This is about friend's bike - 636 2003. It has some issues which we cannot explain so maybe someone can think of the possible problems and solutions.
Since he had bought his bike it had "holes" in the power delivery curve, and the bike was not very responsive to throttle. After the service, he has mounted the aftermarket exhaust (Arrow I think). The bike has K&N filter and power commander.
Later he went to his friend on the dyno table and the bike has been mapped through power commander, but then the problems became more noticeable.
One of the problems is that after few drives, the bike changes its power curve so to speak. One day it works fine, the next day it works like shit and the day after works like superbike on a track.This problem was even confirmed on the dyno table again - the power curves were not consistent which lead to the conclusion that this is electrical problem.
We have realized that if the cranckshaft position sensor is moved for even 2°, the bike loses its power like it is some 250cc bike. The mechanic at the dyno table said that the sensor can be actually moved to 8° for tuning purposes.
This being said, does the crankshaft sensor along with the cranckshaft sensor gear have any known issues on these bikes? Can something be demagnetized during time or the cause for this can be found in other place?
Furthermore, after some time we have discovered that the negative terminal (ground terminal) is not at the same voltage potential on the whole bike.
To explain: when we tried to measure voltage between the battery negative terminal (ground) and the ground black/yellow wire found on the harness near ignition coils we have discovered that there is some voltage which should not be there. I mean the ground should be equal for all the electrical components on the whole bike?!
This is shown in the picture - multimeter black lead goes to the minus of the accu, and the red lead goes to the black/yellow wire and voltage can be measured. I'm not sure is this is some parasitic current generated by the coils, or this is wiring harness malfunction? Can someone verify this on his bike?
Also on the other image it is visible that it has a huge hole in the power curve. As I'm informed this hole is characteristic to these bikes but even so - can you comment on this power diagram?
Also the bike sometimes has idle issues - it either works at 1000 rpm or 1500 rpm like its digital and has only two states 0 or 1 ?
Things that have been changed without improvement:
2. Camshaft and crankshaft sensors.
3. Ignition coils.
4. Fuel injection with throttle bodies.
5. Both TPS sensors....