First gear klunk

[Inhouse Bob]

Hi all,
You know how when you are at a stop and in neutral and then shift to first, you get a pretty solid klunk? I have lately discovered that if, before I shift, I give the throttle a little blip- not much, just a few RPM for a moment- that it shifts into first much more politely. Anyone know why this might be? Not that it matters, but I am a curious fellow.

[ryanschillinger_imp]

No idea. But mine still sometimes goes through neutral into 2nd when I try to hit neutral. Been like that since new. Also get a good clunk into 1st but haven't tried the rpm thing.

[Inhouse Bob]

No idea. But mine still sometimes goes through neutral into 2nd when I try to hit neutral. Been like that since new. Also get a good clunk into 1st but haven't tried the rpm thing.

Slipping past neutral is pretty much normal on most bikes. Of course, so is hitting neutral when you are aiming for second. I think the engineers get a kick out of making me screw up

[Django]

There are 2 shafts in the gearbox, getting connected by different combinations of gear wheels.

The 1. shaft is driven by the engine, connected by the clutch. The 2. one is connected to the rear wheel by the chain.

In neutral 1. and 2. shaft gear wheels are not connected. However, the 1. one is spinning, driven by the engine, even if you open the clutch, as there is still friction in the clutch caused by the surrounding oil. The 2. one is standing still, as your rear wheel is standing still.

Now, when you engage 1. gear, you make a connection between 1. and 2. shaft by the corresponding (1.) gear wheels. Now the spinning 1. shaft gives its rotating energy to the 2. shaft and gets stopped abruptly, as the 2. shaft cannot spin, as the rear wheel is still standing still, brakes engaged.

That is the moment of the <clonk>. From now on, the 1. shaft is also standing still, separated from the engine by the clutch. No, when you close the clutch, the engine will drive the whole engagement forward.

That's also the reason, why you get no <clonk>, when you engage 1. gear while still rolling.

HTH.

[Lord Popgun]

Nice explanation Django.

[Cormanus]

So why does revving the engine a little stop the clunk?

[Django]

So why does revving the engine a little stop the clunk?

Uhm, yes, well, I guess, that doesn't fit into the picture. May be, it does not really stop the clunk?

[Cormanus]

I'll try it sometime, but it doesn't make sense ... unless the additional revs somehow create a 'cushion' for shaft 1.

[AzBob_imp]

The noise is the dogs engaging on the output shaft, slamming the input shaft to a stop. Revving the engine would cause the input shaft to rotate faster, causing the dogs not to engage as easily, smoothing out the engagement, but also wearing the dogs more. Don't do that.

[Inhouse Bob]

The noise is the dogs engaging on the output shaft, slamming the input shaft to a stop. Revving the engine would cause the input shaft to rotate faster, causing the dogs not to engage as easily, smoothing out the engagement, but also wearing the dogs more. Don't do that.

To clarify my original post... I give a small bit of throttle (maybe up to 2k RPM) and then return to idle for a moment. Then I engage first gear and it is less clunky. So I'm not engaging while reving the motor. Would that be a problem? Anyhow, it's interesting.