Oil in magneto

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brian.ashley
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Oil in magneto

Postby brian.ashley » Fri Oct 10, 2014 10:26 am

Good Day to all,
'55 VB: I have removed the magneto to have the condensor replaced. I was advised that there is quite a bit of oil in the magneto which could start to cause trouble for the slip rings etc. The top end was overhauled 1100 mile ago. There does not seem to be excessive oil coming from the breathers and oil consumption is not excessive. I have the rubber seal between inner timing chaincase and the magneto in place. The breather on the back of the timing chaincase has a ball bearing in it which seems to restrict flow, is this correct? I have checked the tightness of the oil pump and I did use a new gasket. What could cause this problem and how can I fix it? Thanks in advance for any help.

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Postby pete.collings » Fri Oct 10, 2014 11:34 am

There is a oil flinger washer that can be fitted behind the magneto sprocket, it does not stop oil entering the mangeto but can significantly reduce it.
See link below

http://forum.arielownersmcc.co.uk/viewtopic.php?f=21&t=1968&p=10959&hilit=magneto#p10959

brian.ashley
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Re: Oil in magneto

Postby brian.ashley » Fri Oct 10, 2014 12:10 pm

That sounds like an excellent idea, thanks very much.

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Dave.Barkshire
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Postby Dave.Barkshire » Fri Oct 10, 2014 2:23 pm

Apart from the oil seal in the magneto you are right to question the engine breathing. The ball can stick and some people remove the ball but there is debate on this matter. An expert will be along shortly...
1938 Ariel Red Hunter VH1 http://www.barkshire.co.uk/bikes/images/ArielVH_1938
1927 Triumph Model N http://www.barkshire.co.uk/bikes/images/TriumphModelN
2015 Moto Guzzi V7 Racer Mk2 (ABS) http://www.barkshire.co.uk/bikes/images/MotoGuzziV7RacerMk2
1954 VeloLE

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brian.ashley
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Re: Oil in magneto

Postby brian.ashley » Fri Oct 10, 2014 6:48 pm

I await the expert.....

david.anderson
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Re: Oil in magneto

Postby david.anderson » Sun Oct 12, 2014 9:49 am

The only seal between the magneto and engine is to stop oil escaping externally at that joint. There is nothing to prevent oil entering the magneto although the gasket paper flinger does help. The reason that oil enters the magneto is due to engine crankcase pressure and of all Ariels the VB is the worst because it displaces the biggest volume into the crankcase.
The best way to reduce crankcase pressure is to fit a one way PCV valve (reed valve type) to the end of the breather. That way the breather only expels air and does not suck it back in as the piston rises, but rather creates a negative crankcase pressure. Ideally the HT HS crankshaft oil seal should also be fitted to better seal the crankcase.
Today I had a thoroughly enjoyable ride of 200 miles at speeds between 60 and 70 mph two up. This is a couple of photos of my bike that I have just taken. There is no oil mist around the timing covers or chaincases. (but it appears that I have just developed an oil leak from the pushrod cups.)
IMG_2243.JPG

IMG_2244.JPG


This is a photo of my sons NH after his last ride of about 100miles at lower speeds. Note the oil mist around the timing covers and crankcase chaincase. It is crankcase pressure that forces the oily mist through the timing cover, chaincase gaskets and it is doing exactly the same into the magneto. With the OHV singles it is a matter of fitting a reed type PCV valve to the end of the timing cover breather and then check if you have any oily joints after a hard ride. If not then you can be pretty sure that your magneto is going to benefit.
The VB has a second breather off the tappet compartment but it is fed through a very small hole into that chamber. It would be necessary to fit a second PCV valve to that breather also. Incidentally my VB has not yet been fitted with PCV valves and has not exceeded 50mph on an engine that is not quite run in and yet I am amazed at how much oil mist is around the timing cover gaskets. You should remove the ball from the timing cover breather if you fit a reed valve to the end of the breather.
IMG_2245.JPG

IMG_2246.JPG

David

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adrie.degraaff
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Re: Oil in magneto

Postby adrie.degraaff » Sun Oct 12, 2014 10:06 am

How can you have the altenator on without eating the gear in 1000 miles?

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Re: Oil in magneto

Postby david.anderson » Sun Oct 12, 2014 10:18 am

Adrie
The Alton has been on there for thousands of miles without a problem. And the bike does get thrashed. Today I was the only one who was two up and I was riding with a couple of 750 Honda 4s and several 1200cc Harleys. So I had the smallest capacity bike and my wife on the back. At one point I was running 70mph in third for an extended up hill run just trying to keep up. When I topped the hill I took the bike straight up to 80mph in third before changing up then backing off.
David

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adrie.degraaff
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Re: Oil in magneto

Postby adrie.degraaff » Sun Oct 12, 2014 10:42 am

Vincent has tried it, I understand that his magneto gear and chain had a lot of wear in short time.

By the way, the oil is dripping from my 1956 mags drain hole for the last 50.000 km, no problem.

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Postby Ian.Taylor » Sun Oct 12, 2014 4:50 pm

Interesting thread on the breather. When I had my 53 VHA I can't remember having to clean oil from the timing cover or any other area after runs.
What it did do was leak from the rubber push rod gaskets between the head and barrel.


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