Inline 4cyl vibration

[thessler3_imp]

I am close to buying a CB1100 and my only concern is the typical inline 4 cylinder high frequency buzzy vibration often found on I4 engines which is particularly bothersome to me. I have owned over thirty bikes since 1968, in many different engine configurations including singles, parallel twins, triples, I4's, V4's and sixes. I am a retired scientist, but will try to keep my explanations simple. "Primary" vibrations are out-of-balance forces that occur at the engine RPM. "Secondary" vibrations occur at twice engine speed. Most vibrations increase substantially with both displacement and RPM. Most inline 4 engines have 180 degree crankpin separation. When cylinders 1 and 4 are at TDC (top-dead-center), cylinders 2 and 3 are at BDC and vice versa. This gives excellent primary balance. Secondary imbalances are caused by differences in piston speed in the upper half of piston travel versus the speeds in the lower half of the travel. Hard to explain, but Wikipedia does it better than me. I attached a link. I4 engines with 180 degree cranks have substantial secondary vibration. This has been known since the early 1900's when Dr. Lanchester wrote on the subject. I4 balancer shafts are engineered to run at twice engine speed and to counter some of the secondary vibes. A single balancer shaft will help, but dual shafts work better. The CB1100 has a single balancer shaft and one rubber engine mount. I have attached a diagram to explain the primary and secondary forces and links to a couple of interesting web pages. I hope it is helpful. If any forum members are interested, I can also explain the vibrations of the v-twins, triples and sixes. Just say so, and I will add those posts.
http://en.wikipedia.org/wiki/Balance_shaft
http://www.autozine.org/technical_school...mooth1.htm
for v-twins http://www.timberwoof.com/motorcycle/V-TWIN-7.html
http://what-when-how.com/automobile/engi...utomobile/
all twins http://dinamoto.it/dinamoto/index_eng.html

[Deanohh_imp]

I recommend you ride one first. Its there but not bothersome to me.... Might not work for your needs.

[rboe]

Coming from a V twin (Moto Guzzi) the CB1100 does have a bit of buzz at freeway speeds (the Guzzi has a vibration but it's low frequency and not an issue, kinda like a power pulse). Around town the CB has no vibration to speak of.

[The Spaceman_imp]

The 90-dgree V-Twin I sold to buy the CB was said to have "perfect primary balance". It seemed ok to me, but the CB felt much smoother. I just rode the new version of the Vee at Bike Week, and it felt like an over-revved steam engine after the CB. Of course neither bike can hold a candle to the Shovelthead Harley I rode for 20+ years. That thing shook itself to death; parts would fall off, the points would unadjust themselves, passengers would need therapy, etc.

Guess its just a matter of expectations vs. perceptions.

[Dynaguy_imp]

I currently own nine bikes. By far, and I mean by far, the CB1100 is the smoothest motorcycle I own. In fact, I would go so far as to say that other than Honda's Gold Wing or ST1300, the CB1100 is the smoothest bike I have ridden. Vibration is simply not an issue with this bike.

[the Ferret]

Man i would think it would be hard for a scientist to be happy with anything.

I agree with Deanohh. I'd definitely ride one before buying so you know EXACTLY what you are getting in to.

[Cormanus]

Man i would think it would be hard for a scientist to be happy with anything.

I agree with Deanohh. I'd definitely ride one before buying so you know EXACTLY what you are getting in to.

Ignorance is often blissful.

[Red Mist_imp]

This is one of the smoothest I4's I've owned and I have owned quite a few, three at present. I would just say the vibration, compared to any I4, is unremarkable, and definitely on the smoother side of the spectrum, especially at cruising speeds. I expect the new six-speed box to be even smoother as the RPM's are a little lower. The new Interceptor, though, might be the ticket for you as the Honda V4 tends to be very nice all the way around.

[INTP_imp]

You can pick up a used 2013 for pretty cheap.

But to answer your question. This bike is like a nicely broken in acoustic guitar. The more it is used the better it runs. Or like a electric guitar amp with a saggy rectifier. Each burst of acceleration blooms, there is the slightest hesitation, but it is very rewarding once it comes into its own.

[thessler3_imp]

Thanks for everyone's advice. I did test ride the CB1100 about a week ago but the test ride was too short to gain my complete confidence. I found it is smooth in top gear at about 70MPH but had some buzzy spots here and there. By the way, it is true that scientists can be picky. I chose the bikes I own because I am hyper sensitive to vibration in my right arm/hand, probably from 50 years of riding bikes that vibrate. I have a Gold Wing, a '73 Ducati 750GT and a Tuono V4 in my garage. I recently sold a 2007 VFR800. All are smoother than the CB1100 and none put my hands to sleep like a few other bikes I have owned. Yes, I am a bit anal. I have made a few mistakes before - buying bikes that I quickly disliked for one reason or another, so I ask the advice of others who own the bikes I am interested in. There is a lot I like about the Cb1100 - nice seat, beautiful paint, air-cooled, simple, etcetera. Again, thanks for everyone's advice.