BIKES, WORK & FUN :
gave quite a bit of thought to the induction system, The supplied
manifolds on the engine were lifted straight from the 500 singles. The
front one was at a silly angle especially for the carburation that the
engine would have been expected to have.|
Even with injection, the throttle body would have been going thru my chest! Not ideal.
So something more appropriate was in order. Originally I envisaged using TL1000 throttle bodies, but they're huge and incorporate the injectors, whereas I wanted the injectors downstream of the TBs and pointing in a straight shot at the valves.
Then another idea occured. Why not have a single throttle body feeding a plenum, which would then feed a manifold/ injector housing which would extend the 2 ports to each valve back several inches? A long ram effect with a smooth flow.
Now individual throttle bodys are well known to give a snappier throttle response compared with a plenum, but thinking about it, on a long straight run on the salt snappy throttle response isn't needed or wanted - you can quite easily induce wheelspin on each gearchange.
So a more damped response is a good thing in this application.
Of course, its easy to forget that airflow needs to be considered holistically (!) Its no good having a perfect port layout if the atmosphere its drawing upon is going the other way at 150mph!
|Heres the pics. You can see that the
throttle body (off a volvo) will point forwards and the plenum is a
curved tube affair to keep it all moving in the right direction.
Ducting is deliberately kept on the large side to provide the plenum
area right up to the manifolds.|
This is the dumpiest little tank I ever made!
Needed to be this height to accomodate the in-tank fuel pump. Kept it short so I can hunker down behind it a bit.
With all the fabrication done, it was time to delve into the engine. Moment of truth!
No rust in the bores! Phew!
Measured the CCs of the head & piston dish; its about 10:1 compression.
Not the 14:1 methanol engine I'd been led to believe.
This was a problem; its too high for forced induction and too low for max output on race gas. Bit the bullet and arranged for Ross Pistons in the US to make some with a bit of a dome. Ross have a minimum order of 4, so I had to get 2 sets made.
They arrived Jan 2012. Nice work guys!
After checking valve to piston clearance, they went off to Camcoat for coatings to be applied. Dry-film lube on the skirts, ceramic heat barrier on top and heat shedding underneath. Every little helps.
I was warned not to mess with the timing gears in the timing chest as they take ages to set up. This proved to be bollocks! The cams have vernier adjustments up top. it doesn't matter how the lower gears are assembled.
I have to say that although the fundamentals of this engine are sound, they way
the top-end assembles is just plain crazy! A real nightmare to work on, not to
mention limitless scope for oil-leaks. Good British tradition?
No wonder the Excelsior-Henderson derivative ended up so radically different!
Obviously I cant just go & buy a gasket set for this engine, so set about making
a batch of 6 out of 18g copper.
Also had Dave Branch insert wire O-rings into the top of the liners.
Final assembly began at the end of Jan 2012. And continues....
.....May 2012 - much progress, some bad!
Bike is all together:
Race entry is in, flights & shipping booked, most paperwork sorted out.
The Microsquirt fuel injection has bee a big disappointment. Spent most of April working on it & got nowhere. Finally got it to start, but ignition timing
erratic. Running badly.
Had to draw the line somewhere - no more time to waste. So the fuel injection has been sold and the timing cover modified to accept Harley type ignition parts.
A Twin-Tec module & coil bought and 2 of the older Keihin screamin' eagle carbs sourced fom ebay. At this point the manifolds have been altered to take the
carbs and the cables are done. I now have about 5 weeks before it has to be loaded onto a container bound for LA. And one more customer order to complete.
How come everything always has to go right up to the wire?
Screamin' Eagle carbs: