Topic: CB750 K0 Restoration - Round #3

[Simpson]

Took bike out on a highspeed run for the first time this season. Hit about 70mph plus for a 5 minutes running stock 16/45 gearing. Pushed bike many times on some fast starts to get good and hot. Seems pretty quick.

-No cylinder head oil leak, although I'm not ready to celebrate yet
-No oil leak detected anywhere, as all engine covers were taken off
-Starts great in cold weather now that the choke is adjusted properly, imagine that
-Air screws need more refinement to the lean side for cruising engine smoothness
-Small brake fluid leak at brake switch still needs to be fix
-Braking is nice and smooth with new rotor

Painter emailed today and explained he had the saddlebads packaged to go but didn't feel good about supportive epoxy job around the hindges. He will disassemble, add metal support plate and repaint. Therefore my arrival is pushed back. 

This guy is a good painter, highly recommended after my first job.
Price is good too. Happy to pass along his info.
The SOHC CB750 is his speciality.
Of course, it will be interesting to see how this paint job turns out.

[Magpie]

Good for you! Nice when it all comes together.
Cliff.

[Simpson]

Well today I adjusted the air screws with the help of my old notes, reading plugs from my last ride and my trusty special screw driver. This is a area of interest because I think it is a wildly over looked area of performance gains (idling, balancing, power) with these old bikes. The AF ratio is critical and the air screw is important because you do most of your riding on the first 1/4 twist of the throttle. The air screw balances the AF on this beginning circuit. You can't adjust them by feel or measuring the RPMs as stated in the Honda Service Manual. I wish there was a better way to dial these suckers to perfection. I gave up on my O2 sensor due to laziness and the Temp gun doesn't seem to clearly read temps. So, I read the plugs and adjust... adjust... adjust...

[Simpson]

Saddle bags and rear tire arrive today.
Paint looks and matches as expected.
Top case (not so important) still in route.

Camera flash deceptively bleaches paint a bit.
Looks different in person. 

[Simpson]

I already have one mounted and I'm ready digging the look of the saddlebags. 
Nice thing is, I can always take them off in 30 minutes if I choose not to have them.

[Simpson]

Looking back, not happy with vacuum measurement reading on 4th cylinder the other day.
Will have to re-seat intake boot and re-sync engine again. Hmmmm
Nothing like doing things 1... 2... 3... times

[Simpson]

I've decided to do a picture flashback of where I started just over a year ago.
Since a picture is worth a thousand words, I won't have to say much...
Here it goes, starting with the pictures from ebay


This segment fills in the gaps and should be at the beginning of the thread.
-----------------------------------------------------------------------------------------

[Simpson]

 

[Simpson]

 

[Simpson]

 

[Simpson]

The first thing I did before even buying the bike was start collecting NOS parts.
I wanted a K0 and was confident I'd get one some day.
This allowed for some good bargain shopping.
Picked up a new HM300 exhaust system for 925USD.
Not too shabby...

[Simpson]

The ebay seller had "spit" shined the bike to make pictures look better than actual.
He sandblasted surfaces like fork cases and ripped away original surface finishes and rattle canned black areas.
The bike did not run as advertised on pickup. He frantically raced the engine to try to get all cylinders running but I asked him to stop, I didn't want to hurt the bike more than he already had....
Blinker were hooked up backwards and the carbs were assembled completely wrong... etc...
I explained my disappointment but took the bike regardless because they are far and few locally.
It  was a 5 hour drive for pickup and I felt committed.
Not to mention the big pile of NOS parts already in my garage.

I started breaking it down the day I got it

[Simpson]

 

[Simpson]

Most everything was coated in a thick oil which was a blessing, helping preserve the bike.

[Simpson]

After 3 cans of carb cleaner and scrubbing the engine could be seen again...

[Simpson]

Frame and all parts ready for paint...

[Simpson]

While prepping the frame the painter found a problem.
A down tube had decayed significantly.
Crap!

[Simpson]

Contacted a friend for a donor frame.
I hacked out a portion and fit into place.
 

[Simpson]

I then ran it to 80 year old guy in town for a welding job.
Believe he did the job for 15 bucks. I tipped him an extra 5.
It was back to the painters!

[fastbroshi]

   So you like the new bikes too?  Looks like a Speed Triple on a couple of your pics there.  I'd like to figure out a way to get a single nut axle on my VFR.  

[Simpson]

  So you like the new bikes too?  Looks like a Speed Triple on a couple of your pics there.  I'd like to figure out a way to get a single nut axle on my VFR.  

Absolutely, this is my S3 at a pit stop in the mountains.

[fastbroshi]

I then ran it to 80 year guy in town for a welding job.
Believe he did the job for 15 bucks. I tipped him an extra 5.
It was back to the painters!

   The older guys usually do the job the best, and they don't charge an arm or leg either.  The fella I had do my 550's head was probably in his 70s and when he saw the head he knew what it was off of.  This guy was good.  He had some kind of midget dragster in the back running half of a 350 with some really trick looking aluminum parts on it that he'd welded up.  Sitting in the corner on an oil drum was a $10,000 cylinder head for a drag car, fully cnc'ed, beryllium seats and all.  He had stuff like this everywhere.
   Hopefully your guy made the welds small as I know the K0 crowd is probably pretty detailed.  But whatever, you can't see that stuff when the tank's on.  

[Simpson]

Early January 2009
While the frame was being painted, I was painting the engine and attaching the new covers I had collected.

[Simpson]

Late January 2009
Luckily after getting a good look at the inside the engine, it had never been touched. Tappet covers had never been removed and nuts never adjusted. Clutch, valve train checked out in great shape. Suddenly I felt very happy to own the bike. Somebody drove it 10k for a few years, parked it, and it sat for 40 years. The engine seemed like a nice time capsule, where the rest had experienced rough aging. Frame and parts came back and it was time to get mounting the engine.

[andy750]

This is a great idea with the photos. I am really enjoying the "photo build". And your attention to carb tuning is an inspiration. More please! Could you also post a video of the bike at idle as you had it spot on before and give some pointers on how to achieve this! Thank you!

And what tire is that in the photo? Dunlop K70?

Andy