Anti wet sumping valve with combined kill switch

[trevinoz]

John,
            What size ball is used? 5/16"?
            Trev.

[olev]

Thanks JohnO,
I'll be assembling my A7 bottom end shortly (been saying that for 6 months).
After reading all the grief experienced with wet sumping I thought it would be nice to be able to get at the valve without ripping the cases apart.
This mod looks like a good thing but I'm not sure how well it will work without other mods added during the roller conversion.
I notice Beeza Bill's (rip) page shows how he did it on 'oil gallery parts drawing' and 'oil gallery dimension drawing' but I'm too thick to understand it.
http://bsa-a10.hailwood.com/mybsaa10rollerconversion.html
Is it as simple as drilling it out and dropping in a spring and ball bearing?

[chaterlea25]

Hi Olev and Trev,
The ball bearing is 1/4in. and the hole 5/16in (8mm)
Remember that the oil must flow past it on the way to the vitals
the ball seats against the back face of the pump, a very very light tap may be used to seat it if necessary,
as the pump body is very soft,
Make sure the gasket doesnt foul the spring or the face of the pump where it will sit against
I make my own close fitting gaskets so as they will not move while assembling the pump
The bottom of the hole is flat due to the end of the grubscrew being faced off
HTH
John O R

[Big Nick]

i have a srm sump plate with a drain nut on it with a magnet, very easy just undo the nut , wipe crud of nut, put back more oil and off we go. best is to use the bike every day then no problems.

[Rocket Racer]

By cutting the timed breather thingy I am able to still use the cork to stop cam end float.

On the topic of the timed breather, I note that an article in classic bike referring to Cake Street Classic's "How to fettle BSA twins" (pre unit) talks about extending the hole elongated to the right to a total length of 12mm.

I also have an article from the NZBSAOC that refers to a letter by David Munro from BSA's technical department to a NZ A10 racer in the fifties, that refers to drilling a new location hole to give the mechanical breather give a 30 degree retard for racing (??)

I'm currently considering what to do to my stock breather timing which is now routed to a catch bottle.

[muskrat]

G'day RR,
                 for your needs I recommend the Bunn and my setup. With it you have no pressure or vacuum in the cases to slow the pistons down.
Cheers

[shabashow]

Rocket Racer - do you still have that article about extending the holes in the timed breather? It would be very interesting to find out the reasoning behind it.

My bike leaks out the back of the head, at the pushrod tunnel, occasionally the base of the cylinders, and I've noticed more oil, black in colour in the primary drive case than I put in, indicating engine oil is being pushed out, where it shouldn't. This is most prevalent if I get the speed up, and if I stick to below 50, there's hardly anything. Engine's ony got about 2500 miles on it since a rebuild. I'm coming to the conclusion that the little hole in the breather won't let much air out, and toyed with the idea of extending the hole. Sounds like a low cost experiment, which, if doesn't work, can't do much harm. I can always get a replacement, or fill the holes in.

John

[Rocket Racer]

Rocket Racer - do you still have that article about extending the holes in the timed breather? It would be very interesting to find out the reasoning behind it.

John

John,
 yes I do, but its in a 4mb pdf. would you like me to mail it to you? I think I can do that as a PM. I'll try... Its quite an interesting article on a period racing A10 in NZ -plunger frame,small jnl,thin flange... 8000rpm!

Tim

[Rocket Racer]

My bike leaks out the back of the head, at the pushrod tunnel, occasionally the base of the cylinders, and I've noticed more oil, black in colour in the primary drive case than I put in, indicating engine oil is being pushed out, where it shouldn't. This is most prevalent if I get the speed up, and if I stick to below 50, there's hardly anything. Engine's ony got about 2500 miles on it since a rebuild.
John

John,
 I'd be thinking about resealing the cyl head gasket and torquing it down a bit more. The 1st time I put an A10 head on (Jan this year) I couldnt find torque settings so used atlas/commando settings of 25lbs and it blew oil out the pushrod joint as soon as we started pushing it hard on the track. Cake Street suggest 28/30lbs and I've seen this forum talk about 40lbs!
Tim

[Rocket Racer]

http://bunnbreather.bigblog.com.au/post.do?id=219490

A very good move Musky.
Rex, who designed the "improved" breather because he was too lazy to pull the barrel of his B40 and do the traditional fix to stop oil running up the stud and leaking from under the head nut washer, has now become a world authority on crank case breathing.
Seems that no one in the past actually did much in the way of research into crankcase breathing each designer just followed the theories of the previous generations ( make a vaccuum in there and it won't leak ). The idea of pulling fresh air into the cases then expelling the old air had just not been done.

Auckland uni ( I think ) has just made a research grant available so they should be some substantial improvements in the next few years.
Most of the ones fitted to members bikes have gone onto singles but a BSA twin is in effect a 2 cylinder single due to the 360 deg crank.
Apparently the historic racers have taken to them big time and get significantly more power & better acceleration from the breathing system.

I caught up with a good mate who happens to be doing the studies at the AUT that are referred to above. For a race engine, particularly one running methanol, running two breathers as Muskrat recommends; removing the timed breather but running that breather with a valved inlet only setup and running a second outlet on the topend with an outlet only will not only liberate power   but also help remove the highly corrosive methanol vapour .
I'm hoping to remove my timed breather next week and trial a set of Rex's valves before the rig hits the track on the 23rd and 24th