After half heartedly chasing a front end clunk on my 6R for the last few years, it finally got bad enough to worry me....and get me motivated to find it. I was thinking something was wrong with my front forks or steering head bearings. After going through just about everything on the front end of the bike the problem persisted and was becoming more annoying. I finally stumbled onto the problem. The ram air intake duct on a ZX-6R looks like a simple rubber boot that connects the ram air inlet to the the airbox. It's actually a rigid structural member that serves a secondary duty in supporting the fairing. The 6mm mounting screws were just loose enough to creat a small amount of relative motion between the duct and the aluminum steering neck that was being amplified by the the hollow aluminum frame, made a kind of kerthunk noise everytime I hit a bump. I went out looking for big bumps to crash into last night to try and see if I could see or identify the source and sure enough, I finally saw the fairing move about 1/2 inch over a big bump. Tightened all four of the ram duct screws and she's quiet again.

Here's the screws, two on each side of the neck.

90% of all issues are simple, overlooked things. How else could a dumbass like me keep motorcycles going without professional help for over 40 years?

Have not been here for a while, but tonight....thank you my old fried....seems like you read my mind. My 6R has been having the same issue. I am going to check it this weekend and will report my findings.

My 6R has been having the same issue. I am going to check it this weekend and will report my findings.

Hi Steven, good to see you back again. Yes, this one is specific to the new generation of ZX-6Rs but seems like a theme that is repeated over and over again...at least with me. We go looking for something complex when we have a problem and it's often the simple stuff we overlook that is the issue. I looked at that ram air duct but concluded that it was just a duct and couldn't be the problem, had to be something else. Early on, I tried shaking the front fairing by grabbing the "beak" and lifting up and down, the amount of fairing motion it takes to make an annoying clunk is amazingly small but it doesn't show up when the bike is static in your garage, it has to be in motion and hit a bump. If you study it for a moment you will realize that without that duct to support the upper fairing, it would eventually fall off the bike, there is no aluminum fairing brace like on our 14s, the duct is the brace on the 6R.

Please let me know if this was the problem on your bike, it took me 2 years to find the problem and less than two minutes to fix it.....lol!

Steven, I have another question on your 6R. I've noticed a high pitch whistle sound almost like a tea kettle as Si wind out the gears. These small bikes spin a lot of rpm and have straight cut primary gears, the pinion is cut right into the end of the crankshaft. Have you noticed the high pitch gear whine under acceleration? Probably normal but I've never ridden anyone else's bike to check it out.

I have checked the screws and they were tight OK. They have blue loctite from factory for a reason. My knock has not been as bad. It seem to demonstrate itself only each time when I pull out from the driveway in the morning. After that I never feel it again. Perhaps the temperature had something to do with it.
Regarding the high pitch whistle, my 6R also has it, however, it seems to be diminishing with mileage. It has 7K on the clock. I have ridden my friend's 6R few times and it seem to be the same. Fist time at 6K, last time at 13K. Your theory about the gears should be correct.
After having been riding open class since mid 90's I never thought I would like this little bike so much. What a hoot.

Hi Steven, my duct screws were were all missing the loctite, I'll pull 'em out and loctite them back in.
My 10R has an identical setup, I checked them just to be sure and they were tight.

Thanks for the feedback on the "whistle", I posted on it over on ZX6R.com and got basically zero response and a couple of lame comments about my chain being too tight. I've noticed a lot of those guys are very young and don't have much experience so the teakettle sound may seem normal to them.

I feel better now knowing that it's normal. Yes, these are fantastic little bikes, just glad I bought mine at the right time, they are now priced at almost $12,000 for 2013.