Proud new owner of a ‘79 750K!

[Blaine750K]

Hey y’all, I just purchased a 1979 CB750K Limited Edition here in Portland, OR and I couldn’t be more excited to get it dialed in for the summer. My previous bike was a ‘78 CB400T so this feels like a major upgrade. The bike starts right up, idles nicely, and rides, but it definitely needs some fine tuning. It struggled in the RPM range from 5-6 on the ride home yesterday which in my limited experience may just be a matter of giving the carbs a good cleaning as it’s been sitting for a while. In anyone’s experience with these bikes, is there anything else that these bikes need urgent attention for before I start tinkering on anything and everything?

 

[Rampton]

First port of call before messing with carbs is compression test and valve clearances, if it's idleing at 1000rpm + - 100 the. Carbs will be pretty clean because the idle circuits are notorious for get blocked, bike looks mint. Best of luck rampton

 

[Biebs]

Run some fresh gas and seafoam carb cleaner in the gas. also check your air filter.

Nice bike!!

 

[ghartt95]

Hey y’all, I just purchased a 1979 CB750K Limited Edition here in Portland, OR and I couldn’t be more excited to get it dialed in for the summer. My previous bike was a ‘78 CB400T so this feels like a major upgrade. The bike starts right up, idles nicely, and rides, but it definitely needs some fine tuning. It struggled in the RPM range from 5-6 on the ride home yesterday which in my limited experience may just be a matter of giving the carbs a good cleaning as it’s been sitting for a while. In anyone’s experience with these bikes, is there anything else that these bikes need urgent attention for before I start tinkering on anything and everything?View attachment 12372

Blaine
I just bought same bike but have some restoration to do. I’m in Wilsonville. Can I take a look at yours for some references on missing pieces?

 

[ghartt95]

Hey y’all, I just purchased a 1979 CB750K Limited Edition here in Portland, OR and I couldn’t be more excited to get it dialed in for the summer. My previous bike was a ‘78 CB400T so this feels like a major upgrade. The bike starts right up, idles nicely, and rides, but it definitely needs some fine tuning. It struggled in the RPM range from 5-6 on the ride home yesterday which in my limited experience may just be a matter of giving the carbs a good cleaning as it’s been sitting for a while. In anyone’s experience with these bikes, is there anything else that these bikes need urgent attention for before I start tinkering on anything and everything?View attachment 12372

I just bought same. I’m in Wilsonville. Can I look at your bike for some references. I have some restoration to do.

 

[BAHNST]

Welcome....not urgent but "to do"..
Think bout a AGMBattery...if still the wet type it can leak over major components due to its position in the bike.
Charging system on these bikes just OK....AGM just needs a charge 4 to 6 monthly...

Check the date codes of your tyres..make sure they not more than 5 years old...ABCD (where AB is the week CD is the year...
Put in a new aircleaner element clean yout fuel strainer (fuel tap)...and just drain/flush the carb bowls....

Check valve clearances if not already done....most likely tight not loose...

 

[Stan C]

I just bought same. I’m in Wilsonville. Can I look at your bike for some references. I have some restoration to do.

I bought one last spring. Believe it or not, the jets and float bowls can be nicely cleaned without removing the carburetors. As soon as you remove the carbs, unless you know what you are doing, you are looking at more problems. The more you take them apart and DON'T know what you are doing, the more problems you will have. Please check the ignition ! ! A bike that old needs new ignition wires and BRAND NEW PLUGS ! BEEN THERE DONE THAT ! ! You can use automotive plug wires, as, original wires are hard to find and also OLD ! Had an issue with misfiring above 6000 RPM. Had cleaned the carbs (2 times removed and once again ON THE BIKE) It seems you can clean a bike too much and get lint into the tank somehow. Red lint found in/on idle jets perhaps from rag etc(?) The fuel MUST BE CLEAN !

 

[davidbartee]

I bought one last spring. Believe it or not, the jets and float bowls can be nicely cleaned without removing the carburetors. As soon as you remove the carbs, unless you know what you are doing, you are looking at more problems. The more you take them apart and DON'T know what you are doing, the more problems you will have. Please check the ignition ! ! A bike that old needs new ignition wires and BRAND NEW PLUGS ! BEEN THERE DONE THAT ! ! You can use automotive plug wires, as, original wires are hard to find and also OLD ! Had an issue with misfiring above 6000 RPM. Had cleaned the carbs (2 times removed and once again ON THE BIKE) It seems you can clean a bike too much and get lint into the tank somehow. Red lint found in/on idle jets perhaps from rag etc(?) The fuel MUST BE CLEAN !

I just got my 10th anniversary bike running good, totally went through the carbs, I bought a set of limited edition carbs in case I needed parts, but the original ones rebuilt great. Since everything went fine on the original ones, I cleaned & rebuilt my backup set. New kits with correct 68 primary jets and 102 secondary, new air cutoff diaphragms, new accelerator pump. They are available if someone needs them for their limited edition cb750k