Shifting on a motorbike by preloading

Question

I have a few different questions that popped into my head after reading about preloading the shifter in motorbikes, here's one of three:

Shifting between 1st and 2nd on a motorbike - will the bike auto-shift into neutral because of preloading and that being in neutral doesn't require any kind of "engage" to happen? If not, could someone help me clear up the specific mechanism going on here?

EDIT: I didn't realise you can only post one question every 40 minutes, so I'll integrate the other two questions into this one:

2. Shifting between 1st and 2nd - as there is a greater gap to kick up from 1st to 2nd, do you need to do anything differently to allow for a smooth transition?

3. Shifting with preload: how much pressure should you put on the shifter? i.e. Should you apply light pressure until you feel it go and then harder pressure to then getting it into gear? Does this differ depending on gear? ...I'd like to know as much as possible before potentially damaging my transmission!

Answer 1

It won't damage your transmission unless it damages your transmission

You have a shift drum. It has grooves in it around the outside diameter that the shift forks follow to slide gears into gear as the drum turns. This is the basis for a constant mesh transmission. It's the reason (other than regulatory) that motorcycles gears are shifted in numerical order. The shift drum rotates to have the proper groove placement that the shift forks will follow sliding in the appropriate gear.

On the outer edge of the end of the shift drum cylinder there are detentes with a spring loaded pin that fits into them. The detente for neutral sits between 1st and 2nd gear and isn't as deeply set into the detente as the gears are.

Here is an answer explaining these transmissions. Some more knowledge regarding how they work can help you understand the damage that you can do and how to prevent it.

• What is the technical reason the engineer decided the motorcycle gear pattern as follows?

We call what you are describing as speed shifting or shifting without the clutch. The easiest way to start if you are good at downshift quickly is to speed shift while slowing down. I recommend not speed shifting into 1st gear, if you over rev your engine you could destroy it and there's really not a need unless you are panic stopping.

As you are slowing in third gear and the revs are about 6,000 RPM, apply pressure to the shift lever with your foot, not much at all. The gears are locked into place by the back torque of the rear wheel. Blip your throttle, it will unload the transmission from the back torque to temporarily unload your gear stack from any power input, at that moment your foot pressure should just slip the bike into 2nd gear, the revs will increase to mach the road speed and your done. Once you have that principle down you can apply to upshifting and any other gear you want that's next in order.

As for as 2nd to 1st and 1st to 2nd, allow yourself to go from 2nd to 3rd and on up as well as down the stack. Once you have it nailed you'll be able to get through the 'neutral hole' easily.

Answer 2

I don't have experience on as many different bikes as some people, but here's what I have found.

But "preloading" the shifter, were talking about pressing on it just a little before you are ready to shift. The force needed from bike to bike will vary, so it's something you will just have to try and figure out. A motorcycle transmission is not like a car's, and you won't get "stuck between gears" or cause any catastrophic damage from practicing this.

That said, I would start the learning process after second gear. Apply a light amount of force to the shifter and slightly drop the throttle. The transmission should just "fall" into gear. It happens quickly and smoothly, so you don't need extra force per se - you just need to make sure you follow through with the shift. In other words, you're not going to have to force it into gear, but you can't just leave your foot in the same position. Follow through with the shift like normal.

I've applied more than a little force to the shifter, and in my experience, it just won't shift until you feather the clutch or drop the throttle a little. Now, I didn't stand on the shifter - I'm just saying there is a definite margin of error in your preloading force.

Now, back to 1st, 2nd, and the gap in between... I never noticed a major issue here, but the follow through is very important (why we practiced it already). Be deliberate about the shift to make sure you don't get stuck in neutral. Also, don't try to go from 2nd to 1st without the clutch. That's normally a pretty rough shift anyway unless the bike is moving very slow.

Answer 3

I "developed" a technique back in the 70s when throttle lock "cruise controllers" were common. I might be approaching a winding curve with a considerable uphill grade, and need to drop a gear and slow a bit. I can do it without touching the throttle lock at all. Just apply downward pressure to shifter and just before it begins to lug bump the clutch twice. Unloads torque to initiate and complete the shift, while the clutch is briefly engaged during the transition. It's hard to envision double clutching a sequential box as there is no neutral between the gears. All I can say is try it, it works so well for me I prefer it under most downshifting conditions