Author Topic: Matt's 75' CB400F SS Daily Rider Maintenance Thread (Read 3797 times)

NYAudioEngineer · « **on:** June 22, 2015, 02:46:53 PM »

Hey SOHC4 members!

I've been all over this site and I have seen some amazing accomplishments. I love reading about all your projects. I am the new proud owner of a 1975 CB400F. I always loved the features of this bike. I live in Brooklyn, NY. I really wanted a light and easy to handle ride that has just enough power to get going around town and I know this is it. I love the classic style so I really just want to keep her original but I'd like to upgrade and maintain the parts needed to make her reliable.

I won an auction on ebay from a motorcycle shop in NYC. She's not in the condition they said she would be but I think she's pretty sweet none the less. I rode her home from the city, half way home she had some smoke from somewhere in the engine compartment. A few hours after I got home I decided to go for a ride to get some fresh gas and discovered she wasn't firing on all 4. I tested spark and confirmed that #1 and #4 are not firing.

I am currently away on the road as I am a touring monitor engineer for a popular artist but when I get home I will be turning wrenches. I will document and post here.

I am not very experienced but I have owned motorcycles before and have performed some basic maintenance in the past.

-MATT

calj737 · « **Reply #1 on:** June 22, 2015, 02:50:15 PM »

If 1&4 are not firing, check the left side coil under the tank. There should be a BLK/WHT wire running to it from the handlebars. Possibly it got knocked out and you no longer have battery power to it. Or, the BLUE wire which brings the signal from the pints/ignition plate from the left side of engine.

Congrats and welcome!

NYAudioEngineer · « **Reply #2 on:** June 22, 2015, 03:44:15 PM »

Thanks calj737,

I've been doing a ton of research on my down time. I totally understand what your talking about.

check this vid out.

https://www.youtube.com/watch?v=gCeDZMX4E9k

NYAudioEngineer · « **Reply #3 on:** June 23, 2015, 12:48:57 AM »

I already have a small list of parts I think I should replace / upgrade. I will be putting in an order while I'm away so that when I get back I'll have some stuff to work on. I believe as with any bike that has had the possibility of sitting, it would do it justice to clean the carbs. I have almost everything I need. I used to own a V45 VF750 and I remember that it was best to use genuine honda parts with anything metal but it was ok to use aftermarket rubber. So, I've been on the hunt using the same idea for this bike. I guess It wouldn't be so bad if I ordered the rubber parts now and waited to see what's going on inside the carbs, get the bike running and see how she's running before I order any metal. This way I can kind of get a feel for what size jets I should be going for. Make sense?

However, first thing is to get spark worked out. I know it was working on my ride home so I just got to trace it down.

so here's a little list:

http://www.z1enterprises.com

All Balls Steering Stem Bearing Kit 22-1011
Motion Pro Vacuum Carb Synchronizer
Fuel Line clear 3/16" ID 5/16" OD 25 Foot Roll
8x NGK 12mm D8EA Spark Plugs
2x NGK Spark Plug Cap 12mm & 10mm 102 degree XD05F
2x NGK Spark Plug Cap 12mm & 10mm 120 degree VD05F
Cable Luber Tool
RI10-100 Regulator/Rectifier
Ignition Kit KL20-6810

http://pages.ebay.com/link/?nav=item.view&alt=web&id=351280878082&globalID=EBAY-US
complete set of Viton (Fluorocarbon) o-ring sets for four Honda CB400F (75-77) carburetors.

MoMo · « **Reply #4 on:** June 23, 2015, 02:35:20 AM »

You most likely have dirty points for 1 and 4 or has cal said a loose connection but I'd bet on the points being dirty from sitting. Why are you replacing the r/r? welcome...Larry

NYAudioEngineer · « **Reply #5 on:** June 23, 2015, 03:14:58 AM »

Hey Larry,

Thanks for the reply.. I'm not going to change the R/R if the ones on the bike are working properly. I just thought I'd have known good replacements as they seem to be an issue.

-Matt

calj737 · « **Reply #6 on:** June 23, 2015, 04:55:05 AM »

I dint look at the product specification, but your plugs or caps need to be resistor type. And I'm not 100% on whether 8s or 7s are the stock plug for your bike. But whichever it is, use the stock temp plug.

Looking at a glimpse of the bike, my instinct says the carb brass is perfectly good, dont replace it. But clean, clean, clean the ever-loving dog piddle out of it. Responsible disassembly and complete cleaning is a must on "new to you" bikes that have sat a while.

Leave the stock Reg and Rec alone, they work quite well. The battery, well, that is likely to be a different story.... Is the igntion kit listed a set of points and condensers? Make certain the points are not Daichi brand as many have problems with them. So QA is unreliable.

Grab the manual, take heaps of pictures, get some bins and baggies, 2 gallons of your favorite degreaser, a stool and a well-stocked fridge. Pull up beside the bike, music on to a polite level, and set to elbow-greasing that little love back to a safe and reliable condition.

Fuel tank needs to be removed, drained, and 100% rust free inside. If you're replacing the steering bearings, then fully service the fork oil, and especially the brake system!

NYAudioEngineer · « **Reply #7 on:** June 23, 2015, 07:10:49 AM »

Hey calj737,

That all makes perfect sense to me.

The ignition kit I mentioned is a set of points and condensers from z1enterprises. The description does not say what brand these are so maybe it's best trying to find genuine honda.

http://www.z1enterprises.com/ItemDetails.aspx?itemDescription=Ignition+Kit+CB350F+CB400F&item=KL20-6810

The tank has a fresh Kream coat.. this was done before me.

Thanks!!

NYAudioEngineer · « **Reply #8 on:** June 28, 2015, 06:12:46 PM »

Here's a link to photos of the bike and all the CB400F info I acquired

https://www.dropbox.com/sh/r6b4fuu9fhrz12z/AAAuxexKVv1mn5-26HsXQq_Ya?dl=0

NYAudioEngineer · « **Reply #9 on:** July 15, 2015, 08:24:04 PM »

I got back home a few days ago and went right to work on the bike.

So far I adjusted the points gap and timing, replaced condensers, replaced spark plugs and caps. I verified coil primary and secondary. I now have spark on all 4.

While I had the tank off I decided to pull the carbs and take a look inside. All of the brass looks good and original however, I found all kinds of gunk and adhesive where someone tried to stop leaks etc.. So here I go with a teardown clean and rebuild of the carbs. I have all the gaskets and o-rings to do it.

There are 2 metal tabs that link holders. One of these tabs is broken and the other looks like it's gonna go. The other part is a plastic or rubber part that runs along inside the holder. I included a photo of the parts page with what I need highlighted in red. Anyone know where to find these?

Thanks
-Matt

NYAudioEngineer · « **Reply #10 on:** July 16, 2015, 07:41:41 PM »

Here's some more photo's of a potential problems.

On carb 1.. the posts where the float pin gets inserted look like they are eroding. Anyone have a solution? Epoxy?

Also, the slide looks like it got chipped? big problem or it'll be ok.. for now?

Thanks.
MATT

MoMo · « **Reply #11 on:** July 16, 2015, 08:14:51 PM »

Jim French, a forum member does micro-welding. That slide looks as though someone used a screwdriver to try and pry up a stuck slide-should be replaced...Larry

calj737 · « **Reply #12 on:** July 17, 2015, 03:39:57 AM »

The posts are toast. Do as Momo suggests, and have them repaired by someone who can do "micro welding" or replace the entire carb body.

I can't tell from the picture, but that might be able to be polished smooth? If not, replacement is required.

NYAudioEngineer · « **Reply #13 on:** July 17, 2015, 10:38:21 AM »

I just ordered another set of carbs off ebay.
I also found someone who reproduces those metal links.
They are called "carb stabilizer springs".

http://pages.ebay.com/link/?nav=item.view&alt=web&id=111401668148&globalID=EBAY-US

-Matt

NYAudioEngineer · « **Reply #14 on:** July 17, 2015, 10:42:58 AM »

I think I'll contact Jim French about micro welding this way I could have a spare set of carbs.. Might be nice to rotate carbs.

-Matt

NYAudioEngineer · « **Reply #15 on:** July 22, 2015, 10:56:34 AM »

Cleaned both sets of carbs.

Sent bad carb body to Jim.

Built one good set and bench synced em'. (set floats, set air mixture, set choke linkage, set slide height etc..)

Ready to install on the bike.

Cross fingers for me.

-MATT

zekd · « **Reply #16 on:** July 23, 2015, 06:32:49 AM »

Loving the bike! Great work, keep it up.

NYAudioEngineer · « **Reply #17 on:** July 25, 2015, 06:39:49 PM »

Got to work on the bike today.

Put the carbs back in and did a compression test. All 4 cylinders are around 120 psi. Put the tank back on and fired her up. She started but was running a little rich so I backed out the air mixture screws by 1/4 turn and everything seemed to just click. The air screws are now all at 2 turns out. She idled at 2000k so I adjusted the idle screw and got it down to 1200k and went for a ride. Not a bad start! Next will be a carb sync. Here's a photo of my "assistant" helping me with the carbs.

https://www.dropbox.com/s/5ml99ati9bi27ve/file%20aug%2011%2C%207%2045%2050%20am.jpeg?dl=0

-Matt

NYAudioEngineer · « **Reply #18 on:** July 31, 2015, 08:25:41 AM »

Jim French does some amazing work. I got the carb back today and everything fits perfectly. It's way better than it was! I now have two sets of carbs. Check out the before and after pics.

Been riding the bike a lot. When she's warmed up she runs great. I'm having a little trouble using the choke. When the choke is on in any position she won't idle. If I start the bike cold and add a little throttle, I can get it to idle within 1 minute. I'm thinking float heights might need to come down or slides might be a little too high?

When I got the bike they failed to mention that the side stand mount was broken at the weld. So, my friends have a shop and I will be getting that done in the next few days. Already have the side stand parts to make it happen..

-Matt

NYAudioEngineer · « **Reply #19 on:** August 09, 2015, 05:56:27 PM »

The bike has been running pretty good and the weather is really nice so I have been riding a lot.
I got the side stand mount welded and painted. Looks good and works great. (I'll post photo's when I have a minute)
She might be running a bit rich, choke will only stall. Maybe I have to lower the floats?
The points have been working fine so I think I will hold off on the idea of an electronic ignition.

I think after this riding season it will be time to do the following:

Rebuild brake caliper / replace brake pads.
Rebuild master cylinder.
Clean carbs, lower floats by 1-2mm.
Replace leaky petcock. (unless you know of a rebuild kit)
Replace cylinder head gasket (slowly leaking)
Oil change / new drain bolt / replace oil filter / new filter bolt
Replace clutch rings and springs.
Replace front / rear sprockets / final drive chain.
Adjust valve clearances.

Hope all is well.
-MATT

calj737 · « **Reply #20 on:** August 10, 2015, 04:18:26 AM »

Your bike not idling with the choke is an indication your pilot jets and needle are not in spec. When you rebuilt these carbs, can you confirm you used original brand Keihin parts, and what size jets and clip position was used?

Also, have you visually confirmed the proper operation of the choke? You would not be the first to have it "reversed" (I suspect this is very unlikely given how much work you've done on the carbs, but hey, stranger things have happened). One thing always possible is a previous owner having drilled the jet to enlarge it and now you have no way of knowing it's true size.

NYAudioEngineer · « **Reply #21 on:** August 10, 2015, 06:38:25 AM »

Hey CalJ,

Well, if turning the choke to the on position means that the butterflies close then yes, I believe I have it right.

I did not replace the jets or needles, I just cleaned everything and put it all back together. They seem to be original and have markings on them that look like the keihin logo and a number. 75 on the main and 40 on the idle. I used the stock middle clip position on the needles.

It's pretty warm around here and the bike will start and idle with a blip of throttle at start.. without choke.

Thanks for the help!
-Matt

MoMo · « **Reply #22 on:** August 10, 2015, 05:22:32 PM »

you need to edit images. sideways and upside down? Do you have an image software?

NYAudioEngineer · « **Reply #23 on:** August 10, 2015, 09:57:22 PM »

For some unknown reason, when I upload photos in the correct orientation, they get messed up in the thumbnails but look correct when clicked. Sometimes the thumbnails generated are not even the correct photo but when clicked, they are correct. Maybe I should start posting links instead.

-Matt

MoMo · « **Reply #24 on:** August 11, 2015, 02:40:25 AM »

Quote from: NYAudioEngineer on August 10, 2015, 09:57:22 PM

For some unknown reason, when I upload photos in the correct orientation, they get messed up in the thumbnails but look correct when clicked. Sometimes the thumbnails generated are not even the correct photo but when clicked, they are correct. Maybe I should start posting links instead.

-Matt

Quote from: NYAudioEngineer on August 10, 2015, 09:57:22 PM

For some unknown reason, when I upload photos in the correct orientation, they get messed up in the thumbnails but look correct when clicked. Sometimes the thumbnails generated are not even the correct photo but when clicked, they are correct. Maybe I should start posting links instead.

-Matt

I didn't click on the image, that is one really odd problem you have. Least I'll know to click for correct orientation...Larry

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Author Topic: Matt's 75' CB400F SS Daily Rider Maintenance Thread (Read 3797 times)