Topic: Hi from an old guy with a CB400f question!

[loudrichard]

Hi everyone I am new here, and I am re-starting to finish the 400/4 part restoration/tidy I started and left unfinished 15 years ago…. I have nearly found all the parts I carefully put away when we moved house, but I am 70 and I have forgotten a few things.   My  question is that I have the original exhaust system that I have not fitted since it was re-chromed, 15 years ago and the clamp where it goes onto the silencer is made up of four parts, the clamp itself 18372-319-300 , the round gasket seal 18391-292-300, a M8 x 25 bolt 92000-08025-OA that goes into a captive nut on the clamp, and a round ‘special M8 nut’ part no. 90315-286-300.  Where does the special nut go?  In the middle of the clamp to restrict the clamping? Or on top of the captive nut?  I think the special nut is basically a round piece of steel with an M8 thread through it, so no flanges for a spanner/wrench.    I can’t remember, so could any of you helpful experts tell me? Or go look at your untouched original bike and figure it out?  I would be very grateful!

[newday777]

Welcome aboard the forum and back to your restoration.
What year is your 400F?

The nut(#568) goes on after the captured nut on the clamp.

These fiches are from CMSNL in the Netherlands

[loudrichard]

It is 1976,  in red.  I look daily for the missing parts that are in my 4 garages somewhere.... I find one or two each day. I have the parts books located now. Problem is I run the HondaXL250K3.com website and I have a few of these and a fair number of spares into which some 400/4 bits have been absorbed.....! Like today I found two of the 8 tapped covers, nicely clean and polished....just 6 more to find!  Thank you for the reply.  I wonder what the special nut is for,  and how it is supposed to be tightened? I have not yet found the part, so I will probably just make one on my lathe in stainless.
Regards,
Richard in England (The Old England)

[MD]

Welcome from across the pond,

-MD

[Tim2005]

Welcome aboard too. England here as well. I am a little baffled by the special nut 90315-286-300 too (photo of one attached), it is 8mm but the clamp has two 8mm bolts & the parts list only has one of these nuts. As it locks a clamp bolt in place, I can only think it is an early form of anti-tamper device to discourage owners from removing their silencers. Other ideas welcome though.  Anyway, I think you can get away with not having one fitted

[loudrichard]

Thank you for replying and for the input. I think that perhaps the special nut is to cover the exposed threads which will get hot and cold as they are on the exhaust,  and this nut may just keep the bolts exposed threads from becoming rusty where the threads protrude.  It is an oddity,  but someone may know for sure. Meanwhile I found more missing bits today, but it is raining and I need to empty some stuff out of the garages before I can delve.  I find
I have 4 tanks and 9 side panels. I also found a complete engine.   My hydraulic ramp is a a German one I bought years ago from a closed BMW bike dealer.  I  have got it working again, new seals and oil, but instead of red like the Chinese ones it is orange. The top was really awful with crap and I have stripped it and primed it ready for a repaint before popping the bike back on it.  Now I await the orange paint,  on order from eBay.   One of my tanks is Varnish blue and I have two left blue side panels, I'd like a right, but seems they are hard to find now.  Otherwise I will paint a spare one. Parts were easier to get 20 years ago, though there are many more pattern parts than there used to be. 
Cheers Richard