Author Topic: My 1975 CB400F project: strange noises at idle (Read 19708 times)

Joel · « **on:** June 12, 2008, 06:05:05 PM »

I was able to get my first ride on the bike today even though I don't have plates or insurance yet. I went into the DMV to get the title process started and they informed me that a police inspection was necessary. I went to the local sheriff's office to find out they had closed a half-hour before I arrived.

The paperwork will have to wait until after I get back from vacation which will add a $21 delinquent fee. Booo.

It was a pretty good ride, especially considering it was my first real ride on any motorcycle at all. The only things I was concerned about are two noises from the engine. One is what I'm assuming is cam chain noise. I tried the adjustment procedure in the 350/400 service manual I downloaded but it didn't seem to do anything. I found a link to a UK 400 owner's page (http://www.cb400f.btinternet.co.uk/cam.htm) that has a couple other suggestions I'll be trying out to see if they'll fix it.

The other noise is a whine during throttle application that goes away when the throttle is released. I've never been around one of these fours before so it may just be a characteristic of the motor.

I bought a tail light off eBay that I believe came off a 400 twin. It's basically square with a slight V-shape along the bottom edge. I cut a piece out of 26 ga steel and bent it into an L-shape to mount it to the stock fender location.

I've got some original turn signals to replace the hodge-podge set currently on it but I haven't been able to find a headlight yet. When I figure out a headlight solution, I'm planning to do some serious work on the wiring to get rid of the mess of wires currently hanging next to the forks.

Joel · « **Reply #1 on:** June 29, 2008, 05:21:34 PM »

I got a $0.99 set of stock fork tube assemblies on eBay. Came to under $25 with shipping. Hopefully they'll be as straight as the seller insists they are. Now I need to order the parts needed to rebuild them so I can take care of that when they get here and get them on the bike quickly. I've seen progressive rate fork springs mentioned in a thread. I checked the links given but didn't see any for the 400F. Does anyone have a good source for them?

Hush · « **Reply #2 on:** June 30, 2008, 04:27:22 AM »

You're a scary man Joel, just looking at that tangle of wires (that should be safely hidden from the world in a headlight bucket) gives me the heebie jeebies!
I didn't even know Honda made a CB400F SOHC 4 cylinder!
Guess we never saw too many of them down here in the lower Pacific Islands.
Mind you the 500 and 550 were rare beasts too, probably because of the prohibitive cost of a new Honda as opposed to the much cheaper Kwakas, Yammies and Spooks.
Are you going to do an original restore on your 400 or just patch it and get some fun out of it?

Joel · « **Reply #3 on:** June 30, 2008, 09:12:16 AM »

Yes, that scary bundle has worked surprisingly well so far. The wiring is next on my list but I'm still looking for a stock headlight bucket to put it in. The headlight on it at the moment looks like a chrome universal piece. I don't think there is enough room inside it for everything. I'm planning on doing some work right away but still riding it. I should have some time during the snowy winter months to fix up other things. I'm going to go toward original but it won't be exact.

tom8Toe · « **Reply #4 on:** June 30, 2008, 09:47:12 AM »

Bump

as I'm interested in following the project.

Joel,

Looking forward to seeing and reading more as your project comes along.

Cheers... Here to you

br,
Chris

kghost · « **Reply #5 on:** June 30, 2008, 12:11:56 PM »

Heres a suggestion for you regarding the tail light.

The 750 brackets and tail light are virtually the same....with the exception of the lower mounting hole.

The 750 has two lower mount holes....the 400 only has one.

The good news is that the one hole on the 400 is in the middle, whereas the 750 has two, one on each side.

If you get a 750 tail light bracket and drill a hole in the lower attach in the center...your golden.

Joel · « **Reply #6 on:** July 06, 2008, 01:05:45 PM »

Along with the on-throttle whine of the engine, there seems to be some slop in the driveline between on and off-throttle while the bike is in gear and the clutch is out. Some of it may be the chain but I'm wondering if the whine and some of the slop is being caused by the primary chain in the engine. I've also noticed that with the engine off and the bike in gear with the clutch out, it will roll back and forth about 4 inches or so until there's some resistance.

malcolmgb · « **Reply #7 on:** July 06, 2008, 01:34:15 PM »

Quote from: Hush on June 30, 2008, 04:27:22 AM

I didn't even know Honda made a CB400F SOHC 4 cylinder!

where have you been all these years!

Hush · « **Reply #8 on:** July 06, 2008, 09:34:29 PM »

In NEW ZEALAND where we didn't get too many of those 400's!
But I'll definately make room in my shed for one if I find one.

gregk · « **Reply #9 on:** July 07, 2008, 07:18:55 AM »

Joel

My experience with these motors is the cam chain adjustment gets "tired' or seized after sitting for some time. You can take the bolt out of the top of the adjuster and manually help the spring with a small screwdriver or some such tool. After you have loostened off the pinch bolt. There is a small hole in the block which allows access to the top of the automatic adjuster. start the motor and press lightly down with the screwdriver and you will be able to feel (and probably hear) the chain adjuster move. This will confirm that the aduster is moving and not seized. I think that after all those years, the springs must get a little tired and don't do the job of taking up the slack on the cam chain.
You don't want to know what the alternate is!

Good luck

Greg

Joel · « **Reply #10 on:** July 11, 2008, 07:43:58 AM »

I've got a new handlebar to go on probably at the same time I swap the stock length forks I bought on. I'd planned on getting new grips because I wasn't excited about the ones on it. Any suggestions on where and what kind are good?

Also, the throttle sleeve is, of course, glued inside one of them. Should I even bother trying to get it out or just look for a new sleeve as well?

Has anyone had experience with the Leak-Proof fork seals? I plan to rebuild the forks I bought off eBay and I've been leaning toward using a pair of them.

troppo · « **Reply #11 on:** July 11, 2008, 07:47:11 AM »

With your grips just buy some grips for push bikes, generally the same size, usually made in the same factory and a hell of a lot cheaper.
Just cut the old grip off the throttle sleeve.

.RJ · « **Reply #12 on:** July 11, 2008, 08:31:48 AM »

Quote from: Joel C on July 11, 2008, 07:43:58 AM

Also, the throttle sleeve is, of course, glued inside one of them. Should I even bother trying to get it out or just look for a new sleeve as well?

Cut the sleeve off, clean up the tube and put a new sleeve on with hairspray or spray adhesive - if you have an air compressor, use some pressure to 'expand' the inside of the grip as you slide it on to the tube or handlebar.

Joel · « **Reply #13 on:** July 11, 2008, 09:16:01 AM »

Quote from: troppo on July 11, 2008, 07:47:11 AM

With your grips just buy some grips for push bikes, generally the same size, usually made in the same factory and a hell of a lot cheaper.
Just cut the old grip off the throttle sleeve.

Does the right-hand grip need to be larger to fit over the throttle sleeve? I figured that was one of the differences between motorcycle grips and bicycle grips.

troppo · « **Reply #14 on:** July 11, 2008, 09:21:33 AM »

well mine fit, right hand side took a little more convincing but the do the job and look right.
And theres about $20 difference to boot, i made a not of the manufacturers name and looked for it next time i went to a bike shop, half the packs had the same name, looked the same but cost a heap more

.RJ · « **Reply #15 on:** July 11, 2008, 09:50:20 AM »

I've never paid more than $20 total for a set of motorcycle grips. I'm partial to the grey renthals.

CBGBs · « **Reply #16 on:** July 12, 2008, 04:48:31 AM »

Hi Joel,

I'm a registered CB400f owner in northern IN. Congrats on the bike!
I can tell you that the throttle sleeves get brittle with age and yours could well be cracked as mine was. This part is not expensive nor are proper cycle grips. You wont need adhesive to mount them either. In fact you can us WD40. I would inspect that camchain again, they are very commonly seized up.

Joel · « **Reply #17 on:** August 05, 2008, 05:01:57 PM »

I've been working on rebuilding my spare set of forks so I can swap them onto the bike. I'm currently stalled at the seal removal stage. I've tried using a 2" C-clamp and a board to pry them out but the clamp is too big to fit inside the seal so it is pulling at an angle and keeps slipping over the seal before pulling it. Any suggestions on better methods? Am I doing something wrong on this one? I saw the C-clamp method suggested in another thread but maybe my clamp is larger across than it should be. I think it pulled it out partially but I can't get it any further.

CBGBs · « **Reply #18 on:** August 10, 2008, 12:55:00 PM »

Use a wrench.

Joel · « **Reply #19 on:** August 10, 2008, 07:10:09 PM »

Quote from: CBGBs on August 10, 2008, 12:55:00 PM

Use a wrench.

What kind of wrench and how?

kghost · « **Reply #20 on:** August 11, 2008, 01:29:09 PM »

Quote from: Joel C on August 10, 2008, 07:10:09 PM

Quote from: CBGBs on August 10, 2008, 12:55:00 PM
Use a wrench.

What kind of wrench and how?

I pried mine out with a set of picks and a screw driver....wasn't pretty but it worked.

They were really stuck

Joel · « **Reply #21 on:** August 11, 2008, 06:12:41 PM »

I worked on one with a screwdriver and some pliers but only managed to pull out pieces of rubber. I tried a seal puller I got from Auto Zone but still couldn't get it out. I may try some heat with the seal puller tomorrow.

kghost · « **Reply #22 on:** August 11, 2008, 07:14:51 PM »

It can be a right bastard.

Dunno that I woul heat it too much.....

The other option would be undoing the bolt and pulling out the tube...then removing the seal.

Joel · « **Reply #23 on:** August 11, 2008, 07:44:24 PM »

Quote from: kghost on August 11, 2008, 07:14:51 PM

It can be a right bastard.

Dunno that I woul heat it too much.....

The other option would be undoing the bolt and pulling out the tube...then removing the seal.

I wouldn't want to use a flame on it. I tried heating it up in hot water once but still wasn't able to get it free. I have the upper tube out already. I don't see a way to remove the seal with it still in.

Joel · « **Reply #24 on:** August 18, 2008, 07:36:09 PM »

One down and one to go. Here's the old seal. I managed to mark up the top of the fork lower as well.

Is it going to seal poorly with all those little dents on the inside? If I have a machine shop hone the inside, will I need to get some bigger outer diameter seals?

Looks like someone before me tried to shove a screwdriver between the seal and the tube in a couple places.

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Author Topic: My 1975 CB400F project: strange noises at idle (Read 19708 times)

troppo

troppo