Oil Leak only at highway speeds

Hey Guys,

I noticed oil creeping over the points cover plate while riding. Upon inspection found oil was dripping from the tach cable connection. I replaced the seals and the leak seemed to happen less often but still happened at highway speeds above 4,000-5,000 RPMs.

I then replaced the entire tach gear guide and installed all new seals, o-rings, and gasket. Now it only leaks above 5,000RPMs at highway speeds around 60mph. It is definitely leaking somewhere on the front of the motor and at speed the oil gathers and pushes over to the right becoming visible while riding over the points cover plate.

I thought oil may have gathered in the tach cable housing and dripped out when the tach gear was spinning at high RPMs. So I cleaned the cable, which did have a lot of excessive oil in it, but still no luck. I also ran the bike with the tach cable disconnected while keeping an eye on the tach gear housing and there were no visible leaks.

I am having trouble pinpointing the leak since it only happens while moving at speed. So I plan on getting a shop fan to try to recreate highway speeds / RPMs. And do the white powder trick.

Anyone have other ideas? Maybe I should buy another new tach gear guide from Z1 (#PM81-2230) as it has two o-rings instead of just one.

If not already done, would check for loose nut on exhaust header clamp.
And if an oil cooler is fitted, check at hose connection.

Good Fortune!

Thanks Patton, no oil cooler but will check exhaust bolts this evening!

I also thought maybe the shaft of tach gear may be out of spec and not sealing properly against the rubber. So I am going to see if I can find the spec for the shaft diameter today.

Is it safe to assume that if I had a leaking or weak head gasket that there would be other more serious symptoms?

rcarver wrote: ...thought maybe the shaft of tach gear may be out of spec and not sealing properly against the rubber...if I had a leaking or weak head gasket that there would be other more serious symptoms?

If there's no oil leakage from the tach drive without the tach cable attached to it (either at idle or when blipping the throttle), I don't suspect a malfunctioning tach drive assembly.

A leaking head gasket should appear evident though the white powder, and without need for much revving.

Do results of the white powder test indicate any particular area of leakage?

Good Fortune!

short on time this evening so I decided to do the simplest test first..and sure enough the exhaust nuts where extremely loose. Tightened them down and going to Highway test tomorrow, but i have a good feeling this was the source of the leak.

Thanks Patton!

By the way not to sound ignorant but how or why would a loose exhaust pipe cause an oil leak?



EDITED: for horrible spelling mistakes...thanks iphone.

Took her out on the highway this evening and so far no visible leaks. Although after the ride I did still find some oil weeping out of the outer sleeve on the tach cable, nothing major just enough to wet the tip of my finger, I think it may be residual oil from before I replaced the seals. I am still waiting on a new cable from Z1 (back-ordered)

Gonna keep an eye on it, but it looks like was from the loose exhaust connections.

thanks again Patton!

rcarver wrote: ...how or why would a loose exhaust pipe cause an oil leak?....

Thinking it's nasty black gunge from the exhaust port that's escaping past the copper gasket to the cylinder fin area instead of being contained within and passing on through the exhaust system.

Good Fortune!

the oil leaking out was some what random in color and clarity. sometimes it was clean oil and sometimes it was "black gunge". Just keeping my fingers crossed that I have it sealed up now.

rcarver wrote: ...did still find some oil weeping out of the outer sleeve on the tach cable...may be residual oil from before I replaced the seals. I am still waiting on a new cable from Z1 (back-ordered)....

Could test whether the new tach seal is properly functioning by removing the tach cable and watching for any oil escaping through the tach drive.

Should be no leakage whatever, at any rpm, regardless of whether the tach cable is attached.

Good Fortune!

rcarver wrote: the oil leaking out was some what random in color and clarity. sometimes it was clean oil and sometimes it was "black gunge". Just keeping my fingers crossed that I have it sealed up now.

Am thinking perhaps damaged or worn exhaust valve stem seals.

Is there noticeable burnt oil smoking from the exhaust, especially following a cold engine start, that continues exhaust smoking for a short while until the engine warms up, and then the exhaust smoke lessens at normal engine operating temperature, and not noticed again until the next cold start?

Good Fortune!

1) Already checked tach drive with cable removed. No visible leaks.

2) and your dead on with the smoke, but it does not smell like oil and is kinda light grey thought it was burning rich.

I am afraid to mention...it smokes on the same side as cylinder-4 and when shimming valves last weekend cylinder-4 was way out in comparison to all others. I also discovered traces of oil in the reed valve above cylinder-4, very very small amount though.

I am planning on changing to a manual tensioner because I found a rather loose cam chain when i pulled off the valve cover.

So how do I determine if I have valve stem seal damage? Not sure i understand why this would resul in an oil leak though??

rcarver wrote: ...discovered traces of oil in the reed valve above cylinder-4... Not sure i understand why this would result in an oil leak though??

Could be wrong, but thinking ---

Leaking stem seal on intake valve: Oil is sucked into the combustion chamber where it burns along with fuel mixture and exits as smoke from the exhaust.

Leaking stem seal on exhaust valve: Oil doesn't enter the combustion chamber, but "puddles" in the exhaust port, where it's blown out with the exhaust. This "unburned" motor oil may be pushed out past a not-quite-sealed exhaust gasket (perhaps due to a loose header clamp nut), or simply seep out past the gasket.



Personal experience is when "clean" oil streaked over the alternator cover following a highway run on the KZ900, and a loose header clamp nut was discovered and tightened, which completely resolved the matter.

And again when "clean" oil appeared on the fins following a highway run on the Z1, and a loose oil cooler hose clamp was discovered and tightened, which completely resolved the matter.

Good Fortune!