Topic: Tried to change the oil....

[jlockwoo]

The other day, I tried to change the oil in my 1975 cb750f. everything was going fine until I added the new oil and it seem it won't leave the tank. I have kicked the bike over more than I wish to talk about, yet the oil is still filled to the top of the tank(put in 3 quarts). I read a how to on oil changes before i did it. Just said to drain the oil from tank, filter, and engine case. Replace the oil filter, and put case lug and tank plug back in. Last step was, Refill oil and kick bike over a couple of time to get oil into case. Did I do something wrong? Any ideas would be a great help.

thanks Jake

[Quail "Owner of the comfortable k8"]

You did it the way I do it. I do know there is a check valve to prevent the oil tank from filling the crankcase.

[Raul CB750K1]

I was doing a pre-ride check a couple of weeks ago and discovered the level was just barely above minimum. I know the bike doesn't consume oil, but as I use it sparingly and couldn't remember when was the last time I ckecked, I just assumed it was low, but as I know too that the check valve is not completely oil tight, I started the bike and left it running for a couple minutes. I thought it would be enough for the oil to circulate. By looking at the tank, the oil was circulating but the level didn't change, so I just filled it.

Needless to say, at the first coffee stop I rechecked the level, and it was well above the maximum, almost to the brink of the tank!!! Seems that it takes more than two minutes for the oil to fully circulate.


Raul

[puppytrax]

Needless to say, at the first coffee stop I rechecked the level, and it was well above the maximum, almost to the brink of the tank!!!

Did you get a straw and a paper cup from the coffee shop and "adjust" the oil level?? 

That would have been worth a pic...   

[nteek754]

jlock did you try  kill switch off so it wont start and  spin engine over till the oil goes down  prob just got like an air bubble in there  hope this helps good luck seven fifty four ever Craig in Maine

[Steve F]

I can't get the proper reading until I start the bike and let it run for 30 seconds or more.  Shut it off and then check the level again.

[jlockwoo]

No, I haven't tried to turn it over with the electric start. I have a wiring issue that I must fix first. I am just worried about cranking it over like crazy with no oil in the case. Does anybody no how much oil the tank can hold? I have put 3 quarts in and its filled to the brim.

Thanks again Jake

[SohcCBs]

Open this plug and kick it over....maybe on the center stand in 4th rotate the tire.  If oil is cycling thru, it WILL come out this hole.  Don't ask how I know that....it'll make a bit of a mess.

If you don't get any oil thru this hole, since you've only put in 3qts., you might be able to prime the engine here with just a cup (or drain a cup out of the tank first if needed), but that'd be a guess on my part, but it may be why that hole is there.  To rid the system of air and priming.

[Raul CB750K1]

Did you get a straw and a paper cup from the coffee shop and "adjust" the oil level?? 

That would have been worth a pic...   

No. The first coffe stop was about one hour from home, so I thought it nothing happened for the oil been way too much over the max level, nothing should happen for the rest of the day. I rode about 300 miles that day, and back home, I used a big syringe to remove the excess oil.


Raul

[Bodi]

The tank connects to the pressure oil pump. That pump feeds the engine through the oil filter and oil galleries to the bearings and rocker area, then the oil just dribbles down to the sump. Once the sump fills enough to reach the scavenger pump inlet the scavenger pump sends it back to the tank.
It takes a fair bit of pumping to fill the oil filter and galleries and start oiling stuff so that the oil starts dribbling to the sump. After enough has gone through the engine to reach the scavenger and start coming back into the tank you can check the tank level and fill it to the full mark.
There's a check valve in the scavenger pump that keeps oil from going back into the sump... sometimes that leaks a bit or even sticks open, so it's best to check the oil level just after shutting the engine off after a few minutes running; sitting overnight enough oil might have gone back through the scavenger pump that the oil tank will overflow (nasty mess) with the motor running.
You will have to kick the engine over for a leg-wrecking amount of time to get the oil system fully functioning after changing the filter and draining the sump. Unless you suspect a bad oil pump for some reason just assume all is well, and remember to add the rest of the oil when you get the motor running.

[jaknight]

Hi jlockwoo,

     Whenever I change the oil on my 750 K4, I put in just short of 3 quarts.  Then, with the kill switch on, I use the kick starter for 15 to 20 cycles.  Then I start the engine, let it run for 2 minutes.  Stop the engine, then check the oil level.

     From there, top off with oil as needed.  This is a recommended procedure by a man who was once a professional Honda racer............

     Perhaps one should remember that this was recommended for the earlier K series 750s; I am not positive this is a valid procedure for the f series bikes; just a thought.........

     ~ ~ ~ jaknight ~ ~ ~

[jay]

i have 1978CB750f changed oil last night. i  was only able to get a little over 2 litres in.  i had to put kill switch off crank engine for a while. then i started the bike it seemed like it was circulating. toped it off . 2 litres and its over full .never had chance to take bike for ride because of rain. but hope i did every thing right.

[bobsmith]

You cant really "overfill" the drysump system, The excess  will simply show as overfill or if too much, overflow the tank (bad for right hand cornering) the scavenge pump will keep the sump from windage no matter how much oil is in the tank,  low oil is another story..