Topic: CB400F revival

[spurlock]

Back in 1976 I was wrenching at a Honda shop in Davis, California and a '75 CB400F came in for its second crash repair with only 1,200 miles on the clock. The rider was a reckless kid and his parents wisely pressed to sell the bike back to the shop to save their son from himself. Bayard, a good buddy of mine, bought the bike from the shop and proceeded to ride it for the next 25 years, accumulating 35,000 miles. He quit riding at some point, as did I, and for the last 15 years or so the bike has been sitting unused in the front room/indoor shop of his house.





Fast forward to a couple of years ago and I attended a local vintage motorcycle show with Bayard and another old riding buddy and I got the bug again. I soon bought and restored my CB125, two GB500's and my XL250. Since then, while on rides I've stopped off regularly at my pal Bayard's place to chew the fat and talk about the old days, how we both started out on C110's, graduated to S90's, 305 Super Hawks, his CB450 Black Bomber and so on. During each visit I would walk past his dusty, dormant 400F and have the urge to grab some wrenches and polish and whip it  back into shape. Bayard was on board with the idea so I brought the bike into my shop a few weeks ago and got started.

Being only a two owner bike and always stored indoors makes this a dream project. Its only problems were lots of oil leaks, slipping clutch, and lots of tarnish and dirt. So step one was doing a thorough cleaning prior to top end tear down to fix the oil leaks. Some before pictures:









As I mentioned, the original owner had crashed twice. I did an insurance repair the first time, but Bayard bought the bike as-is after the second crash. The damage was fairly minor, slight scratches on the exhaust and this nasty scrape on the alternator case and cover plate.



The case was originally painted silver with a clear coat, so I did an epoxy fill on the case and repainted. We obtained a NOS cover plate from David Silver and one major scar was fixed.





The engine was in good shape, but with 35K miles I went ahead and freshened it up with a light hone and new rings. Amazingly the piston-to-cylinder clearance was still well within spec at .001". Bayard changes his oil religiously. The head is out having the valve seats ground for new valves. I replaced the cam chain and clutch discs, along with all O-rings and gaskets. Meanwhile lots of cleaning, soda or glass bead blasting, painting, and buffing is bringing out the eye candy in this wonderful bike.

The forks got new seals, buffing and clear coat. Master cylinder and caliper got new seals, paint and brake lines.



Center and side stands got painting and hardware polish and clear coat.



The frame only needed minor touch up and polishing.



Engine covers got new silver paint and a coat of catalyzed clear coat.



The front hub is buffed and clear coated, and relaced with new spokes.



After buffing I decided that yes, this has got to be the world's sexiest exhaust system.



I cleaned the carbs and replaced all O-rings. Still to do are cylinder head install, then replacement of swing arm bushings, rear wheel rebuild, and clean up of the aftermarket Koni shocks. Oh, and taking my buddy out on some favorite local rides.

More to come.

-Bill

[SOHC4 Cafe Racer Fan]

This is going to look mint when you're finished.

[spurlock]

I'm still waiting for the cylinder head to come back from having the seats ground, but meanwhile I've just about run out of parts to clean, buff, paint, or otherwise make right. The swing arm is back on after removal to replace bushings, and the Koni shocks are painted and chrome bits polished. I had wanted to pull the Konis apart to change their oil, but was not able to get the seal retaining nut off despite making a special pin spanner for the job. One of the shocks leaks a bit, and I haven't been able to find a source for seals for these 35 year old shocks. If anyone knows any parts sources for old Konis I would appreciate knowing. So for now I decided to just leave them as-is and come back to them later if I find some parts.



The newly respoked front wheel is back on, along with the rebuilt caliper.

 

The rebuilt master cylinder is filled and bled, and a NOS right switch assembly and grips are in place, ready for new Triumph style bar end mirrors.



All wiring except ignition coils is back on and hooked up, ready for testing.



This bike has a very cool aluminum rack. We used to install them at the Honda shop back in the '70's. Pricey but classy looking and very light weight. This one was fairly scarred up so rather than the original buffed finish I took a Scotchbrite pad to it for a brushed aluminum look, followed by a clear coat. The taillight bracket was rusty chrome, so I sanded it and sprayed it semi-gloss black.



I buffed and clear coated the rear hub and brake panel, buffed the rim and laced it back up with new nickel plated spokes.



The carbs got a thorough cleaning inside and out, and all new O-rings.



The shift lever and its very cool heim joint linkage has new rubber boots.



So for now I'm down to looking through muffin tins of parts and hardware, looking for anything else that needs attention while I wait for the head.

-Bill

[Bootsey]

That luggage rack looks pretty awesome. Looks like a tidy bike!

[OneWheelDrive]

Great looking job so far!  I need a shifter, linkage, brake lever, and pegs from this very bike!

[jerry h]

Very nice!!!!  Keep posting more pics, can't wait to see what's next.   

So is this your bike, or are you restoring it for your friend?

[MickB]

Spurlock a very nice resto, looking forward to seeing the finished article.

[spurlock]

Thanks guys. I'm restoring the bike for the owner, a friend of 40+ years. Gonna get him back on two wheels again so we can go for some rides together. This afternoon I got the top end back together, and by tomorrow she will be making noise. More to come.



-Bill

[MickB]

Bill ya gotta loose the pack rack, the bike's looking too good for the rack.

[spurlock]

Bill ya gotta loose the pack rack, the bike's looking too good for the rack.

Hey Mick, yeah I know the rack adds a bit of a dork factor to the bike, but it is very functional and the owner really likes it so it will stay.

Completed assembly today and got the bike running and tuned. Very sweet machine, pics and details to follow.

-Bill

[MoMo]

I used to ride a 400 four every where back in the day(whatever that is???) and cannot imagine commuting without a rack.  How else are you going to  lash down a case of beer??   Larry

[MickB]

Down the front of your tshirt of course!

[Pan1cReaper]

Thebeardedone and I stuff chocolate milk in out jackets when we go on rides sometimes, I think you would have to stick to single large bottles or cans. Or bring a backpack! This thing is looking amazingly clean. Cant wait to see it

[spurlock]

This thing is looking amazingly clean. Cant wait to see it

Thanks, here ya go:

Excited to get the cylinder head back the next day, I spent the other evening out in the shop prepping and finishing up whatever other assembly I could do. With 35,000 miles on the clock I wanted to replace the cam chain, but did not want to split the crankcases to do it. But David Silver sells a rivet-type master link, allowing replacement by breaking the old chain and the new chain, then riveting back together. As it turns out the old chain showed less elongation than I had expected for the mileage, another testament to the value of the owner's frequent oil changes.



I installed new countershaft and rear sprockets to go with the new chain on hand. The oil pump got tear down for inspection and all new O-rings since it was one of the major leaks.



The ignition advance got disassembled, cleaned and lubed, and I installed and static timed new points.



All cables got cleaned outside and lubed inside.



Had to stop and pet the shop mascot, then stepped outside to watch the full moon behind fluffy clouds. Rain was forecast for the next day so that would make for a perfect shop day to install the head.





My buddy brought the head over the next day, and after leak testing we installed the valves and torqued it down. Here the cam is in and we're ready to crank the starter to confirm oil pumping to the top end. Two steel tubes running parallel to the cam have small holes that squirt oil directly on each cam lobe. As well, the cam lobes dip into an oil bath with each revolution.



Last thing for the day was bolting on the cylinder head cover and calling it a day.



Next morning the coils went back on. The plug caps have been cleaned inside and out and a thin coat of dielectric grease applied to the insides and wire connections. Is it just me, or are cooling fins just a beautiful feature of air cooled engines?



By the end of the day the bike was complete - valves and cam chain adjusted, carbs installed and synced, timing set, and that gorgeous exhaust system installed.



Then of course it was test ride time! The bike is just an absolute joy to ride. It runs like a top and has rock solid handling and electric motor smoothness.



A few more glamour shots:













This has been a fun and very satisfying project. I will be doing a few shakedown rides and followup tuning before reluctantly handing the key back to my buddy, the bikes owner. Then we will be hitting the road for some nice rides, two old friends on our vintage bikes, just like the old days but for all the grey hair. Ride pics to follow.

-Bill

[calj737]

Stunning workmanship and an extraordinary result.

[jerry h]

Hi Bill

Beautiful !!!!!!!!!!!!

So what engine paint and clear coat did you use? Looks really good.

So nice to see a stock restoration.

[spurlock]

Thanks for the kind comments guys. There was a lot of detail and time involved, but it has been a very satisfying project. Basically it was a nice survivor bike, always stored indoors and cared for mechanically in some respects but neglected in others, then just stored for the past 15 years or so. Mileage was high at 35K so there was major service due on the engine and other systems. But for its age it was way above average. As the saying goes, it's easy to hit a home run when you start out on 3rd base.

So what engine paint and clear coat did you use? Looks really good.

So nice to see a stock restoration.

For silver paint I like Dupli-Color DE1615 Aluminum engine paint. It's a very close match to the original. For clear coat on the hubs, engine cases and fork lowers I used Spray Max 2K clear gloss. It's a spray can with a button on the bottom to puncture a hardener reservoir. Once punctured, you have a few days to use the product. Around $20 per rattle can, but it is really tough and fuel/oil resistant. For other hardware I use Dupli-Color 1636 clear.

-Bill

[Pan1cReaper]

Turned out awesome, thanks for sharing. Looks cleaner than factory new. I agree, those 4-1 exhausts look better than any aftermarket. Im not crazy about the rack but can appreciate it. Sweet bike!

[MoMo]

Excellent, I'm sure your friend will be happy as a clam with that beautiful varnish blue machine

[MickB]

Bill it looks schmick.

[spurlock]

Bill it looks schmick.

Schmick - I had to look it up, "suave, ultra cool, . . . ) OK thanks, that works. As I tell my wife, I can get a hard-on just polishing these exhaust pipes.

-Bill

[spurlock]

One of the last parts of this project was rebuilding the leaky 40 year old Koni shocks. Koni still makes automotive shocks, but discontinued production of motorcycle shocks in 2000. They licensed rights to their cycle shocks to a new company in Australia named Ikon. San Francisco based Ikon Suspension USA can supply seals and other parts for later model Koni shocks, but the earlier models on this CB400F were different. Luckily I was able to get new seals from an independent Koni specialist, Robert Haag  (rhaagusa [at] yahoo [dot] com), who has sourced parts that will work for these early style Koni shocks.  Besides the leaky seals, the tiny orifices in the shocks were clogged with gunk, making the rebound dampening extremely stiff. So after thorough overhaul, the shocks are now working properly again.



Besides the grime and corrosion of age, one of the major problems with this bike was its oil leaks - it had leaks from the rear shocks, front forks, brake master cylinder, and multiple engine leaks. So after replacing all gaskets and most seals and O-rings and test riding I was disheartened to see a bit of oil on the cylinder fins after the first couple of test rides. The problem turned out to be something I had never run into before, a couple of porous spots in the cylinder casting. These were very slight leaks and hard to pinpoint, but thanks to a tip from the excellent web site of Mike Nixon (http://www.motorcycleproject.com/) I was able to find and repair them. Mr. Nixon's tip was to clean the area, then spray on some aerosol athlete's foot dry spray powder, then run the bike and watch for the source of the leak. The spray goes on like white paint, allowing you to see any oil leak as a dark spot. Here is the cylinder after spraying:



I took off on a test ride, stopping every mile or so to inspect. After about 2 miles I could see a couple of tiny dark spots between the fins. After 5 miles the spots looked bigger, but there was still no visible shiny oil. I continued to ride for about 15 miles, including several miles of 65 - 70 mph running. Back in the shop there was still no visible liquid oil on the fins, but the discolored area on the spray powder was bigger. Apparently the dry power was absorbing the oil which would have otherwise run out onto the fins. Here is how one of the leak sources looked after the extensive test ride. The arrow points to the leak, just a small discolored area:


After applying epoxy and test riding the bike looks leak free now. I dropped the bike off to the owner, and we are planning a ride together this week. Thanks to Mike Nixon for the tip on finding oil leaks. They were such slight leaks it would have been impossible to pinpoint them otherwise.

-Bill

[knowsnothing]

Wow, don't think i have ever seen a leak like that.     Glad you figured it out and fixed it.  I am pretty sure i would have been permanently stumped. 

[SOHC4 Cafe Racer Fan]

That is NOT a normal spot for a leak (on the cylinder wall).  I wonder if epoxy alone will hold up over time.

[spurlock]

That is NOT a normal spot for a leak (on the cylinder wall).  I wonder if epoxy alone will hold up over time.

Agreed, it's definitely not normal. However both leaks were at those front outside stud holes, which are oil return holes from the #1 and 4 exhaust valve areas. And the leaking spots were rough, porous looking spots in the casting. So it must have been a one in 1000 case of a bad casting job. I am fairly confident the epoxy will hold, but if it doesn't it would be very simple to grind it out and go to another material. I have used a cement sold for exhaust patching on the muffler of another bike and it has held up fine, so that would be my plan B if the epoxy fails.

-Bill