Topic: She LIVES!

[CBR_Rod]

My inherited 1979 CB650 lives once again.

I was waiting on some parts from Sirius for my carbs (completely torn down and needed Air Cut-off valves and float needles).  In the mean time I bought a complete used set of carbs on Ebay for just over 40 bucks shipped.  Figured they'd be OK for parts, that is how they were advertised.  I received them today and removed the float bowls and used carb cleaner on the main bodies.  I put the pieces from my original carbs on this new/used set since they were already chem. dipped and had the new seals installed.  This new to me set of carbs had a like new air cut-off valve in the #1 carb(didn't separate the units) and a like new accelerator pump.  I wiped off the float needles, all of which had good internal plungers compared to the ones in my old carbs and reassembled everything.  After a little cranking she fired right up!  Runs great on Choke, not so great off choke (and I blew out all the passages).  Might I need to adjust the idle circuit screws?

I was wondering if the lack of wanting to idle with the choke off would be affect by not having the air cleaner assembly on, anyone have any input on this?

My #3 float needle is apparently a little sticky, she runs out the drain on this bowl.  I set all floats to 1/2" as per the manual.  I didn't let it warm completely up so that may attribute to the off choke idle problem.  I had a catch can below the #3 bowl and didn't want it overflowing.

I'm just happy she runs, and it still sound strong and smooth, no engine noise and no exhaust leaks of any kind.

Here is the link to my original post on this bike for anyone wanting to get up to speed on it.  http://www.sohc4.us/forums/index.php?topic=19655.0

[keiths]

Great news Rod.
The lack of the air filter might give you problems running without the choke. I would expect it to run a little lean without the filter and the choke would richen it up a bit.

[CBR_Rod]

I went ahead and changed the oil and filter (I'd previously just put in new motor oil until I knew it would fire up).  She seems to run OK with and without the choke, but is more responsive with a little bit of choke (without the choke and setting the idle down it has severe hesitation coming off idle).  So I'm thinking you are correct, that the lack of air cleaner is making it run lean.

Still need to put a new float needle in the #3 carburetor, but other than that the carbs seem pretty good.  I'll have to adjust the idle mixture screws, I have them set to 2 full turns out each (that is what the original carbs were set at). 

[Faol]

Congratulations, Rod! I'm another 79 CB650 owner, although I spend more time searching than posting - this is my first bike and my insights are pretty limited. That said, I wanted to mention that there are indeed 8 tappets which need adjusting. Exhaust clearance is 0.08 mm (0.003 in) and intake is 0.5 mm (0.002 in). I have the Clymer, Haynes, and Official Honda Shop Manuals, so if it's something I can look up, I'm golden.   

I look forward to hearing more of your progress, and probably glomming on to your experience as well.

Lee

[CBR_Rod]

Faol,  You may have cleared something up.  You said there were 8 tappets, I think of them as rocker arms (I think of Tappets as lifters).  I hae a Clymer and have indeed adjusted the intake and exhaust valves to the measurements you provided.

[CBR_Rod]

and PS.  This 79 CB650 was originally the same color as the one in your avatar, black/maroon.  It is now a Blue metallic that matched my mom's Buick.  Since it runs, it will soon be some sort of Orange metallic most likely (something like what is on the newer shadows or VTX).

[CBR_Rod]

Well part of the problem was I forgot, in my hast to hear it run, to install the needle jet and holder in the #2 carburetor:)  It is installed now.  I also swapped out a used float needle on the #3 carb to see if it would quite overflowing.  Well, not only did it not help the situation, but overnight the #2 and #4 decided they would like to over flow as well.  Least I have some Float needles on the way.

Is there anything special I should do to true up the float needle seat, and if so, how do I go about it?

[keiths]

I can't seem to find it now, but someone mentioned cleaning the seat with toothpaste by spinning the needle in the seat.  Keep each seat/needle combo together. Maybe someone else remembers more.

[CBR_Rod]

The rubber ends on the float needles I have seem supple.  Might be worth my time to try the tooth paste on the old ones.  Surely it wouldn't hurt anything.

[Pinhead]

You definitely need an air filter (and possibly the filter cover) for the bike to run right. When I removed my filter cover, I had to move up to 102.5 mainjets. Stock jets are 95's, I believe.

A lot of people keep everything stock, but run 98 mains. It definitely wouldn't hurt.

[scott_cb650]

I also have a ’79 CB650 and have an inconsistent idle, so I was wondering if you determined the usefulness of the air cut off vales on the carbs.

I have recently found where they can be disabled if desired.

So did you end up using your new air cut off vales or by-pass them?

[CBR_Rod]

The bike runs, and that is what I was aiming for before I went too much further.  I haven't done much since except to buy a battery for the bike.  I intend to install the air cutoff valves in the original carbs (carbs on the bike are a set of parts carbs from ebay that were better than expected), along with the new float needles and assemble the airbox and see how she performs.  My current running situation is without any sort of air box/air cleaner which makes me think she is lean.

When I get a chance to install the carbs and air box, I'll post back on the matter.

Good luck with yours.

[Pinhead]

You're lucky you can even get it to run without an airbox/filter. My bike (when it had stock jets) would barely idle after it had been extensively warmed up without the filter cover, and it'd die without the filter.

However, once you get the airbox and everything put back together, I recommend going up to about 102 main's and lose the filter cover. That gave me a huge increase in performance and helped my gas mileage. You can run the cover during the winter and not worry about running the choke all of the time.