Topic: CB550k3: oil overfilled

[1977_cb550k]

I’ve had weepy gaskets for the last few 300km+ rides. The leaked oil blows back off the fins and horizontally across the side covers, frame and rear suspension etc. Very annoying.

I figured my oil level would be a little low so I checked it today whilst the bike was cold in the morning. To my surprise the oil level was over the full line! (Yes I wiped the dipstick and didn’t screw it in to check the level, and the bike was on centre stand).

I’m surprised by the ‘overfill’ as I used the correct oil volume during my last oil change as per the manual (3L metric). And drained it while engine was warm etc.

Two questions:
1) could the overfilled oil level be forcing the gaskets to weep?
2) what occurs with an overfilled crankcase?

[TwoTired]

Is your crankcase venting system working properly?   If it is blocked or clogged, an increase in pressure will find any imperfect seal to leak from.

However, the oiling system is always under pressure.  And near each end of the cylinder head is an o ring that seals the passageway from lower end to cam and lifters.  These orings gets hard and brittle with heat and age, cracks and leaks.  Usually it just weeps a little, needing a weekly wipe off.  But, can turn into an annoying issue.  Must remove cylinder head to restore seal, in that case.  And then the cylinder base gasket gets disturbed, requiring its replacement  , too.

As to overfilling, the wet sump oil level is determined by where it is, relative to the rotating crank assembly operating inside the crankcase so as not interfere with it in high rev situations.  If it makes contact, oil collects and builds up on the assembly weighing it down, and the thrash can make the oil foam up.  In extreme conditions it can cause an oil starvation issue.  But, the crankcase case vent should keep it from making crankcase pressure.

You have any easy decision, to remove some oil and restore proper oil level, and check the venting system. However, blown seals seldom restore themselves.  Whatever the true cause of leak introduction, expect to live with the seepage or taking the top end apart to replace seals you find offensive.


Cheers,

[ekpent]

 Might want to take a whiff of the oil/dipstick just to make sure you don't smell any gasoline that may be infiltrating from a pesky leak in the petcock causing the level to rise.

[bryanj]

Never use oil volume to fill you fill to level on stick

[1977_cb550k]

Thanks. Looks like I’ve got an easy job (reduce oil level) and a hard job (rings and gaskets) ahead.

Does Honda still make NOS gaskets for CB550’s? Where’s the best place to get a complete replacement set?

[TwoTired]

Why would you need rings?  Is it burning oil or making crankcase blowby?

[1977_cb550k]

Correction ‘o-rings’

[HondaMan]

PM me for a pair of slightly thicker O-rings that will go thru the head gasket. Modern head gaskets are thicker than OEM enes were, which leads to oil weeps (or outright leaks) from these O-rings when replacing the head gasket. The modern head gasket is about 1.0mm thck, while the OEM one was 0.80 mm thick: these O-rings make up that difference.

[TwoTired]

PM me for a pair of slightly thicker O-rings that will go thru the head gasket. Modern head gaskets are thicker than OEM enes were, which leads to oil weeps (or outright leaks) from these O-rings when replacing the head gasket. The modern head gasket is about 1.0mm thck, while the OEM one was 0.80 mm thick: these O-rings make up that difference.

Doesn't that lower the compression ratio, too?

[bryanj]

You are talking a bit of a mm so technicaly yes but not enough to notice

[flatlander]

Never use oil volume to fill you fill to level on stick

^^
that's it (for next time).

on an oil change, i fill it up to about half way between the low and high mark on the stick, maybe bit more. for measuring, stick rests on the treads, is not screwed in. then i run the engine for half a minute or so and shut it off. leave it over night, then top up the oil as needed.

this "run and rest over night part" may sound paranoid but i figure that way you measure again after the new oil has been circulated a bit, and dropped down to the pan again either together with some oil that may have been be left in the head, or some of it staying up there.

[Deltarider]

Never use oil volume to fill you fill to level on stick

^^
that's it (for next time).

on an oil change, i fill it up to about half way between the low and high mark on the stick, maybe bit more. for measuring, stick rests on the treads, is not screwed in. then i run the engine for half a minute or so and shut it off. leave it over night, then top up the oil as needed.

this "run and rest over night part" may sound paranoid but i figure that way you measure again after the new oil has been circulated a bit, and dropped down to the pan again either together with some oil that may have been be left in the head, or some of it staying up there.

When the CB550F2 was tested by the German magazine Motorrad in 1977, they reported a problem with the airfilter element being fouled by the blowby gas system, resulting in less performance. The remedy (possibly advised by Honda Germany) was to fill oil no further than halfway the marks on the dipstick. I remember also Dutch owners practiced this or simply abandoned the breather connection altogether. Now IIRC the K3 breather element differed from the F model somewhat, but I have seen also K3 airfilter elements that had this typical wet light brown spot. Simple solution: don't top up all the way and just check more frequently.