Occasional trouble downshifting

Hey guys, just wondering if any of you have experienced this problem. I've had it happen on a couple of bikes I've owned, actually. CBR250R and a Grom. Anyway, the problem goes a bit like this:

You pull up to a stoplight and find that you can't shift down into first. Say you're in 5th gear when you roll up, pull the clutch in and start tapping down. The shifter moves, but it doesn't go into a lower gear. Indicator displays a dash. Eventually I got it into gear by rocking the bike back and forth a bit and fiddling with the clutch and shifter.

Mechanically speaking, what causes this? Why does it happen to me on 3 bikes I've owned? Has this happened to your VFR or another bike?

 

Your riding it all wrong, so the problem is operator error I’m afraid.

A motorcycle gear box is totally different to a car box in that you need to go through the gears ( sequentially) both up and down. To do this the gearbox must be rotating so the selector drum can be used to locate the correct dogs.

What you need to do is to go down the gears as you are coming to a stop. Clicking into first as you stop.

Not the best video out there but it explains the theory.

 

LOL! Maybe I didn’t word it well, I mean that as I am still decelerating and approaching the stoplight, I’m trying to click down but it just won’t go. The dash displays “-“. Maybe I’m doing it too quickly, or from too high of a gear?

 

That’s usually a sign of a missed shift. Occasionally happens with me, but going up the box.

Blip the throttle as you downshift

 

Are you downshifting one gear at a time? Or are you pulling in the clutch once and then clicking down on the shifter several times in one bout? If the latter, I think the issue is that the engine slows to idle while your transmission's still spinning away, and all the drag between the clutch plates slows your transmission input shaft very quickly in a situation where it actually needs to accelerate with each down shift. The greater the difference in speeds between the input and output dogs of your next gear ratio the more unlikely it is your shift will take, and the more likely your shift forks will be left in the no mans land between gears where it doesn't want to go in either direction because your input shaft has slowed to the same speed as the engine.

(At least I think that makes sense)

The easiest way to downshift is to click the shifter down immediately after pulling in the clutch, do your engine rpm matching blip as you let the clutch out, then rinse and repeat for all following gears, preferably maintaining a comfortable engine rpm the entire time as you decelerate. If that's too much work then just hold off down shifting till you're almost at a standstill.

 

This will happen when down shifting through several gears at a time, versus one at a time when slowing down. I often do this if I come up to an busy intersection and decide it's safer to do a quick stop than chance running through a yellow light. Once I come to a complete stop I'll let the clutch out slowly and the transmission will typically pop into gear and I may have to repeat this action depending on the gear I end up in once I've completely stopped.

That being said, if the lever just doesn't want to move and/or you hear grinding when moving the lever, you may need to check the clutch action, perhaps bleeding the line would be a place to start.

 

^^^^^^^^^^This!

 

Which part of ^^^^^this do you mean?

 

The whole post is very accurate. But yeah, may not have needed the carats. Oops.