This just started in the spring, and seems like its getting worse. The sound, as best I can describe it, is like the sound small hail makes when hitting your windshield when driving your car. It starts at 4K rpm, and after 6K its no longer there? A few more things I've noticed. If I keep a steady rpm, say 5K, for a while, it seems to get quieter. Yet if I hit some bumps in the road it "rattles" louder for a few seconds again then quiets down???

The sound can be heard when driving, or when parked and just running the engine up to the rpm range where it can be heard.

The bike is a completely stock 94 CBR600F2 with 46000 KLM (28750 miles). I've ordered the manual cam chain tensioner, and will install it when it arrives. I'm just guessing that it's a worn cam chain, resulting from the poor design of the hydraulic factory unit wearing out the chain, OR, the hydraulic cam chain tensioner is failing and causing the noise?! But I could be way off base, which is why I'm throwing it out here, just in case someone else has had the same issue and has resolved it.

P.

 

Checked your valve clearances yet? You can try the CCT, but usually you can hear the clatter at idle speeds and lower RPM more.

 

I think your fine changing the cct. A manual one is far better than the factory one anyway, so your really not out anything if its not the issue.

adrenalnjunky brings up a good point. If the noise is still there afterwards, the valves would be the next step to take. I've always described loose valves as the sound of bb's rolling around in a tin can. The loose valves I've heard usually rattle at those rpms, and because of other noises, get drowned out at higher rpms.. But, when you let of the gas, valves will usually give a good rattle as the rpms drop. So if you hold a steady rpm at say 8,000. as soon as you let off the gas, they would rattle some. But, the cct could do the same thing.

As for it changing sound when you hit bumps. I would bet your actaully changing throttle postion as you hit bumps. Its nearly impossible to hit bumps and not move the throttle slightly, even if you don't realize it. So if the sound is throttle sensitive, it would certainly lead to making the noise change.

I guess since you have that many miles, a valve clearance check wouldn't be a waste of money either. even if they are not making noises, keep in mind valves don't only loosen up, they also tighten up.

 

Well, the manual cam chain tensioner arrived today. However, its raining....again! So I'll wait for better weather before I change it and take the bike out for a test ride. I spoke to a local shop, and was about to book it in for service to do the valves, but they recommended that I change the cam chain tensioner first, and see if that does'nt solve the problem first. According to the mechanic, he has seen this before on this year of bike, and found that by changing the tensioner, the noise went away. He did mention that the valves may be in need of adjusting, if my oil pressure is way low, or I ran the engine dry of oil, and wore them out. But failing those two scenarios, he feels that the most likely and common cure is the tensioner. Either he's really honest, or doesnt know what he's talking about. I'm hoping he's honest and the cam chain tensioner ends up being the cure.

I'll post back when the work is done and I've had it out on "dry" roads.

Thanks for the replies to my question, it is really appreciated and has been helpful.

 

The mechanic was right. I installed the APE manual cam chain tensioner, and ALL the engine sounds magically disappeared! The noisy rattle on startup, the one that makes the bike sound like it has a diesel engine for a minute or three, AND the pinging sound that starts at 4K rpm is gone as well! It looks like the cam chain was getting loose at higher revs, and causing the valves to open and close out of time with the engine. It also appears that the mileage has increased as well as the power. I can pull the front wheel up considerably easier now, and I definately increased gas mileage, which is a bonus!

So in short, I have a bike that runs and sounds great, and it only cost about $60.00 in parts. I'm gonna have to buy that mechanic a beer for being honest enough to tell me something that in the end, cost him a bit of work, and cash.

 

Can't complain about that. doing my APE install this week hopefully.

 

Very Very easy to install, took only 40 minutes from the time I took off the RH faring till it was back on and the bike was ready to ride.

I hand tightened the tensioner after bolting it on, started the bike, and continued to tighten until the sound stopped, turned 1/4 more and locked it in place.

The only suggestion I have is the O-ring. I worked it down the threaded shaft to where it is supposed to be seated with a mini-screwdriver. I felt that by doing so I would not damage it by letting the lock nut push it down on the threads of the bolt. An O-ring is not a tough item and can be easily damaged. The last thing I wanted was oil leaching out and making a small mess while driving.

Enjoy the quiet ride after your done.

P.

 

I wish - the bike's been hanging from an engine hoist for the past month while I did a bunch of other rehab due to the prev. owner's neglect.

just last night I got it set down on it's own wheels again. Hopefully it'll start coming together much faster now. APE, cooling system flush, brake bleed & and oil change are the immediate tasks required before I can get it back on the street.