"Bouncing Jitter" going to first

[Yakaru]

So I had this on my 250 but I've also noticed it on my 300 and given how sensitive my 300's clutch is I'm at a complete loss. (I originally chalked it up to not having the clutch fully engaged).

Let's say I'm coming to a complete stop and just want to shift into first (saying I should always be in a usable gear is fine, but let's set it aside for the moment). If I'm running at a fair high speed, say over 25 MPH, and try to shift into first I can't. It feels like I'm fighting the gear box -- the shifter kind of vibrates/bounces when I push down like it is hitting a gear or something. The clutch is way-past fully engaged, so I don't know why this is happening -- it shouldn't matter if I'm going 1000 MPH or 0 -- the engine should be completely disengaged from the gears with the clutch pulled in. No other gear causes this issue.

Can anyone enlighten me?

[Motofool]

Yakaru,

Are you blipping the throttle after you clutch-in and before you push the shifter?

[Yakaru]

Negative, throttle is at "zero".

[Motofool]

Then, I would say that the problem is the lack of blipping.

Read this, please:

http://www.ninjette.org/forums/showt...t=downshifting

[Yakaru]

Correct me if I'm wrong but it sounds like he's referring to blipping before dis-engaging the clutch. This happens with the clutch fully engaged the entire time.

[Motofool]

If he does, he is wrong.

You have only two gears in synchrony: 2nd.

While that is happening, the gears for 1st are rotating at very different speeds (about one half of the other).

During the transition, we need to synchronize the gears for 1st, duplicating the speed of the gear linked to the engine.

The gears can help if the synchrony is not perfect, but if the difference in rotational speed is excessive (your case), the dogs (side connectors) cannot engage (that is what your feet feels).

[Yakaru]

Originally Posted by Motofool

If he does, he is wrong.

You have only two gears in synchrony: 2nd.

While that is happening, the gears for 1st are rotating at very different speeds (about one half of the other).

During the transition, we need to synchronize the gears for 1st, duplicating the speed of the gear linked to the engine.

The gears can help if the synchrony is not perfect, but if the difference in rotational speed is excessive (your case), the dogs (side connectors) cannot engage (that is what your feet feels).

Interesting. I'll give it a shot and see if this helps.

[Motofool]

Originally Posted by Yakaru

Interesting. I'll give it a shot and see if this helps.

It is hard for me to explain; here is some help:

Link to original page on YouTube.

Link to original page on YouTube.

[Yakaru]

Originally Posted by Motofool

It is hard for me to explain; here is some help:

Link to original page on YouTube.

Cool, but the first video actually confuses me on the issue. Watch at about 1:25 -- he has the clutch fully engaged and shifts to first without blipping the throttle. Note, as I said, this usually happens when I'm going a bit faster, which from what you're saying is probably the reason (?)

[Motofool]

Originally Posted by Yakaru

Cool, but the first video actually confuses me on the issue. Watch at about 1:25 -- he has the clutch fully engaged and shifts to first without blipping the throttle. Note, as I said, this usually happens when I'm going a bit faster, which from what you're saying is probably the reason (?)

That is just an animation, and it is not very accurate.
The increments in engine's rpm is what I wanted you to notice.

I have found the gear ratios of the 300, so we can see the real difference:

http://www.kawasaki.eu/Ninja300/Specifications

Second reduction: 1.789
First reduction: 2.714

Assuming that you are downshifting to overcome a load (such like a hill), the speed of the bike, rear wheel and corresponding gear remain constant and, switching from 2nd to 1st, the engine should increase its rpms' in a percentage = 2.714 / 1.789 = 52%

Assuming that you are downshifting while you are braking, the gear connected to the rear wheel will be slowing down; hence, you should be able to engage at a lower differential percentage.

The clutch never disengages completely, because the viscosity of the oil among the discs.

Many riders don't even use the clutch for downshifting.

[csmith12]

hmmmm.... 25mph sounds a bit fast for 1st under casual riding. Maybe a bit slower and you might not have to fight it as much. What rpm is a 300 running at 25? Gearing is taller in 1st for a 300 right?

[rojoracing53]

Originally Posted by Yakaru

So I had this on my 250 but I've also noticed it on my 300 and given how sensitive my 300's clutch is I'm at a complete loss. (I originally chalked it up to not having the clutch fully engaged).

Let's say I'm coming to a complete stop and just want to shift into first (saying I should always be in a usable gear is fine, but let's set it aside for the moment). If I'm running at a fair high speed, say over 25 MPH, and try to shift into first I can't. It feels like I'm fighting the gear box -- the shifter kind of vibrates/bounces when I push down like it is hitting a gear or something. The clutch is way-past fully engaged, so I don't know why this is happening -- it shouldn't matter if I'm going 1000 MPH or 0 -- the engine should be completely disengaged from the gears with the clutch pulled in. No other gear causes this issue.

Can anyone enlighten me?

When you pull in the clutch a shift down multiple gears then chances are buy the time you get to the third shift your rpms are probably down to bellow 3k and your transmission speeds aren't anywhere close to synced so it become hard to shift. It your going down multiple gears in one go then try lightly releasing the clutch just till it starts to drag(bring the rpms back up a little) and pull it back in then shift another gear. You don't have to do it for every gear you down shift but if your going from 6th to 1st dragging the clutch to re-sync a couple times while going down will help match the gear speeds.

Like Moto said blipping or rev matching could help but its merely one solution to your problem so pick what works best for you.

I use ether method depending on the current alignment of the Algo solar system with Jupiter & Venus.

Don't mind my humor I swear there's useful info in this post somewhere

[Alex]

Originally Posted by Yakaru

Let's say I'm coming to a complete stop and just want to shift into first (saying I should always be in a usable gear is fine, but let's set it aside for the moment). If I'm running at a fair high speed, say over 25 MPH, and try to shift into first I can't.

Sometimes simple is easiest. Don't do that. Downshifting into 1st on a small displacement bike with typical gearing while over 25 mph isn't ever a great idea. It is certainly possible if revmatching correctly and with a smooth clutch lever release, but there's no purpose in doing it. It's accelerating clutch plate wear and risking (however small) more gearbox abuse, for no safety or riding pleasure benefit. If you must downshift to 1st while moving at all, consider doing it at 10 mph or less. If the bike is rolling at all, there's never a requirement to get below 2nd.

[Motofool]

Originally Posted by csmith12

........Gearing is taller in 1st for a 300 right?

Correct !

For the 250 the first / second ratio = 2.60 / 1.79 = 45%

I agree with Alex; for stopping, shifting to first should not be done until the bike is moving very slowly.

If we see it the other way around, make note of the normal (or comfortable) range of speeds and rpm's for first while upshifting from a stop.
Let's say that 9000 rpm correspond with 25 mph (don't know the exact number) during acceleration, then the engine must be spinning close to 9000 at the moment that the gears for first are engaging.
Blipping that high is possible, but it does not sound correct (specially in a new bike): better wait to reach lower speeds and blip more gently, if possible.

[Yakaru]

Usually when this happens it's because I'm coasting to a stop sign or some such; so I just get in first and 'love tap' my front brake into it. It won't be that hard to just shift as I slow, instead of doing it all up front. I was mostly just curious why this was occurring at all -- moto's explanation at least makes a bit of sense out of it.