Topic: New Project - 1972 Honda CB750

[God of Thunder]

Went ahead and got the grips on! Already looks more like a motorcycle! 



Had trouble finding some pan head screws - I found some in 30mm but the heads were huge. I opted to buy them AND buy some hex heads. I put the hex in for now - this CB750 will never be mint, so maybe I'll find some silver hex's and leave them....or maybe we'll just get the right ones and hope I never have to take them off. 

[Alan F.]

This guy's a member here and has been selling these kits for a very long time now:
http://www.metrocast.net/~spillane/index_002.htm

[HondaMan]

The local hardware stores will be selling ISO metric screws, which will have heads 50% larger than the older JIS type screws. You can get the JIS screws from the bike shops, all carry them. They're called "OEM screws" these days, about $1-$2 each.

The world went ISO in the 1990s regarding metric, hence the difference: for those who don't know, the JIS is "Japanese Industrial Standard", started in the early 1950s while Japan rebuilt from WWII.

[God of Thunder]

The local hardware stores will be selling ISO metric screws, which will have heads 50% larger than the older JIS type screws. You can get the JIS screws from the bike shops, all carry them. They re called "OEM screws" these days, about $1-$2 each.

Thank you so much! That helps a lot!

[Stev-o]

I like the 6mm stainless socket head screws, I get 'em at a bolt specialty store, very inexpensive. You'll never strip one!

[HondaMan]

I like the 6mm stainless socket head screws, I get 'em at a bolt specialty store, very inexpensive. You'll never strip one!

Something to be watchful for: stainless fasteners are often made slightly smaller than the steel ones to reduce galling tendencies. If the cases have had lots of screwing-in-and-out before, which thins down the threads a bit, the result of this combination is easily-stripped screw hole threads for the shorter screws. One place where this happens a lot is on the cam cover.

[God of Thunder]

Well its been a hot minute - but that doesn't mean much has got done. I still have a gas leak in carb #4, and sometimes but less often #3. I've got a rebuild kit for the one, and now I might as well redo it for all of them just to prevent future problems.

With that said, I decided I had enough trust in it to do the "first ride" - See below a small sample my wife took.
(I tried to embed this but apparently YouTube is uploading this as a 'short' for some reason)

https://www.youtube.com/shorts/Spha1OOOz0M

I learned some stuff from this ride. First - it was around the block, which was about .25 of a mile. I think the throttle cable has a place where it can hang up. As I had some moments where it just revved up and the only way to bring it back down, was the manually move the throttle grip. The gas tank is not secured so that might be part of the issue. The front brakes don't work - and has such they're (now) locked on. I found a clog in the link that I am working to clear out.

And finally - I am still a terrible motorcycle rider. Stalled it numbers times, nearly ran into someones yard - and all of this in less than a half of a mile. I've taken the course - but I'm just a scared rider!

Lastly - The front brake line was wired strange and a lot of it was sticking up above the handle bars.....I found an empty clip on the fork and thought maybe it should be going through there, which made it run like this (see below!) - does this look correct??

[Alan F.]

Don't forget to air up your tires before test rides.

[HondaMan]

Lastly - The front brake line was wired strange and a lot of it was sticking up above the handle bars.....I found an empty clip on the fork and thought maybe it should be going through there, which made it run like this (see below!) - does this look correct??

Umm...nope...
That hose is VERY extra long, it looks like something from a chopper with hi-rise bars! The hose is supposed to come straight down from the handlebars into the fitting, from above.

The clip you found is supposed to be for the tach cable. I'll see if I can get a picture of mine as example.

[God of Thunder]

Been a minute - but that doesn't mean work has stopped. After I cleaned the carbs, another carb started leaking gas again......

So I opted to take it to the professionals and they're going to get it running and starting easily every time so that I don't have to worry about it anymore. I've had trouble with it only wanting to run with the choke on, be all over the place with the idle, etc etc, so with my knowledge, I felt like I gave it all I had, and it was time to let the professional get it perfect, so I can start thinking about paint. It should be back this week or next, and then it'll be paint time!

I know I've got a clog in the brake line, so I've got to fix that first actually, but it'll be darn near paint time! Does anyone know the code for gold for the K2?

[Stev-o]

Does anyone know the code for gold for the K2?

There are no paint codes for it.  But, here is one place you can buy paint...

https://vmrpaints.com/products/honda-motorcycle-candy-gold-restoration-paint?_pos=12&_sid=cff18610a&_ss=r

As far as the brake line, a lot of us order replacements from Apex...

http://www.apexbrakes.com/custom.asp

[tourmax]

Been a minute - but that doesn't mean work has stopped. After I cleaned the carbs, another carb started leaking gas again......

So I opted to take it to the professionals and they're going to get it running and starting easily every time so that I don't have to worry about it anymore. I've had trouble with it only wanting to run with the choke on, be all over the place with the idle, etc etc, so with my knowledge, I felt like I gave it all I had, and it was time to let the professional get it perfect, so I can start thinking about paint. It should be back this week or next, and then it'll be paint time!

I know I've got a clog in the brake line, so I've got to fix that first actually, but it'll be darn near paint time! Does anyone know the code for gold for the K2?

Be aware that as brake hoses age, they can actually collapse or close up inside which appears as a "clog". Only cure is to replace the line. If yours have any serious age on them, I'd recommend throwing on a set of new hoses and be done with it...good time to upgrade to stainless braid lines or if you like a more "classic" look you can get the same hose but in a black exterior.

[MauiK3]

Definitely get brake lines, safety first.

[newday777]

Lastly - The front brake line was wired strange and a lot of it was sticking up above the handle bars.....I found an empty clip on the fork and thought maybe it should be going through there, which made it run like this (see below!) - does this look correct??

As Mark said, that is definitely not correct.
Straight down from the top as in this part fiche shows.(too early to go and take a real picture for ya)

[HondaMan]

Lastly - The front brake line was wired strange and a lot of it was sticking up above the handle bars.....I found an empty clip on the fork and thought maybe it should be going through there, which made it run like this (see below!) - does this look correct??

Umm...nope...
That hose is VERY extra long, it looks like something from a chopper with hi-rise bars! The hose is supposed to come straight down from the handlebars into the fitting, from above.

The clip you found is supposed to be for the tach cable. I'll see if I can get a picture of mine as example.

Another observation: with that down-up loop on there, it will be VERY hard to ever bleed that front brake!

[God of Thunder]

Just got the bike back! Ran great when I got it home - but then the next day it still has odd issues. Like the choke seems to have it idle lower, and then when you turn the choke off it speeds up. Which seems backwards to me. I feel like I always have to adjust the idle screw - and then once its ran for about 5-10 minutes, it seems to be in a good spot.

I was going to try and go around the block today - despite the front brake....however I moved the bike to my parents house. I ran it for about an hour, then it stopped. I went out and could hear pressure, so I opened the gas tank and gas exploded out of there. I must have a vent clogged or something. Then, I went to put more gas in it - and my dad put 2 stroke gas in a normal gas can. So now I've got to drain the tank.....oh joy.

[newday777]

Just got the bike back! Ran great when I got it home - but then the next day it still has odd issues. Like the choke seems to have it idle lower, and then when you turn the choke off it speeds up. Which seems backwards to me. I feel like I always have to adjust the idle screw - and then once its ran for about 5-10 minutes, it seems to be in a good spot.

I was going to try and go around the block today - despite the front brake....however I moved the bike to my parents house. I ran it for about an hour, then it stopped. I went out and could hear pressure, so I opened the gas tank and gas exploded out of there. I must have a vent clogged or something. Then, I went to put more gas in it - and my dad put 2 stroke gas in a normal gas can. So now I've got to drain the tank.....oh joy.

"I ran it for about an hour, then it stopped. I went out and could hear pressure, so I opened the gas tank and gas exploded out of there"

Did you just let it idle for an hour? No fan pointing to the motor? Very bad to do grasshoppah.
These air cooled motors need air flow over the fins to cool it off. Use a fan when setting idling not moving.
 Learn from your lesson.

[tourmax]

Just got the bike back! Ran great when I got it home - but then the next day it still has odd issues. Like the choke seems to have it idle lower, and then when you turn the choke off it speeds up. Which seems backwards to me. I feel like I always have to adjust the idle screw - and then once its ran for about 5-10 minutes, it seems to be in a good spot.

I was going to try and go around the block today - despite the front brake....however I moved the bike to my parents house. I ran it for about an hour, then it stopped. I went out and could hear pressure, so I opened the gas tank and gas exploded out of there. I must have a vent clogged or something. Then, I went to put more gas in it - and my dad put 2 stroke gas in a normal gas can. So now I've got to drain the tank.....oh joy.

You still don’t have your carbs dialed in right or you have a problem you haven't found yet (like a vacuum leak, cables binding, etc).

Slow on choke and poor idling once up to temp seems to indicate a rich condition. But its pretty difficult to diagnose a carb issue over the internet. A vacuum leak can cause similar problem as well.

Generally, a better idle when warm indicates a lean condition, as the available fuel vaporizes better once the engine is up to temp.

Does it have a “hanging idle” or does it stumble down below idle and return to the correct rpm with a throttle blip? Each condition can indicate certain causes.

These are all just general suggestions. Rich or lean can present with similar symptoms and sometimes its not intuitive which is which.

Carbs aren’t “black magic”, they’re relatively simple devices. The problem is in know what its doing and what need to be adjusted. Thats where the “a bit science and a bit art” comes in. Book knowledge only gets you so far with carbs, the rest is hard won experience working in them.

Here’s a good general article to read through:

https://www.cycleworld.com/story/bikes/kevin-cameron-explains-how-to-tune-carburetors/

Pretty hard to beat motorcycle articles written by the infamous Kevin Cameron….

[God of Thunder]

Today was a day of ups and downs - but we ended on an UP!

I wanted to drive it today - and was determined today was going to be "the day" - and it didn't start off great. I determined that first - I needed to fix the front brake. I did some research and it seemed doable. I bled the brake-fluid - put new fluid in - and unbelievably, the brake worked as intended. So that was a win. Then - it was TIME. I've gone 1.3 miles on it - and I was ready to go.

Except - now the bike wouldn't start.

This was mind blowing to me as I had started the bike a few times throughout the day. On an off chance, I discovered that the headlight wasn't working. The motor would turn over, but wouldn't start. It didn't make any sense as clearly the switch had power, but the headlight didn't have any power - and I knew it was good as I was showing my wife it earlier today. So this made me think something with the switch was faulty. I removed the headlight, and as soon as it was removed......it came on. So - I looked inside and found a few wires that were cut - didn't have any exposed wires, but that was the only issue I could determine. So I took them, put electrical tape around them, reinstalled the headlight - and BOOM - started right up to a perfect 1200rpms.

It was time.

As I mentioned, I'm not a great rider, but something about the history of these motorcycles makes me care enough to keep chancing it. Today though, when I put it in first and took off......everything went perfect. I didn't stall it one time, was able to drive perfectly, shift through the gears - and as of now - I've put a total of 4.9 miles on the motorcycle! The ride went perfect, it was a blast - a lot of bugs. But I'm slowly getting all the kinks ironed out. It'll be getting even closer to paint now!

With that - the motorcycle was put away for the night - and tomorrow we'll try again! I finally got those zippers off!

[Alan F.]

That's great news congratulations!
It wants to ride, just act like it's got a soul and don't say anything bad in front of it....

[God of Thunder]

Another good ride the other night. I did notice one of my carbs was still leaking a little gas - so I've got to get that sorted asap. Additionally, the throttle is really hard to turn. It's doable - but really wears you out after a few miles. What could be the primary cause for something like this?!

[Alan F.]

A stiff throttle can have a few causes. There could be dirt or old lube between the throttle grip tube and right hand handlebar. Your throttle cables could be dirty inside and in need of a good cleaning and re-lubrication. Your carb linkage could be stiff needing adjustment. Or you might just have a heavy throttle return spring on your carbs.

Have you had the two throttle cables disconnected from the carbs lately? That'd be the easiest way to determine if it's a throttle tube or cable issue.

There are lots of old threads discussing the heavy throttle return spring.

[God of Thunder]

Well - TODAY was a good day. One. Its Friday. But now - she looks the part!

Today - I got a new seat. out with the old......





And IN with the new!!!! I got it off of eBay, and I have no clue if its real or a reproduction. It was priced decent and looks great. I "thinK" its real - so that probably means its a reproduction!  The new seat does sit higher though. For a short guy like myself - its a bit harder!








So at this point - we only have a few things left. The throttle cable still wears me down after 5 miles. I need a left handlebar controller. A new front brake cable as this one is too long, and new side panels/logos/decals and PAINT!!

I'm almost there!!

[newday777]

The reason for the stiff throttle is too long and miss routed cables.

[God of Thunder]

The reason for the stiff throttle is too long and miss routed cables.

There were considerably longer bars on here when I bought it (see post 1) - so that is my thought as well.