Topic: Silly exhaust question - CB400f

[normalguy]

Okay, this may seem like a silly one:

Why are the 1 and 3 pipes on the CB400F 4-to-1 exhaust bolted to the collector, but the 2 and 4 are welded?

[Bodi]

Hmm. Mine (the stock ones) are all welded, 1976.

[normalguy]

So mine aren't stock!  I knew the muffler was a MAC (or the like) megaphone.  Didn't know about the header.

[normalguy]

Just found this picture of what I assume to be a stock 75 CB400f from motorcyclistonline.com.  Brackets on 1 and 3.   Maybe the exhaust on my 76 was pulled from another year?  Regardless - why would they do that on _any_ model?

[heffay]

would like to be able to answer but... i've wondered the same myself.   i was thinking that it might ease installation i.e. more flexible than a completey welded unit.

[oldbiker]

Your exhaust set up IS stock. The header has pipes 2 and 4 welded to the collector and pipes 1 and 3 join the collector with gaskets and clamps. This is shown clearly in the parts list and parts are still available from 'David Silver Spares' in the UK. As far as I know the CB400f was never supplied new with all welded header/collector.
David Silver has a silencer (muffler) which is a very good copy of the original for 42 British pounds.
As to why Honda designed the exhaust this way, I can only guess that difficulties in welding 4 pipes accurately in position without distiortion due to the heat of the process led to problems in spacing of the pipes when fitting the header to the cylinder head. Alternately, welding 4 pipes together at the collector with such close spacing might have been difficult. Have you ever tried welding in confined spaces?

[Uncle Ernie]

I tried some in a closet once. It was hard because I could only see after I started welding. My face got really hot. I have to use a braille keyboard.

[Einyodeler]

Whats up with the the braille keys on drive-up ATM`s?

[normalguy]

Now you're just making fun.   

[Bodi]

Hmmm again!
The stock pipe that came on the bike I have (that suffered in a crash and has the #4 pipe mangled) is as you describe, with 2 clamps. The replacement I bought from another 76 where the owner installed an aftermarket system (this was in 1980 or so) is welded. It may be a copy of the stock system but if so the collector box is almost identical to the original, however it's rusted to crap while the original one still looks fairly OK except for the mangling.
Jeez, if Honda had made the #4 pipe removable it would have been a bunch easier to fix a scraped exhaust.

Why do we park on the driveway, drive on the parkway, pay tolls on the freeway, and have to be sober on the highway?