This motor is basically the same as the original Gen 5 early configuration, but has the Carrillo Ti "H" Beam rods and some other simple goodies listed below. The Keihin FCR carbs have shown to really help this motor breathe up top as we have seen on some testing with our "Mule" (see graph at right). These carburetors have been the "Unobtanium" or "Holy Grail" of carburetors for this model of bike. So, the fact that we have a set seems to be a miracle in of itself. They are difficult to tune and are notorious for not accepting throttle under 8,500rpm. Needless to say, getting them working well on the racetrack will surely be a challenge. So far, we have not raced with these carburetors.
The engine was originally assembled with CP Pistons, but we ran into some issues that led us to work with Cosworth Engineering in the UK on some newer pistons (see Part Evolution: Pistons). I was able to work directly with the Engineers there to specify exactly the pistons I wanted. What they delivered was more like jewelry than engine components they were so beautiful.
All of the internal components of this engine were sent to CryoScience Technologies to have their REM & Cryogenic processes applied to reduce friction and increase longevity of the parts. The end results were asstonishing as we gained between 3%~5%hp gain just from this process. We have torn the engine down several times since having the parts processed and have seen no significant signs of wear. It appears to be working.
In my quest for the ultimate piston, I believe I got greedy. I measured the piston-to-valve clearance of the CP Pistons and felt the pockets were too deep in some areas. So, in specifying the pocket depth to Cosworth, I wanted to raise the pockets to decrease the combustion chamber total volume (increase the compression). I asked for dimensions that would give me 0.030" (0.762mm) clearance on the Intake pockets and 0.060" (1.524mm) clearance on the Exhaust pocket. Only through "Trial & Error" did I discover this amount of clearance was not enough for the Exhaust valves with stock springs.
In looking at the clayed piston of a surviving cylinder, you can see that the dome angle was slightly different than the valve angle. This could have been from the amount of rock the piston had in the bore. You can see that the tighter side was at 1.5mm, just as I specified, and the valves were making contact. Where as at the depper end of 2.0mm+ there was no contact. Therefore, for future pistons, I changed the specification on the piston to add 0.5mm of clearance to be "Safe". In addition, on future engine builds, I changed the cam timing specs to add just a bit more clearance.
Although the end result was another destroyed engine, we were able to try many things with this engine and learned a lot about what works and how far we could push things. It was definitely an expensive mistake on my part, but the results were a better piston (Cosworth v2) and higher output engine from less friction and more durability (REM & Cryo). We achievded the best hp for this engine that practically matched our best-ever power on pump gas. We were depressed about the set-back, but excited about getting the new engine back together with all that we just learned. We were definitely making forward progress.
Although this engine only raced a small handfull of races, Mark Elrod was still able to use the 428cc Clubman Engine to win the 2008 and 2009 450 Superbike Class Championships. He was leading the 2010 Class Championship, winning every race he finished. But he crashed out of one race, then had an electrical wire break causing a DNF in another. This put him just short on points and he ended up 2nd in Class. We're really hoping to get that Championship back in 2011.
SPECIFICATIONS (Gen 5.1Ti):
Bore x Stroke: 57.0mm x 44.5mm
Pistons: Cosworth v1/G-Force Design
Rings: Yamaha FZR400 [+1.0mm O/S] (2-Rings)
Bores: Bored Stock Cast-Iron Liner
Rods: Carrillo Ti "H" Rods
Crank: Marine/G-Force Billet Crank (2nd Generation)
Cams: Stock VFR Cams with RLR Slotted Adaptors
Max rpm: 14,500rpm
Carbs: Keihin FCR32V HRC Racing Carbs
Race Fuel: R-Tech "Pro-V" Racing Fuel
Cost to Build: ~$15,000
DEMISE: Piston-to-Valve contact. Destruction of engine Top-End and 1 cylinder/piston