’ve been wanting to try.  Just protect the heck out of the paint on the tank.

The carbs aren’t bad if you just tank your time. 

These are great bike.  The front brake means you need to rebuild your caliper and flush out the bad fluid. 

Also check out the cam chain adjuster is free


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[SOHC4 Cafe Racer Fan]

No question. Strip the old degraded liner and start anew. Use something that will hold up to today's Ethanol-mixed gasoline like Caswell epoxy liner.

[SOHC4 Cafe Racer Fan]

I’ll offer you some different advice about the tank...

Buy 4 gallons of Acetone and fill the tank. The Acetone will eat the Kreem, and what it doesn’t dissolve, you’ll be able to shake loose and pull out by hand (drop a dozen or more hex nuts in the tank after the soak to help dislodge the remnants).

Instead of the normal “liners” I’ve used recently a product called Master Coat. It’s a moisture cured urethane and so far, it’s pretty darn impressive stuff. It flows better than Caswell, dries thinner, and covers better. Costs the same for a quart of it as Caswell, but you won’t need a full quart to line the tank.

Carbs - do NOT buy and use “rebuild” kits. More than likely, your carbs are leaking due to having sat, and the internals/o-rings are simply dehydrated. Fresh fuel, let gas get into the bowls, and then rap the body of the carbs with the handle of a screwdriver to help the floats settle. If there’s debris from the liner reaching the carb, then drop the bowls and empty them.

Use care when installing the bowls back onto the carb body. The screws will strip the threads if you over-tighten them.

Brake - with the caliper still attached to the brake line, remove the caliper from the bike. Fill the reservoir with fresh fluid, using care to protect the tank paint. Pump the piston out of the caliper. Drain the fluid completely. Replace the master cylinder with a new repro unit. It’s easier than rebuilding the old one, guaranteed to work, and costs less than $50. Replace the piston seal (it’s the O-ring in the caliper body) and make sure the piston is spotlessly clean (the seal groove too!). Fill everything with new fluid, bleed the system, and go on.

Battery - Scorpion AGM is a popular, correctly sized battery that is very cost reasonable. Make sure you hook the cables up correctly 

Tires - Bridgestone, Avon, Metzlers, and so on. Many to choose from, just no Dunlop retro crap tires please 

Exhaust - repro mufflers are available via David Silver Spares (check their website, they have a US location too). Not cheap, but available. The 400 exhaust is very elegant and hard to find in original, great condition.

Thanks for chiming in about the Master Coat.  I could not remember the name of the product.   I haven't used it, but it sounds promising.  Caswell can be tricky, because it is pretty thick and you need to move it around to distribute it well.  If you let it sit, it will pool and create a very thick layer decreasing your tank volume.

[CTCB]

Hey y’all, thanks for the tips. Hope to start in on the tank tomorrow.  Nothing like a nice acid bath, sounds caustic!


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[CTCB]

Ok good. What I have in mind is a combination of cellophane and masking tape.  The paint is in good shape but I’m a little concerned a full masking job may pull up or damage the decals.


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