1st Ride out and Primary Leak?

Tripler

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I have recently purchased a Mk3 Commando, i bought the bike in need of commissioning, the motor had been totally rebuilt but the bike has stood for 15 yrs or so. i checked n changed fluids. put fresh oil down the rocker covers checked i had a return to the oil tank n oil up to rockerbox.
the bike fires up and runs beatifully. i did a 20 mile run today and when i got back i noticed a leak which appears to be coming from the rear of the primary (maybe mainshaft seal) please excuse my ignorance as i am totally new to commandos. so before i start stripping the primary i thought it wise to ask here.
on the plus side the bike runs and feels lovely. really smooth.
 
Thanks i had a look under the bike and it looks to be rear of primary, just looked at the manual and it looks like primary off and new seal on the inner primary casing
 
 
I would be inclined to clean it up and take it for another but shorter ride . 20 miles can spread the flow a long way . Take a good look at the grommet on the inside case where the alternator wires pass through . Don't be too quick to assume it can only be coming from the back
 
Thanks for the help. i shall clean it up 1st, will get the tools LAB as i am sure to need to them. luckily for me RGM is just round the corner so spares supply shouldnt be an issue
 
Thanks for the help. i shall clean it up 1st, will get the tools LAB as i am sure to need to them. luckily for me RGM is just round the corner so spares supply shouldnt be an issue

As well as the replacement gaskets, tab washers, etc. there should be a gasket '27A' between the tensioner body '27' and the plate '29'...
https://andover-norton.co.uk/en/shop-details/16850/gasket-p-chain-tensioner-body
...often missing because it isn't on the parts diagram.
 
I would be inclined to clean it up and take it for another but shorter ride . 20 miles can spread the flow a long way . Take a good look at the grommet on the inside case where the alternator wires pass through . Don't be too quick to assume it can only be coming from the back
I agree with this. I would not be in too much a hurry to take her down.
Plenty of time for that. May even be coming from the swing arm pivot.
Ride it around, get used to it. May be other issues to resolve once apart.
The Mk 3 primary is a little more complex than the others.
A drippy spot of oil is not a big deal and can be resolved in time.
 
Yes take your time with this and keep up the primary and gearbox oil levels . If one is low then that is suspect .
The swingarm is unlikely. MK 111 uses a for life Welsh plug seal .
To locate the leak clean and wash the area . Drive it . Observe again with a flashlight and a rag in hand . Is the drip leak thicker transmission oil or the thinner 20 W / 50 primary chaincase oil is the goal to ask yourself .
 
I agree with this. I would not be in too much a hurry to take her down.
Plenty of time for that. May even be coming from the swing arm pivot.
Ride it around, get used to it. May be other issues to resolve once apart.
The Mk 3 primary is a little more complex than the others.
A drippy spot of oil is not a big deal and can be resolved in time.
like your thinking šŸ˜œšŸ˜€
 
Gave it a clean up and noticed the engine cradle bolts were loose particularly the primary case centre stud. I have been round the bike and tightened all fastenings. Going to take primary cover off today and check the nut on the centre stud in the case
 
Gave it a clean up and noticed the engine cradle bolts were loose particularly the primary case centre stud.

Going to take primary cover off today and check the nut on the centre stud in the case


The positions of the Mk3 chaincase steady stud nuts at front and rear of the inner primary case are used to set the case alignment so the inner nut needs to be set in position before tightening the outer nut.

Also, the stud assembly is not as drawn on the parts diagram.
The longer threaded end of the stud '23' goes to the outside with thin nut '25' and one washer '24' on the long thread, plus you may find additional spacing washers, not on the parts diagram between the hexagonal section of the stud and the outer face of the cradle.
Diagram of the correct assembly (but with additional washers missing) from the Mk3 manual, section C34, Fig. C45 (inset).
1st Ride out and Primary Leak?
 
Thanks LAB, just having a read of the manual now, bit confused now. reading the manual it suggests primary alignment is checked with engine sprocket and clutch chainwheel. to remedy out of alignment shims are used behind the clutch basket.
so what bearing does the centre stud have on alignment ??
 
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just having a read of the manual now, bit confused now. reading the manual it suggests primary alignment is checked with engine sprocket and clutch chainwheel. to remedy out of alignment shims are used behind the clutch basket.

That's the primary chain/engine sprocket/clutch chain wheel alignment, not the primary case alignment.
C34, 6:
1st Ride out and Primary Leak?
 
took the outer primary cover off today to have a nose, i think i have found the culprit, the crossover shaft oil seal has become dislodged from its position in the inner primary cover. if my thinking is correct i should be able to remove the cross shaft fit new seal and refit cross shaft.
could it be that easy? thought from the people who know appreciated please
 
also, ways to keep the rear crankcase to engine plate bolts/nuts tight are important. Many use suitable loctite / nylocs
 
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