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Author Topic: Honda Cb 400 Four 1977  (Read 3904 times)

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Offline Paulo Fonseca

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Honda Cb 400 Four 1977
« on: October 02, 2015, 05:52:55 AM »
Hi,

I'm Paulo from Portugal and I'm the new owner of a 1977 CB 400 Four that is in really bad shape and didn't run for more than 10 years.

Before I rebuild the bike, I wanted to know if the engine was working, so I cleaned up and unlock the carbs. One of them is leaking and they need to be tuned and it doesn't have the air filters, but was enought to put the bike running.

One of the problems I've found so far it's that the engine makes a noise when I put one gear in the bike and start to release the clutch. The noise keeps going with the bike running. Sounds like a rotating whistle (I will try to make a movie). Any idea?

I was expecting more of this engine ... compared with a CB 400 N from 19884, the four is much slower (I know that is not tunned), but this big difference in performance is normal?

The engine will be repaired in a mechanical, but as you have more knowledge of this engine, any suggestion is welcome. Common problems, improvements that can be easily made, ...

Thanks,
Paulo

« Last Edit: October 02, 2015, 06:00:56 AM by Paulo Fonseca »
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Offline calj737

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Re: Honda Cb 400 Four 1977
« Reply #1 on: October 02, 2015, 06:32:13 AM »
Whistling would not be uncommon with no airbox or filters. It would also make far less power.

You can download a manual from this site, and be diligent to perform the 3k Service.
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Offline Paulo Fonseca

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Re: Honda Cb 400 Four 1977
« Reply #2 on: October 02, 2015, 06:40:19 AM »
Thanks for the reply. The whistle cames from the engine, and it's only when I leave the cluch and running the bike, in neutro the engine don't makes any noise. It's like something spinning...

I've wrote that the carbs didn't have the filter because I suspect that it could cause less power, but it's a big difference. Does anyone ever run this to bikes that could tell something about how they run?
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Offline vames

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Re: Honda Cb 400 Four 1977
« Reply #3 on: October 02, 2015, 08:21:32 AM »
A well running cb400four should produce a lot more power than the 1980s cb400twins. Running the 400 without the airbox will inform you that the engine runs, but it won't tell you much about its capabilities.
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Offline Don R

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Re: Honda Cb 400 Four 1977
« Reply #4 on: October 02, 2015, 08:32:10 AM »
Without the airbox mine needed 1/4 choke to ride it. It is possible to rejet the carbs to run without the airbox but it's easier to just put one back on.
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Offline calj737

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Re: Honda Cb 400 Four 1977
« Reply #5 on: October 02, 2015, 08:36:08 AM »
I am speculating the noise you are describing is the cam chain.
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Offline Paulo Fonseca

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Re: Honda Cb 400 Four 1977
« Reply #6 on: October 02, 2015, 09:24:47 AM »
I can year the noise even when release the clutch and use the brakes so the bike don't move.
I will make a movie on the weekend.
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Offline Duanob

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Re: Honda Cb 400 Four 1977
« Reply #7 on: October 02, 2015, 09:39:19 AM »
Awesome and Welcome! No offense but that is the ugliest 400F I've ever seen  ;D You've got your work cut out for you but the board can help with any of it. Any plans for it? Restoration? Cafe?

The whistling noise and lack of power might be contributed from an air leak in the intake somewhere. When idling spray some ether (starting fluid) around the intake and see if it changes engine speed.

I've been to Portugal and absolutely loved your country. The Portuguese are a super friendly people. And Lisbon is a beautiful city. Sorry for the gushing but I am reminded I haven't travelled anywhere outside the US and Canada for 3 years. Time to go see more of the world. On 2 wheels will be even better!
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Offline Paulo Fonseca

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Re: Honda Cb 400 Four 1977
« Reply #8 on: October 02, 2015, 11:32:26 AM »
Hi Duanob

Thanks for the coNot a valid %s URLmpliments about my country and the portuguese people. Although a samll country, we have sll kind of landscapes,  mountain, land fields, beach , snow ... and yes, we are very friendly.

I like to think about myself as the saver of this bike ...it's not preatty right now, but will be soon, as a cafe racer (with most of the original parts)

About the noise, here it is the video
« Last Edit: October 02, 2015, 12:13:09 PM by Paulo Fonseca »
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Offline flybox1

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Re: Honda Cb 400 Four 1977
« Reply #9 on: October 02, 2015, 11:36:20 AM »
go on and save that bike, Paolo!
as mentioned, get the honda manual and be diligent in doing all of the 3000mi maintenance items.
start a build thread in that section of the forum, and keep us updated with your progress, photos, and questions.

good luck!

~fly
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Offline Paulo Fonseca

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Re: Honda Cb 400 Four 1977
« Reply #10 on: October 03, 2015, 07:46:10 PM »
Anyone can help with the noise? Video above
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Offline MoMo

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Re: Honda Cb 400 Four 1977
« Reply #11 on: October 03, 2015, 09:14:18 PM »
will the bike move forward? welcome...Larry
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Offline Paulo Fonseca

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Re: Honda Cb 400 Four 1977
« Reply #12 on: October 04, 2015, 01:24:34 AM »
Yes, the bike runs and all the gears work fine. I just use the brake to make the video and show.the noise.
« Last Edit: October 04, 2015, 07:28:37 AM by Paulo Fonseca »
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Offline Redline it

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Re: Honda Cb 400 Four 1977
« Reply #13 on: October 04, 2015, 05:45:40 AM »
the reflector on the front fender is sweet.
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Offline MoMo

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Re: Honda Cb 400 Four 1977
« Reply #14 on: October 04, 2015, 06:14:24 AM »
Certainly sounds like a bad bearing, either clutch or trans.
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Wobbly

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Re: Honda Cb 400 Four 1977
« Reply #15 on: October 04, 2015, 07:01:17 AM »
Quote from: Paulo Fonseca on October 02, 2015, 11:32:26 AM
Hi Duanob

Thanks for the coNot a valid %s URLmpliments about my country and the portuguese people. Although a samll country, we have sll kind of landscapes,  mountain, land fields, beach , snow ... and yes, we are very friendly.

I like to think about myself as the saver of this bike ...it's not preatty right now, but will be soon, as a cafe racer (with most of the original parts)



Welcome to this site. I went to Portugal in 1982 to go to a mc meeting in Faro and had a great time. Portugal was very inexpensive back then. Nice place to ride a bike.




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Offline Paulo Fonseca

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Re: Honda Cb 400 Four 1977
« Reply #16 on: October 04, 2015, 07:35:05 AM »
Hi wobbly, when I made 18 years old I made 800k on a bike to went to the faro "international" bike meeting. .. its great, I hope ta have this cb 400 four working soon to make the same trip with it. Loved your pictures :) makes.me.want to go there write  now
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Offline Stev-o

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Re: Honda Cb 400 Four 1977
« Reply #17 on: October 04, 2015, 07:36:26 AM »
Welcome from Texas. 
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Offline 754

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Re: Honda Cb 400 Four 1977
« Reply #18 on: October 04, 2015, 08:01:51 AM »
Take the clutch apart to check it, and if there is a way, check that the topend is getting oil to the rockers..
 Pull off some of the rocker covers..see if it's oily in there.
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Offline Paulo Fonseca

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Re: Honda Cb 400 Four 1977
« Reply #19 on: October 04, 2015, 01:59:19 PM »
 I also would say that the noise came from the clutch, because we can ear it with the bike stoped

Thanks for the welcome.
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Offline BomberMann650

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Re: Honda Cb 400 Four 1977
« Reply #20 on: October 04, 2015, 03:37:54 PM »
Quote from: Redline it on October 04, 2015, 05:45:40 AM
the reflector on the front fender is sweet.

I thought it was supposed to have a red&green lens to help identify port and starboard sides?

CoolBoat400
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Offline Redline it

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Re: Honda Cb 400 Four 1977
« Reply #21 on: October 08, 2015, 09:41:01 PM »
Quote from: BomberMann650 on October 04, 2015, 03:37:54 PM
Quote from: Redline it on October 04, 2015, 05:45:40 AM
the reflector on the front fender is sweet.

I thought it was supposed to have a red&green lens to help identify port and starboard sides?

CoolBoat400

CoolBoat Patend that like now! That might be as intense of an inventive design at least as much as what Led's did for the mono filament light world, shoot, make it an led. And make the whole front fender a quick release and you could mount that fender on your bow, because if you left it on in the parking lot, it'd be gone sure as anything. That chrome, wouldn't it be also a radar target for foggy days? They'd probably redesign the entire highway system just like a port...no more stops signs. I'd buy one. 
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Offline BomberMann650

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Re: Honda Cb 400 Four 1977
« Reply #22 on: October 08, 2015, 11:03:54 PM »
Quote from: Redline it on October 08, 2015, 09:41:01 PM
Quote from: BomberMann650 on October 04, 2015, 03:37:54 PM
Quote from: Redline it on October 04, 2015, 05:45:40 AM
the reflector on the front fender is sweet.

I thought it was supposed to have a red&green lens to help identify port and starboard sides?

CoolBoat400

CoolBoat Patend that like now! That might be as intense of an inventive design at least as much as what Led's did for the mono filament light world, shoot, make it an led. And make the whole front fender a quick release and you could mount that fender on your bow, because if you left it on in the parking lot, it'd be gone sure as anything. That chrome, wouldn't it be also a radar target for foggy days? They'd probably redesign the entire highway system just like a port...no more stops signs. I'd buy one.

Forge an Anchor Shaped kickstand and call it Cafe' Nautique.

Lay teak on top of the tank and make a custom fit fuel cap.

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Offline Rob69

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Re: Honda Cb 400 Four 1977
« Reply #23 on: October 09, 2015, 12:26:35 AM »
Take the clutch apart and inspect the bearing. It should rotate smoothly D ; no notchiness or binding should be felt. While you're in there inspect everything for wear and/or damage, as per the service manual.

Sent from my C6730 using Tapatalk

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