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Old 10-03-2008, 04:36 PM   #1
Costas
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Transmission clatter/rattle under hard braking

I've noticed when I'm at the track, sometimes I brake really hard in some corners with both rear brake and front more so than usual (like diamonds edge at MSRH). It's happened a couple times so far, and the first time it caused me to go wide on a turn because after the clatter noise, it popped into neutral somehow. Anywho, basically what happens, is I'll jam on the brakes and clutch in and start clicking down on gears while keeping the clutch lever pressed in. When I do that, the transmission starts clattering and making all sorts of weird noises. It's almost as if too much inertia is making parts shift around and not operate like they're supposed to. I've never had any tranny issues before. The bike is an 04 ZX-6R with around 24K miles. Haven't detected any sort of slipping or anything, so kinda unsure of what it could be.
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Old 10-03-2008, 06:37 PM   #2
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so my friend told me the chatter comes from when you apply too much rear brake or lock up the rear going into a turn, which forces the chain to stop movement, which in turn is connected to the transmission, which in turn causes the chatter. makes sense.
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Old 10-03-2008, 06:46 PM   #3
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The engine crank is connected through the clutch to the transmission gears, to the chain. when the rear tire locks up or moves slower then the output will allow, the clutch becomes the weakest point in the system. Its like shifting without using a clutch since the transmission is a crashbox design.

I've done it a few times in a panic
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Old 10-03-2008, 07:07 PM   #4
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Sounds like you are getting a false neutral where the transmission is not in any gear. The 636 is known to have engagement problems that may cause it to pop out of gear. That is why a lot of people with 636 race bikes have the gears undercut. I don't think all years had the issue but I don't recall which ones did.

If you are going down more than one gear at a time without letting the clutch out you might try letting it out between each shift to help keep the tranny happy and the engine speed more closely matched to what the next gear down will need. Its hard to image where you would need to drop multiple gears that quickly. If you get a false neutral like that you always want to upshift after it happens to be on the safe side. If it goes to a lower gear than expected it could mechanically over-rev the engine or cause the rear to lockup with bad results.
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Old 10-03-2008, 08:22 PM   #5
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Some good advice in here. First time it happened was at Sugar and Spice at MSRH. I was on the straight then I clicked down a couple gears to get ready for the turn while holding the clutch in and all broke loose noise wise and then it popped into neutral, went wide, and off in the grass I went lol.

This past weekend I was at TWS (Texas World Speedway) going into turn 3 and came up on a big group of slower people and locked up the rear coming into the straight. Same thing occurred. 99% of the time I'm downshifting and revmatching as I prepare for the turn but there's always that 1% when I kinda screw up and gotta use up all my braking power and forget to do much with my left foot. I've had the rear tire lock up on me on a few occurrences when I didn't revmatch back in the days when I started going to the track, and ever since then I've made sure to do so, but it's kinda hard to revmatch when at the same time you're applying max front brake pressure.

I just gotta get smoother and stop trying to do so much at once I suppose, but at least I know what the source of the problem is now (apart from me lol)
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Old 10-04-2008, 09:37 AM   #6
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I would suggest not using the rear brake at all, at least not until you have a lot of experience. If you are braking really hard then the front brake will be providing pretty much all of your braking force due to weight transfer to the front wheel. The rear will provide almost no appreciable stopping power and like you have indicated will most likely just cause the rear to lockup causing all sorts of problems. It is far more important to focus on good braking using the front brake along with getting a proper downshift going to the corner than it is to get another 2 percent of braking force using the rear brake. Let engine braking handle the rear wheel braking.

Also, if you do your downshift really quick with minimal clutch pull time then the bike will pretty much rev match on its own. If you downshift slowly or hold the clutch in too long the revs will drop and there may be a big mismatch and need to blip to get it back up.

Just my 2 cents.
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Last edited by lorin70; 10-04-2008 at 09:40 AM.
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Old 10-04-2008, 10:12 AM   #7
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I've been going by what I learned at MSF a year+ ago but I guess the same methods don't apply when you're trying to go fast lol. My friend sounded surprised when I told him I use the rear brake, so I'll try to use it a bit less, I think it's caused more trouble than it's worth for me in the past.

As for revmatching, the few times it did lock up on me a long time ago, I remember I was letting out the clutch reallll slow. I believe ZX-6R's have slipper clutches so as long as I do it quick like you mentioned I should be okay. Can't wait for the next TD to try out some new things You've been a great help
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Old 10-04-2008, 10:17 AM   #8
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only the 05+ 6r's have slippers, your 04 doesn't. only the 03-04RR had a slipper those years.
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Old 10-04-2008, 10:27 AM   #9
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FAILLL
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