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Does the primary chain case need to breathe?

Ducvelo

Well Known and Active Forum Website User
VOC Member
I'm trying to eliminate the oil leakage around/through the dynamo. If you seal this successfully, do you need to introduce a new breather to the primary chain case? I've read conflicting stories. Also, if it does need to breathe, where are the best places to introduce this? I've read putting a breather hole in the filler cap, in the level plug, in the dynamo cover plate etc?
Views appreciated?
Ducvelo
 

John Cone

Well Known and Active Forum Website User
VOC Member
You shouldn't have to put a breather in, providing your not using sealed main bearings. If the engine oil can weep from one side to the other then air can get back.
 

clevtrev

Well Known and Active Forum Website User
VOC Member
I'm trying to eliminate the oil leakage around/through the dynamo. If you seal this successfully, do you need to introduce a new breather to the primary chain case? I've read conflicting stories. Also, if it does need to breathe, where are the best places to introduce this? I've read putting a breather hole in the filler cap, in the level plug, in the dynamo cover plate etc?
Views appreciated?
Ducvelo
That is your breather. Putting another one in, means you will now have two leaks. Fix the problem. You are pressurising your crankcase. So you need to fix that first.
 

Bracker1

Well Known and Active Forum Website User
VOC Member
Start with the simple. Check to make sure the oil level is at the correct level. Too high and it will fly all over the sprocket and find it's way out. The alternative if your engines in good shape, cut a small piece of large radiator hose(about 3/8 inch long) , fit over dynamo face and sandwich between the case and dynamo. Seals and doesn't leave a mess. Of course, if the rings are shot there, will be too much pressure and nothing will keep oil in. I think J. Healey told of this remedy, but don't quote me. Dan,
 

ogrilp400

Well Known and Active Forum Website User
VOC Member
Seal the generator drive and don't worry about a breather. Been running my Norvin like that for 33 years of daily riding. No oil leaks.
 
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