Where's The Leak?

Status
Not open for further replies.

Tornado

VIP MEMBER
Joined
Dec 5, 2017
Messages
4,956
Country flag
My 850 MKII has a good amount of oil leaking happening left side down around rear side of primary case. However I'm not convinced it's chain case oil (I'm using same as engine oil at this point) getting out the rubber perimeter seal. Checking carefully with a mirror and lamp laying down beside bike on CS, I can follow the oil path from header pipe bottom side, drops along chain case seam, to a little river running vertically down from the front sprocket drive chain casing flange. Chain is putting up a lot of fling and looks a bit wet after riding...the stock chain oil was disabled by DPO...yet I also see the remains of that system, up high in front of rear mud guard. the felt containing tube with associated clamps, appears quite wet with oil....so could that be the ultimate source here?
 
If the oil has a strong chloride smell, it is gear oil and could be coming from the drive side transmission seal. If it has no strong smell then probably oil from the primary case. If so you could get lucky by just replacing the primary "O" ring. Could also be a crack. Did you overfill the primary case?

This forum has a lot of searchable information about the proper method of installing the inner primary case.
 
When you install new primary seal , fill with red ATF ford type .... then you can eliminate that as a source quickly ... atf is all I ever use , yup I read manual and decided I like the atf better than engine oil in chain case .... like all leaks , process of elimination on your part , right ....
Craig
 
Thx. I put Royal Purple gear oil of spec'd weight in the tranny. It went in with a purple colour but the leak seems close to what my fresh VR1 engine oil is. Have not tried a smell test...will check it.

I did replace the primary seal when I first had the cover off to perform a first inspection in there when I got bike 7 months ago. I used a softer type of seal recommended by Walridge to replace original harder rubber seal. Also used some sealant on it which seems to be holding. Filled it to the fill hole dribble point...but bike wasn't on the level...rear end downhill a bit so might be a bit over. If that is the leak source, I would think it would have drained off enough by now to correct range again. Will use red ATF-F in there next time so identifing will be easier.
 
Just a follow up...leak described above seems to have abated nearly entirely immediately following install of a check valve on the crankcase breather hose. Used a locally available automotive brake vacuum check valve as other threads had mentioned. Seems to work a treat. If it doesn't hold up in long run, will go the proper reed valve route.
 
I can follow the oil path from header pipe bottom side, drops along
----------------


- then the leak probably originates from the left side exhaust rocker cover or possibly head gasket
and because the motor is canted forward the leak gets to the header pipe and then down, as you say-which makes sense as you have relieved head oil pressure by adding the breather one way valve

as regards the suggestion of using ATF, this is a good idea in a chain primary pre-Mark 3

but a Mark3 from my understanding has a hydraulic primary chain tensioner designed to be activated
with thicker oil such as the same oil the motor uses
 
Could be right, but from what I could see with the mirror/light, there was a trickle coming down the left side but from near/around the drive chain sprocket. The flanged shape on the inner casing had a heavy black/wet path coming down to underside primary cover seam, then ran along forward dripping on header and sidestand. That appears to have ended. I also had a good leak at intake rocker cover, just under the hold down nut, not on the gasket seam. This was enough to give smoke puffs at traffic lights as oil reached the hot rear side of cylinder head/block. Also tended to end up thrown rearward onto catb/air cleaner when doing long Hi way runs.
Solved it with Locktite 515 under the nut sealing surfaces.
 
Does the intake rocker nut have a sealing washer under it?
 
When I got the bike, no washer present. After seeing one listed on the parts diagram, I fitted a fresh copper washer of correct size and it did not halt the leakage. I will add my covers and nuts are chromed (DPO) and the sealing surfaces seem to be uneven as the chrome formed convex curves on the relatively narrow contact band . I did Glass & wet/dry fairing on the cover contact bands where gaskets go...took hours to get those convex curves flat. Did not considered doing the nuts...maybe one day. Was thinking to find rubber or dowty type washers to go under the nuts. It's only the intake nut that seemed to leak significantly.
 
The studs on the rocker covers can leak oil up the stud itself and can cause oil to drip down the head and to the primary case, pull the studs out and put some sealer on the threads them put them back in put your rocker covers back on and do up the nuts with washers and let sit over night, it usualy the botton studs that leak, this is a comon area where they leak oil, mine started to leak there after 38 year without any problem at all then started to leak, at first I throught it was a head gasket but after cleaning and riding traced it to the rocker studs, pulled them out sealed the treads and have never had any more leaks there, I now run a Yammy 650 reed valve on my breather a good $24 investment and will work better than a brake valve.
The rocker stud leak was the first major oil leak my Norton ever had since new on the motor.

Ashley
 
Status
Not open for further replies.
Back
Top