oil dripping out of top of primary

Head

Head

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Jan 26, 2021
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well folks hope ye all well

my 73 commando has sprung a leak but its a weird one
i have oil slowly coming out of the top of primary case when running
i have not opened it up yet so few questions for the Gurus here

is primary O ring reuseable ?
this to me the problem is pointing towards crank seals ?
if so is it massive job getting new one fitted and what brand is best ?
i use Andover Norton for most of my parts so they should have seal in stock
i will pull primary cover off later this evening and try see where oil is coming from and give ye update
thanks as always ur buddy from southeast Ireland
 
hi Jan,
i have not done anything yet with the bike just noticed the oil coming out of the top of the primary cover
if the o ring is ok what else could it be mate ?
i will check the oil level tonight first then pull off the primary cover
 
Assuming you filled to the level plug when last topping up remove the plug and see if there is any excess oil. If no excess then your leak is from the O ring seal split or deformed or the case has an issue. An excess means the crank seal and the 3 primary inner case to crankcase retaining bolts need looking at.
 
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Head said:
hi Jan,
i have not done anything yet with the bike just noticed the oil coming out of the top of the primary cover
if the o ring is ok what else could it be mate ?
i will check the oil level tonight first then pull off the primary cover
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How long ago did you last open up the primary cover ?
Its sounds over full so far...
 
thanks Komm i be over the moon if it is only the o ring seal, but with the low level of oil in the primary i doubt the oil would get out on the top have of the primary, i did full oil service few weeks ago all oils filled to exact levels
 
Drain the oil and pull the outer cover off if to much oil could be a blown main seal are you loosing motor oil out of your oil tank, wet sump, blown main seal, filling into primary, guessing no good drain and look inside its not a hard job.
 
Head said:
i doubt the oil would get out on the top have of the primary
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The oil in the primary is mainly for the chain which dips into the oil and then flings it in all directions including up. The O ring even if it's not split or deformed takes a set over the years and eventually offers little to no pressure on the mating face. A new O ring restores the seal.
 
Head said:
thanks Komm i be over the moon if it is only the o ring seal, but with the low level of oil in the primary i doubt the oil would get out on the top have of the primary, i did full oil service few weeks ago all oils filled to exact levels
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Sounds like.. the old O ring in a square hole problem ... ;)
A new plump O'ring sounds like the go
 
i really hope ur right it be easy fix, i will check the level of oil in the oil tank tonight first then i will open inspection hole on primary casing , tt is not flowing out on top not even a half a timble over 100 miles
 
When you say "top" do you mean you see oil trace along the primary outer to inner casing joint? Or is oil exiting the via the felt "seal" behind the inner primary cover where the front chain sprocket is? Another thing to check is the alternator wire exit hole. Should be a grommet around the wires in the hole to help stop leaks. Some silicone gasket maker it a good idea around this grommet and even around the whole big O-ring.

You can try using some baby powder on the casing and run the engine to try to identify where the leak is exactly.
Check how much oil is in the casing via the level plug at bottom of casing. any more than a few drop out when bike is sitting on CS, then you've added too much or you have engine oil entering the case via a blown crankseal and/or a leaking inner case to crankcase bolt (there are three under the front sprocket...recommend using new locking tab washers PLUS blue Locktite product on these).
Replacing a crank seal is not too difficult assuming you have the tools needed to dissassemble the primary (clutch tool, clutch sprocket holding tool and a puller to remove the front sporcket). Seal itself comes out with gentle prying using a pick or small flat screw driver blade. New one just taps in with a suitable sized socket. I used a bit of locktite on the outer ring of seal to make sure it stays put.
 
well folks, i opened the small bolt in primary and some oil did come out but i do recall putting a little extra in it 2 weeks ago when changing it

so there was excess oil in it as for quantity i dont know it did not cover the primary chain and the over flow was no more than egg cup full guessing, i was low on engine oil too but again im not sure as i only changed that last week too and i normally give it a run and top up, so i topped up engine oil and drained primary to correct level i will give her a good spin this weekend and test all on return
as for leak it just comes out in one spot at the top of the primary cover so i will order o ring seal anyways
the help and advice here is unreal thank you all so much really appreciate it folks
 
If you done a oil change a week ago one thing with Commando's is to only fill the oil tank to the 1/2 way mark on the dip stick if you keep it on the top mark you will lose oil and you will think your motor is using it and keep topping it up but just filling it to the 1/2 mark it won't lose it the high mark on the dip stick is to high, the oil tank needs that extra air space.
It's just one of those little things with Commando's but seeing you are new you will learn these little things.
 
ashman said:
If you done a oil change a week ago one thing with Commando's is to only fill the oil tank to the 1/2 way mark on the dip stick if you keep it on the top mark you will lose oil and you will think your motor is using it and keep topping it up but just filling it to the 1/2 mark it won't lose it the high mark on the dip stick is to high, the oil tank needs that extra air space.
It's just one of those little things with Commando's but seeing you are new you will learn these little things.
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ur a gent thanks mate , quick one for u, is it ok to replace the primary o ring and take her for a good 60 or 70 mile spin as oil in primary was a little high when i changed it last week i think i have it at correct l;evel now, it is only coming out in same exact spot on top of cover, if the crank seal is gone can i do damage by riding her ?, as its hard to determine if the crank seal is gone withoput pulling her apart ?,

so i was going to replace oring seal and ride her for a good spin
 
When my rocker box covers dripped, a little oil ended up on top of the primary.
JFWIW


I way overfill my primary, up to cover the bottom chain run, with no oil coming out whatsoever.
Your o-ring is likely in need if replacement, as mentioned above.

OP, I had the great priveledge to ride my bike through the Wicklow Mountains, TWICE, (and a rental car twice) during my holiday 2017. Breathtaking views!
 
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concours said:
When my rocker box covers dripped, a little oil ended up on top of the primary.
JFWIW


I way overfill my primary, up to cover the bottom chain run, with no oil coming out whatsoever.
Your o-ring is likely in need if replacement, as mentioned above.

OP, I had the great priveledge to ride my bike through the Wicklow Mountains, TWICE, (and a rental car twice) during my holiday 2017. Breathtaking views!
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great stuff, i live one hour from wicklow its a beautiful place great biking roads
 
Just keep 7 fl oz in the primary to much oil and depends on what oil you use will effect the clutch the oil in the primary is designed to slash on the chain and the best oil for the primary is ATF brand F being red will tell if other oil gets mixed with it or if red drip on the ground tells you its coming from the primary.
 
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ashman said:
Just keep 7 fl oz in the primary to much oil and depends on what oil you use will effect the clutch the oil in the primary is designed to slash on the chain and the best oil for the primary is ATM oil brand F being red will tell if other oil gets mixed with it or if red drip on the ground tells you its coming from the primary.
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i will buy this today if i can get it in ireland
thank u so much again love the help here from everyone
 
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