testy

Author Topic: CB400F Light Winter Resto  (Read 134 times)

0 Members and 1 Guest are viewing this topic.

Offline jakec

  • Hot Shot
  • ***
  • Posts: 363
CB400F Light Winter Resto
« on: November 05, 2018, 01:10:14 pm »
I changed the title of this thread because I figured everyone's tired of dual disc threads, and this winter project has a wider scope than just that, anyways.

I'm getting ready to start on my 400 as soon as I finish up this CL175 that I've been working on. The engine is out and i'm currently debating going down to the frame for paint. I thought I was was goingg to rebuild with new cases but for now I think I'm going to start with a head gasket. I will also be getting another 400 that I found for a good deal down in Portland. Not as clean but it has a dry engine with about 8,000 miles. I'm debating swapping the dry engine into the nicer bike.



Anyways I'm doing my research for the front end stuff right now and I needed a place to organize the shopping list. I also have questions. Right now here's what I have:

1. Mike in NY says he's got all the brake parts I need as well as a fork lower for $150. This seems like a fair deal to me considering most nice calipers on ebay ask $100 and I'm getting all the small bits too.



I've read that most people go to a GL master cylinder for a dual disc swap, is that because the piston diameter is larger? Those seem to go for $60+ on ebay in nice condition. What if I had only one disc but upgraded my lines to stainless and went to an MC with a larger piston? Would that improve grab a bit?

2. Next I've found a fork seal and dust cover set from 4into1 tha's cheap. Normally I would get Honda parts but 4into1 always seems to be high quality.

3. RT emulators, I have read a ton about them here and it seems like those are the best to get and use with straight rate springs. I've also read that you can use the stock springs because the ~3/4" difference of the emulator will act as preload on tired springs. Is this sound logic? I wouldn't want to spend $160 on emulators and not able to feel the benefit because of old springs. But I will save myself $150 on new springs if I can.

4. All Balls, seems pretty straightforward.

5. Fork brace, I would like to get a stainless "period" looking brace, but I don't want to pay $250 for a tarozzi one so we will see if anyone has any good suggestions.

6. Swing arm bushings.
« Last Edit: November 07, 2018, 09:12:36 am by jakec »
1975 CB400F
1972 CL175 K2

Offline slikwilli420

  • Master of Disaster
  • Master
  • *****
  • Posts: 1,854
Re: CB400F Front End & Dual Disc
« Reply #1 on: November 05, 2018, 01:21:16 pm »
These are light bikes compared to their bigger 550/750 brothers. Im a huge fan of dual disc, and with that in mind, I would keep this one single disc. Find a bit bigger diameter disc and adapt a better caliper (AP Racing, Spondon, Grimeca) and enjoy much improved braking without adding a lot of front end weight to what is a currently a very nimble machine.
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
Rickman CR Parts Kit Refresh: http://forums.sohc4.net/index.php/topic,154837.0.html
AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
'76F CB750 Patina Redemption: http://forums.sohc4.net/index.php/topic,174871.0.html

Offline jakec

  • Hot Shot
  • ***
  • Posts: 363
Re: CB400F Front End & Dual Disc
« Reply #2 on: November 05, 2018, 01:32:04 pm »
I do find the braking to be a bit soft (with recent master rebuild but no upgraded lines yet). I wanted to improve the braking but keep the stock/period parts, at first I considered the 450 triple/550 forks, but I don't want to lose the stock look.. anyways I thought this would be a fun challenge with unique results. Do you think the added weight will have a noticeable negative affect worse than keeping it stock? I also considered mildly drilling the rotors.
1975 CB400F
1972 CL175 K2

Offline Tim2005

  • Expert
  • ****
  • Posts: 896
Re: CB400F Front End & Dual Disc
« Reply #3 on: November 05, 2018, 03:00:38 pm »
A lot depends on the fork lower you've been offered... is it a right-side 400f one with the caliper mount too? That's a very rare RSC part, and came with different damper parts and springs. If so, I'd use that, get a modern twin disc master cylinder (sizing is going to be tricky), drill the discs and add braided lines too.

If not, what is it?

Offline jakec

  • Hot Shot
  • ***
  • Posts: 363
Re: CB400F Front End & Dual Disc
« Reply #4 on: November 05, 2018, 03:10:11 pm »
It is a standard 400F left side lower. My plan was to mount it with the calipers inverted (it has been discussed in other threads here before). I found a couple users who have done it or seen it done in the past.

I thought I had it all worked out, the only modification being the speedo drive plate. But I had forgotten about the need to modify the asymmetrical fender. And Kevin (a user here) says I might need to shave the lower as well which I would not know how to do. He suggests I just get a moden caliper and lines. However I did want to keep the caliper stock / in appearance.
1975 CB400F
1972 CL175 K2

Offline Don R

  • My Sandcast is a
  • Really Old Timer ...
  • *******
  • Posts: 10,462
  • Saver of unloved motorcycles.
Re: CB400F Front End & Dual Disc
« Reply #5 on: November 05, 2018, 03:49:56 pm »
 CB360 forks are the same as cb400F and cheaper but still don't have the right side brackets.
If the things you own end up owning you, it's better to be owned by some cool things.

Offline jakec

  • Hot Shot
  • ***
  • Posts: 363
Re: CB400F Front End & Dual Disc
« Reply #6 on: November 05, 2018, 03:50:44 pm »
Can anyone comment on the emulators + stock springs combo? I wish I could find the thread but unfortunately there are about a million threads on the topic already. This thread contradicts that advice and says that you don't want to use the stock springs (says they wont even fit)

http://forums.sohc4.net/index.php?topic=156699.0
1975 CB400F
1972 CL175 K2

Offline robvangulik

  • Honda Fourever
  • Hot Shot
  • ***
  • Posts: 611
Re: CB400F Front End & Dual Disc
« Reply #7 on: November 05, 2018, 04:40:22 pm »
I think you are overthinking it all a bit.
When I got my 400 some 10 years ago (for free, the owner asked me if I wanted it or it would go to the scrapyard) I immediately decided to do with it what i previously didn't know how to, about 40 years ago, and make it FAST.
And that meant it had to stop fast too, so after fixing the bike to a riding condition, it took me a week to source a caliper and disc, and the next weekend it had a double disk! I welded the mountings to the right forkleg, drilled the discs, adapted the speedo drive and used the standard mastercylinder.
Of course it was an advantage that I had done this several times before on a 500, a 550 and a couple of 750's, the only real difference was the welding to the right leg.
I never felt the need to do anything to the front suspension than filling it with thicker oil, the roadholding is excellent, even at the topspeed of 183km/h on my gps, some 115mph.

Offline jakec

  • Hot Shot
  • ***
  • Posts: 363
Re: CB400F Front End & Dual Disc
« Reply #8 on: November 05, 2018, 05:04:54 pm »
Did you cut the caliper mounts off of another lower and weld it to your left lower? I see in the photo that you have three lowers so I assume that's how you did it. I can see how that eliminates some of the problems with my approach like the asymmetrical fender. However I see you also have the small steel tube at the end of the brake line on the left side caliper, did you bend that yourself to be the inverse of the other side?

Since I don't know how to weld I would have to find someone to do that for me (unless you're offering   ;) )
1975 CB400F
1972 CL175 K2

Offline robvangulik

  • Honda Fourever
  • Hot Shot
  • ***
  • Posts: 611
Re: CB400F Front End & Dual Disc
« Reply #9 on: November 05, 2018, 05:15:41 pm »
No, that is a normal right forkleg, so i'm able to put it back to standard if needed.
I modelled a clump of aluminium to fit.
I think welding over there will be cheaper than postage to Holland and back  ;D
Metal brakelines can easily be bent by hand.
Oh, and fender supports can easily be bent to fit properly too!
« Last Edit: November 05, 2018, 05:21:12 pm by robvangulik »

Offline jakec

  • Hot Shot
  • ***
  • Posts: 363
Re: CB400F Front End & Dual Disc
« Reply #10 on: November 05, 2018, 09:24:19 pm »
That is awesome that you were able to build one like that from scratch. I'm not sure that will be an option for me though. If you did bent the fender, shave the speedo mount, and bend the steel brake line then I think that's similar to the work that would need to be done through the approach i'm proposing.
1975 CB400F
1972 CL175 K2

 

;
Honda