It is time to do some engine work on the Bonneville. The cam chain is worn and whipping around, and the standard pistons and rods have been run for three years at Bonneville and 21,000 miles on the street. The 2008 runs were real brutal. Compression is fine and there is no piston slap. I simply want to put in racing quality components. A fragged piston or snapped rod would end my land speed career.
The big decision. Should I build a hot engine and go for records in my 1,000cc modern engine classes? Should I build a strong, but not radical, street motor? All of us face this decision. I have a few times. A hot engine requires a lot of money, hours with the spanners, and maintenance. This time, for once in my life, I decided to put thought before action.
The benchmark in my class, a threat to all records I could attempt or set, would be a new BMW S 1000 RR. I would have to equal or exceed this bike. Advertised specs are 190.42 horsepower at 13,000 rpm for an engine just under 1,000 cc.
Consider volumetric efficiency. I could bore and stroke the Triumph out to 1,000 cc and produce 120 hp, naturally aspirated. This would take lots of money and I would need to tear it down after every session on the salt to check the bearings, etc. Volumetric efficiency would be about 120 hp per liter. The BMW has about 190 hp per liter when you roll it off the showroom floor.
Let's look at redline rpm. Assuming two engines have equal volumetric efficiency, the one with a higher redline can run gearing with a greater numerical ratio. This engine will exert more leverage on the track and it can go faster. Right now I run the Bonnie between 7,000 and 8,000 rpm through the mile. Folks with higher tuned Bonnies stretch them out to 9,000 rpm. The BMW, out of the crate, has an advertised redline of 13,000 rpm. Clearly, the Bonnie has no hope of being a serious land speed racer. This has been for awhile, and is getting to be more so, the era of the four.
The one thing the Bonnie is real good at is racing for the pleasure of going faster every year. It is relatively easy to work on and not very expensive to hop up. Besides, it is paid for and a harmless old guy on a slow bike can run in most events. Elvington and Lake Gairdner await.
This winter the engine rebuild will be posted. It will be basic, but folks who have not torn down a motor might learn something. Lots of younger people have not taken an engine apart. It will be awhile. I have to save up money for the parts.