Topic: Foaming Oil Causing Overflow?

[HotCarl73]

I just got done refurbishing the rear end on my CB750 K3. new tire, tube, bearings, rebuilt and painted swingarm and chain guard, polished hubs and pipes, and cleaned up 40 years worth of crud. went for a ride last night and wanted to see if i could crack 100 mph, now that i wasn't scared of the ancient tire exploding on me. it cracked 100, but when i got home, all my hard work was covered with oil. i replaced the oil breather lines while i had everything apart and they're routed correctly. valve cover to atmosphere, top oil tank tube to atmosphere, bottom oil tank tube to rear of transmission. i know about wet sumping and it's not over filled. engine runs strong and has 155 psi on all 4 cylinders. i check the oil after each ride, and a few weeks ago, when i was pushing it hard, the oil in the tank looked like a shaken up soda. lot's of foam. i'm pretty confident that this has been happening all along, but the old oil breather hoses were routed to halfway down the back of the engine which was all covered in oilly cruddy crap. my new hoses hang below the swingarm, which is why it all made it back onto the tire, instead of just all over the engine. i'm not sure yet whether it's coming from the valve cover or the oil tank breather. i'm going out to see if i can tell in a little while. i'm running regular old castrol gtx 20w-50. i don't see anything on the bottle that says low detergent. i think my problem is that with the small parts and high revs (and maybe the dry sump system) the oil is foaming up and spitting out the tank breather. i'm gonna try changing the oil to a motorcycle specific oil (not synthetic), and see what happens. i'm not looking to start an oil thread, i just want to check with the experts and see if my theory is sound. thanks.

[jamesbekman]

Ive had that happen in a car and it was due to the oil being over pressurized. 

Only other thing I can personally think of is did you put too much oil in it?

-James

[HondaMan]

I just got done refurbishing the rear end on my CB750 K3. new tire, tube, bearings, rebuilt and painted swingarm and chain guard, polished hubs and pipes, and cleaned up 40 years worth of crud. went for a ride last night and wanted to see if i could crack 100 mph, now that i wasn't scared of the ancient tire exploding on me. it cracked 100, but when i got home, all my hard work was covered with oil. i replaced the oil breather lines while i had everything apart and they're routed correctly. valve cover to atmosphere, top oil tank tube to atmosphere, bottom oil tank tube to rear of transmission. i know about wet sumping and it's not over filled. engine runs strong and has 155 psi on all 4 cylinders. i check the oil after each ride, and a few weeks ago, when i was pushing it hard, the oil in the tank looked like a shaken up soda. lot's of foam. i'm pretty confident that this has been happening all along, but the old oil breather hoses were routed to halfway down the back of the engine which was all covered in oilly cruddy crap. my new hoses hang below the swingarm, which is why it all made it back onto the tire, instead of just all over the engine. i'm not sure yet whether it's coming from the valve cover or the oil tank breather. i'm going out to see if i can tell in a little while. i'm running regular old castrol gtx 20w-50. i don't see anything on the bottle that says low detergent. i think my problem is that with the small parts and high revs (and maybe the dry sump system) the oil is foaming up and spitting out the tank breather. i'm gonna try changing the oil to a motorcycle specific oil (not synthetic), and see what happens. i'm not looking to start an oil thread, i just want to check with the experts and see if my theory is sound. thanks.

You're on the right track: Casrtol's automotive oil is one of the highest-detergent oils out there. That's why they advertise about is "stopping sludge". Heck, it foams in my lawn mower!

 At 155 PSI, you may have a modified engine? Typically a 9.8:1 or higher compression value brings up numbers like that at altitudes like LV. Just curious...

If the valve guides are worn, this will greatly increase the blowby pressures in the crankcase, which will contribute mightily to the out-the-breather oil vapors. The K3 often has worn guides, as that was the beginning of the cast-iron valve guides. Those last about 25k miles with average maintenance, 35K tops. Worn valve guides, if the valves are still the ones that belong in their respective holes, won't prevent the bike from running pretty well, but it does increase the crankcase pressures. For short-term "fixes" of this in the past, I have connected the oil tank's breather tube to the cam cover's breather tube. This raises the level (physically) that the oil has to climb to get out, and can get you home from a long tour with a much cleaner bike. I wouldn't recommend it long term, as it makes a mess by blowing out the oil cap breather vent instead, so you will end up with an oily rear brake switch and right-side exhaust pipe(s). But, it helps keep it off the rear tire until you can get home.

[Duke McDukiedook]

I would recommend switching to a JASO-MA rated oil very soon if you do not want to encounter more oil problems.

Mark- When you say connect the valve cover and oil tank breather tubes do you suggest a 'T' connection that drains down?

[HotCarl73]

i check the oil level right after a ride with the engine running or within a minute of turning off the key. it's always right at the top mark except for last night with the top speed run it was about an inch from the bottom mark. it's all gone out the breather, i guess.

i don't know if the engine has been modified, but i would suspect if my compression numbers are off it's either my gauge or technique. it's craftsman and i'm sure it's intended for automotive use. carbs were not attached and i think all the other spark plugs were out. it was a dry test, i didn't put oil in the spark plug holes. my bike has 36k miles so i guess the valve guides are pretty close to needing replacement.

i just got back from cycle gear and out of their meager selection of non synthetic oils, i picked motul 3000 20w-50, it doesn't say low detergent, but it says it has anti foaming agents. and is jaso-ma rated. my plan is to clean up the mess, change the oil, fill it to halfway up the dipstick, and give it a whirl. no more top speed runs, i just wanted to get it to 100. it's funny i have a 2005 honda 919 and it "accidentally" does over 100 every other time i look at the speedo.

i know that pulling the engine and doing some serious work is not far off, i just want to try to put it off for a little while and get some fun out of my new bike. i've wanted one of these since i was in high school (class of 91). i bought a k4 a few years ago and immediately stripped it to the frame. i ran out of steam on it, and it's languishing in pieces in the garage. i never even got to ride it.  i don't want the k3 to suffer the same fate, before i get some fun out of it. i don't think i'll have a problem just pulling the engine, fixing it, and putting it back. with the k4 i just tried to do everything at once. it will get done eventually, though.

[Duke McDukiedook]

You should wait 10-15 minutes after a ride to check your oil level.
Odds are you are overfilling it.

[70CB750]

i bought a k4 a few years ago and immediately stripped it to the frame. i ran out of steam on it, and it's languishing in pieces in the garage. i never even got to ride it.  i don't want the k3 to suffer the same fate, before i get some fun out of it. i don't think i'll have a problem just pulling the engine, fixing it, and putting it back. with the k4 i just tried to do everything at once. it will get done eventually, though.

Evolution not revolution is the key.  Modifications while you can still ride it to keep you motivated.

[HotCarl73]

You should wait 10-15 minutes after a ride to check your oil level.
Odds are you are overfilling it.

i thought that right after a ride with the engine running is when it would be at it's highest point. i'll admit that i'm no expert and it may just be over filled. i've checked the oil level under every circumstance i can think of except for when i'm actually riding. it's never been over the full mark. i've only got 2 oil changes under my belt with this bike so far, and i never measured how much i actually put in, ive been doing it with gallon jugs, but i'd guess 3ish quarts. when i change it this time i'm gonna put in 3 quarts and see how that looks. i've only found an owner's manual for a 74 online and it says "approximately 3 quarts". i think i want to shoot for the middle of the dipstick not the full line. maybe that and the hopefully less foamy oil will fix this.

[HotCarl73]

i bought a k4 a few years ago and immediately stripped it to the frame. i ran out of steam on it, and it's languishing in pieces in the garage. i never even got to ride it.  i don't want the k3 to suffer the same fate, before i get some fun out of it. i don't think i'll have a problem just pulling the engine, fixing it, and putting it back. with the k4 i just tried to do everything at once. it will get done eventually, though.

Evolution not revolution is the key.  Modifications while you can still ride it to keep you motivated.

you got that right. i learned that lesson from the k4. that's why i'm trying not to do the same on the k3. truth be told, i'd rather have the k3 any way. that's what i wanted when i bought the k4, but couldn't find a k3. i was born in 1973. once i got the k3 home, i was pleasantly surprised to find that it was not only born the same year as me, but the same month too! (january) wish i could find out the day. maybe i don't want to know, i only have about a 10% chance of it being born on my birthday.

[HondaMan]

I would recommend switching to a JASO-MA rated oil very soon if you do not want to encounter more oil problems.

Mark- When you say connect the valve cover and oil tank breather tubes do you suggest a 'T' connection that drains down?

Well, no: I just plugged them together with a piece of tubing, like plastic or brass. This can only be done on the pre-1975 models, before the hoses became 2 different sizes, though. When the "EPA breather" gadget got installed, the hoses didn't fit together anymore.

[bikerbart]

I would recommend switching to a JASO-MA rated oil very soon if you do not want to encounter more oil problems.

Mark- When you say connect the valve cover and oil tank breather tubes do you suggest a 'T' connection that drains down?

That is what I did. I put a T fitting. Has worked fine thus far.

[HotCarl73]

just an update and one last question. i changed the oil to the motul. i filled it with 3 quarts and that put the level right on the full line. i took 10-12 ounces back out and the oil level is about 1/2 inch below the full line. i also replaced the breather lines (again) and left them a little longer to keep them from pointing right at the tire. i also made them different colors so i can identify where it's coming from if it happens again. i rode it about 30 miles, but didn't run it up to redline, or even close to it. i cruised at 70 for about 15 minutes. not a drop of oil came out of the breathers. i'm still a little worried about what's gonna happen when i get frisky with the throttle. when i got home and checked the oil, the first time i pulled the dipstick it was wet all the way to the base of the cap. i wiped it off and dipped it again and it's 1/2 inch below the full line. is this normal? is the tank filling all the way up while i'm riding or is it just sloshing around and staying wet because oil is kinda viscous? i think this is what happens on cars and everything else with a dipstick but i always wipe them as i'm pulling them the first time and never really looked. then again cars are wet sump. thanks for all the help everybody.

[70CB750]

The oil is sloshing around in the tank, looks like you are fine.

I added an oil pressure gauge on mine as one of the first things, if you dont have it I would highly recommend it.  It eases the anxiety and gives me a good idea on the engine temperature.  It depends on the oil of course, but fully warmed up my engine idles at 20psi.

When I push hard on hot day, with the synthetic oil I have in it now, the idle goes to 10psi - while cold engine is well over 60, you got the idea 

[HotCarl73]

i was looking for an oil pressure gauge when i got sidetracked into this oily adventure. i'll get back on it. thanks.

[70CB750]

 Anytime

I am easily amused engineer, this morning I went for a ride in Blue Ridge and when the Skyline went down the hill to Front Royal I shifted to the convenient neutral between 4 and 5 and coasted for several miles, quite pleasant experience actually. 

Anyway, engine idling at speed 40 miles an hour with temperature somewhere under 20 Celsius will cool the oil enough to show 50 psi pressure.

I said I am easily amused 

[bollingball]

Anytime

I am easily amused engineer, this morning I went for a ride in Blue Ridge and when the Skyline went down the hill to Front Royal I shifted to the convenient neutral between 4 and 5 and coasted for several miles, quite pleasant experience actually. 

Anyway, engine idling at speed 40 miles an hour with temperature somewhere under 20 Celsius will cool the oil enough to show 50 psi pressure.

I said I am easily amused 

Damn it why don't you just rub it in I would love to go out the door and roll down the parkway. I go there every chance I get. It to me is the best ride on the east coast. Maybe the world if it is not tourist season. I am aware that everyone has their favorites this one is mine.
Ken

[70CB750]

Well we gotta ride together one of these days - or years