Valve covers and sight glass leak - pressure or just leak?

[millenium7]

Just bought a 1995 ST1100, short test ride before I bought it was fine but after an hour ride I notice there's a bit of oil around the valve covers and quite a lot of oil under the sum
Took it home to assess and after warming up can see a tiny amount of oil leaking from the valve covers sure, but a miniscule amount from the sight glass, could barely detect it with baby powder. Not indicative of the road test on the highway under heavier load and more revs

For now I've just applied black UTV to the covers and it's holding, but have ordered new gaskets/seals. What I don't want to do is blow out the new ones, so is there a way to determine if it's excessive crank pressure that caused the gaskets to leak. Or if it's just a simple matter of it being an old bike that needs some new ones

 

[Bush]

There is a hose that connects to the bottom of the air box and connects also to the crankcase for venting purposes. Offhand I don't remember where that engine end attaches, but if you disconnect the hose from the air box, you should be able to blow through it to see if it is clear.

The Honda Service Manual would show you the routing of that hose, if you have one.

 

[TerryS]

Don't replace the gaskets, but do replace the rubber washers under the cover hold down bolts. They pack down with age and apply less clamping force to the gaskets. And DO NOT OVERTIGHTEN THE BOLTS.

 

[jfheath]

Two common causes for leak from valve covers :

1. the last time the cover was replaced, the rubber mat heat shield was trapped under the cover at the back. You have to get your fingers over the cover and run them along the joint above the inlet ports to be sure that the heat shield hasn't been nipped.
2. The half-moon shape in the cylinder head and the corresponding shape in the cylinder head gasket have not had sealant appiled. The gasket does not need sealant, except at the right angle corners formed by the straight joint and the semi circle recess.

I would imagine that it is difficult to prove a sight glass leak with oil seeping from a location above.

 

[Upt' North]

Welcome from Northumberland, England.
I suspect like others it's incorrectly fitted, old and U/S gaskets.
Clean it off and fit the new as advised above.
A compression test would be the way to go but ensure the breather is clear too. If it's not obviously burning oil I would think the compression would be OK anyway. But if the breather is blocked that needs sorting first.
Good luck.
Upt.

 

[millenium7]

Definitely wasn't pinching anything, its actually leaking more on the outside facing edge of each valve cover gasket, slow leak - enough to have seen a little bit of oil after running for 10 minutes, but not enough to really go far
The sump area was the bigger question mark as the sump was completely drenched, seemed like a lot of oil yet as already mentioned it was barely even visible on the driveway or with a short ride

For now the sealant has held but havn't gone on a ride longer than 15 minutes. If the bleeding rain stops i'll get a proper run in with just the sealant and see how it goes. The gaskets do feel a bit old and crusty so will end up replacing the gaskets anyway once I go to check the valve clearances, sync carbs etc

Will blowing through the breather actually work? Is it the only point into the case and thus will just pressurize? Don't want to get a false reading, but do like the suggestion

 

[Roger]

A thin bead of sealant round the face of the cover gaskets, especially round the half-moon area is all you need. And don't overtighten the hold-down bolts. ...And renew the gear change shaft oil seal.... Lay the bike over on its side to do that.....

 

[Ned in Utah]

The oil sight class is a known leaker. It's an easy fix. Don't even have to drain the oil. Just put it on the kickstand, remove two bolts, pull the sight glass, remove the old o-ring and replace with a new one. I did mine last year. Got the o-ring off Partzilla.

 

[Loki WRX YZF]

The oil sight class is a known leaker. It's an easy fix. Don't even have to drain the oil. Just put it on the kickstand, remove two bolts, pull the sight glass, remove the old o-ring and replace with a new one. I did mine last year. Got the o-ring off Partzilla.

What's the correct torque value for those two bolts?

 

[Uncle Phil]

What's the correct torque value for those two bolts?

I can't seem to find a specific torque value for them so I guess you would have to go with the 'standard' ones based on size of bolt -

 

[millenium7]

Tight enough that it doesn't come undone
Not so tight that you hear a crack

Anywhere in between is fine

 

[Loki WRX YZF]

Thanks, gentleman. I was hoping for a specific to that part of the crankcase, but I'll go with 7 ft-lbs.