Topic: Got it running after 40 years

[twright3]

You might recall from other posts of mine that I bought a 1971 CB750 about a year ago. (I had a K0 and a K1 back when they were new.) So yesterday I got it running for the first time in 40 years judging from the last license plate.
https://photos.app.goo.gl/zZNZRB5oQBmugw318
Why so long? For over a year I was acting as the general contractor for a 50x60 vehicle storage building and a 24x30 shop. Boy, was that exhausting!
Next I need to fix the front brake and get some new tires so I can take it for a ride.

[denward17]

Welcome back to the madness.....

Good Luck with the project and please shares some pics.

[CycleRanger]

Congrats! That's always great feeling. 

[newday777]

Congratulations on getting it running.
Did you finish your shop?

[twright3]

The garage (bigger, blue building) and shop are done except for some paving in front to be finished in October and the lighting in the garage. (The car in my garage is my 1936 Cord 810 Phaeton, looking extra rakish without its windshield. The moving blanket is because the hood is just laying there, not attached.) The garage is off the grid. This weekend I'll be working on a battery/solar powered low voltage lighting system. I don't want to clog this forum up with off-topic stuff, but I think off-grid motorcycle storage is close enough that if things work out as hoped I'll post just pointers to YouTube and/or PDF files for those who are interested.
Next week I'll be returning to my property where the CB750 is currently stored and get the front brake (now totally dry) working. The 40+ year old tires don't look that bad so I'll risk a short, low speed jaunt up and down my dead end. I'll post pictures.

[newday777]

Those buildings will do the trick.

[Stev-o]

Nice garage!  You have a lot of room for more cars and bikes!!

[twright3]

I returned to the bike and did some work yesterday and this morning. First I attacked the front break. I've worked on a lot of cars and bikes over the last 60 years and I've never seen anything like it. I already had a rebuild kit but so far I've been unable to disassemble the master cylinder. Used one aren't expensive so I may buy a used one that's more rebuildable. Then there was the #4 exhaust pipe. The muffler had a 3" hole in it. I bought one on eBay that was a bit beat up but not unlike my other ones. In spite of the visible HM300 on the replacement, the mounting/footpeg bolt hole was off by 50%. With a ratchet strap I was able to persuade the holes to line up. I was tempted to take it for a brief ride without a front brake, but it was running a little rough. I used my infrared thermometer and found 3 and 4 to be cooler. Later I noticed a bit of gas on the pavement and decided I needed to check the floats on the right side. That'll be next trip.

[newday777]

That brake fluid is a bit on the dry side of life....
I worked on a K4 that it looked like caramelized brown sugar.

Replace the brake hoses with stainless steel hoses.

[HondaMan]

That brake fluid is a bit on the dry side of life....
I worked on a K4 that it looked like caramelized brown sugar.

Replace the brake hoses with stainless steel hoses.

Yum!

[twright3]

Progress has been slow because of working on lighting for the new shop and supervising contractors working on the paving. But I did make it to the old shop a couple of times.
I'm all for preservation when appropriate. (I have a 1947 Lincoln Continental Cabriolet that has 18k miles on it; it was invited to Pebble Beach in 2015, the experience of a lifetime.) But safety trumps preservation. So i replaced the front brake hoses. I attempted to rebuild the master cylinder but the now main part would not slip into the old housing without trickery and then wouldn't move except with great effort. So I set that aside for possible future work and bought a $40 new one that's quite close in appearance. (1st picture) I've also started cleaning up nuts and bolts with the wire wheel on my Harbor Freight buffer. I also did this with the hard brake line at the lower end. (2nd picture)
Then I turned my attention to a carb overflow problem on #4. Oops, now it's #1. Oops, now it's #2. Enough of this whack-a-mole approach! I decided to remove the carbs again, but this time I will replace all the needle valves and floats. Progress then halted because my heat gun is at the new shop to use with heat-shrink tubing on the wiring. I guess this is going to be a problem for a while: being at one shop and needing a tool that is at the other shop. Last trip to the new shop I was stopped by needing the Dremel tool from the old shop (which I fetched). So I'll head to the new shop Friday to continue work there and will bring back the heat gun for the next trip to the old shop. (3rd picture)
BTW, the new pavement will have cured within a week and I can start moving the vehicles. Eventually everything will be in the new buildings and the problem will vanish.

[rocket johnny]

lucky you to have a cord !    one of my dream cars !

[twright3]

I spent a day at the old shop and made some progress. I removed the carbs and and did a partial rebuild on each. The bike has only 18,000 miles so I didn't see the need to replace the parts that wear out. And the gas in the carbs evaporated in the first few weeks it was parked before the gas could go bad, so I didn't replace the jets and so on. I only replaced the floats and the parts related to the needle valves.
I also replaced the tattered "boots" at the top of each carb. It's amusing that rebuild kits for 4 carbs totaled only $25 but the little rubber boots, being actual Honda parts, cost $20 each.
I reinstalled the carbs and found one overflowed, but popping off the bowl and giving it a jiggle got it working.
However I found contorting things to put on the new boots seemed to disable the return spring. I left fixing that for the next visit.
PS. Next week we start moving vehicles to the new shop.

[twright3]

This week I hoped to be posting results from my first ride on this barn find but it didn't work out. First I misplaced the throttle return spring. I've looked quite a bit but can't find it so I'll be ordering a replacement.
Then I decided I could do a short test drive without it. After all the first bike I owned was a new 1970 Sportster and back then Harleys had no return springs to begin with. So I got the carb's back on and installed the velocity stacks case and the air cleaner and fired it up! But then the clutch wouldn't slip. So I'll be taking that out to see if it needs new parts or just cleaning up.
This bike has reminded me how cold blooded a CB750 is. From January 1970 to December 1972 (and beyond) I owned what were considered the three hot bikes on the era: a Sportster, a CB750 and a Norton Commando. I'm convinced if you had a race with all starting cold on a 50 degree day and the finish line say a mile away, the Sportster would be first, the Norton second, and the CB750 last. If they are warmed up first, it would be the opposite order.
Since I've had the carburetors off and on a few times now I'll be doing a post on that to the tips section.
(In my new off-the-grid storage building I now have solar charging the big battery. I started wiring for trickle chargers and expect to get that working with the inverter next visit. I've moved three more cars in.)

[BenelliSEI]

Don’t pull that clutch apart yet! The one on my K1 sometimes sticks a bit after winter storage (or even a few months). Get the bike running, push your self down hill in neutral and try using the clutch and gearbox. Might make a few noises but generally comes free right away.

If left on the side stand (and the check valve in the oil pump keeps oil back in the tank), the clutch pack cavity is pretty much dry. The plates are probably just lightly stuck together.

[grcamna2]

Nice shop buildings ! 

[twright3]

I took the clutch apart and found the disks were stuck together and the metal disks were somewhat rusty (see photo). I was able to clean these up using a wire wheel on my Harbor Freight buffer (other photo). I also lightly wet sanded the pads on the other disks using motor oil rather than water. I put it all back together more than once until I was shure things were in the right order.
In spite of replacing the four floats and needle valve parts, #1 overflowed. Nevertheless I took it for a 100' ride, the first time the bike had moved under its own power in 40 years. Yeah!
I'll address the overflowing again next trip. Also, the front brake is dragging too much so I'm going to put in new disk pads I bought and clean up any deposits in the calliper. By then the throttle return spring to replace the one I lost should have arrived.
(Earlier this week back in the new shop I got the first trickle charger working off the inverter.)

[BenelliSEI]

When looking for the “overflow” check the obvious. If all looks OK, have a close look at the pipe inside the float bowl. I found a mysterious crack at the bottom of the tube (almost invisible) that thwarted all my efforts for quite some time. A small drop of solder cured it. I can only guess that at some point a bit of moisture collected there and froze, ever so slightly damaging the pipe.

[Sw1ssdude]

You can check your brass floats by shortly submersing them into hot water. if bubbles escape, you have a crack (do not boil them for too long, or they will pop).

if there is liquid trapped, hold them so that the crack is at the lowest point, and gently heat them up. do not use a lighter, for obvious reasons... use a hair drier, thats enough heat. the internal pressure will force all the fluid/gasoline out. then you can try resolder the float. you can also wick away the solder blob that closes the float. then rinse with carb cleaner to get all varnish out of the float, and close the hole up afterwards.

since you already have the soldering iron out, you can also smoothen out the small impression on the valve tab formed by the needle valve stem. with a smooth tab, its way easier setting the float height correctly.

[twright3]

If you watch my vehicle oriented TV shows you may have noticed a trend: new parts that don't work.
Such it was with my new floats. The rods were too small, allowing them too much freedom of movement. Eventually they got in some position that would not stop the flow of gasoline.
So it was off with the carb's again back to my original floats (after testing) and needle valves and seats (after cleaning). Then it was reinstall the carb's (and cables, velocity stack housing, air filter and gas tank).
Also I disassembled the caliper because the brake was dragging too much. The book said the alan bolts would be tight and they weren't kidding. Leverage with a 3' pipe on the wrench did the trick. I had to use pressure from the master to get the left pad out. I used a vice to push the piston back to keep the pressure properly aligned. But after getting the pads out I was able clean things up. The brake now has the normal light drag and works properly.
The engine ran with no gas leaks but it was a little rough. I had to go to a meeting so fixing this will wait for my next visit.

[newday777]

"If you watch my vehicle oriented TV shows you may have noticed a trend: new parts that don't work."

Do you have the link to your TV shows??

As to parts that don't work.....
There are many posts here in the forum of aftermarket carb parts being inferior. Original Honda carb parts are far better than new aftermarket parts. Honda still offers many parts for the carbs.

[MauiK3]

I really like the color!