vibrations at 4000rpm

Hi, when going through the gears I always find that at 4000rpm the bike vibrates and isn't as smooth or as quiet as at any other engine speed, as if something in the engine is loose. Once I pass 4000 all the way up to redline it is smooth and quiet, as if whatever was loose got tightened by the increased engine speed. There is also a constant ticking coming from the engine. Just my uneducated guess, but I am thinking this may be related to my cam chain tensioner, or something along those lines needing adjustment. If the bike runs fine, it's just anooying having to avoid 4000 RPM, then can this problem wait till winter?

On this one, I'll start with your last question "can this problem wait till winter"...

Your bike but for me, oh hell no would I wait... For what I have invested in $$$ & time getting her to where I have the old girl why take a chance and destroying her if it's something that truly is a serious problem waiting to turn real ugly....

It may be normal for her or something simple where the old girl is informing you of major FUBAR coming unless you repair.

4k pending your motor & gearing, this is a common rpm range @ 50-60mph so a good 40% of our driving is spent here... Get off your ass and fix her or at least spend a weekend confirming it's not a serious issue...

Now onto the issues....
"4000rpm the bike vibrates"...

Is it only @ 4krpm or is it a range from 4000-4500 for example?

I realize what you wrote once you pass, just insuring we understand fully...

Is this when riding only or in the garage slowly twist the throttle up and hold her @ 4krpm?

If vibrates in garage....
Are all your engine mounting bolts torqued to specifications?

Have you noticed if it's only in a specific gear when it occurs? Example, rear jacked up (center stand) it doesn't occur in idle or in 3/4 gear no problem, but does occur when shifting from 2nd to 3rd gear etc....


If riding only....

Raise the front end and free spin the tire, is it balanced?

In the manuals, they have a procedure to check your suspensions, front turn radius checks, frame neck bearings etc....

Do the same for the rear tire and suspension...

Ticking sounds...
Timing chain or head exhaust to header leak...
Possibly valve to shim clearance...

This should be a good starting point for you... Others will chime in a swell...

OMR

I have never noticed the vibration when parked in neutral, but it happens whenever I am riding. When I accelerate it begins at about 3800, and ends at 4000, so it's only a small window, but it's annoying. It seems worse with the lower gears, so by the time I am in 5th I barely notice it. The PO removed the centrestand and I have not found one yet to replace it with, so I cant jack it up easily so I don't know how I could try shifting through the gears in a garage unfortunately. The reason I was not too worried about it is because my 550 had a similar situation at 4000 rpm, it was less evident, but at 4000 the bike would not run as smooth. I thought since it was similar on both bikes that this was just something that was common on old bikes, and I could wait to fix it. I think I am getting a raise from work soon so I may take it in the shop and get a valve adjustment and a timing chain adjustment (is that the same as the cam chain?)

If it's happening at a certain engine speed wouldn't that eliminate the tire balancing and suspension possibilities? I would think that if it is happening in all gears ie. at different bike velocities, but at the same engine speed it must be the engine..is this a fair assumption? Or is it in your experience(s) that it may very well be something not directly related to the engine.

One other thing I just remembered, my 550 used to have a similar ticking sound...so I am guessing whatever ails the 550 similarly ails the 1000 only a little moreso.

GEEZ, this is my 3rd edit: When I had my tank off to cahnge my plugs and wires I noticed that this bike has less room between the valve cover and the frame rail than my 550, if I were to take the bike into the shop would they have to remove the engine to do the valve adjustment, or is there enough room to do it with just the tank off? One day when I have my own garage I will not hesitate to do these kinds of things myself, but for now I have to resort to the shop.

Bummer on SHOP prices,Here there $60-$70 dollars an hour. Not to many people make more then $20.00 per hour working. Unfare shop charges. Makes one think there living room and evenings after work would be a great place to become one with the bike (and this web site) and save the money for gas to Ride.

Trust me I would love to, but I live in a tiny ass apt. We are saving for a house right now so soon enough I will be able to work on my bike myself. I had a vavle adjustment on my 550 done and it was 280 after tax (CAD) with new plugs and wires, so thats not bad, I am just worried about them jacking my because they can't take the valve covers off

Others will chime in. My KZ900 actually buzzes at 4400 rpm to about 4700. At first I thought it was odd but others told me it was just normal for a 900 inline. Kind of like trying to find the sixth gear that does not exist. The ticking sound is another matter. That sounds like you should look into it...Russ

cool, yeah maybe "buzzing" is a better way of describing it actually. I will have the valves adjusted as I have not had them looked at since I got the bike, and will have the cam chain looked at while they are in there.

My 650 starts buzzing about that same range and goes away. My thought is that your engine may not be running quite right and at that rpm the slight imperfections of running resonate with a majority of the bike at that frequency and then go away. If it repeats at 8K then you may need to look at what will smooth out your engines operation. Things such as good plugs, synched carbs, valve adjustment, cam chain adjustment, spark advance, etc. Just an idea.

my xj750 had a similar issue, it has to do with engine harmonics, i know the early 80s yamaha 750 inlines actually came from the factory with harmonics dampeners(little rubber swuares shoved in between specific cooling fins on the cylinder head) to help eliminate this, maybe you could do something like that to see if it helps.

if you have vibrations at certain RPMs, check to make sure all your motor mounts bolts are tight.

Same type of vibration in my 77' 1000. Always has.

jswag5 wrote:

my xj750 had a similar issue, it has to do with engine harmonics, i know the early 80s yamaha 750 inlines actually came from the factory with harmonics dampeners(little rubber swuares shoved in between specific cooling fins on the cylinder head) to help eliminate this, maybe you could do something like that to see if it helps.

Thats the information ive acquired straight from yamaha, and it has been seconded by more than one source, the little vibration dampner plugs are available from yamaha still, and i have another source that when i bought some only had to pay pennies compared to the yamaha price. Once i replaced them the bike was extremely smooth, not bad for a few small pieces of rubber and a few dollars even numbness in the hands was lessened by installing them. (i may be willing to divulge if asked nicely) its worth a try, i am planning on ordering another package or 2 to put on the kz here in a few weeks.



i have added the pic of the yamaha head, the absorbers are numbers 11-12(i think they are different sizes, but i was unable to tell the difference) and the part numbers are
11 434-11161-00-00
12 4H7-11161-00-00