B Rapide venting oil mist at hi speed

[craig]

Hi Greg, Thank you , I am sure you are correct as the hole is tiny, but I don't want to add plumbing out the rear at this time. My solution this week end is to rubber band a napkin over the oil cap. The series B Rapide UFM has an unregulated chain oiler/vent...which appears to be a messy affair. Not like the needle valve block on most Vincent UFM.
The structure of the oil cap is venting out the tiny hole at top, but the path starts by venting around the loose fitted eye at the center? yes?
I see an added hole in this "eye" area on David's picture.............maybe adding drain holes to the cap will resolve this issue? or make it worse?
Bill, Thank you , I am running Brad Penn 10-40 green oil, hotter months I run Brad Penn 20-50...........I am not thinking too thin.
Cheers
Craig

 

[craig]

B UFM oil filler neck

 

[craig]

I did some review of original pieces and compared to recent reproduction pieces I am using.
1) the original cap (more complex construction) to left in photo has venting completely around brass funnel piece, a much heavier spring, and looks like custom construction with tiny funnel.
2) repro engraved oil cap seems to have only venting thru small hole under center brass washer
3) repro cap with no engraving has only center hole vent, but uncovered.
Is it possible this oil venting is a problem that was identified during the Vincent years.......appropriate caps were obtained and used.....and as reproductions were produced combined with a lack of research, that the modern oil caps are the problem?

 

[greg brillus]

The upper frame on my rap is a B and my oil cap is a genuine one....at one time I had it up to around 80 to 85 mph and it started bleeding oil out of the tiny vent hole. It was then that I realized that the chain oiler/vent was blanked off. I removed the blank....vented the line with a T to the engine breather, and ran a 10 mm bore hose out the rear....it hasn't happened since. You may be right re the cap but I think it is a Vincent thing.....as I call them...."A work in progress" cheers and good luck.....Greg.

 

[vibrac]

Never had the problem in all the years racing and road . But odd thoughts arise -wasn't a D1 BSA bantam petrol tank cap or similar stink wheel cap the same size? and diddnt it have an extended tube for mixing 2 stroke? and if that was artfully cut away......?

 

[craig]

I remember riding my standard Comet at 70mph, several times, on the local hiways for about 30 minute sprint (C series UFM, chain oiler shut off, repro oil cap) and the Comet also spit oil out the vent hole in the cap. I don't normally do this, so I ignored the problem. This Rapide doesn't mind doing the now 80mph norm to keep up with local soccer mom traffic, but the oil spit is not tolerable.
Looks like a carb slide could be a used as a baffle.

 

[tatty500]

Craig,
My B Rapide was made in 1947 The return and breather tubes are oriented differently from yours.
Firstly both pipes remain cylindrical right up to the brazed capping.
The tubes are sort of back to back with the holes facing away from each other. So that the return oil flows around the the filler neck and does not squirt across the center.
Mist entering the breather would come off the wall of the filler neck on the opposire side.
My breather is blocked off and my love of doing about 85 on the slight uphill of the Atherstone bypass has never resulted in any oil leaving the cap vent. (My pistons and bores are the original ones so I bet I've more blow-by than you)
Two things in your picture strike me.
1) Your tubes seem a little flattened at the top resulting in a slightly upturned return hole
2) the oil return hole faces across the neck
This is so different to mine (Engine 373) that I assume yours predates mine. I presume the factory then came up with the solution for production with the tangential holes. So I assume your bike must be earlier than mine.
Looks like the baffles were "invented" as a retrofix.
Someone is keeping tabs on these B changes I think.
Regards
Tatty 500

 

[craig]

T5, We need photo of your oil neck please. I put my original oil cap, shown above, back on and tested at 80 mph. One drop came out after 10 miles.....so the oil cap has a lot to do with containment. I will continue to test this cap with out baffle. Yes this is B Rapide 323, sold new in West Virginia, USA, TRIAD Motors Inc. first owner William Worthen.
C Rapides must have the same problem, as they spit oil directly across as well.
Cheers
Craig

 

[craig]

 

[tatty500]

Craig,
Sorry for the delay.
I struggled to get any worthwhile pictures down the filler neck, but those latest pictures you posted are more like mine for direction of squirt, BUT mine have a greater difference in height.
Resting the end of a 6inch rule on the bottom edge of the oil return hole, it is 49mm down from the top of the neck......whilst the brether/chain oiler hole is only 34mm down.
I do know of one C that had a problem. Ten years ago Minivin was trying to sell a solid nylon deflector that he had constructed to cure his problem. However when I looked, the block that C's have was fixed in at an angle, giving a slight upwards squirt.
I am trying to add the one decent picture I have. I've not always been been lucky, but here goes.
Regards,
Tatty500