1981 Honda CBX "School Bike" Basketcase Rebuild

Aloha - here's a thread documenting my rebuild of a 1981 Honda CBX.

This is a project I have no business taking on, because I am at best a hack mechanic and the CBX engine is regarded as one of the most technically complex motorcycle engines ever made (an inline 6 cylinder DOHC with 24 valves and 6 Keihin carbs).

This bike came as a separate frame and motor - the two parts were split up from the same original bike and were owned by 2 different people, but had been stored near each other up on the North Shore here on Kauai. The total price for frame and engine was $400 - how could I possibly say no?

It is one of the fabled "school bikes" - one that has never run a mile. These were donated by Honda to vocational training programs to teach future mechanics how to work on DOHC motors.

You'll be able to see the condition of the parts in the photos in the thread...some like the frame, have sat out in saltwater air for many years and look like shit. Others, like the carbs, head, seat, rear fender, etc look like they are brand new. There's several pieces of NOS bodywork and a complete set of NOS rings, boots, and gaskets. Although this is a school bike, it looks like it didn't spend much time being worked on as the majority of the bolts have no tool marks and the few that do have minor marks.

Here's a couple of the major hurdles to getting this bike together...
1) I've never rebuilt a motor before - just stuff like brakes, valve adjustment and minor things of that nature
2) The bike came in pieces so it's hard to inventory every piece to be sure all the parts are here
3) I've never seen a running CBX and no one I know on Kauai has one (though rumor has it that maybe there is one...)
4) I am not going to spend more than maybe $1000 total to get it running again

So that's why I thought you guys would like this thread. I has something for everyone....

if you're a skeptic you can be all "no way mate...you'll never do it...you're in over your head!"

If you're a fan of old Hondas you'll cheer me on for not parting it out and trying to get it back on the road

If you like the underdog, then you'll root for me because unlike many of the guys I see here on DTT and other forums - I have no fucking clue what I'm doing. (Seen "Idiot Abroad"? Like that...).

And if you like those "Race to Rebuild" shows, you'll love this because my "ringer" is TONY...he's a really nice guy who has offered to come from Sydney Australia to Kauai help me rebuild this bike - but we've only got THREE DAYS to do it.
This will all go down just 10 days from now and I might even set up a ustream live webcast so folks can tune in and see our progress/mock us.

Here's a few photos to give you a feel for where I'm at...

definitely set up a live stream

The first time I came across a CBX was probably 20 years ago. I was riding my 87' Hurricane, I pulled up along side this guy on a stripped down Black one. From the side it looked like a 400cc Honda Hawk! When the guy took off he left a 25 foot patch down the street and then came up on a little wheelie! . It was then that I noticed two extra cylinders hanging off each side! lol

I've been a fan ever since!

Good luck! I'll be following this build for sure!

My dad is currently building one also, good luck.

Thanks guys.

I've started the live webcast of the rebuild.

http://ustre.am/U2en

This is more of test than anything. But feel free to say hi on the chat.

If you're somewhere cold, you might enjoy just seeing the sun more than watching me clean carbs...

Here's the URL...obviously it won't be active all the time...but worth a check. I'll be on here for a few hours now.
And it'll be a firestorm of activity between 2/24 and 2/26.

Thanks for looking.

Life sure isn't fair. You have a CBX and are in Hawaii....Arrrggg....How lucky can one person get????

Cool idea video streaming the work...

mydlyfkryzis said:

Life sure isn't fair. You have a CBX and are in Hawaii....Arrrggg....How lucky can one person get????

Cool idea video streaming the work...

Click to expand...

After a while it's easy to forget how lucky we are. Thanks for reminding me Mydlyfkryzis!
(love that name btw..)

The webcasts of the frantic 4-day CBX rebuild will begin tomorrow (Friday Feb 22) and will go through Monday or Tuesday of next week. Drop on by and see what we're up to...shoot us a chat message and tell us where you're watching from. Apologies in advance for the commercials that ustream puts in there.

Here's a rather ambitious tentative schedule with webcasting times in Hawaiian Standard Time:

Friday 2/22 15:00 - 18:00 (going over parts and planning)
Sat 2/23 9:00 - 17:00 (am:doing carb and valve work; pm: honing cylinders, beginning motor assembly)
Sun 2/24 9:00 - 20:00 (am: motor assembly; pm installing motor/tank/seat/bodywork on bike)
Mon 2/25 9:00 - 17:00 (am testing motor and ignition/electricals + fairing; pm brakes and maybe forks if they come in time)
Tues 2/26 TBA

This is all subject to change obviously..
Here's the stream link again. Hope you can pop in.

http://ustre.am/U2en

Well after an intense 3-day session, my friend Tony from Oz and I were able to get the CBX back together again. Tony's a CBX pro - and with his wisdom and guidance and a LOT of wrenching, I now have a CBX in the garage.

Rather than go through each nut and bolt, I wanted to simply pass along the three problems we encountered and how we dealt with them in case this could be of help to others on DTT.

(Keep in mind we only had 4 days to do this entire build, so there was no ability to get new parts once we began..)

Problem 1: 2x missing valve spring seats
Problem 2: 4x stuck carb float valves
Problem 3: Only running on 4 cylinders initially - #2 and #5 DOA

Solved thus...
Problem 1: There's no Honda dealers on Kauai; there's only a Suzuki dealer and a HD dealer. The HD guys weren't too helpful, but the guy at the Suzuki shop pointed us to a ladder and a case of parts waaay up in the rafters, gave us two flashlights and said, "Have a dig". Up in the dusty bins we found two valve seats from who knows what that were the right size and hardened...bingo.

Problem 2: 4 of the 6 float valves (those tiny ass springy things that attach to the float bowl) were completely frozen. The pins would not go down at all. We did have 1 extra new one, but with six carbs ya gotta have em all. Lots of carb cleaner...nope. Brake cleaner blasting...nope. Compressed air...nothing. Finally I remembered I have an ultrasonic cleaner I used for jewelry - filled that puppy up with a small amount of brake fluid, leaned it on one side to make a small pool of liquid, closed the lid and stood back (you could see the brake fluid turning into a "fog"...thought that might ignite..). 60 secs of that and already 2 of the four were working! The others worked with a few more rounds. By the end they were all very clean and worked perfectly. (Disclaimer...this seemed super sketchy, and I wouldn't recommend putting even a small amount of brake cleaner in an ultrasonic machine. We had no other real choice if we wanted to complete this build)

Problem 3: This one wasn't so bad, but it's more of a reminder that just keeping at something will yield a good outcome. The #2 and #5 cylinders were stone cold. No spark. Looked like it was the coil. Pulled out voltmeter and tested everything. Did all the swapping of leads and all that. Definitely the coil. We dicked around with it for a while but nothing worked. Finally we noted that the coil is attached with a large metal bars that run through the body via a bolt. OK, these are maybe the high V grounds? Checked the backside and it was all rusty and thus no current getting through the ground to allow the coil to fire. Sanded em up and bingo.

One bullet we dodged was that the carbs were still in synch. Tony had everything we needed to make changes, but none were needed. whew.

So bike is all done aside from last bit of brake work which maybe I'll get done today. Scroll up and look how shitty it looked and even though it's not all perfect now, it is basically stock, the motor, head and carbs have been completely rebuilt, and it starts and runs well. And it only has 4.2 miles on the odometer - I don't think it's ever gone even a mile under power...maybe at Honda factory?

I'm still under a grand at this point and my only other cost will be new tires.

Summary:
Cylinders honed
Pistons cleaned with new OEM rings installed
all 6x carbs completely cleaned and synched (Mike Nixon-style)
24x new Viton valve seals installed
All 24 valves shimmed to spec
NOS camshaft tensioners
NOS plugs
mint condition (NOS?) forks installed
3x brake rotors rehoned
nice condition front brake calipers x2
New 530 chain
VHT-painted stock OEM exhaust ("flameproof 2000º Cast Iron color" over "flameproof 2000º primer"); cured on bike
various bits cleaned up, painted with BBQ and black hi-temp crinkle paint, sanded, etc.

Here's how it looks now...very much like a stock '81 CBX.

bravo

Hear hear - what a job!

Thanks guys.
So I got the brakes bled and finally got to ride this 1047cc 6-headed monster.

Fun facts:
Me = never ridden anything bigger than a 650 before
This CBX = never been ridden before by anyone
This situation = I've never ridden a bike I built from parts before.
Brakes = untested

So it could've been a recipe for disaster, but I put 3 miles on her before I came home with no drama. There was some weirdness in the turn-ins..felt really strange...and the front brakes are crappy but that can be fixed. There was an "ambience" of braking let's say. The best part was giving it some throttle in 2nd gear...the bike shot up to about 45 in a second or two....damn. I'm not used to that at all...but I can learn!

Today I pulled off the left brake and cleaned out the completely clogged brake line. If you're working on an old bike, check these brake lines carefully as they get full of Magic Pixie Brake Fluid Powder. Blast em real good with brake cleaner - whack em against a palm tree - spin em around your head and strip paint from everything in a 20 ft radius - that's my technique. Wipe em off and blow through them and you can tell when they unpucker. Did all that got the front system re-bled and we'll see where we're at now.

One thing that was kinda bizarre but may have helped my handling issue was I forgot to put any air in this bike's oddball air suspension system. Both the front forks and the rear giant monoshock have air valves like a bike tire and you put 15 psi in the front and 30 psi in the back. My friend was helping and while I sat on the bike it started levitating like Kris Angel. Seriously it rose up about 1" both front and back once the air was in. I'm curious to see how it changes handling. Before the air you could get too much travel on the front shocks...maybe 4"? Now it's much less and feels more normal.

Also since this was a school bike, I've found several places where parts we installed all wrong. I could not get the seat on properly no matter what I tried, so today I decided to pull it all apart and really look at how it should go together. One washer had a special "finger" and I know a Japanese engineer did not make it like that for no reason. Looked around and saw where this special finger goes (we all know where the special finger goes...but I digress) and saw it matches up with the rear grab bar. Then more looking revealed they were swapped L to R...swapped em back and got the seat on properly finally.

Cut off the old turn signal mounts from the saddlebag rack and plan to either weld em or bolt em to the frame so I can have rear signals. They are the huge-ass square ones and I love the look. Like shitty Power Rangers Style.

Well done. A great resurrection. 8)

GREEN (With Envy).

Helpful hint - when you have the chance, just replace the brake lines with stainless steel braided ones. The y are better then new originals, and far better then old, ready to burst from age ones.

jay leno has one, you should send him a message about this build. i know for a fact he would love your bike(loves original and un-restored, loves this bike, perhaps top five gear heads in america)

canuk said:

jay leno has one, you should send him a message about this build. i know for a fact he would love your bike(loves original and un-restored, loves this bike, perhaps top five gear heads in america)

Click to expand...

I've thought about this - and I dropped a hint on his YouTube channel. But my guess is he's got one, so he doesn't need another.

In fact I then used Google Earth to find his Big Dog Garage and saw the streets he drives down for his videos....all around the Burbank Airport..it's the place with the Solar Panels on top. It's next to a place that rents cars as movie props...kinda fun to poke around if you're a fan like me..
https://maps.google.com/maps?q=burbank+airport&hl=en&ll=34.206239,-118.361083&spn=0.003758,0.005037&sll=33.670193,-117.87328&sspn=0.005348,0.010074&t=h&hq=burbank+airport&z=18

The CBX is almost completely done - brakes work now and just waiting for new tires (Avon Roadriders) to come in a week or so. Already ridden about 12 miles around the 'hood, but the 32 year old tires are scary-hard.

And yeah mydlyf - that's exactly what I was thinking too. Gonna order up some nice new SS brake lines soon.

A little drama today as I tried to get new tires. Bike stalled out 3 times in just a few miles...and here there's only a very narrow (less than 4 feet) shoulder to pull off onto here on our single highway. Super sketchy with trucks wheeling past as I tried to get the bike running. People get killed on the shoulder of our roads all the time.

Decided to remove the huge fuel filter as it seemed to be causing a vapor lock - it was way too big. Just pulled it off with my bare hands and hooked everything back up. That got the bike running again. I need to pull the petcock as it seems like there's crud fouling it....bike runs better on reserve than on "on" even with a full tank...so that's my guess.

Anyway, finally made it to the tire place, got the new Avons on, discovered a clutch cable that was binding on the steering head, and the bike is handling much better now. The ride home was much more relaxed. I'm up to 40 miles now so it's basically time to change the oil and filter because I know it's full of crap. Even just looking in the oil you can see it's hazy.
Here's a pic of the progress...finally not one in front of the garage.

that's a pretty bike....It will be simply awesome once the gremlins are worked out.

1981 Honda CBX "School Bike" Basketcase Rebuild

This thing is so cool! Keep up the good work!