ET: Engine (Twin) Main Bearing

Robert Watson

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Like this
20171117_152141_HDR.jpg
 

mercurycrest

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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

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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

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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

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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

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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

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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

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BTW... at the risk of being excommunicated, who is Cecil Mills and what bike did he have?
 
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