Throttle Magic: Part Three

How are you going to get your 450 lb. bike moving without stalling, bucking, jerking, or shooting across the road into a ditch and falling off? This scenario is a real possibility for you, but here is some information that might help.

It’s useful to know a bit about the characteristic way your engine delivers power to the rear wheels. The following is a torque and horsepower graph for the F650GS. It’s very similar to the older F650 that I have and in fact almost identical to other 650cc dual sport singles as well. Other bikes, including multi-cylinders, aren’t much different in principle either. An exception is the enormous low-rpm torque available from a big V-Twin..

DynojetRobert1071

The torque is shown in the upper curves and the horsepower in the lower one. My bike idles at 1400 rpm, and the graph shows that I need to approach 2500 rpm before I can expect to see the beginnings of the power needed to accelerate, about 15 horsepower at that point.

As I am sitting stopped, I have the engine idling and the clutch “in” (disengaged) so the engine is disconnected from the transmission. I have pressed the shift lever down into first gear, but I can rev the engine and the bike doesn’t move. If I let the clutch out with the engine idling, the engine will stall. If I let the clutch out while simultaneously twisting the twitchy throttle, I get the unstable behavior mentioned earlier. By the way, forget the kill switch. You won’t have time to hit that before you are on the ground.

The basic idea is to rev the engine up to at least 2500 rpm and hold it there while “throttling” on the power by partially, then fully, letting out the clutch. When I do this I end up travelling at 15 mph in first gear without moving the throttle at all. Let the clutch out just enough to get the bike moving and then let it further out gradually to speed up. With practice, the procedure becomes more fluid and you can smoothly add some throttle after the bike gets moving a bit. But the basic idea is still the same – get the bike moving with the clutch. In fact you can “ride” the clutch partly out and travel pretty much as slowly as you want. That’s how you get through the parking lot riding test when you get your license.

Unlike a car with an automatic transmission, you don’t start off with the accelerator. You hold the engine revved a bit to get some power and then use the clutch to get it moving.

A very common difficult startup scenario is turning onto a road at an intersection, either turning left by crossing the near lane to enter the far lane, or turning right into the near lane. You can’t afford to overshoot or undershoot. After the bike starts moving, remember to look where you want to go not straight ahead. As the bike picks up speed with traffic in the turn, you begin to transition from clutch to throttle and you can get confused if you need to slow down or speed up. With experience, it becomes easy to execute this maneuver. Until then, go slow enough to stay in control. Most cars will give you plenty of room to do¬† your thing.

As Peter Egan says, “Ride your own bike”.