Topic: quick question, 81 cb650 (edit: new questions!)

[heffay]

Those open T's - I have them without, and IF your float valve will not close properly, the overflow will go there and end up on the engine.. Which may be tricky while it's running..... I had it once, but nothing happened...lucky me 
But to install them, you will need to separate the outside carbs from the bank.

or run 4 flexible hoses off each carb up to all the Ts being above the carbs and accessible.   
thanks bub... and everyone else too!

maybe in the morning.

[CBJoe]

When you rebuilt the carbs, did you check the condition of the air cut off valves ??  (located on the side of each carb).

Joe

[CBJoe]

I'll see if I cant take my manual to work and scan in the carb section.  I'll post it later today I if can get it done.

Joe

[Buber]

Rememeber - we are talking here the CV, not the piston ones...

[heffay]

air cut off valves?

now, bub?  when you say piston... i think these cv carbs look more like pistons internally than the slide carbs do... you're referring to the slides as pistons, correct?

[Soos]

If it's a '81 cb650 motor in that frame, theres (almost) no chance they are the PD50 a(or b) carbs.(mechanical slide type carbs)
They are likely VB44a or VB44b carbs, the CV type.


The easy way to identify them... is the cap on top of the carbs a long oval or round?
Long oval, Mechanical Slide type, round the CV type.


And no there are not air cutoff diaphragms on the CV carbs, and yes there is(should be?) an accelerator pump on carb #2.



Have you taken bowl #2 off and confirmed the pump is squirting gas?
If you remove the floatbowl you should be able to press on the stem for the accel. pump and get gas squirting up.(as long as there is gas in the floatbowl while pressing on the stem )


Bypassing that vacuum operated petcock is a MUST (IMO) for determining whether the carbs are good or not.
The diaphragm can go bad, it could be stuck from gas residue, or posibly even clogged.


A '80(?81) 650 I bought at one time had epoxy(and a McDonalds straw to boot!) in places epoxy should NEVER touch carbs...should epoxy EVER touch carbs??

After doing all I could to them, it wouldn't get gas unless I bypassed that vacuum operated petcock.
The petcock needed cleaned and it worked fine after that.
The old gas had formed into a paste sticking it closed.


Good luck getting that thing going!


Wish I was still living in Denver... Helping you would give me a reason to go on a ride.
I miss Colorado!!!
Sane people, Sane drivers(Doubt me? you drive on I-15 and say the drivers are saneout here in utah)...

Nothing revolves around behive this and that, or mormon this or that...
Just simply to have a conversation about ANYTHING without "THE CHURCH" cropping up would be a nice change!
Utah people freak me out.... Meth labs and mormons.... Not much else it seems.
There is a few normal people out here... but the religious people(and their attitude once they figure out you are not mormon) BOTHER me.
Fine be religious... but don't talk to me about it!


And now for something COMPLETELY different...



l8r

[heffay]

i was thinking the petcock was not vacuum operated... i spose it could be now that i think of it since it must pull the fuel up from its reservoir.  or are you talking about the round thing above carb 4?  what the hell is that damn thing.

i cleaned the tank petcock a few days ago.  should be flowing fine.

i just bypassed the thing on top of carb 4 and ran gas straight to the carb intake between 2 and 3... kinda seemed like it wanted to start a bit more but still no start.

carb type has never been in question for me.     these are cv carbs...  ones like i've never seen since there is no rubber diaphragm but i've only been in newer style cv carbs... they're still the same theory.

[Soos]

Yeah that round thingy on carb #4...I think it's called a vacuum operated petcock...
I dunno, thats what i call it anyways, don't mean I'm right though.


And yeah... they are a bit "different" than most CV carbs I've been into as well.
That big 'ole piston assembly in there almost seems like it wouldn't work on air pressure alone....


Not sure what else I can pitch to you to help.


Have you double checked the vacuum line going to the "vacuum operated petcock" is not leaking air?
Or the brass tube that hose hooks to?
( I ask, because the epoxy covered carbs I have had a cracked brass tube causing difficult starts at best)

Is the airbox on the bike?
If not, try holding your hand over 1 or 2 of the carbs while cranking her over.
You should get a hand covered in gas... if not, try again with each of the 4 carbs...

If none of them get your hand wet with gas, possibly something in the common fuel rail is amiss?


l8r

[Hush]

My CB650 has the older mechanical carbs but a thought does arise, did you take the carbs apart fully?
I think I saw that you did, if so did you reassemble the accelerator pump on carb #2 correctly?
I rebuilt mine and it looked right but I had put the small pump spring on the wrong side of the diaphram, gave same indications as you speak of.
It looks right but you have to follow the book precisely or no gas and no start.
If carbs are getting gas (checked by unscrewing the bowl drain plugs) and still no start, did you put the floats in upside down?
Don't laugh, I did on all 4 carbs and cursed myself everytime I cut my knuckles undoing all those horrible wee cross heads!
Hey maybe I'm preaching to the converted and you are a lot more mechanically minded than me but I like to learn from my dumb mistakes and your problems seem to mimic the ones I created for myself.
Best of luck and hope she fires up soon........Hush.

[Buber]

....Don't laugh, I did on all 4 carbs and cursed myself everytime I cut my knuckles undoing all those horrible wee cross heads!
...

On my 2nd time having the carbs out, I swapped all screws for allen head. As well as all the cover screws for the engine, and camshaft cover ones too...
Just makes the life A LOT easier.....

[Hush]

"SNAP" me too, best $10 I ever spent, 12x allen head screws and now no problem tourquing them up to stop leaks.

[CBJoe]

air cut off valves?

My bad ... I've been staring at the mechanical carbs so long, I forgot the the CV type didn't use the air-cutoff valves.

I wasn't able to scan the manual yesterday. I'll try and get it today.

Joe

[heffay]

thanks for more responses guys...

actually, i only removed bowls, jets, slides, etc... i did not pull the carbs completely apart.  which may end up being something that i have to do.  LAME... will still be less times pulling these off than on my zx7r though.  and there's a lot more crap in the way on that plastic bike!

also, on these carbs, it is impossible to install the floats upside down or the float pins will not install.  i checked to make sure new float pins were exact same length as well since float height is non-adjustable in these carbs... not to mention the only removable jet is the main!

CBjoe... just so long as you copy the right manual... i already have a copy of the WRONG manual.     but, once you get it scanned i'll send it off to glenn so he can post it as well.  thanks joe.

these cv carbs, are they sync-able?... just by the idle screws?  or are they just non-sync carbs?

[CBJoe]

I've failed completely for today.  I got the entire chapter copied to normal sized paper and then I tried to fax it to my work e-mail.  When I got home and checked my e-mail, only the 1st page showed up    I'm not sure what happened.  I'll just have to go to Kinko's tomorrow to scan it in properly. 

Sorry for the failure.   I've got the entire Haynes manual for '80-'82 CB650's with the spine removed, so after this, I think I'll just get the entire thing scanned in and provide it to the forum for posting.

Joe

[CBJoe]

Heffay... PM and E-Mail Sent

Joe

[Soos]

actually, i only removed bowls, jets, slides, etc... i did not pull the carbs completely apart.  which may end up being something that i have to do.  LAME... will still be less times pulling these off than on my zx7r though.  and there's a lot more crap in the way on that plastic bike!

also, on these carbs, it is impossible to install the floats upside down or the float pins will not install.  i checked to make sure new float pins were exact same length as well since float height is non-adjustable in these carbs... not to mention the only removable jet is the main!

CBjoe... just so long as you copy the right manual... i already have a copy of the WRONG manual.     but, once you get it scanned i'll send it off to glenn so he can post it as well.  thanks joe.

these cv carbs, are they sync-able?... just by the idle screws?  or are they just non-sync carbs?

Yes they are synch'able...

Look at the shaft linking the main butterflies.
there are 3 adjustable spots on there, each "adjuster" screw is held tioght with a nut... so adjusting them is... well not easy IMO.
I like the '79 carbs for synching myself, a tad easier IMO.

And no the idle screws will not synch them very well.
As far as the floats being able to go in upside down...
Dunno!
I can provide a pic of the ones I have if you like.


And I have tried to figure out a way to remove the pressed in slow (idle) jets.... And have yet to figure out a way without damage yet. So good luck getting the emulsion holes clean!!


If you find a bike wrecker yard (for replacement carbs) you want to look for VB44c or VB44d carbs.
I have heard of the VB44c carbs having both the pressed in and screw in slow jets, but the only set of VB44d carbs I have seen had screw in ones.

While i'm mentioning alternate carbs....
If you want to go nutz... look for '85(or thereabouts) kawasaki ninja carbs.
they are a drop in fir pretty much.
The spacing VS the CV 650 carbs is negligable.
Not to mention easier to clean, synch and all jets are removable.

But the starting of them leaves something to be desired though.
If you do a search, i've posted my results so far using a set.
Mine are on a '79 head using the kawasaki ninja(GPZ 600cc) isolators to allow them to fit to the '79 head.
They are a DEFINATE plus for anyone wanting to upgrade to a larger venturi carbs....
More better power.....


l8r

[Soos]

Hey Heffay, you ever get that thing to start?

l8r

[heffay]

its been such a #$%* for 3 weekends i decided to fluff my own bike's ego this past weekend!