chattering noise

[elbandtioCA]

thanks everyone for all the tips so far.  in the few months i've owned the bike i've learned a lot about it, and it is running pretty smoothly after the valve adjust, carb synch, and a new chain. 

i'm still bothered by this VERY noticable buzzing/mettalic chattering noise that the bike makes almost precisely when it reaches 6-6,500 rpms.  people suggested tightening down bolts and i've done that--exhaust bolts, chasis bolts, all the nuts holding the cyl head, etc--but it didn't seem to make a difference.  i also checked the cam chain when i did the valve adjustment and at didn't show any signs of wear, and it seemed to have good tension.  the sound gets quieter after the bike is completely warmed up, but its hard to tell if it goes away completely.  i only rode the bike a few times before having the carbs rebuilt, and i don't recall it making the noise, but that could just be my memory.  would anything in the carbs make such a loud buzzing noise at a specific rpm--like would the needles possibly rattle against the jets if the slides were worn out, and would i be able to hear it loudly while wearing my helmet and going 40mph?  i know the bike is going to make some noises because it is old, but this sound is pretty unsettling.  maybe if i were more of a veteran rider i'd be better at telling the difference between an innocent loud noise and a serious loud noise.  it doesn't seem to be accompanied by any change in performance, however.  should i just ignore it?

[pmackie]

I can't really speak for the 400, but my 2G 600S also has a very raspy bit of vibration from about 5500 to 6500 rpm. Most people who have ridden a 600 comment on it, including the magazines. I was able to reduce the effect slightly with the changes in jetting (richer), but it is still there and very noticable to most who ride my bike. I seem not to notice it so much, likely because I sub-conscieously ride just below, or run right through the vibration zone.

Some have commented that it may be a resonant vibration from the intake camshaft, but it is definately a resonant vibration from the engine.

Any un-counterbalanced 4 cyl bike will have some vibration at some point in it's rev range, so that may be what your feeling. Maybe some 400 guys will pipe in with their comments on vibration on their bikes.

If it is NOT normal, and it is rpm sensitive (as you say it is) as oppossed to speed sensitive, places to start looking could include:
1. Cam Chain and tensioner and cam sprockets
2. Clutch basket/plates
3. Primary Drive Gear wear

You can also check all the items under the tank. Maybe something is touching the tank slightly when the engine vibrates. Look for any patches of paint wearing, etc.

[interfuse]

I took my bike in for the same thing... mechanic checked the cam chain play and the rode it around... said it's fine, just ride it and don't worry about it. As was noted above, I typically ride outside of the RPM range with the vibrations. Without being able to hear it, its impossible to be able to say it's the same thing. If you're really that concerned have a professional check it. .

[GooseMan]

I'm curious to see if anyone can figure this out. I have the EXACT same problem with my bike. When I got the bike, it never made the noise, but one day it just popped up out of nowhere!

After doing my valve adjustment, it was still there (I was hoping something was loose on the bike, and after taking most of it apart and tightening everthing it would solve the problem). I then took it in and tightened EVERYTHING, exhaust bolts (where the header meets the engine), engine mounts, pretty much everything I could reach. That SOLVED the problem....for a while. The noise seems to have come back.

I tightened everything again, but its still there. So I'm wondering if it was just a coincedence.

When its warmer out, I'm going to have my bike serviced for a carb clean and syncro...so hopefully that will solve it.

[elbandtioCA]

interesting that a few of you describe the same thing.  in a way that is reassuring--it doesn't sound like your engines burned out or anything.  and yes, mine also seems to have about a 1000rpm window and above that it stops, so i just try to keep it above or below like you all do.  it really sounds like its coming from the top part of the engine, but it is hard to tell.  i didn't see any rubbing on the tank when i had the tank off.  but the clutch/gear possibility is interesting, because yesterday, when the bike was warm, i reved the engine in neutral and it didn't do it, then when i put it in first gear it did it again.  i haven't played around enough to get something reproducable.  if it is just some intrinsic vibration, then i'm not going to worry.  but i suppose i should check the cam tensioner like people have discussed on here--i didn't bother with that because the cam chain seemed taught when i took the valve cover off.  i'll let you know if i have any success with getting the noise to go awy

[elbandtioCA]

hey gooseman, just out of curiosity--is your bike stock, or do you have a jet kit/aftermarket muffler on the bike? i'm wondering if you've changed anything with the tuning and if that made a difference.  pmackie comments that changing the jetting made a little difference--i might give that a try since when the carbs were rebuilt we changed the jetting all around (and it might not have made the noise so loudly). 

[Banditmax]

I had this and it got worse when my cam chain tensioner broke. I think this is just a case of the cam chain and the engine both hit the same vibration frequency at this point. But if it gets really bad i would think about getting a new cam chain. Im tempted by one as mine got worn flat when some moron mechanic thought you just screwed the screw in the automatic one inwards till the screw was tight.

[GooseMan]

My bike is 100% stock! No jets kits, as far as I know (I bought it used), and the exhaust is stock. My carbs are probably dirty and in need of a good clean/tune, so that could be the problem.

I'm thinking its the cam chain tensioner too, as the last time I posted about this, everyone said the same thing.

[Banditmax]

Changing the carbs isn't going to change the frequency of the vibrations.

[elbandtioCA]

but does it make sense to check the chain tensioner if i just had a look at the timing chain when i did the valve adjustment?  there didn't seem to be any slack.  or is the chain tensioner only an issue at higher rpms?

[gsxr400 racer]

the cam chain tension-er will look fine as well its when its automatically adjusts to the tensioners limit or where the cam chain has broken in and the cam chain tension er has ridden there for so long that it has a problem see at times i stays tight then on occasions it backs off a notch and makes noise then clicks back out till one day it just don't adjust anymore .

[elbandtioCA]

if its the clutch basket or primary drive gear making the chattering noise, would it still do it if i had the bike revved up in neutral with the clutch lever pulled in?  it still makes the noise then.  i also notice that as the bike warms up it starts making the chattering/buzzing at a higher rpm, so cold it does it around 5500, then hot it goes up to 6500 hundred, and maybe even a little higher if i go for a long ride in the hills.  i do notice the other symptoms for the clutch basket noise, however--i.e. the sound when it is idling that goes away when i pull the clutch out.  is the loose clutch basket causing damage to the clutch?

[elbandtioCA]

horay!!!!  it looks like i fixed the buzzing noise.  don't want to count my chickens...but it is definately a cam chain tension issue (as many people/threads suggested).  I took the tensioner off, inspected it, everything seemed fine with the spring action/ratchet mechanism.  But when I fitted it back on (big pain to do with the carbs on the bike) and fired the bike up, the 6krpm buzz is totally gone.  I rode around for about an hour and it didn't come back.  so perhaps the tensioner is just on the verge of going bad? or it was stuck and needed a little nudge?  anyhow, i'm just going to enjoy this minor success for the time being.  thanks everyone for suggestions.

[GooseMan]

oooh! I'm gonna try that too! Maybe order a "new" one off ebay.

[gsxr400 racer]

lol