Help me diagnose this scary chatter at TMP Turn 2 | GTAMotorcycle.com

Help me diagnose this scary chatter at TMP Turn 2

Corsara

Corsara

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Fact 1: springs are way too light for my weight, based on zip-tie they get completely bottomed.

Fact 2: preload all in.

Fact 3: a bit more compression damping in the front, but still bottoming.

Here is the 20 second video of Turn 2 at TMP, this chatter made me run off a couple of times. Happens only on Turn 2, right when I downshift (slipper clutch, no blipping on that day). Btw, the slipper works fine on Turn 1.

What could be the problem?

[video=youtube;CpbaNhw1QnI]http://www.youtube.com/watch?v=CpbaNhw1QnI[/video]
 
Corsara said:
Fact 1: springs are way too light for my weight, based on zip-tie they get completely bottomed.

Fact 2: preload all in.

Fact 3: a bit more compression damping in the front, but still bottoming.

Here is the 20 second video of Turn 2 at TMP, this chatter made me run off a couple of times. Happens only on Turn 2, right when I downshift (slipper clutch, no blipping on that day). Btw, the slipper works fine on Turn 1.

What could be the problem?

[video=youtube;CpbaNhw1QnI]http://www.youtube.com/watch?v=CpbaNhw1QnI[/video]
Click to expand...
Is it in your hands? through the bars? cause it sounds and looks like driveline (rear wheel and chain slap and chatter
 
Yep - my guess is that you are using the rear brake. Leave your foot off the brake completely and I bet you solve it. I had the same issue exactly in Turn 1 last year - was *sure* it was the forks but I was just plain wrong.
 
Hmm...

No, not using the rear brake. However, now that you guys mention it, it happens right at the moment I downshift, and I don't blip but rely on the slipper to do the work, which is probably the exact moment the rear skips...hmm
 
I had front end Chatter on the same 2003 GSXR with stock front end in one corner only at MT. Tremblant. I was only there for one day and didnt figure out why.....was playing with pressure and suspension settings.
Maybe try the same....add some rebound damping etc. Good luck.
 
your rear wheel and chain is doing the hokey pokey because your really rough and sloppy when clutching and downshifting. hard on tranny. basically you suck . lol.
 
TLDeano said:
your rear wheel and chain is doing the hokey pokey because your really rough and sloppy when clutching and downshifting. hard on tranny. basically you suck . lol.
Click to expand...

I know I suck, but didn't know it was because of this---I installed a slipper clutch with the purpose of being sloppy on the downshift, which was supposed to take care of that.
 
your gearing is so far off its crazy. you don't even change gears! I don't think your at high enough revs for everything to slide and slip smoothly.for 1 and 2 you should have very little weight on the rear, you should be gearing down and feathering clutch and using engine braking so your rear wheel is just about sliding, just floating and sliding, when it all settles in, throw the bit*h down, and rail it through. its a garbage track, stop and go, point and shoot. so hard on bike body and suspension.
 
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TLDeano said:
your gearing is so far off its crazy. you don't even change gears!
Click to expand...

I change gears, lol. That particular video cut-off was from Lap 1 of Session 1, although the chatter is throughout. I'm in 2nd => 3rd => 4th => 5th (sometimes) to Turn 1, then down to 3rd, very rearly to 4th before Turn 2, though this chatter kept me in 3rd yesterday on the second straight. Then yeah, I'm in 2nd throughout the infield. Here is from Session 2:

[video=youtube;N7ez0ARC02s]http://www.youtube.com/watch?v=N7ez0ARC02s[/video]
 
TLDeano said:
your gearing is so far off its crazy. you don't even change gears! I don't think your at high enough revs for everything to slide and slip smoothly.for 1 and 2 you should have very little weight on the rear, you should be gearing down and feathering clutch and using engine braking so your rear wheel is just about sliding, just floating and sliding, when it all settles in, throw the bit*h down, and rail it through. its a garbage track, stop and go, point and shoot. so hard on bike body and suspension.
Click to expand...

These are great tips, thank you. I've been dumping the clutch thinking I'm golden. Will definitely attempt to do it differently next time, maybe my problem will be gone.

Also, please keep in mind I'm just starting with track, of course I'm doing mistakes and things the wrong way.
 
Does not sound like a front-end chatter. I agree with others that it sounds like driveline.

Smooth out your downshift and rev-match with the throttle so that the gear-change is as bumpless as possible. Don't rely on the slipper clutch.

Some slipper clutches have the capability of adjusting the slip threshold. That may be another option, but it's still better to smooth out your riding so that you are not relying on it.

I have seen some riders who don't blip the throttle but gently ease out the clutch to smooth its engagement (as if they were starting off from a standstill). I don't like doing that because it tends to let the revs drop way low and then require a large change in revs - very easy to make a mistake and let out the clutch too quickly, which will result in a big rear-end slide.

I know that I do gear-change-related stuff without thinking about it - like hold the clutch partially in for a moment while changing gears to intentionally slip it a little so that there are no jolts transmitted through the driveline.

Next time you are working on the bike, make sure the chain slack is correct (at the loose end of the recommended range) and make sure the little cush-drive rubber things in the rear sprocket are in good shape without excessive sloppiness.
 
But...let me make sure I understand:

1) Slipper won't work unless it's at high rpm when downshifting? I was doing my braking, then downshifting towards the end when RPM is lower, thinking it's better..?!

2) The reason I was dumping the clutch was because I was thinking this will help it slip. Last season when I started going to the track, I didn't have a slipper clutch and was blipping, and my lap times were 4 seconds better than my best yesterday.. I feel very lost and confused at what to do and try next :(
 
Brian P said:
Does not sound like a front-end chatter. I agree with others that it sounds like driveline.

Smooth out your downshift and rev-match with the throttle so that the gear-change is as bumpless as possible. Don't rely on the slipper clutch.

Some slipper clutches have the capability of adjusting the slip threshold. That may be another option, but it's still better to smooth out your riding so that you are not relying on it.

I have seen some riders who don't blip the throttle but gently ease out the clutch to smooth its engagement (as if they were starting off from a standstill). I don't like doing that because it tends to let the revs drop way low and then require a large change in revs - very easy to make a mistake and let out the clutch too quickly, which will result in a big rear-end slide.

I know that I do gear-change-related stuff without thinking about it - like hold the clutch partially in for a moment while changing gears to intentionally slip it a little so that there are no jolts transmitted through the driveline.

Next time you are working on the bike, make sure the chain slack is correct (at the loose end of the recommended range) and make sure the little cush-drive rubber things in the rear sprocket are in good shape without excessive sloppiness.
Click to expand...

Thanks for the great reply, Brian. I'll think and read over this again before my next trackday, and try to change my shifting, I'll probably start rev-matching again, this slipper should probably just be for an extra degree of safety cushion..

As for adjusting the slipping threshold of the clutch---yes, I can do it, but I was afraid it will start slipping under acceleration.
 
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Corsara said:
Fact 1: springs are way too light for my weight, based on zip-tie they get completely bottomed.

Fact 2: preload all in.

Fact 3: a bit more compression damping in the front, but still bottoming.

Here is the 20 second video of Turn 2 at TMP, this chatter made me run off a couple of times. Happens only on Turn 2, right when I downshift (slipper clutch, no blipping on that day). Btw, the slipper works fine on Turn 1.

What could be the problem?

[video=youtube;CpbaNhw1QnI]http://www.youtube.com/watch?v=CpbaNhw1QnI[/video]
Click to expand...

After going over the vid better guys are right you need to rev match your just dropping the clutch
 
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Watch my vid to see how much I rev match even with the STM slipper.
The back is jumping a bit, also try braking into the corner, not just before it, braking hard before the turn, letting off during, and throttle open when yor exiting.
 
carboncat said:
Watch my vid to see how much I rev match even with the STM slipper.
The back is jumping a bit, also try braking into the corner, not just before it, braking hard before the turn, letting off during, and throttle open when yor exiting.
Click to expand...

Yes, it seems to be the consensus that I'm locking the rear with little to no traction available to it by dumping the clutch. I wasn't rev-matching AT ALL. I did so last year, but now I thought "hey, I have a slipper now, no need to do anything but dump it", which was a total misunderstanding on my part. I can't wait to get out there again as soon as possible, sadly I feel like I wasted yesterday's track day in terms of getting better by getting seat time :(
 
Not only that, you need to change the date on your Go-Pro.....



lol
 
Corsara said:
As for adjusting the slipping threshold of the clutch---yes, I can do it, but I was afraid it will start slipping under acceleration.
Click to expand...

On a Kawasaki slipper clutch, the threshold at which it starts slipping under back-driving conditions is adjustable independently of the main clamping pressure.
 
webb70 said:
Not only that, you need to change the date on your Go-Pro.....



lol
Click to expand...

It's a Drift HD170 Stealth camera, and it's been nothing but problems, I would never recommend Drift to anyone. It's been resetting the date at random times, and I don't understand why (maybe vibrations making the battery disconnect for an instant). Also at one time it stopped recording unexpectedly just before I ran off at Turn 2 for the first time, then started again.... I've had the camera for a year and this is the second time I'm using it, it's a piece of junk.

Brian P said:
On a Kawasaki slipper clutch, the threshold at which it starts slipping under back-driving conditions is adjustable independently of the main clamping pressure.
Click to expand...

The clutch I installed came off of a 2005 Suzuki GSXR 1000, and it has three pins---the further in they are, the more it will slip, but based on other peoples experiments on the internet, it starts slipping under acceleration if they set too much in. And since I can't ride the bike on the street to experiment, I set the pins at the recommended depth where I'll know for sure it won't slip.....and it's time to start blipping that throttle!
 
i started riding a bike without a slipper clutch this year and found it easier to blip without it...not sure why.
 
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