Is there anyone who have tested their BSA A65 for power ? could be interesting to konw what horsepower a 650 ccm gives on the backwheel as standard and also bigger bores with different kind of setups, porting, valves..
I do not know how a BSA head is fitted but check there is no raised area around the stud holes. Make sure the gasket is a good fit. Anneal the gasket properly. Use copper coat on the gasket. Clean the threads and use a torque wrench. Run the bike a few minutes, let it cool overnight and retorque and then retorque a couple of times again in the first 1000 miles.
Retorquing is usually more important with composite gaskets not copper gaskets.
Joined: Sep 2002 Posts: 7,812Alex
BritBike Forum member
BritBike Forum member
Joined: Sep 2002
Inertia or drum dynos are the most common dynos around because they are substantially cheaper than brake dynos. They work by measuring the angular acceleration your bike can produce on a drum and therefore have to make some compensation for the inertia in your drivetrain. This can give errors up to 5%. Brake dynos actually use a large brake (can be fluid, friction, or electromagnetic) and can essentially measure power at any fixed rpm without the impact of inertia in the drive system. There aren't a lot of brake dynamometers around for us normal folk so we make do with the inertia dyno.
Anyway, yes, it's 650 cc. The pistons are slightly lighter than stock but I don't remember how much right off hand. It does also have a substantially lightened flywheel and carillo rods. The valves are stock size.
The cam specs: 542-x1 Road race profile. Mid-range and top-end Lift: .400" Duration: 280° 103° power. Use racing springs and pistons. Intake open/close: 37 btc/63 abc exhaust open/close: 63 bbc/37 atc.
I have only run BSA stock cams beside this one. This cam has really nice midrange and keeps the torque broad and in a manageable range while continuing to produce power past 8000 rpm. Not sure I'd wanna run it on the street.
A smattering: '53 Gold Flash '67 Royal Star '71 Rickman Metisse '40 Silver Star '37 Rudge Special sixtyseventy Lightboltrocket road racer...and many more.
My own experience with a bike set up for lsr trials has been a best of 52+ hp and 115.5 mph on a standing start mile with official timers. The motor uses 74.5 mm pistons to meet the 650 class. Stock cam, stock valves, flowed head, 32mm Mk1 carbs, 10.4 cr, mufflers. 20/47 gears. Pazon ignition. I have also used 2 different 'racing' cams and was surprised to find that the Beezer cam was best with mufflers. With Megacycle X-8 and megaphones running 11.8 cr the bike did 121.5 at the same track. PRT
Oleandreas, how did you menage to install a Norton bearing on the timing side of the engine ? My impression was their outside diameter is much larger than space available. By the way Norton engine is another design with a crank floating in the cases ( rollers both sides ) and somehow it works ??? It means BSA engine should work as well with this bearing configuration.
If you look at the photograph, it has a needle bearing on the timing side, not a Superblend roller. What I would be interested in knowing is why he used a needle bearing for the intermediate gear shaft? And not even a full compliment needle at that. A bush has a very high load capacity and I do not remember when I had to replace one due to wear. Also, why change from the two front inner bolts to one central one? It appears to be right at the back end of the rocker support.
DM, it has the threads there for the other bolts, maybe its an extra, I've never looked where it would come out but maybe it would be useful. With an alloy block esp with smaller studs and bolts the head cannot be pulled down to the std bolts 33ftlb, not that that seems a problem from my experience, but it may help stop oil leaking up the front where A65s sometimes seep. Some dowls on the oil drain holes would probably help that.
needle bearing for "intermediate gearshaft" idler wheel or what its called, I dont see it as any important upgrade. I had to replace the weared bushing, and I decided to change for a roller. I dont see any special benefit in this, probably much more useful on the camshaft....