Topic: New CB750K owner with questions

[baelzbub]

I just picked up my new 1981 CB750K last night.
I've been dreaming of owning a CB750 for a long time and it was a wonderful ride home.


I've got a few "newbie" questions:
a) Around 5,000 rpms I get a "buzz" which goes away if I rev higher or lower.
The whole bike seems to vibrate.  Is this normal?  It's almost exactly when I hit 5k besides that, the bike is very smooth.

b) I've got this mysterious wobble that I can't pin down.  I was travelling along around 80mph on the highway and the bike was stone-solid.
I came down to 70-75 and then brought it back up and the front end started to wobble.  I slowed down, came up again and it was fine.  This happened, maybe, two more times on the 1 hour ride.

I chaulked it up to different ruts in the road/different road surfaces/etc. But I was wondering if it's something I should be worried about.  My normal cruising speed is around 70mph,  but I like to let the bike stretch it's legs from time to time.

Thanks in advance for any help!

[ProTeal55]

Welcome to the board, and congrats on your new purchase..

Do yourself a favor and do a complete once-over on your new bike.
Just take some time and go over every nut and bolt, and make sure all is tight, and where it should be. I do this to my scoot every few weeks, as it is cheap insurance to making sure the wheel doesn't fall off the thing while I am going 70mph.

It also wouldn't hurt to find someone in your area who deals with older jap bikes, and have them do a once over / complete tune-up. You never know what the previous owners could of done to that thing...

Better to be safe then sorry (or worse)...

[bryanj]

At 81 that should be a DOHC not a SOHC so we cant help a lot with that one. The are very critical of head race adjustment and tyre type/pressures though

[prsman23@hotmail.c]

cb900c.net is a great source for the DOHC bikes, I had an 80 750 and the site was very useful to me.

[dusterdude]

guys,while ill agree with your dohc assesments,his questions are reasonably generic,i would think someone here could help him with his problems.

[nickjtc]

a) Around 5,000 rpms I get a "buzz" which goes away if I rev higher or lower.
The whole bike seems to vibrate.  Is this normal?  It's almost exactly when I hit 5k besides that, the bike is very smooth.

b) I've got this mysterious wobble that I can't pin down.  I was travelling along around 80mph on the highway and the bike was stone-solid.

a) Check that the engine mounting bolts are all torqued to the correct specification. Do a tuneup and balance the carbs. This made a huge difference to the buzzy-ness of my bike.

b) What shape are the steering head bearings in? Is there a notchiness as you turn the bars from side-to-side with the bike on the centre stand and the front wheel off the ground? How are the tyres? Matched front and rear? Lots of tread? Correct pressures? Are the wheels aligned? (Don't assume that the markings on the swing arm are correct). Any play in the swing arm? How are the wheel bearings?

And so it goes on!! Lots to check over. Good luck.

[dusterdude]

way to step up nick.

[baelzbub]

Thanks for the replies!
Whoops! Sorry - I DO have a DOHC.
(can you tell I'm really new to the Honda scene)

I've owned a bunch of different bikes, but I've always longed for a CB750 and when one fell in my lap yesterday, I quickly ran to get it.
Now that I have one, I plan to learn more about them.  Sorry for posting in the wrong section (forum?).

I'll give the bike the ol' once over this weekend, I thank everyone for giving me some pointers in the right direction.

[Bob Wessner]

Sorry for posting in the wrong section (forum?).

No sweat, happens frequently. Let us know what you find.