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ET: Engine (Twin) Main Bearing


erik

Well Known and Active Website User
VOC Member
When i ordered new main bearings at the spares Company i have got the ball bearing on the drive side enclosed! should i open the bearing complete or should i open it only on one side?and if i leave one side closed ,to which side shoulde the open side be direkted? to the engine or to the primery drive? Erik
 

mercurycrest

Well Known and Active Website User
VOC Member
I was taught the scroll feeds oil to the bearing and the seal should be on the side next to the primary case. It has worked this way for me.
Cavat.... If it blows up, you didn't hear this from me. :eek:
 

timetraveller

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VOC Member
Oh Dear! I thought that the scroll was intended to try to keep oil back from the ball race and that it got lubricated by splash. One of us is wrong? I would keep the seal on the primary chain side and take the one off that is on the side inwards to the flywheels as mercurycrest writes above.
 

mercurycrest

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VOC Member
Oh Dear! I thought that the scroll was intended to try to keep oil back from the ball race and that it got lubricated by splash. One of us is wrong? I would keep the seal on the primary chain side and take the one off that is on the side inwards to the flywheels as mercurycrest writes above.
You're probably right and my memory is wrong. I haven't got a scroll laying around to look at anymore, but Erik does and it should be obvious. Makes me wonder about sealing off the primary from the chain case side too.
 

timetraveller

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VOC Member
I think that the sealing should work as a lot of people run their bike with a seal on the outer end of those main bearings to stop the primary chain case filling up with oil.
 

oexing

Well Known and Active Website User
VOC Member
In my modified engine, under construction, I have not decided on seals there. But basically due to depression in the crank case there should not be any filling of the primary case from the engine oil, no ? How is the primary case vented anyway ?

Vic
 

vin998

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VOC Member
VOC Forum Moderator
Primary case is vented where the dynamo enters the primary case unless you seal the dynamo to the primary with silicone which I have seen owners do and then wonder why the primary case starts to collect moisture in there and contaminate the primary oil.
 

timetraveller

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VOC Member
On the ex-Cecil Mills bike there is a small banjo bolt in the middle of the chain case filler cap with a length of 1/4" tube extending rearwards to act as a breather. It works well but does not look standard. I remember years ago an article in MPH by someone who did a very complicated outlet from near the top of the dynamo drive extension. From memory this required breaking through into the threaded hole at the rear top of the extension and then making a small hole behind this to allow any pressure to escape. I imagine that this last hole had a fitting to allow a tube to pass to the rear of the bike to let out any excess pressure. With the Walkernators I supply a sealing system to go between the drive bump and the dynamo replacement. So far this does not seem to have caused any problems or, at least, no one has reported any.
 

Pete Appleton

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VOC Member
VOC Forum Administrator
VOC Forum Moderator
Don't I recall reading about someone finding their primary case filling with engine oil due to the outer seal on the bearing acting as a one way valve to the crank case pressure? I have removed both seals and fitted the ET236 oil seal modification, as per Richardson. Available from the spares co.

N.B. 'Seal' is a misnomer. It is a dust excluder and not designed to retain oil.
 

davidd

Well Known and Active Website User
VOC Member
I have always run the the drive bearing with both seals in place. Carleton Palmer did also. The bearing company maintained that the lubricant inside the sealed bearing would last for the useful life of the bearing. They made a good case that the bearing would last a lot longer if it were not exposed to dirty oil. On an engine that John Renwick built many years ago he used the sealed bearing as well as the ET236 seal carrier on the case as described in Richardson.

Just as a note, there are at least two different ET236 seal carriers available as I have received both. I prefer the one from Maughan because it is designed so you can leave the bearing circlip in place. I believe the one from the Spares Co. requires the circlip to be removed.

David
 

mercurycrest

Well Known and Active Website User
VOC Member
I have always run the the drive bearing with both seals in place. Carleton Palmer did also. The bearing company maintained that the lubricant inside the sealed bearing would last for the useful life of the bearing. They made a good case that the bearing would last a lot longer if it were not exposed to dirty oil. On an engine that John Renwick built many years ago he used the sealed bearing as well as the ET236 seal carrier on the case as described in Richardson.

Just as a note, there are at least two different ET236 seal carriers available as I have received both. I prefer the one from Maughan because it is designed so you can leave the bearing circlip in place. I believe the one from the Spares Co. requires the circlip to be removed.

David
I have heard that the sealed bearings were Ok to run that way too, but just never had the guts to try it. Thanks for the information David.
 

Hugo Myatt

Well Known and Active Website User
VOC Member
Peter Appleton is absolutely right. The so-called seal will work as a very efficient flap valve. For the whole saga see 'Another Ten Years' but briefly with this sort of sealed bearing installed on my Rapide I managed to make the primary case completely oil tight including the dynamo drive. The result was the primary case pressurised with a ratcheting effect so much so that it drove all the oil out of the chaincase and into the gearbox leaving the primary case dry, raising the level in the gearbox and pressurising the gearbox. Be very cautious. Hugo
 

chankly bore

Well Known and Active Website User
VOC Member
Some, or maybe all "sealed" bearings have a thinner inner ring which gives less support to the PD2 Engine sprocket sleeve. I seem to remember someone on the Forum noting this as a problem. Furthermore, I would never dispense with the outer circlip in fitting a mainshaft oil seal.
 

robin

Well Known and Active Website User
VOC Member
If you use a Japanese manufactured sealed bearing, you will find that the ET60/3 engine sprocket butts onto the rubber seal. Solution:- always use european manufactured bearings. Japanese bearings have a thin inner race whilst the European races have the standard thick inner race. Even better is to machine Et60/2 and PD2 and use PD21 in lieu. PD21 has the correct thickness and O/D to suit both the oil seal and keep the primary chain alignment.
 

vibrac

Well Known and Active Website User
VOC Member
Never has a problem with a 'Richardson' seal but I run untimed one way breathers on the bikes.
and that includes the racing big twin that had belt drive and a sheet cover never saw a drip.
(breathers on front exhaust and rear inlet)26942
 

Cyborg

Well Known and Active Website User
VOC Member
On the ex-Cecil Mills bike there is a small banjo bolt in the middle of the chain case filler cap with a length of 1/4" tube extending rearwards to act as a breather. It works well but does not look standard. I remember years ago an article in MPH by someone who did a very complicated outlet from near the top of the dynamo drive extension. From memory this required breaking through into the threaded hole at the rear top of the extension and then making a small hole behind this to allow any pressure to escape. I imagine that this last hole had a fitting to allow a tube to pass to the rear of the bike to let out any excess pressure. With the Walkernators I supply a sealing system to go between the drive bump and the dynamo replacement. So far this does not seem to have caused any problems or, at least, no one has reported any.
I'll just throw this on there.... suggest that I believe it came that way from the factory and exit stage left....

1954 Black Lightning L engine.jpg
 

Cyborg

Well Known and Active Website User
VOC Member
BTW... at the risk of being excommunicated, who is Cecil Mills and what bike did he have?
 

john998

Well Known and Active Website User
VOC Member
Hello, The bearing spacer is a labyrinth seal not a scroll as it can be fitted either way round. John.
 

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