Author Topic: quick question, 81 cb650 (edit: new questions!) (Read 4041 times)

heffay · « **on:** September 09, 2008, 05:32:19 PM »

i'm sure this will be obvious once someone points it out but since the only manual we have online are not for the cv carb 81 cb650 model... i'm having trouble finding where the top of tube 8 in the picture fits on to.

thanks for the help.

heffay · « **Reply #1 on:** September 09, 2008, 05:34:23 PM »

right now, it goes over the manifold that is between the filter and carbs and just sits on top of there, right in the middle, facing forward... can't find where it might go.

KingCustomCycles.com · « **Reply #2 on:** September 09, 2008, 05:50:02 PM »

Looks like your valve cover breather line. Should be a fitting on the rear of the cover about the middle,

tonycb650 · « **Reply #3 on:** September 09, 2008, 06:00:51 PM »

Yes, it goes to valve cover on one end and if you look at the parts fiche there is a connection point under that # 26 washer just above that oblong hole in the air box. (kind of hard to see on the parts fiche)

heffay · « **Reply #4 on:** September 09, 2008, 06:07:00 PM »

ok, then thats the wrong line... i'll go take a pic... the one to the valve cover i know.

heffay · « **Reply #5 on:** September 09, 2008, 06:14:31 PM »

i'm still pretty sure its number eight as it ends up at the bottom front of the airbox... the right fitting in the above schematic.

tonycb650 · « **Reply #6 on:** September 09, 2008, 06:36:11 PM »

OK, ill go look at mine. OH Ok , that one should have a tee on it with 2 smaller hoses going to the float bowl vents.

heffay · « **Reply #7 on:** September 16, 2008, 05:47:48 PM »

i haven't taken the carbs back off to really give it a look but if someone could post a pic that would be great... still can't find where it goes.

tonycb650 · « **Reply #8 on:** September 16, 2008, 06:40:57 PM »

there should be two plastic tees between carbs 1 and 2 and between 3 and 4.

heffay · « **Reply #9 on:** September 17, 2008, 05:30:03 PM »

nope... are you sure you're talking about the CV carb model?

i'm wondering if someone removed the Ts and left the tube. everything looks in order except for the loose hose.

scunny · « **Reply #10 on:** September 17, 2008, 05:43:43 PM »

should be 3 fittings on the cabs. 1/2 3/4 and one in the middle
EDIT. had a look at my CV's in the garage and looking thru 2 manuals I'm gueesing that the centre pipe activates the vacuum operated petcock seen on some of these bikes ?

heffay · « **Reply #11 on:** September 17, 2008, 06:05:23 PM »

ok... looks like there is one hose in the middle... no T
then there are no hoses connecting 1-2 and 3-4

float bowl vents, someone said earlier.
i don't really see this causing too much of a running issue... especially the problem i'm having of 3and 4 not firing... but, good to know what is going on.

scunny · « **Reply #12 on:** September 17, 2008, 06:11:12 PM »

my carbs have the hoses to 1/2 3/4, and as Tony said they connect together.....sorry can't dismantle them at the mo(bloody shoulder surgery)

heffay · « **Reply #13 on:** September 17, 2008, 07:10:58 PM »

actually, i should correct my statement... there is spark, just no heat.

scunny · « **Reply #14 on:** September 17, 2008, 09:48:47 PM »

spark+gas(at correct ratio) + timing = bang(heat)
as TT would say, break it down into components

heffay · « **Reply #15 on:** September 17, 2008, 09:52:18 PM »

yep, right now i'm working on fuel flow... it only started on two w/ the air filter out. w/ a new air filter it never restarted.

i'll be checking all the others after a petcock check/clean.

can those "vents" be open air?

tonycb650 · « **Reply #16 on:** September 18, 2008, 06:55:41 PM »

Without those tubes being hooked up to the air box, it will cause a rich condition at higher rpms(about 4500 +up).Open air pressure becomes relativly high pressure when airflows though the carbs at high speed, causing carbs to "suck" more fuel from the float bowls.Connecting theses vent to the airbox will make the pressure drop in the float bowls at the same rpm area.

heffay · « **Reply #17 on:** September 22, 2008, 09:42:50 AM »

ok, this bastard child 650 will not start.

spark ok
started kinda while jumping cuz the batt was dead... we think it was only running on 1 and 2, 3 and 4 were cold
batt has been recharged completely since then and cranks just fine.
put it away for a couple weeks... added a new air filter, which it was kinda running w/out one at all... it hasn't restarted.

since then, i've cleaned the petcock... it was bad! but none of it made it to the inline filter so i think the freshly cleaned carbs are ok.
i also hooked up my 350 tank to assure it was not tank related and still no start.

these are CV carbs. new carb kits are the same and no settings were changed. except for maybe idle screw setting, which i do not know. i've read some people have as many as 6 turns out.

during this service the gaskets were changed down to the base. i've since gone back in to check timing and camshaft install... all seems ok aside from my frustration level.

i'm thinking if the idle screws are out of whack i should still be able to start it up on the mains if i try hard enough... anyone w/ an online manual for this particular style of cv carbs on the 81 cb650 model please let me know.

the bike was having running and idling issues prior to service.

tonycb650 · « **Reply #18 on:** September 22, 2008, 06:06:27 PM »

I will normally pull the air filter out and spray some carb cleaner in the intake to see if it will run better. If it does ,i would assume there is still an issue with the carbs.

heffay · « **Reply #19 on:** September 22, 2008, 06:26:39 PM »

i'm pretty sure its not flowing fuel... just doesn't look like its flowing thru the filter... at least not like my 350 looks w/ the same setup.

tonycb650 · « **Reply #20 on:** September 22, 2008, 06:55:18 PM »

If you have the vacuum operated fuel valve thing, check to make sure its working properly or bypass it temporarily

heffay · « **Reply #21 on:** September 22, 2008, 07:19:51 PM »

doesn't look to be vacuum op from the inside of the petcock from what i could tell.
also tried my 350f tank which gave same results.

after putting it all back together this morning and not really changing anything cuz it looked good... it wants to start a little bit more. but still no start.

i think its not flowing somewhere between the tank and carbs... that is an accelerator pump there on top? damned no manual!

tonycb650 · « **Reply #22 on:** September 22, 2008, 07:33:51 PM »

That thing on top that the fuel line runs to is the thing im talking about. You should have a fuel line from the tank to this and a fuel line from this to the carbs.It also has a smaller vacuum hose to the carbs somewhere to pull a vacuum on the diapham inside this thing to open the valve inside to let fuel flow.You can run a piece of fuel line from the tank directly to the carbs to bypass this temp. to see if it will work or leave it bypassed.

heffay · « **Reply #23 on:** September 22, 2008, 09:09:39 PM »

glad to see we're on the same page only i didn't know it.

Buber · « **Reply #24 on:** September 23, 2008, 12:06:23 AM »

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.

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Author Topic: quick question, 81 cb650 (edit: new questions!) (Read 4041 times)

KingCustomCycles.com