Hoople
Account Removed
How come when you start bike and put in first gear you get the clunk? But, while still holding clutch in, put back into neutral, let clutch out, pull clutch back, put into first gear again, but this time no clunk? Mine,2010 FatBoy, does this every time.
So is it the trans clunking? Or is it the compensator taking up slop first time after shut down?
wilks3
Do you REALLY want to know why. If so, here it is in all it's Glory......
The reason why that happens is because of Inertia. Heavy objects once in motion want to remain in motion. (or at least remain in motion until Friction slows them down). Understand that point, and you will understand the reason for the "clank"..
Lets look at the entire drive train as follows. The transmission is just a box that has an input shaft and an output shaft. The input shaft is attached to the engine side but can be detached from the engine via the clutch. The output shaft of the transmission box is directly attached to the rear wheel. The input & output shaft from the transmission are directly coupled to each other EXCEPT when in neutral. (1st Key Point!)
The Clutch also has an Input shaft & an output shaft that is directly coupled to each other EXCEPT when the clutch lever is pulled IN. (2nd Key Point!)
So mentally look at the drive train as follows.. ENGINE=>CLUTCH INPUT=> CLUTCH OUTPUT=>TRANS INPUT=>TRANS OUTPUT=>REAR WHEEL.
** Once again Remember that TRANS INPUT =>TRANS OUTPUT can only be broken (or uncoupled) when the gearbox is in neutral.
** Once again remember that gears & metal parts have inertia and once in motion want to remain in motion.
** For discussion purposes only when it is said that your clutch LEVER is OUT (or released), it means the clutch input shaft and output shaft are DIRECTLY coupled to each other.
So if your still with me up to this point, the rest is easy...Here we go.
Your bike is in neutral,, and your clutch lever is out and you start your engine. At this point the engine is turning,, the clutch input & output shafts are turning and the Trans input shaft is turning. Since the trans is in neutral, Trans output shaft is not turning.
You now pull the clutch lever in. Since the Trans input shaft and gears have inertia, they continue to spin even though the clutch input to output shafts are no longer directly coupled to each other. Since the Trans input shaft is spinning and the out is standing still, you hear a loud clank when those two shafts engage from your foot placing the gearbox in 1st gear.
Now lets do it again, but this time you wait a bit.
Your bike is in neutral,,and your clutch lever is out and you start your engine. At this point the engine is turning,, the clutch input & output shafts are turning and the Trans input shaft is turning. Since trans is in neutral, Trans output shaft is not turning.
You pull the clutch lever in BUT THIS TIME YOU WAIT a bit. The turning Trans input shaft has time to slow down and loose it's inertia. The input shaft of the Trans slows down and maybe even stops. Now the Trans input and Output shafts are BOTH STOPPED. Now when you shift into 1st gear, there is "less clank" because you not engaging a moving part with a stationary part.
Note: (There are also other parts of the process which need to be mentioned but not discussed. One is parasitic drag of a wet clutch. Even though a wet clutch may be dis-engaged, the output shaft will continue to spin due to parasitic drag of the oil or fluid. Another issue is sticking of clutch friction plates and the 1st time they need to "Break Free" from each other from sitting in a compressed state while not being used. But for the most part, all the above holds true)
Still awake?