Henchai
CB750 New member
Hello All! I was recently handed a CB750k from a friend, a friend who bought it from a previous owner who lived in another state. The bike was purchased pre-covid and ever since has sat in his garage. He then decided he didn't want it anymore and gave it to me, except its been sitting in his garage and I have no idea what type of work has been done to it. I'm no mechanic, but I'd like to think I have a decent head on my shoulders when it comes to mechanical stuff. I've recently started to work on it and there was been a handfull of issues that I need help with. Keep in mind, this is my first bike I've ever tried to fix, the last one I rode was pretty new so it didn't need much mechanical care.
First thing I did was an oil change, I used 10w-40 full synthetic motorcycle oil that I bought from Oreillys, 4 quarts. I also replaced the battery and fired it up. It was running soundly, but when I checked the cylinders by spraying some water on it, cylinder 2 was cold.
I then replaced the spark plugs, the old ones I took out were D7RES but the new ones I put in were D8EA as per the specs I found online.
I then did a compression test and found that each cylinder was only pushing out a womping 80-85psi.
I put the whole thing together again and fired up the bike, with cylinder 2 now hot but cylinder 3 cold this time.
The bike was also cutting out while idle, which it didn't do before, and when I rolled the throttle, it seemed unstable, I would roll it a certain amount and wait, and the rpm would slowly rise then all of a sudden shoot up real fast.
I started to test the coils to see if each spark plug was sparking up, and during that time the starter starting dying out.
It sounded like it was out of battery, but I thought this was weird since it is a new battery, but I have been turning on the starter to test for a while, maybe that killed the battery?
I tested the battery with a multimeter and it had ~16v, which I thought was good. I forgot to test it while trying to kick the bike on.
I put the battery on a tender and tried to kick the bike on, but the lights just dim and fade out and the solenoid clicks once.
Thats all the work I've done so far, its still in his garage and I can only check on it one weekends, if I'm not busy.
I really want to try and work on this myself, at least as much as I can as a personal project without it taking too much of my cost.
I can get a knockoff leakdown test from amazon and test it, but if a major issue with the engine comes up, I might not be able to handle that myself,
even though I'd be more than glad to try and take it on, I just don't have the space to work on an engine, nor the right tools.
Alkso, is my battery really dead? I admit I should have left the battery on a tender over night, but I didn't want it to be plugged in without knowing when the next
time I can check on it.
Also, what do you guys think of the low psi? 80 sounds super low, and quick tips on how to check for big leaks like that?
If all else fails, I just need to get it up and running so I can take it to a shop.
Also, my friend who bought it from previous out of state owner never even transfered the title, so I have an out of state title with the previous registered owner, and I
went to the dmv to transfer the title and was told they need to physically see it in order to verify the VIN and issue out a license plate, as there is currently no license plate.
This is my first post, so I am sorry if I am breaking any rules in posting for help, and I thank anyone for stopping by and reading.
Have a blessed day!
First thing I did was an oil change, I used 10w-40 full synthetic motorcycle oil that I bought from Oreillys, 4 quarts. I also replaced the battery and fired it up. It was running soundly, but when I checked the cylinders by spraying some water on it, cylinder 2 was cold.
I then replaced the spark plugs, the old ones I took out were D7RES but the new ones I put in were D8EA as per the specs I found online.
I then did a compression test and found that each cylinder was only pushing out a womping 80-85psi.
I put the whole thing together again and fired up the bike, with cylinder 2 now hot but cylinder 3 cold this time.
The bike was also cutting out while idle, which it didn't do before, and when I rolled the throttle, it seemed unstable, I would roll it a certain amount and wait, and the rpm would slowly rise then all of a sudden shoot up real fast.
I started to test the coils to see if each spark plug was sparking up, and during that time the starter starting dying out.
It sounded like it was out of battery, but I thought this was weird since it is a new battery, but I have been turning on the starter to test for a while, maybe that killed the battery?
I tested the battery with a multimeter and it had ~16v, which I thought was good. I forgot to test it while trying to kick the bike on.
I put the battery on a tender and tried to kick the bike on, but the lights just dim and fade out and the solenoid clicks once.
Thats all the work I've done so far, its still in his garage and I can only check on it one weekends, if I'm not busy.
I really want to try and work on this myself, at least as much as I can as a personal project without it taking too much of my cost.
I can get a knockoff leakdown test from amazon and test it, but if a major issue with the engine comes up, I might not be able to handle that myself,
even though I'd be more than glad to try and take it on, I just don't have the space to work on an engine, nor the right tools.
Alkso, is my battery really dead? I admit I should have left the battery on a tender over night, but I didn't want it to be plugged in without knowing when the next
time I can check on it.
Also, what do you guys think of the low psi? 80 sounds super low, and quick tips on how to check for big leaks like that?
If all else fails, I just need to get it up and running so I can take it to a shop.
Also, my friend who bought it from previous out of state owner never even transfered the title, so I have an out of state title with the previous registered owner, and I
went to the dmv to transfer the title and was told they need to physically see it in order to verify the VIN and issue out a license plate, as there is currently no license plate.
This is my first post, so I am sorry if I am breaking any rules in posting for help, and I thank anyone for stopping by and reading.
Have a blessed day!