Topic: 1985 CB650 dead cylinder(s)

[fflier9]

I have a 1985 CB650 that I haven't ridden for about a year. It was running great then, and I'm surprised I'm having this many problems with it now. It runs like crap, and upon closer inspection (temp of exhaust headers) it appears cylinder 1 is not firing and cylinder 2 is firing intermittently. I changed the plugs and put in fresh gas with a splash of carb cleaner. Same deal.

It appeared the battery was sagging under load, so I got a new one. Didn't help.

The problem cylinders ARE sparking, at least outside the cylinder. I also changed the plug leads around from the two 'good' cylinders and it didn't change anything, either.


It seems that cleaning the carbs is the logical next step. I thought maybe something in there is clogged.

Could this be the problem?

Is tutorial somewhere for these specific carburateurs? I've been dodging this because I've never worked on bikes, nor carbs. I don't have many tools (except the basics, of course) and I'm a pretty poor college student, but I do want to get back on the road, and this bike is in great shape otherwise. If, somewhere, there's a tutorial on basic cleaning of these carbs if someone could point me over there that would be great. I do have the Clymer manual as well.

OR...maybe there's something else I should check first? Thanks guys, just trying to learn.

[fflier9]

Just checked, thin ring of soot around the lower part of the threads but dry. Smells of gas. Bike hasn't been run in 2 days though, and the plugs only have 15 minutes on them. Should I run the bike again, and check the plug in the bad cylinder right after running?

[scottly]

Wet and sooty, but in good shape.

Wet and sooty= fouled by too much fuel

[fflier9]

The old ones were definitely sooty when I pulled them out, but I just checked the new ones and updated my response to you.

[fflier9]

They were still sitting on the bench. Kind of sooty, and I'm pretty sure I remember them being wet with gas when I pulled them. Obviously now they've had time to dry. 2-3 years old.  These are from "problem cylinders", 1 and 2.

[goldarrow]

Get new plugs and run the bike, then report back

[fflier9]

I did, brand new plugs and it behaves exactly the same way as described in the original post.

[scottly]

What do the new plugs look like right after running the bike? The porcelain around the central electrode is the main concern. 

[fflier9]

I will test it tomorrow after work and report back. What exactly should I be looking for? Should I check all the plugs, even from the working cylinders?

The plugs may be dirty, too, because right now the bike won't run without choke. When the choke is removed, even after running for 5-7 minutes, it drops to about 1200 rpm and steadily decreases till it dies. Wouldn't really expect more for running on 2.5 cylinders

[scottly]

With clean plugs, if it won't run without the choke, you have a lean condition. The previous fouling may have been from over-use of the choke?

[fflier9]

Yes. This actually makes total sense. As I was fixing some things, I had to adjust the choke cable as all of the choke bodies were slightly open even with the choke "closed" on the handlebar. When I saw this, I had a flashback from winter in WI, extremely hungover and trying to get to class in 30 degree weather. Choke lever was stuck, I forced it, and it "popped". This, I think, was the cable slipping where it attaches to the carb.
I put it back, and now the choke closes completely, but the problems may be from the choke always being slightly "on", even with it "off" at the lever after that incident.

But then...shouldn't it have been OK with new plugs?

[scottly]

But then...shouldn't it have been OK with new plugs?

Yes, until they fouled again from the partially closed choke(s)... 

[fflier9]

But I replaced the plugs after I fixed the choke situation...or would that not matter?

[fflier9]

Does anyone know if there is a decent tutorial/guide to clean the carbs on the cb650? I think the carbs may be dirty and causing some of the problems. They haven't been cleaned for years and the bike has been sitting around a lot.
Do I need any special tools? Also, is there anything in particular I should check to see if its causing some misbehavior as described?

Thanks.

[cb650]

your might try the DOHC site or the nitehawk site.   They would be more familiar with your bike.   I have a 94 I'm parting out if you need anything.