Bad running 1200I

[jdvorchak]

I understand your frustration. But remember those of us who do a lot of carbs often have to pull and tweak or clean them 3 or 4 or 5 times before we get them right. Never used a sonic cleaner. I prefer to do them by hand.

I have a very good friend that tried to clean his carbs on a 75 CB750 twice. Then took them to the local Honda shop and rented their commercial sonic cleaner for 45 minutes. Still running on 3. I used the ice cube trick to see which wasn't running at idle, #3 in this case. Pulled them one more time and found his idle jet on #3 was still plugged and the idle circuit above it clogged solid. I then pulled all 4 idle jets and cleaned them by hand. Did the other 3 need it? Don't know but I didn't quit until I had all of the gunk out every one. Idles and rides fine now.

Take a breath and pull them once more. This time make sure that you can get a good stream of carb/brake cleaner to shoot all the way through the jets with a solid stream. Use a magnifying glass to get a good close look at the jets. Pull those idle mixture screws all the way out and make sure you can squirt a steady stream all the way through the carb body. Visually confirm that each idle passage way is clean by squirting brake/carb cleaner through each hole and see that it comes out in the throat of the carb.

One more time please! You'll get them right.

[terry_208]

The last set of carbs I went through, I decided to save time and cleaned them 4 times before installing them on the bike. It was my cousin's bike and he said it ran great. I don't know if it really did or not as he passed before riding it.

[6adan]

Thanks guys I will keep at it.

[6adan]

Today I tried something I had not thought of before, I traded # 4 slide with # 3 and the problem went with the slide. It will now run on 4 but not 3. I can't see any problems with the slide or diaphragm. What could cause the slide not to work beside the diaphragm? I am going to try to find another slide now that I have found the trouble. Anyone have one they do not need?

[rcmatt007]

I would think only the diaphragm, but it may be a small problem difficult to see.

[6adan]

I hate to bring this back up. I thought I had found the trouble when I switched the diaphragm from 4 to 3 but no. I replaced the diaphragm but no change. This bike is not running on #4 at all RPMs. I have cleaned this carb several times with spray cleaner and ultrasonic cleaner and do not see how I have missed anything. Is there suppose to be a hole in the small opening by the screw hole? I have got to the point I just do not know where to go from here, any help would be great.

Thanks Dannie

[rcmatt007]

have you taking out the jets to clean them?

[6adan]

Yes! have taken everything apart several times. I am even thinking of trying another carb.

[ericheath]

What does the plug from #4 reveal, wet or dry? You said earlier good compression and you swapped plugs. Have you confirmed a healthy spark at the plug? If the plug is dry and has good spark, it must be carbs. Just suggesting this because you've looked pretty close at carbs. You have several wings, so you're probably aware of the resistors in the plug wires. Sometimes they can get pretty corroded. I'm not even sure 1200's have the resistors like the early models...???

[bthacker]

It sounds fuel related. Are you sure you are getting fuel into the bowel of that carb. Loosen the drain screw and see if you have fuel in the bowel. Have seen floats stick or the float put back in up side down and no fuel getting into that carb. You can also remove the air filter and take some starter fluid and squirt into that carb intake and see if it starts running on that cylinder.

[6adan]

Sorry I have not got back to everyone about this earlier but have not been dong much on it till I got a different #4 carb. It will now start and idle on all 4 carbs. Now when I ride it it starts out good but will drop a cylinder or two. I have never had this much trouble out of a set of carbs. Anyone got any ideas on this new problem?

Thanks Dannie

[salukispeed]

Missing or crushed manifold "O" ring?? Plugged idle circuit. . You could try a small directed squirt of starting fluid at the carb to see if it pops/runs then. Or possibly a small squirt thru the sync screw in the manifold. Be careful extremely flamable.