The CB1100 Community Forum

Hi Everyone,

I have been looking for a simple, upright, old-fashioned bike for a little while. I am familiar with the cb's and like them, so I was surprised to see the new Honda 1100 available.

But I'm disappointed in it because of vibration - or "Rumble."

I thought I would register and submit an idea to everyone about the cam timing - "asymmetric cam timing" business, if I have that complicated name correct.

I do not think the timing was done for a Rumble - why go through the trouble of manufacturing a balance shaft and then put vibration back in.

And to keep hearing that 1 and 2 are one set of timing and 3 and 4 are a different set, that just did not make sense.

BUT! someone here mentioned the manual is not correct, that the two outer are the same, and the two outer are the same!

THIS makes sense if you think about heat problems... The longer duration for the inner cylinders might reduce the dynamic compression ratio, causing them to run cooler.

Wouldn't this make more sense than "Rumble?"

Already there's a limiter, incredible sparkplug threads, and special cooling for plug region.

I would bet that the cam timing was needed to get the cylinders cool enough to meet reliability requirements...

Just a guess. Anyone have better experience with this question (cam timing, dynamic compression, and cylinder temperature)?

G'day Honda.1100 and welcome to the forum.

Your first post has to be approved by a moderator which is why this didn't immediately show up. You're now good to go. I'll delete the other post asking about this one.

Howdy and welcome to the forum

We can only go by what Honda says, and in the "designers talk" series on Honda's website they go into great detail about the 3000 rpm rumble and the assymetrical timing. Not being an engineer myself I can't speak to what does and doesn't make sense, but that is what the Honda engineers who designed the bike said they did. I'll take their word for it.

http://world.honda.com/CB1100/engineer-talk/episode1/

AS far as how it worked out in real life, for me the bike is very smooth in the rpm ranges I ride in.

I measured the cranking cylinder pressures for cylinders 1 and 4. They were 195 psi and 180 psi respectively. This confirms that cylinders 1 & 4 close their intake valves at different points.

(01-05-2017, 02:13 AM)SimiPair_imp Wrote: [ -> ]I measured the cranking cylinder pressures for cylinders 1 and 4. They were 195 psi and 180 psi respectively. This confirms that cylinders 1 & 4 close their intake valves at different points.

I'm still getting used to this forum "thing", so sorry if I don't quote correctly.

From a previous post:
this is a misprint in the shop manual, happens all the time with a non procedure specs.if this was a service check procedure red flags would have flown very early from feedback from service engineering and field service techs.i'm sure it will be corrected by next shop manual printing if Honda knows about it.
correct spec should read-
intake timing for cyl #1 and#4 opens at 5 degrees atdc, closes 28 degrees abdc
intake timing for cylinders #2 and #3 opens 5 degrees atdc, closed 38 degrees abdc
Paul. Sr.Tech. Specialist, American Honda Motor Co.Inc= Retired.
correct spec should read-
intake timing for cyl #1 and#4 opens at 5 degrees atdc, closes 28 degrees abdc
intake timing for cylinders #2 and #3 opens 5 degrees atdc, closed 38 degrees abdc
Paul. Sr.Tech. Specialist, American Honda Motor Co.Inc= Retired.
[/quote]


Thank you Sr. Tech

38 would lower dynamic compression - reduced temperature...

I think that is your answer right there.

As far as the compression test. I am a little suspicious of something you might have done - not being confrontational about it or something, just there's so much that could be slightly different and give you that 5% difference...

A leak down test would have a lot fewer places to go wrong, for example...

Could be. Would be a logical way to cool the center cylinders.

I'll test cylinders 2 & 3 next time I have the tank off. Just for my own edification.

No idea at all. They build it and I ride it. It runs and I'm happy. That about sums it up for me.

Sent from my SM-T350 using Tapatalk

Honda.1100,
That is a great find, thank you for sharing. What is your background, if you don't mind me asking?
I was temping the exhaust headers and noted that there was not a significant difference between the inner and outer egt's as measured through the exhaust runners, and this is as good an explanation as I've heard.