1982 CB650SC newbie

[galliononeNC]

Hello all! My name is Trevor and live in NC aviation mechanic by day wanna be motorcycle mechanic at night. New to street bikes grew up with dirt bikes and ATV's . Recently picked up a 1982 CB650SC of CL for $250 13K on the odometer. I've had it running for a few minutes then it cuts out like all the carbs run out of fuel at the same time. Hope to get some valuable info from the forum members. PO left me with lots o extra parts (tank, side covers, seat fairing) all in decent shape. Not sure if I want to restore her to former glory or custom build, I just want her to run for more that two minutes. I'm also afraid the PO did some shade tree wiring to her b/c the harness is sliced open and a mess. So please any info and direction would be appreciated

[cgswss10]

If the bike has only 13k on it, its certain it has done a lot of sitting. I would recommend you take off the tank, and remove the petcock. There is almost certainly rust in your tank and a goo chance the strainer in the petcock is partly clogged. I used lacquer thinner and drywall screws to clean out mine ('81) I dumped a gal of thinner in the tank and a bunch of dry wall screws and shook the H out of it. Then I shook some more. I had to use a magnet on a stick to get the screws out. When you re install, use new fuel line and put in an inline filter.

When the bike was new, it had a vacuum petcock. This is mounted on the carbs and has a lot of plumbing. If your bike still has this little trouble maker, you will want to get rid of it and run you fuel line directly to the fuel rail.

set the tank back on the bike, open up the petcock and let it fill the carbs (put the petcock in the "res" position just in case you didn't put a lot of gas in the tank. Now look at the bottom of the carbs. Each one has a little nipple and a screw head. Get something to catch the gas, and open one of those screws. I use something that is clear so you can see if there is crud in the gas. If the fuel flow is good, you will get a nice steady stream of gas out that nipple.

If asll is good, time for another test run.

[galliononeNC]

Thanks for the info. So far all I have done is pulled the carbs and cleaned them. At first they were pouring gas out of them. Took the top caps and float bowls off gave them a good clean and put back together. Leaks have stopped but thats about it. For now I'm going to used a fuel IV (empty gear oil bottle) as a surrogate tank. I can only get her to start with starting fluid. I Did notice some cracks in the plug wiring and also some possible arching issues (burnt wire connecting the two coils) general loose wiring. Pics will be up soon had some issues with size last night . thanks again

[galliononeNC]

She's Alive!! Played around with her this morning using a surrogate gas tank and she fired up with full choke. The bike is still wanting to die (you have to keep throttle and play with choke to keep her going). Unfortunately the carbs started leaking gas again so I'm going at least change all the orings and float bowl gaskets. As for the pine sol soak how long do you soak them, should i do that after i take the caps and bowls off, Should it be full strength, and Hot? Also do you think agitation would help(inspired by faux ultrasonic cleaners using belt sanders, saw it on YouTube) Then what do you clean them off with afterwords? As for the vacuum petcock, was it located on the 3&4 carb area ? If it was, I removed it and started to get good fuel flow.

[cgswss10]

Ok, get a can or two of carb cleaner. Take the carbs off.I would suggest you take one carb apart-and bag the parts, then the next ect. With the float bowls off, remove the floats, and pull the needles out. The needle and needle seat are the things we are going to work on first. Soak the needles in a small container with some pure pinesol (straight from the bottle.) Get some q-tips and spray them with carb cleaner and scrub the needle seat. I actuly chuck the q-tip in a drill motor and polish the heck out of them.

Next take the little plastic tube for the carb cleaner, and sharpen it. you can use about any fine abrasive, I'm lazy so I just sharpen it on the side of my grinder.

Now you are going to use that little sharpened wand to to push into every port you can find and squirt the fluid. You should have cleaning fluid come out somewhere. If you have some clogged ports, then we are going to talk about soaking and other ways to un-plug the ports. I would pull the jets, and ump them in your soak as well. Use the carb cleaner to try to squirt cleaner thru them

let us know how you come out.

[galliononeNC]

Thanks for all the info! I am ordering the carb oring/gasket kits and going to get started on the soak after this weekend. While that is going on what are peoples thoughts on tank cleaning/lining? Do I need to line the tank? There is some interior surface rust, could I just use a chemical stripper or chemical with an abrasive/media?

[cgswss10]

Lota people use a lot of different ways. I used thinner with a handful of drywall screws. I shook and shook, then shook some more. I used a magnet to get all the screws out.

I used the Cadwell tank sealer kit. Worked great for me- but don't believe the instructions... use the whole kit for one tank.

The only o-rings would be on the fuel rail and the accel pump tube. (OK-the little o-rings on the air screws-but those have nothing to do with a leak)

Is the leak coming from the fuel manifold? If you plan to replace those o-rings, you are going to have to separate the carbs from the rack. Not a fun job. If you are going to do that, PLEASE get 8 M3 X 6mm socket button-head screws, and some red loctite. These are for the choke plates. The original screws are split to prevent them from backing out. You should not reuse them.

I'm betting your fuel leak is is because your needles are not shutting off the fuel when the fuel bowls are full.

[Volker_P]

Welcome here, Trevor!

Seems like you already fixed some issues.
Cleaning the tank is crucial, you may find some options how to proceed in the fuel tank issue thread.
If it does not leak afterwards, no need for a liner.
If you don't get it perfectly clean, consider to install a fine enough inline filter. The filter screen in the petcock is too coarse.

[galliononeNC]

Hello all,
Well bike fired right up again and was able to take her for a spin around the block. Upon return I noticed that the 1&4 pipes were hot but 2&3 not so much. After digging around my tool box for an 18mm socket that would fit I remembered the PO sent me a package the other week......it was the factory toolkit with "special spark plug wrench". So I started pulling plugs #1-4 all black and oily threads.....So now i guess its back to the manual for trouble shooting

[cgswss]

Don't care about the threads- what about the insulators (the white part in the middle).

So we gave you a lot of hints-what have you done so far?

[galliononeNC]

Well so far pulled carbs again and soaked. Traced leaks to #2&3 float bowls (gasket&orings kits in the mail), nothing with the tank right now using a surrogate tank for now. As for the insulators all black. Not sure what direction to take?

[cgswss]

The reason carbs normally leak is because they are over filling. If the fuel level in the carbs is correct the gas is all in the float bowel and the only leak would be if the drain screw wasn't sealing (then the fuel would leak from the bottom)

There is a breather higher up on the carbs. Normally these breathers are connected together with tubing. That tubing rots out. So if the carbs overflow, you get gas leaking out of the carb higher up on the side. This is why I recommend you clean the float needles and seats real good.

If the needles don't stop the gas coming into the carbs they will flood out and of course the bike will get way too rich. If the tube connecting the carbs don't have "t"s in them to a vet tube, one bad float needle can effect several cylinders. Bottom line, If you put your bike up on the center stand, and the float needles are sealing, you should have no leaks regardless of gaskets.