Hello!
I'm excited to join this group. I'm resurrecting/restoring/reviving (pick your r word) a 1975 CB400F. This forum has been very helpful so far. Here's a bit about the bike and what I've done (a long first post I suppose):
'75 400F - 5500 miles, got it from a close friend's dad. He was the original owner. He didn't modify anything on the bike.
Rebuilt the brake master cylinder, new caliper, brake hoses. (the old brake fluid appeared to leak past the piston seal in caliper before solidifying...I tried to get the old brake pads out then said heck with it).
New battery, spark plugs, air filter, oil and oil filter. I improvised for that little foam piece under the air filter. The old one crumbled on contact.
The carbs, ah yes, the carbs. 2 of the 4 throttle slides were 'glued' inside the carb body. There was also what looked like used motor oil in the float bowls but it was solid. Cleaning everything required a bit of soaking and scrubbing (with nylon brushes, no metal). I was able to clean and re-use the jets and freed up the throttle slides eventually. For one of the slides, it looked like someone tried to take a a screw driver and pry it up as there were grooves at the bottom edge. I found a replacement on Ebay as I think these grooves might mess with the operation of the carburetor. I decided to discard the old slide in favor of a smooth new one.
For the vent lines between the pairs of carburetors (10-15mm long, not sure the diameter but small), I went to the hardware store and bought fuel line for a gas gardening tool.
Looking back, it was really hard to undo the throttle cables because the 2 throttle slides were stuck, preventing the full throttle motion. After cleaning, its a breeze undoing the throttle cables (to look at the starter switch...)
Replaced the overflow hoses under the carburetors, the vent tubing, and the bigger engine breather tube.
The muffler. The old one had a 2 inch x 1 inch hole in the chrome on the underside closer to the junction with the headers. The motorcycle was loud when it started up. I bought one of the 'reproduction mufflers' out there but it did not fit as well I believe it should. Not quite a Honda fit.
I purchased a genuine Honda muffler gasket and it fit well on the exhaust junction underneath. However, the muffler didn't fit over the gasket, or even start to fit over the gasket (I'd understand if it started to fit and needed pressing on). Common sense would be to take the muffler back but its a holiday weekend and I wanted to exercise the bike. I took a dremel to lengthen the notches in the muffler and pliers to spread apart the 'tongs' or whatever you call them. I was able press on the modified muffler using a ratcheting strap. I'm not sure I recommend this (modifying the muffler that is).
The headlight. It didn't work and I traced it back to the starter switch as I've read in this forum. I pulled apart the switch (undoing the throttle cables was easier now) and found shards of plastic and a ball bearing and spring. I'm still researching how to fix this ($100 or so for another part is holding me back at the moment).
Where I'm currently at: I ride it around the neighborhood with a big ole smile on my face. Need to fix the starter switch. I want to check engine compression. Sync the carbs. Need new tires/tubes, chain. Service the forks.
A note about parts: I've seen a couple of instances where parts from online vendors aren't quite the same as stock Honda parts even though they say the parts should fit. The muffler is one, the upper brake line (new is ~2 inches longer than the original and does an unhealth 'S' bend behind the headlight), the oil filter gasket is another. Its something I've learned.
