Author Topic: 400F rebuild (Read 5585 times)

dmcgrego · « **on:** November 02, 2011, 08:02:59 pm »

This is how the 400F looked when I got it home from the PO. What you can't see is the locked up front brake and the 1/4" of tar in the float bowls and petcock...the result of being in storage for years. The good news now is that the front brake is now working and the carbs are clean and the bike is running. There is more to be done before it's ready to ride, but there has been some progress.

dmcgrego · « **Reply #1 on:** November 13, 2011, 07:22:55 pm »

I got the bike back together and took it for a quick ride. It ran OK except the idle would hang up for a few seconds and then drop back down to a normal idle. The number 2 and 4 cylinders also turned a light golden color making me think they were running hot. The idle problem makes me think it's running lean, but just having the gold on cylinders 2 and 4 make me think the timing might be off on the points for that set of cylinders. I'll check the timing first and if it's OK then I'll tackle the leanness. The stock muffler is leaking due to rust, so I'll replace it and see what affect that has.

Over all not a bad start for a bike that hasn't run for five years. I love the sound of the 4 into 1 exhaust!

toytuff · « **Reply #2 on:** November 13, 2011, 07:40:05 pm »

Very nice!

tt

dmcgrego · « **Reply #3 on:** November 14, 2011, 06:10:24 pm »

Here are some before and after pictures of the 400. Instead of buying parts I kept my self busy with cleaning and polishing some parts...I have a question for the group, where does the green wire attach (looks like a ground wire) that is just to the left of the fuse box in the picture. I can't find a place to install it. Thanks for the help.

MoMo · « **Reply #4 on:** November 14, 2011, 06:17:12 pm »

Common question about the green wire-it is extra. Green on Honda is ground. Welcome and good foundation you have there...Larry

grcamna2 · « **Reply #5 on:** December 02, 2011, 08:03:38 pm »

dmcgrego,
How's the bike doing now ?

strynboen · « **Reply #6 on:** December 03, 2011, 04:48:23 am »

green are prob.. ground for blink relæ..not used on newer relæes

dmcgrego · « **Reply #7 on:** December 07, 2011, 06:12:30 pm »

Bike is all back together. Still not running as smooth as it should and the idle hangs a couple grand too high then drops back when it is up to operating temperature. Checked the compression and it's 150,140,140,150 so that was good. Most of the valves were too tight, especially the exhaust so they were all adjusted. It must have some of the cheap points installed, because the dwell was off and when I set it to 46-49 I didn't have enough movement on the timing plate to get the timing aligned. I'm going to try the tricks Hondaman mentions to see if I can reset the dwell and still get the timing set right.

It seems like it might be too lean, so the next step is to take the carbs back off and see if the emulsion tubes are blocked. I didn't think about doing it on the first cleaning and I am regretting it now. Are there any tricks that allow installing the carbs with the air cleaner plenum installed? Getting the plenum back on the number 2 and 3 carb was a royal pain.

dmcgrego · « **Reply #8 on:** December 12, 2011, 08:17:18 pm »

The carburetor emulsion tubes on cylinder #2&3 were dirty and partially plugged. I guess that explains why those 2 cylinders seemed to be running hot. Cleaned and soaked all of the jets again just to be sure there wasn't any other debris I had missed before. This is the first time I've ever worked on a bike where the emulsion tubes were blocked. I should have know looking at the tar in the bowls...

Well it sure made a huge difference in throttle response and power! Next step is to synch the carbs. When warm it seems to be a little flat right off of idle. I'm hoping synching the carbs will help. Oh the joy in getting a bike running that has been sitting for years! I keep wanting to start it up just to hear it run:) More good news, the idle hanging up at 2-3000rpm when it got warm has also gone away.

dmcgrego · « **Reply #9 on:** January 24, 2012, 07:02:56 pm »

I've been spending time polishing parts on the 400. Here are the before and after of a few...

dmcgrego · « **Reply #10 on:** January 24, 2012, 07:16:17 pm »

Before polishing the front forks I installed the new headling bracket, mirrors and blinkers. Next up is the new sprockets and chain, then it's time to get it back on the street.

dmcgrego · « **Reply #11 on:** January 24, 2012, 07:17:54 pm »

Here are the side views...

strynboen · « **Reply #12 on:** January 25, 2012, 03:56:32 am »

nice bike. just get better and better
.think i have one.. i.never have finish..think i must go on..and have it running

Killer Canary · « **Reply #13 on:** January 25, 2012, 05:36:40 pm »

What do you think she'll top out at? And when will I find one?

JustinLonghorn · « **Reply #14 on:** January 26, 2012, 07:00:17 am »

God, I love me a baby 4.

dmcgrego · « **Reply #15 on:** February 08, 2012, 06:22:50 pm »

I've finally got the tag situation with the DMV all straightened out and I've been riding it to work everyday. It seems to be running a little better every day, but it has a stumble right off of idle when it;s all warmed up. Everything points to a too rich condition at low speeds.

It's a blast to ride and I love how it sounds when you get above 5K. My twins back in the day ran better than this, was our gas just better back then, or did the 400'd run like this back then?

On the question of where it will top out...from everything I've read just over 100 on a good day.

I wish it had a quicker throttle. I have to regrip it to get to full throttle!

It sure seems to get a lot of attention, my 98 superhawk sure doesn't get any.

Thanks to everyone on the site for all of the good information, it's really helped.

dmcgrego · « **Reply #16 on:** April 11, 2012, 06:38:32 pm »

I've put in the new 38 jets and the bike is running a lot better. When it's cold it runs great! When it warms up it stumbles a little when you blip the throttle on down shifts. It starts up and runs cleanly with no choke and the exhaust exit is still black, so everything seems to be pointing toward it still running rich. They don't sell jets any smaller to lean out the low speed circuit, so I don't know what to do next. Does anyone have any ideas? The bike has a little less than 20k miles and runs great except for the stumble right off of idle. Does something wear out in these carbs to make them run richer?

grcamna2 · « **Reply #17 on:** April 11, 2012, 07:32:27 pm »

I was thinking you're bike takes 35 pilot jets? I could be wrong but I think they're still avail.

dmcgrego · « **Reply #18 on:** April 11, 2012, 08:01:57 pm »

I thought 36's were available, but service honda, bike bandit and honda parts nation all show 38's as the smallest. I don't know where else to look.

If you know of someone else that stocks smaller ones I sure could use help finding them.

grcamna2 · « **Reply #19 on:** April 11, 2012, 09:52:52 pm »

I've removed 35's from Honda CB100/125S models and they look exactly like the correct configuration as the CB400F; are you sure that the problem is the pilots being slightly too rich?..if so try www.jetsrus.com I was able to get some push in jets from them w/ o-rings included.They're website may have a way to exactly measure you're size pilot jets...I don't know computers too well..or they're website to know how to navigate different sites.

When you have the carbs apart it's a good idea to check All the small vent holes and tubes,etc. on the carb bowls and all over those carbs.I think there is one or two in the top of the carb body inside the float bowl chambers of each carb....it may take you a while to thoroughly go through all the little orifices and passages inside that rack;those carbs have very small passages and it may take a few good cans of strong Gumout or other cleaner along with a fine little guitar string to fully clear them completely..it wouldn't hurt to give them All of that.

Nice Blue CB400F by the way; how much would you charge me to polish both my fork sliders as nice as your's are done ?

dmcgrego · « **Reply #20 on:** September 18, 2012, 05:37:06 pm »

help! The 400 started having electrical problems with an intermittent headlight.

Wiggling the key got it to work for a while and then nothing helped. I've bypassed the ignition switch with jumpers with no luck. The signature is that I have 10.5 volts at the connector until I plug in the headlight and then it drops to zero, and then back to 10.5 when it unplugged. It's the same for both the low and high beam.

Everything else works fine except for the high beam indicator and it has the same voltages as the high beam headlight.

I had a similar problem with my Alfa and it turned out to be a bad ground wire by the headlight. Is there a another ground for the headlight besides the one under the seat at the back of the tank?

Thanks,

Darrel

iron_worker · « **Reply #21 on:** September 18, 2012, 07:34:57 pm »

Sounds like you have a short somewhere.

IW

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Author Topic: 400F rebuild (Read 5585 times)