Topic: '77 Honda CB400F

[mwc400f]

After searching on craigslist for years for a completely stock example, here's my newly acquired project bike loaded on my pickup. It runs, but the front brake drags pretty badly.

[mwc400f]

After getting the bike home and taking a closer look, I found the following problems:

1) front brake drags badly, front brake lever feels loose.
2) seat is torn.
3) gas cap door is hard to open/close
4) Mirrors are losing reflective backing
5) front forks feel sticky
6) Fuel tank interior rusty
7) ignition switch works intermittently

[mwc400f]

2) seat is torn.
.
I replaced the torn original vinyl upholstery with the new, leather upholstery provided by the seller. *Much* nicer. Thankfully, the foam padding underneath was intact.

[mwc400f]

5) front forks feel sticky.

I drained both forks and refilled them with 150cc each of Type F ATF fluid. The original fluid was pretty dirty -- the forks worked great after the change.

I noticed the preload on the rear shocks was set to the lowest level. I set the preload to the recommended middle position, and quickly found out why the previous owner had set the preload low -- the original shocks have *no* dampening at all -- hit any moderate bump and bounce all over.  I replaced the rear shocks with a pair of SKU RS-02 reproduction chrome shocks from 4into1.com. These reproduction units work great! The bike handles great now.

[mwc400f]

1) front brake drags badly, front brake lever feels loose.

I drained the front brake M/C and disassembled the caliper. What a mess -- the seal in the calilper was gone and brake fluid had leaked past and crystalized around the brake pad, restricting its movement. I replaced the OEM caliper assembly with SKU CA-SOHC from 4into1.com. Doing that was straight forward.

I ordered a genuine honda M/C rebuild kit SKU 45530-377-305 from 4into1.com. The brake fluid had likewise leaked past the seal in the M/C, and filled the boot with crystalized brake fluid. The lever felt loose because a previous owner had disassembled the M/C + brake lever assembly, and lost the little rubber cylinder that's held in by the metal shield beneath the assembly. This shield is held in place by the lever pivot bolt, and is easy to lose if you're not careful. I replaced the missing rubber cylinder with a piece of 6mm plastic hose. It fit perfectly.

Disassembling / reassembling the M/C is a royal pain -- give yourself plenty of time and patience. I bought a pair of Motion Pro M/C snap ring pliers (SKU 08-0279 @ 4into1.com) to accomplish this. There's a great post in the "brakes" section of proven tips & tricks forum that recommends reinstalling the lever pivot bolt and using an L-shaped allen wrench to hold the M/C piston in while you get a hold of the snap ring to remove it. The same trick also helps when installing the new parts.

I reassembled the M/C + brake lever and installed it on the bike, then attempted to bleed the brake. Bleeding the caliper was easy, but I found I couldn't get rid of the sponginess in the lever -- it took 1.5 to 2 lever pulls to get full braking power. I noted that the "tips & tricks" brake topic recommended bench bleeding the M/C, and I was preparing to remove the unit from the bike to do so when I noticed that if I pulled the lever in about 1cm, bubbles came out of the pin hole in the M/C fluid cup. I kept pumping the lever to just 1cm from the completely released position until the bubbles stopped. Problem solved -- M/C was bled and the lever was firm.

The front brakes work perfectly now -- no dragging, smooth, easy effort on the lever. The weird looseness problem of the lever was solved by that little piece of 6mm plastic tubing in the recess in the lever.

The brake squeals a little when applied -- I figure that will go away with time.

[mwc400f]

3) gas cap door is hard to open/close

Looks like one side of the metal pin in the cover broke off.

I bought the following from amazon (420 Stainless Steel Spring Pin, Plain Finish, 5/64" Nominal Diameter, 1" Length), and ground it to length with my bench grinder. I put a small piece of shrink tubing on either end and heated it to shrink it. Works great, but the shrink tubing isn't very robust. Suggestions welcomed.

[mwc400f]

7) ignition switch works intermittently

I took a close look at this switch and noticed the plastic piece at the bottom of the lock assembly was cracked and starting to fall apart. I replaced this part with a EMGO 40-15800 repair unit that I got on amazon. Fit perfectly and works great.

[mwc400f]

4) Mirrors are losing reflective backing
I bought genuine honda replacement mirrors.

6) Fuel tank interior rusty

The fuel tank was pretty rusty. I emptied the tank, and removed the fuel petcock/filter. I filled the tank with evapo-rust and followed the directions. After emptying the tank, I was astounded at how good the tank looked -- it looked brand new -- so did the base of the cap. The instructions say to rinse with water after emptying the tank. I made the mistake of using hot water for this -- the tank flash rusted. No matter -- I refilled the tank with the same evapo-rust, and gave it another 3 hours. Looked great again. This time I rinsed it with cold water, and then rinsed the tank with a can of sea foam to get out any remaining water.

I replaced the petcock with a genuine honda fuel petcock SKU 16950-KCP-J01 from 4into1.com

[mwc400f]

OK, I've caught you all up on my project.

Here are my next steps:

adjust valve tappet clearance.

I'm waiting for the tools to arrive for me to do this. I have put in a feeler gauge 0.002" or 0.05mm in -- but the space is so tight, how can you be sure you're actually measuring the right clearance instead of feeling a drag because the gauge is bending? Should I bend the end of the feeler gauge? Any suggestions welcomed.

9) Replace plugs, points, condenser. The points are pitted, and the plugs are black with carbon. I bought 4 NGK D8EA plugs and the aftermarket SKU 333-TUNE-UP kit from 4into1.com. Unfortunately, the screws holding the points/backing plate in the ignition assembly are kind of messed up. Anybody know of a source of replacements for these screws? (I'm beginning to hate philips screws, JIS or otherwise)

10) I drained the float bowls of the carbs -- what came out was green. So, I bought 4 SKU SP70-1804 carb repair kits from 4into1. I'm kinda nervous about tackling this job -- after all, the bike runs, but I don't think I should mess with settings on them without rebuilding them. Pointers helpful.

11) Replace head gasket.
The head gasket is leaking oil. When the bike runs, it doesn't smoke at all, so the cylinders / rings are in good shape (the bike has less than 11k miles on it). If I decide to tackle the head gasket, what gotchas should I look out for? What should I replace while I'm doing this?

Finally, a general question: It seems that any screws that have not been tampered with are easy to get out, while screws that have been taken out (long ago) seem to build up some deposit  (I suppose it's the steel and aluminum difference in metals that's to blame). Did honda coat these screws with something when they originally assembled it? From what I understand, I should be coating any screws with either blue loctite or using permatex never seize + lock washers. Both loctite and never seize are supposed to protect the metals from the galvanic reaction that takes place when the two different metals are in contact.


Thanks.

[KennyRedman]

Awesome.

[newday777]

That's a great looking 400F you found. Are you keeping it?

Do yourself a favor and buy a genuine Honda points plate assembly and dump the aftermarket points you bought(only use TEC points and condensers!). The Honda points and condensers hold up far better. The points plate assembly have unfortunately been discontinued from Honda but some can be found NOS parts by sellers who bought up dealer parts rooms when Honda told the dealers to dispose of their parts rooms some years ago. You'll also get the new screws you want too.(or replace with allen head screws of same size in stainless steel.
The other option is changing to electronic ignition to eliminate the points assembly.

30200-333-004 is the points plate assembly part number to get if you want to stay with points.

https://www.ebay.com/itm/GENUINE-Honda-NOS-30200-333-004-POINTS-ASSY-/232480415065

David Silver Spares also still offers the Genuine points plate for $133

https://www.davidsilverspares.com/CB400F-SUPER-SPORT-FOUR/

Hondaman also offers a transistorized ignition to add to the points plate assembly to eliminate arcing of the points to extend the points life.


http://sohc4shop.com/catalog/index.php?cPath=23&osCsid=83592c51a64a7a0ca0a404a1f56e11c9
Adjustment of the valves: you want a little tension felt on the feeler gauge but not bending it. Put a little oil on the gauge between your fingers so it slips easier without binding.

Screws were zinc coated to protect them from corrosion. There are places to send your good condition screws to get new zinc coatings on otherwise buy new screws as needed from Honda.

[Stev-o]

Nice project and progress!  I rarely use Loctite but never-seize is a good idea.

[mwc400f]

Awesome.

Real looking 550F. I'm thinking of adding a 550F and a a 750F for a complete collection. There seems to be some problem with seeing the pictures you posted on your progress. Is that a problem I'm having, or have the pictures disappeared from the website?

[mwc400f]

replying to newday777:

Thanks for your response! Yes, I'm keeping it. I've wanted one of these since I was in high school in the 70's and it's a blast to ride. Thanks for all the ignition related pointers. I'll take a look. I figured the condensers were bad so the points pitted.

[mwc400f]

I forgot to mention I replaced the front and rear mounting rubbers for the fuel tank with genuine honda parts from David Silver Spares (DSS). The rear mount was shredded by a previous owner probably using pliers to pull the rubber portion over the fuel tank tab to remove the tank. I'm thinking I'm going to put a 1/4" or so thick pice of rope in the rear rubber to facilitate removing tank. It's hard to remove the tank without damaging the rubber -- pulling on the rope to get the rubber far enough back to grasp with fingers should help.

When I was taking off the valve tappet covers, I noticed the screw holding in the tach driver was buggered. I tried removing it with JIS impact screw driver and it just got worse. I followed the advice I got over at the SOHC/4 Bikes forum. I replaced the screw with a stainless steel allen head 5x20 screw.

[Mark1976]

   Drop some pic's of the points and it's plate, see what points and condensers you get and go from there. Ya better look closely at the plug caps, if their original they're likely to be faulty. They're likely to be 10 ohm caps so get you volt ohm meter out and check 'em and while your at it trim the leads a smidge. The replacement caps are normally found in the 0 to 5 ohm range. they'll make a big difference when it comes time to start her up. Your best bet will be to by Hondaman's transistor ignition, it'll eliminate the condensers that can become so problematic these days. The dyna is a real voltage drain, it was on mine, I replaced it with the unit from hondaman and couldn't be happier. Can't remember the last time I've adjusted the points. 

[carnivorous chicken]

I'm waiting for the tools to arrive for me to do this. I have put in a feeler gauge 0.002" or 0.05mm in -- but the space is so tight, how can you be sure you're actually measuring the right clearance instead of feeling a drag because the gauge is bending? Should I bend the end of the feeler gauge? Any suggestions welcomed.

Doesn't look like anyone tackled this, but the answer is yes -- you can bend a feeler gauge to make it easier. Motion Pro also makes feeler gauges with the gaps for your bike that are bent and easy to handle for a few bucks. And I always check the gaps with a feeler gauge one size bigger after I've done the adjustment just to verify that the right gauge fits (with a little friction) and the bigger one will not.

400Fs are great bikes, and sounds like you're well on your way.

[mwc400f]

Thanks for all your suggestions. I bought the $133 genuine Honda back plate assembly from DSS as recommended, and bought a set of genuine Honda points as well. Who knows when vendors will run out of the genuine part. I'll also check out hondaman's transistor ignition.

For now, I'm using the aftermarket points/condensers I had previously bought just to see how they work out. I replaced all the screws on the back plate assembly with stainless steel allen head versions. I also bought some Standard Motor Products SL2 Lubricam for the felt pad.

I've been reading up on how to remove  the head to replace the head gasket. I originally figured I could adjust the tappets when I had the valve cover off.  After finding out that on this engine, the rocker arm shafts and rocker arms are installed in the valve cover, I'll be taking your advice and checking out those motion pro "bent" feeler gauges.

While I have the head off, any suggestions for what components I should be checking for condition, etc?

At the moment, I can't spend as much time as I'd like on the bike, but that should change after the holidays.

Regards, Mike.