Topic: CB750K4 white goo on underneath of oil fill cap?

[Jake88]

Hello.  With 65 or so miles on a recent rebuild, I just noticed that there is some white substance building up on the underneath of my oil fill cap.  The oil still looks and smells pretty clean. What is this stuff?  My only thought is maybe moisture / oil vapor coagulating up there. Seen this before?

[69cb750]

Mix of water and oil

[newday777]

Definitely moisture caused.
Did you clean the inside of the tank during the rebuild?
Did you dun it just short times?

[Jake88]

Ok.  Yes, all of my rides have been fairly short really. A handful up to 10 or so miles maybe.  When I was rebuilding the top end, the motor set open for a handful of months. I feel like nearly all of the old oil drained out of it throughout the process.  I take it this is something that will fix itself as I run the bike more? 

[TwoTired]

Short runs will always have the moisture from humidity condense in side the motor and oil tank.  It normally vaporizes/evaporates after the engine oil has reached operating temp and held there for 15-20 minutes. When weather is cool, air cooled engines have a harder time getting to and holding temperatures high enough to boil off the condensation.  The water then builds up inside the oil containment vessel.

You know,
Mayonnaise is made by mixing oil and water into an emulsion. So, if you are using vegetable or olive oils oil in your bike, it might add extra pizzazz to your sandwiches!

[newday777]

Ok.  Yes, all of my rides have been fairly short really. A handful up to 10 or so miles maybe.  When I was rebuilding the top end, the motor set open for a handful of months. I feel like nearly all of the old oil drained out of it throughout the process.  I take it this is something that will fix itself as I run the bike more?

Pull the oil tank and clean out the old sludge that is probably built up in it from the years. And yes do some 40-50 mile rides to fully heat it up.

[Henning]

Breather hose pinched between swingarm and engine casing? Running too rich (too cold)? Too much blowby (rings)?

[HondaMan]

You know,
Mayonnaise is made by mixing oil and water into an emulsion. So, if you are using vegetable or olive oils oil in your bike, it might add extra pizzazz to your sandwiches!

Hey! Maybe we have a unique situation here where we can market 'survival food condiments for the hiway life'?
Just use detergent oils (to help clean the environment?) and short-haul rides, bring some baloney and bread, and you can travel light - until the clutch stops working, anyway.

...makes as much sense as most ads I see on TV now...