TECH TIP OF THE WEEK Caught on video! In this video we were running a bike with a poor exhaust. When we saw what it was doing we decided to video it. This is a simple step test. We simulate a load on the bike and open the throttle until we get to certain levels. Usually 250 rpm increments. During this test we watch to see the air/fuel ratio reading on the far right side of the screen. This ratio should hold steady once the target RPM is reached. It should also be easy to maintain the target RPM. You will notice that it is hard to maintain the target RPM during this test and as the operator tries to maintain it, the air/fuel ratio will go up into the red zone. As the air/fuel ratio goes into the red zone, the oxygen sensors send a signal to the bike computer. When that happens the computer tells it to deliver more fuel in an effort to get the the proper ratio. Im this case, it tries to deliver a lot of fuel because the engine is running so lean. That causes the ratio to go very rich. In a couple of the RPM levels it is not bad but in others it is terrible. This bike would be almost UN-rideable ! This bike had a 2-1 exhaust that was very free flowing and the rear pipe was very short. Clean air was being sucked up the back of the pipe and influencing what the oxygen sensor was reading. People think that exhaust flows out the back of the pipe evenly. It does not! It flows out in pulses. When a pulse ends, clean air can be sucked up the back of the pipe all the way to the sensor. When this happens, the system cant compensate. This is one of the reasons we need some restriction in the exhaust system. Next week we will show the after video and discuss what we had to do to get this bike to run good. Brought to you by the brilliant Jim Egizio! Ride safe!
Posted on: Thu, 07 Aug 2014 18:06:44 +0000
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