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Trouble Shooting Help

motocommuter

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Hey All, just trying to narrow down a small vibration and figured I'd reach out for help. I have been noticing a small vibration at 4k RPM. I have searched the forum, and I do know there are already threads talking about the 4k and the 3k vibrations/throbs. However, those threads became very long and off topic. Plus, I am not wanting to know if it is normal. I really just want to know where it's coming from.

So, about 500 miles ago I changed my rear tire myself. I also pulled the weights off of the front and rear rim and installed the counteract balancing beads. Ever since then I have noticed a small fast vibration that makes the mirrors go fuzzy at 4k to 4.5k RPM. I can't tell if this is new, or if this was already there and I am just being hyper sensitive. I work a rotating 12 hour shift schedule, and I can tend to fixate on things that are minor. Basically, I am trying to figure out if I did something wrong with the recent tire change. This vibration happens at every single gear.

So, here's my thought process. If it was tire balance or improper mounting, this would happen at certain speeds regardless of RPM (example; going 60 mph with vibration in sixth, down shift to fifth and the vibration should still be present). Wouldn't that be the case if it was directly related to the tires? If it was the drive chain, shouldn't it be even more specific (example; vibration in every gear but at different RPM depending on speed and how much throttle is being applied)? In my case, this vibration is at 4k rpm in every gear. I have adjusted the chain three times to rule that out and added more counteract beads to the tires. So the question is......would you say this vibration is in the motor some where and has probably been there all along and I am just being crazy? I am totally fine with the amount of vibration. I just want to be sure it wasn't caused by me! Thanks guys, and sorry I am so long winded right now. Third cup of coffee, and I am chasing it with a Monster!
 
Getting off topic or rule things out:

Some of us would say ditch the beads..........and balance the tires with the tire, motorcycle and auto industry accepted methods. Not to mention your pulled the weights front and rear. Balance Beads are controversial at the very least which could make this thread a love em or they are magic and a waste of time and money and do not work or worse can cause problems ?????

The other tire related issue since you changed the tire .......is the tire bead evenly seated on the rim all the way around. It is very easy to not seat the bead and can be hard to judge how well the bead is seated. Did you use a lot of lube on the bead (lube is a good thing).

I know this tire related testing is contrary to your RPM theory.........but you started with I changed my tire and balance on both tires and now............ and your rpm theory has real merit.........but you have changed many things all at once and you could be chasing "smoke" so:

Ride another NC in the exact same conditions back to back and decide if they are the same and your just being "hyper sensitive" as you put it..............

There are engine vibration has smooth sweet spots and "roughness spots" on the NC. But I general the NC is smooth.
You mentioned chain 3 times......too tight is a very bad thing. But chain speed is back to vehicle speed.

On your engine rpm theory: retorque all the engine mounts bolts, check the shop manual there maybe a specific bolt order on tightening.
 
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If it's something you did, you must have snuck into my garage and worked on mine too. :). I don't remember ever having a bike that didn't have a certain rpm range where vibration became noticeable, and on the NC it seems to be in the 4000 to 4500 rpm range. The good news is that at least on mine it's relatively minor. Just enough to blur the image in the rear view mirrors a bit. According to the road tests Honda purposely intended for the bike to have a little "character", and this seems to be the rev range where the harmonics from the engine become most obvious.

At any rate the short answer is that I would vote for engine, and yeah mine does the same thing.

Bob
 
False correlation is one of the greatest causes of a missed diagnosis. "It all started when I did blaaaa." When I was a young engineer I was called to a glass plant in Keyser, WV because the batch plant control system had been down for two days. The Plant Engineer said "It all started when we changed the drive controller on the batch feeder" so their efforts over the two days were solely directed towards what they might have changed or gotten wrong related to the drive controller change. In about two hours I had determined that the problem was a control wire broken in a door harness on a different control panel. It had just flexed open and closed one more time than it wanted to. I found it by starting at the top of the ladder diagram with about three ranking locals telling me that I should have my head stuck in the drive panel like they had been doing.

It is OK to analyze the tire change as part of your diagnosis. Chain slack, chain alignment, bolt torque, etc. But if it doesn't fit the symptoms, throw it out and look somewhere that does. I think your logic will serve you better than the "last thing changed" routine. I would never run beads in my tires, but it is not likely that they are the cause of an RPM-specific vibration in every gear. What about no gear? Does the vibration occur with the bike in neutral on the centerstand with the RPM's held in the 4000-45000 range? If you have a way to fix the front wheel to the ground so you won't launch the bike like a Navy jet, you can even run it in gear on the stand. But I don't want to hear from your lawyer if you screw it up.
 
Just got back from a short ride............I would say there is slight change in vibration around 4000 rpm in all gears and is obvious engine speed related just as you described. Reason who knows .........total wild ass Internet guess the balance shafts are tuned to be more be effective at a lower rpm range.

Totally agree with Beemer in tires and chain etc are not rpm related.
Unless you enjoy chasing wild geese for little value I would not bother doing a lot of extra work. I would balance the tires but not to fix an rpm vibration.

If it did not show I am also not a balance bead fan. :eek:
 
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Counter Act Beads work fine in all tires but the Pirelli Diablo series. It is actually built with a "V" shape inside the tire. They typically are extremely well balance on their own but the beads tend to collect in the very center of the tire and over compensate if you go by recommended amount for that tire size. They actually work really well especially if you have fancy rims.
 
Thanks for the help guys. I will try running the bike at 4k on the center stand. Either way, sounds like it has always been there. I'll stop being so sensitive!!! I get why Honda engineered some vibration in, but I could have done without. For me, the smoother the better.
 
I remember seeing many comments in video reviews and other printed review about the NC last year before I purchased mine about a silghty engine buzziness at about 4k rpms. I've experienced it myself as well. That used to be my shift point, wouldn't look at the tach, feel the vibrations and shift. I shift at a lower rpm now to try and get a little better mpgs.
 
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