Topic: 78 Hawk II - Engine Buzz?

[ybarsabal]

The bike has started buzzing around 3800+ rpm, and it's a sporadic buzz. I think it's coming from the engine, but it's difficult to target the noise while riding. I don't hear it while revving at a stop. Performance doesn't seem to be affected during the buzz.

I just took the top off the carbs and sprayed some carb cleaner to clean it out. There was a noticeable increase in smoothness while accelerating through low rpms, so I thought it helped. The buzzing happened a few days later. Do I need to resync after cleaning?

Any ideas?

[Gordon]

Check and tighten all of the engine mount bolts.

Can you feel the buzz, or just hear it?

[ybarsabal]

It's only a sound.

[ybarsabal]

Oh man, it was the tank lid that covers the gas cap! I had been cleaning that area and removed two pieces of electrical tape that appeared to be useless. Yay for easy fixes!

[KB02]

My wife's hawk had the same issue. I finally tracked it down to the gas cap lid. I figured I would solve it by putting a rag between the lid and the cap. It stopped the buzzing, but it also stopped the vent in the gas cap.  Live and learn. I replaced the rubber bit and all is well. 

[crazypj]

What's a 78' Hawk II?
With an actual model you would get more specific help.
 Take a look at frame plate.

PJ

[KB02]

Us Hawk owners knew what he meant. 

1978 Honda CB400T II (as apposed to the CB400T I - which is clearly the inferior machine with it's drum front brake and no electric start).

1978 CB400TII

    * It came in one of two colors: Tahitian Red or Candy Sapphire Blue
    * The gas tank and side cover stripes were black and orange
    * The instruments had both a speedometer and a tachometer
    * The bike had comstar wheels rather than wire spokes
    * The front brake was a hydraulic operated disc
    * It had both an electric starter and a kickstarter
    * The engine was a 395cc OHC 3-valve parallel twin with dual carburetors
    * The transmission was a 5-speed
    * The serial number began CB400T-4000048.




1978 CB400TI

    * It came in two Colors: Helios Red or Excel Black
    * The gas tank stripes were black and orange
    * There was no tachometer -- only a speedometer
    * The wheels had wire spokes and the brakes were mechanically operated drum
    * There was only a kickstarter (no electric start) The engine was a 395cc OHC 3-valve parallel twin with dual carburetors
    * The transmission was a 5-speed
    * The serial number began CB400T-2000022.

[Alan F.]

I've got a T2 engine for my CM400C project, I'll get it together with the CM engine then fit the kick/elec start motor just for the cool factor. 

I just listed my non sohc4 daily ride on craigslist, if it sells I'm gonna need this CM rideable quick so I'll be posting questions here for sure as well as the twins sites.

-Alan

[crazypj]

Ah, now I know it.
 We didn't get a cool name for the  MkII Wet Dream 
 That had the Comstars that self destruct, the clutch cover had to come off at first service (and third, etc) to set balancer chain, and ignition low speed trigger coil stopped working on thousands of them.
 Great bike 

PJ