Topic: Carb Advice needed on a 1979 CB650

[Cosworth]

I recently picked up a 1979 CB650 with horribly gummed up carbs, I disassembled all the carbs got them all freed up ungumemed and reassembled back on the bike. I have the pilot screws all out a 1-5/8 turns as the manual says but I cannot make the bike run unless its on full choke. I can make it run off choke only if I rapidly punch the throttle....
 
The bike has all new plugs and I have verified all the cylinders are firing. Both coils have cracks in the casing but they do not seem to be breaking down in signal (I will replace these once I get the bike where I can make it run)

Does anyone have any ideas where im going wrong?

[cb650]

Did u pull the idle jet?   They are "nonremovable" but can be easily enough.

[onepieceatatime]

Did you check for cracked or leaking carb to intake boots?

[Cosworth]

boots were very old and stiff with a few very very small cracks in a couple of the boots nothing longer than a 1/4" but even covering the holes it doesnt change the idle or spraying them with fluid.

I did not mess with the pressed in jets other than spraying through them with compressed air and carb cleaner. That may be the place to start... Ill have to look into that in my manual.

[cb650]

You might check for leaks around the boots first if they are that bad. 

[Cosworth]

Ill give it another shot and pay closer attention to it this time. I suppose excess air drawn from leaking boots could cause the problem and having the choke fully on would lower the air drawn in.

[scunny]

you will still have to pull those jets and clean them properly.

[Cosworth]

Ill pull them off and do that first then. Is there a good writeup about pulling the idle jets?

[cb650]

if not hare there is on the 650 site.  Youll want to look for 79 or 80 carbs.  The 81-2 are way diff.

[Cosworth]

Sure enough the slow idle jets were badly clogged took quite a bit of persuasion to get all the gunk out. Bike idles much better but still not quite right and the thing is insanely cold natured it takes a good 4-5 mins to get warm enough to idle off choke but I guess thats normal for these bikes? I dont see much of a way to sync these as they are all on the same rod with only 1 adjustement so I assume the only thing left to do is get the idle screw correct on all the carbs?

[jerry h]

To sync them, take the cap off the top of the carbs, there will be an adjustment screw with a lock nut.

[TwoTired]

Sure enough the slow idle jets were badly clogged took quite a bit of persuasion to get all the gunk out. Bike idles much better but still not quite right and the thing is insanely cold natured it takes a good 4-5 mins to get warm enough to idle off choke but I guess thats normal for these bikes?

The carbs rely on induction pressure drop (stock air filter) and exhaust back pressure (stock exhaust) for correct mixtures.  If either of these have changed, then the carb jet orifices and mixture adjustments must be changed to compensate.

A hotter heat range spark plug can aid cold engine operation.   But, it is better to have the standard heat range during the heat of summer.

[Cosworth]

I have the stock intake on the bike, and I believe stock exhaust just 4-2 chrome. I will take the caps off again but I only remember a adjustment on 1 carb rod and the rest just had grub screws

[jerry h]

Here's your best friend       .......  http://cosky0.tripod.com/

Another site you should check out (if you haven't all ready)  http://www.hondacb650.com/

[Cosworth]

Thanks, I will sync the carbs this weekend. I still  have my 4 carb sync tool from when I owned a VMAX. This is a bike my dad picked up he's wanting to get it going and cruise around.  So I really appreciate all the help getting this little project going.