Topic: Starting a K8 project with almost no mechanical aptitude...what could go wrong?

[BenelliSEI]

Nick…. Did you get the brackets that connect the pipes together and to the foot peg bolts? They are quite an odd shape and you really need them to hang them correctly. I might have one (only).

[newday777]

Hmmmm
Is that tire gone bad?

[scubanerdnick]

Greetings everyone.  Not sure if you all remember me but as a quick summary I picked up a 1978 CB750K8 in honor of my father who passed away from cancer in March 2023.  I was posting here pretty consistently up through November 2023 and was super excited about the build.  At that point I was about 1 year out from retiring from the military.

I went into the Christmas holiday that year in good spirits and then before I knew it I was leaving my final assignment in the military and preparing for a civilian internship for the final six months of my time in service.  During one of my pre-retirement medical appointments I was diagnosed with cancer (at 41) and catching it was both a stroke of luck and blessing.  Men - do not neglect your men's health appointments. 

Needless to say the bike got put back together in a hurry (running but not running well) and I wasn't able to do much with it.  So in the year and a half since I last posted an update I have been fighting cancer, I fully retired from the military, moved off the military base into a new house and got a new job.  Cancer is still there but I'm getting better and have a positive prognosis. 

That said, I am committed to getting back into this bike project and want to see it through to completion.

So where I'm at now is the bike will start and idle just fine.  It does not respond well to being in gear at all and will not go far without stalling out and dying.  I am replacing the battery and have decided to pull the carburetors off to give them a bit of a clean.  I have rebuild kits but have never done a carb cleaning let alone a rebuild so I'm seeing what I see when I get them off.  I'm hoping with a bit of a good cleaning and a new battery I'm able to at least take the bike around the block.

Major projects I'm going to tackle still include:

Removing 4 into 1 exhaust and installing the stock 4 into 4 exhaust I picked up before I caught the cancer.
Swapping the front forks from the 1982 dual disk to the original front forks/wheel/brakes.  I bought all of this before I got sick and I want to do something with it.

At any rate I look forward to getting back on the forum here and gathering inspiration from everyone.  Attached is a picture I took of the bike last fall when I was preparing to move homes.

[grcamna2]

Greetings everyone.  Not sure if you all remember me but as a quick summary I picked up a 1978 CB750K8 in honor of my father who passed away from cancer in March 2023.  I was posting here pretty consistently up through November 2023 and was super excited about the build.  At that point I was about 1 year out from retiring from the military.

I went into the Christmas holiday that year in good spirits and then before I knew it I was leaving my final assignment in the military and preparing for a civilian internship for the final six months of my time in service.  During one of my pre-retirement medical appointments I was diagnosed with cancer (at 41) and catching it was both a stroke of luck and blessing.  Men - do not neglect your men's health appointments. 

Needless to say the bike got put back together in a hurry (running but not running well) and I wasn't able to do much with it.  So in the year and a half since I last posted an update I have been fighting cancer, I fully retired from the military, moved off the military base into a new house and got a new job.  Cancer is still there but I'm getting better and have a positive prognosis. 

That said, I am committed to getting back into this bike project and want to see it through to completion.

So where I'm at now is the bike will start and idle just fine.  It does not respond well to being in gear at all and will not go far without stalling out and dying.  I am replacing the battery and have decided to pull the carburetors off to give them a bit of a clean.  I have rebuild kits but have never done a carb cleaning let alone a rebuild so I'm seeing what I see when I get them off.  I'm hoping with a bit of a good cleaning and a new battery I'm able to at least take the bike around the block.

Major projects I'm going to tackle still include:

Removing 4 into 1 exhaust and installing the stock 4 into 4 exhaust I picked up before I caught the cancer.
Swapping the front forks from the 1982 dual disk to the original front forks/wheel/brakes.  I bought all of this before I got sick and I want to do something with it.

At any rate I look forward to getting back on the forum here and gathering inspiration from everyone.  Attached is a picture I took of the bike last fall when I was preparing to move homes.

Good to hear from you again,and glad to know you're still fighting it 
I'm looking forward to your carburetor overhaul;which brand of carb. rebuild kits did you buy ?

[scottly]

Swapping the front forks from the 1982 dual disk to the original front forks/wheel/brakes.

Hey Nick, the '82 brakes are much better than the original brakes, and you *may* be able to keep the spoke front wheel if that's your concern.
http://forums.sohc4.net/index.php/topic,89771.125.html

[newday777]

Welcome back aboard Nick, congratulations on your retirement and keeping on with your fight. Keep looking up.

As to getting onto your carbs cleaning. They are intricate and special care is needed for cleaning the accelerator pump system so it sqirts properly into each carb when done. Lots is written on it and videos too.
Don't use aftermarket brass parts from kits. Clean and reuse the original Keihin brass parts.( If you need new float valves only use them from Honda dealers.)
The small rubber tubes between the carbs have brass in them so do not discard them, reuse them.
Be very careful removing the float pins, you don't want to bust the posts. If the pins are stuck from gummed old gas, I've found using a small torch(I bought a mini torch on Amazon for $30 that is used for specialty food prep) to heat up the posts and pin ends to melt the gum and use a tiny nail drift pin or a nail of correct size flattened off to tap carefully on the pins. When the gum sizzles, it's time to tap the pins loose.
The slow jets are pressed in and you need to pull them out with pliers to clean the emulsion tubes if you want it to run good.

A good tutorial for cleaning the PD42A carbs(78F carbs), which are similar to your 42B carbs , and how to clean the accelerator pump system.

http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204



K8 carb disassemble to cleaning video

Cleaning

Reassemble the carbs

Keep on keeping on.

[newday777]

Swapping the front forks from the 1982 dual disk to the original front forks/wheel/brakes.

Hey Nick, the '82 brakes are much better than the original brakes, and you *may* be able to keep the spoke front wheel if that's your concern.
http://forums.sohc4.net/index.php/topic,89771.125.html

Thanks Scott for the link, it's timely for me as I just ordered some dual piston calipers this week that should arrive today to use on my F2 or my F1 that might get the GL1000 front end???

[Stev-o]

Welcome back Nick, keep the fight going.

Cant stress enough about not using aftermarket carb kits...

[grcamna2]

Welcome back aboard Nick, congratulations on your retirement and keeping on with your fight. Keep looking up.

As to getting onto your carbs cleaning. They are intricate and special care is needed for cleaning the accelerator pump system so it sqirts properly into each carb when done. Lots is written on it and videos too.
Don't use aftermarket brass parts from kits. Clean and reuse the original Keihin brass parts.( If you need new float valves only use them from Honda dealers.)
The small rubber tubes between the carbs have brass in them so do not discard them, reuse them.
Be very careful removing the float pins, you don't want to bust the posts. If the pins are stuck from gummed old gas, I've found using a small torch(I bought a mini torch on Amazon for $30 that is used for specialty food prep) to heat up the posts and pin ends to melt the gum and use a tiny nail drift pin or a nail of correct size flattened off to tap carefully on the pins. When the gum sizzles, it's time to tap the pins loose.
The slow jets are pressed in and you need to pull them out with pliers to clean the emulsion tubes if you want it to run good.

A good tutorial for cleaning the PD42A carbs(78F carbs), which are similar to your 42B carbs , and how to clean the accelerator pump system.

http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204



K8 carb disassemble to cleaning video

Cleaning

Reassemble the carbs

Keep on keeping on.

Thanks for your post Stu.

[scubanerdnick]

Thanks everyone for the kind words on the cancer.  Please do not neglect those health appointments.  Glad you are all well.

I will take everyone's advice on the carb kits and just try to clean up what is already there.  I figure I'll know when I get there but is there anything I should be on the look out for in case the previous owner already tried one of those kits?  Are there any kits out there that are good to use or are all of them garbage?

Regarding the front wheel/tire swap - I acknowledge the brakes from the '82 are most likely better so I may look into just running with what is on there.  Of a larger concern to me is the fact the front brake and master cylinder is one of those generic front brakes and not from the same '82 front end the rest of it is from.  Its a long ways down the line so nothing I need to worry about right now. 

[newday777]

I recommend to stay away from 4Into1, 
The gaskets from most of the aftermarket are probably ok to use. Just stay away from using the aftermarket brass parts in the kits.
You can usually clean and use the original floats and brass.
Original Keihin brass will have this stylized K on each of the brass parts.

These are Keihin slow jets off the earlier roundtop carbs.

[denward17]

Welcome back to the fold!

Again, Thank you for your service and I hope your health battle will be in the rear view mirror soon.

[scubanerdnick]

So I have the carbs off.  The boots were on there pretty good but a bit of heat from heat gun loosened them and I was able to get them off pretty easily overall.

Not sure if this matters or not but when removing the rear plate (stay plate?) there were 8 screw holes but only 3 screws.

I took the float bowl off of carb 1 to see what it looked like (picture below) and also photographed the inside of it.  Would love some opinions on how bad this looks, but I didn't think it was too bad.

I am awaiting arrival of an ultrasonic cleaner I ordered during Prime Day to help me get these cleaned up.  So far I'm just going slow and taking a ton of pictures in addition to watching videos.  I've got separate containers for each carb as well as smaller containers for the small parts.       

[newday777]

Dang Nick, those don't look half bad inside. Mine were hardened molasses inside. It's either been cleaned or was kept running properly.

[BenelliSEI]

Dang Nick, those don't look half bad inside. Mine were hardened molasses inside. It's either been cleaned or was kept running properly.

+1…. Those look pretty good! Take lots of pictures, particularly the throttle and choke linkage connections. You’ll need the reference when you go to put them back together.

[MauiK3]

Have to have all 8 screws for the carbs.
Hopefully you have JIS screwdrivers, those Phillips looking screws aren't Phillips. Vessel makes the tool.