BSA B50 -500 APG Build

[Old Scrambler]

Looking very sanitary...................

[tauruck]

Nice work Tom, would you say you're almost ready?.

[Jon]

Looking nice Tom.
TIG come in handy for making manifolds etc?

jon

[Koncretekid]

Thanks for the complement, Dennis.  And Mike, I think I'm almost ready, but with the revised ratio rocker arms my valves will come very close together on the overlap at TDC - - about .025-.30" short of touching.  So, if I survive the dyno run, and Loring, then we'll see.  Also, I'll be comparing the new dyno run near sea level with my old dyno runs at a mile high altitude on somebody elses dyno, so I really won't know if the new manifold is better, or the new rockers, or the new crankcase evac. system I'm working on, or the altitude.  Also, I won't get back to the bike until June and I still have to modify the fairing for the shorter exhaust after the dyno run.  Should be interesting.

And Jon, the TIG welding is still in a learning curve.  Butt welding the .060" wall intake tubing was a new experience, as the butt weld appears to take a lot less heat.  I also did some vertical welding on a bracket on my roadrace B50, and that was different.  But I like the idea that (I think) with the TIG, you either get it right or you burn a hole - - no false beads laying on top.

Today I made a reed valve crankcase breather to replace the PCV valve I had been using.  It is made from two top covers and a reed valve breather from a Kawasaki.  We milled a .080" deep groove around the inside of each of the two identical covers to allow the reed valve block to nest between them, as they originally just held the reed valve into a recess on the Kawi.  We then threaded the two open holes to 3/8" NPT to accept standard spigots to attach to case on the BSA.  I also plan to connect the outlet to an exhaust extractor to boost the crankcase vacuum.  I'm not expecting miracles, but maybe I can gain 1/2hp or so - - significant when you only have 44 to begin with.  Baby steps.

Tom

[DND]

Hi Tom

Yrs ago i built a cross ram I/R set up for a SBC using 8 Harley Tillotson carbs, we used the biggest tube we could fit and for the carb size.
As it turns out the carb was way too far from the valve, she made a ton more power at 4000 - 5000 but ater 5500 it died from too small of intake runner.
When i looked at your new manifold it reminded me of my problem, maybe you could use some rubber hose of different lenghts to find the sweet spot then make a steel one.
With my cross ram style i could not shorten the runners or go to a larger tube, so we had to shelf the project we just used a Trans - Am box manifold with a flat plate and mounted the carbs standing up 4 on a side.
It worked pretty good but with a gravity feed carb it would only take a lb and a half of fuel pressure, and it would get lean at the top end.
Good luck with your testing, Don

[tauruck]

Tom, that's a lot of work. That reed block looks like it takes a two petal reed. Does it take a Carbon reed?. PM sent and good luck with your build.

[Milwaukee Midget]

Thanks for the complement, Dennis.  And Mike, I think I'm almost ready, but with the revised ratio rocker arms my valves will come very close together on the overlap at TDC - - about .025-.30" short of touching.

That sounds tight.  They're at - what - 60 degrees to each other?  Valve control will be key, but the higher ratio rocker may actually be your friend on this one.  With the higher lift rocker ratio, the spring has more control over the rest of the valve train - you have more mechanical advantage with respect to the push rod side of the valvetrain.  As long as you have enough spring to keep the valve train from throwing off the valve and actually follow the cam profile, I'm thinking you'll be okay.

That was an issue I ran into.

Have the spring pressures been checked?  DO NOT RELY ON THE ADVERTISED SPRING RATES.  The Crane springs I was using were WAY OFF OF WHAT THE CLAIMS WERE.

[Koncretekid]

Don,
When I put the bike on the dyno, I will have some different lengths to try.  The 11" (valve to end of carb) steel one is sort of the worst case as far as interference with the seat, cable length, and oil filter relocation, so anything shorter should fit.  I wonder about just a rubber hose, as we are trying to tune to a specific pressure wave reflection, and I'm not sure the rubber would have the same dynamics as a rigid steel or aluminum one.  I will make some steel or aluminum stubs with a short hose to connect to the carb to try,and I can make a short seat for the dyo runs.  I will make the change permanently to whatever, if any, makes the most hp.  At least in land speed racing, we only need to look at maximum hp, as it is unlikely that hp requirements will be an issue in the two mile acceleration (1-1/2 at Loring).  Remember that hp requirements go up at the cube of speed, so we just need to get the speed and the hp maxed at the same time.
Mike,
The reed valve is a 2 petal one, one of 2 that came from the Kawisaki ZX600 breather.  Reeds are thin steel. There shouldn't be too much actual flow unless I've got blow-by.
Chris,
The valves are at about 67* included angle.  At TDC at overlap, the intake is open about .183", the exhaust about .200".  At about .220" intake lift and .195" exhaust lift, I will get interference.  A missed shift could be disasterous!  I unfortuneatly did not check spring pressures or coil bind, but they are R&D valve springs.

Tom

[Rex Schimmer]

Tom,
On your intake track length, as I remember the "rule of thumb" for a rough cut at the tuned length is: 84000/length. With an 11 inch long carb/tube to valve length the sweet spot should be around 7600 rpm, which is right in your area.

Crank case "evacuator": Your addition of the two pedal reed valve may be more effective than doing something with the exhaust extractor. You have the best possible case for using the engine itself to pump the crank case, i.e. as your single piston goes down it pressurizes the case, the air goes out the breather and the reed valve prevents the case from refilling and if your engine is pretty tight, a real challenge for anything from England, every time your piston comes down it should continue to pump out any accumulated gases. When you have a multi cylinder where you have one piston going up and the other(s) going down this may not work as well but for a single I would bet you can get some real case vacuum and probably see some good power increase. Be sure to put a vacuum gage on the case and report back!!

Rex

[saltwheels262]

Kkid, the above two paragraphs make a lot of sense. I'm not that familiar with either one of those subjects. especially reed valves. I'm sure that you're on the right track. especially having a thumper.

I will try to apply the intake track equation to my V twin. thanks, Rex.

Franey

[Koncretekid]

" the reed valve prevents the case from refilling and if your engine is pretty tight, a real challenge for anything from England"

Rex

Do you think it will be a challenge?  Photos of my B50 road bike after a couple of hours on a Colorado Jeep trail.

[wobblywalrus]

Yamabond #4, the grey stuff, work good for sealing those bikes up.

[Koncretekid]

I have decided to bite the bullet and switch to cast aluminum rims for peace of mind.  My spoke wheels have always had about .050" run out at the weld where the factory welds the aluminum together.  I also had a lot of trouble mounting ZR tires on these rims and pinched a few tubes in the process.  Trying to find cast aluminum rims has proven tough.  At the rear, my problem is the close spacing of the sprocket to the centerline of the wheel.  The BSA B50 actually has the motor mounted 1-9/16" left of the bikes centerline, just to get the sprocket 3" off the centerline of the wheel.  I'm stuck with that.  Most of the 17" cast rear wheels have their sprocket centerline close to 4" or more off the wheel centerline.  I have had to find a rear wheel which was narrow enough with a close sprocket centerline.  Following is a list of some of the possibilities I have found:

Honda CBR125R rear - 2.15" wide, centerline unknown, but largely unobtainable and too narrow
Kawasaki EX250, 2008 and later - 3.5" wide, centerline not measured, but is a lot more than 3" and these wheels are in high demand because of new racing classes, so are expensive
1982 Suzuki GS450 - 2.15" wide, too narrow
1989-1997 Suzuki GSX600 and 750 - 2.5", but very wide centerline
1994 and later EX500 - 3.5", centerline not measured but as with EX250, sure to be too wide a centerline
1988-1991 VTR250 Honda - 2.5" with centerline measurement of 3-5/8", with a drum brake

This last one is the one I decided to use.  The drum brake is actually a bonus for me as I already have the bike set up for a drum.  The following photos show the machining we had to do to lose 1/2", reducing the centerline measurement to 3-1/8".  I can lose a bit more if I have to.  Basically we reduced the sprocket seat by 1/8", and then milled 1/4" off the cush drive blades.  Another 1/8" was gained by reducing a spacer between the drive plate and the hub.  We did not compromise the integrity of the hub itself.  The final photo is the finished, newly painted wheel with sprocket.

Front wheels are a bit easier to find, but most have a fairly large disc mounting spider.  I found a nice XJ600 Yamaha one, 2.5" wide with modern hollow spokes. I plan to make a disc to cover the ugly brake disc mounting lugs, as we are not allowed to take any material off the wheel itself

Tom

[Peter Jack]

I think that's a great move Tom. I hope it works out for you. As I've expressed before I've ridden a flat rear down from roughly 60 - 65 mph a couple of times because of a torn tube. I definitely wouldn't want to try it from double that speed.

Pete

[tauruck]

I know all the stuff you went through on matching that wheel. It's no joke but it turned out great and looks awesome.