Engine vibrations above 6k RPM

Recently I started to notice vibration in the engine.
Was barely noticeable at first, but now it feels like riding a 250cc twin.

Engine vibrations become evident at 6k RPM and amplify with RPM increase. This happens while stopped and on the freeway while riding. If I pull the clutch at high speed, the engine goes to idle and the ride is perfectly smooth. There is also an overall loss in power.

So I tried some test - 8k -10k rpm about 80mph I turned off the ignition via killswitch - vibrations were still there as the engine was gear braking. So I'm a little stumped.
If the ignition was somehow involved - in the above test it should have smoothed out. Would it be the same for carbs?

Bike has 61k miles, and there is a small leak from somewhere in the chain sprocket area (1-2 drops a week). Clutch is brand new.

Any ideas would be appreciated.

update:

Air filter is K&N serviced 10k miles ago - just a little dirty. No oil on it.

Did a compression test - 115 115 120 115 - all within spec.

Check plugs for clean firing, see pics below. Were very slightly oil wet when I pulled them originally.

Oil was clean and clear - no metal flakes. I even fished around the pan with a magnet.

The only thing that was wrong is the fuel filter - had not been changed in years and it literally fell apart in my hands, I'm surprised any fuel was flowing though it at all.

So now I'm stumped. Plugs okay, compression there, no signs of canibalism.

 

carbs synced? could be out of balance...

 

No, still need to find someone who has a sync tool. But would that not only cause vibration when the engine is under load? The engine vibrates even when ignition is off.

 

loose engine mount?

 

I tightened the 4 bolts on the frame, but they were already pretty tight. Is there a specific mount?

 

trying to go thru the obvious here given your limited symptoms:

in general the vfr engine is very smooth, so for it to vibe one (or more) of the following are to be checked
carbs out of sync?
engine mounts?
firing on all cylinders/missing?
broken/damaged clutch basket
flywheel

just trying to narrow down the possibilities

can you rev it to the vibe zone w/o the fairings on and see why it's vibrating? visible engine mounts, put hand on exhaust and feel for a misfire... does it vibe (while not moving) with the clutch in? on neutral?

 

This might sound kind of screwy, but are the engine mounting bolts a tight fit in the engine cases? From what you are describing, it sounds like specific mechanical vibration (as in "no internal combustion involved"). The only other thing I can think of right off is the clutch basket bearing going bad (provided the main bearings are in good shape).

 

I have the same problem on my 02 VFR. After the bike heats up, I get the vibrations. Vibrations come on at 6K and increase with RPM. For me the vibration is mainly in the handle bars. Other parts of the bike vibrate too, just that it is very noticeable and annoying on the handle bars. The vibrations then cause numbness to set in. Cos it is like this constant buzz going through my wrists. Pulling in the clutch causes it to go away. Gonna head in to the shop tomorrow to get it checked out.
1) Gonna get the spark plugs checked.
2) Engine mount
3) Chain ( loose or needs to be replaced)
4) Check tire balance

 

Going to throw it back together and check for vibrations visually, and the exhaust. Did not think about that.

The clutch basket does make a rattling noise when in neutral, which is gone when pulling the clutch in. The bearings are $80 though! Also I thought the rattling noise from clutch is a normal Honda thing.

 

It will be the carb balance. The 750 is well known for this sort of vibration when the carbs are out of balance. Do this before you look elsewhere it will save a lot of time and trouble.

 

Xeipher, when you take your bike in, if you find the culprit please post. I have an 06 and have vibes in the handle bars starting around 6k rpm. I was thinking it was just me but it can be annoying. I was going to check my engine mounts and chain (too tight/loose) but if your mechanic tells you something pass it along. If not I am going to try either sand or liquid barsnake in the bars to try to quiet it down. Thanks.

 

The rattling is generally the drive plates rotating back and forth in the basket, and is pretty normal on a lot of bikes. The hub bearing would be a long shot, FWIW. I offered it as a suggestion because of the continued vibration after you killed the ignition at high RPM with the engine still spinning and the vibration continued, and the same vibration is present when you rev the engine with the bike not moving (if I read your text properly). The primary gears and the clutch basket are the only things I can think of that are constantly spinning (besides the engine) in both situations.

But there have been similar threads related to the same type of issue (high RPM vibes). Other than tune-ups that have cured the problem, I don't remember anyone commenting on anything that was found as a direct cause.

 

Borrowed a gauge-type carb sync tool. The readings were all pretty close, but now I think I'm going to build a manometer, as the gauges measure the vaccum in 10's of inHG. And the allowed difference is 20mmHg. (20mmHG = 0.8inHG)

 

hey, I am all for garage experimentation and saving money and all, but a vibrating VFR engine is not to be played with. Wouldn't it be sensible to take to a dealer and spend the $100 or so for a carb sync and go over? I cant imagine spending any more than that, and the time/fabrication cost of these vs. peace of mind that the problem is resolved (and nothing more serious) seems to me money well spent. In the end it's your money and bike, but if it were mine, I would have a pro look at it.

 

Also, can a bad exhaust can cause vibrations? The one i have now has fallen appart inside, and has been jb-welded together by yours truly on multiple occasions.