Carbs stumped me again

[5.4L to Freedom]

I've been reading a lot of the other carb posts, and this is similar but different issue. I have the CV carbs on a bone stock 650. Season after season this thing has been incredible... but this season its not so incredible.

Carbs are perfectly in sync, jets are perfect, choke functions perfectly, and from an inspection standpoint looks great. Last Friday around midnight, my friend and I set off on a 400 mile round trip ride and her Honda Nighthawk has started causing grief.

On the return portion of the trip I noticed severe carbon smoke (black streams) coming out all 4 exhaust pipes, however much heavier on 3&4 than 1&2. Its mileage dropped from 125 miles per tank to right about 80, and has a VERY VERY weak top end. (cannot break 65mph or it starts surging and then lots of black smoke pours out)

The black smoke indicates a super rich condition, but the jet sizing and all that is perfect. What could have gone wrong that would cause a perfect set of carbs to all of a sudden go mega rich from idle to redline?

I dont know these CV carbs thru and thru... they are much different than my Bendix Zenith. On the zenith a bad accelerator pump and worn needle and seat would cause this phenomena, but 4 needled and seat failing at once? Could this be a result of bypassing the vacuum on off?

Also the airbox is saturated with what feels like gasoline and dirt? If the floats, needles, and seats took a dump could gas flow up into the carbs and into the airbox?

[cb650]

If you have the stock airbox try removing the cover on the filter.

[Volker_P]

E.g. a piece of cloth in the airbox or fallen out main jets may case this kind of trouble. Maybe choke (both or one half choke cam) hanging half open due to spring failure.
Or just half a gallon of diesel fuel.
If you overfill the engine with oil, the airbox may get flooded with oil and block the air filter. However a slight, glibbery gasoline/dirt layer everywhere in there is no reason to worry.
Bypassing the shutoff should have no effect provided you closed the vacuum hose. Could be possibly tricky in case previous adjustments were done with a leaky hose. In any case, look whether all hoses are in place and intact, maybe just one fell off.
Also check whether the tank vent is free. If you don't find something suspicious, have a look on the plugs whether they all look equal. Maybe it runs only on three now.

[5.4L to Freedom]

I tried the airbox lid and removing the air filter completely... it actually made it worse, other steps is reaching in and verifying the choke is open all the way (like I said the bike dont need a choke to start) and I can feel loads of heat coming out all 4 pipes. Looks like the carb rack is coming off... could a bad needle and seat do this?

[Volker_P]

So it directly occurred after the vacuum valve removal or what?
Forget about regular wear, that's something for several thousands of miles. Main jets falling out could be an option for a sudden change. If you fill in ethanol, some seals might fail quickly and have similar effect but carbs would probably leak like hell then, too.
As you were not the lucky guy with regard to PO manipulations at your own CB also consider that a PO might have tried to compensate a partly defective shutoff valve by significant manipulations of the carbs or so. This means check sizes of jets and needle positions and keep an eye on traces of manipulation (like e.g. reamed jets).
Another thing to look for is whether camchain might have jumped over one tooth.
Do all four pipes get equally hot?

[5.4L to Freedom]

Well new findings/ and response to previous post:

Previous post follow up:

-Yes, all 4 pipes get equally hot
-The PO very well might have reamed the jets because these carbs show signs of molestation

New Findings:

-I pulled the carb rack and all jets and accelerator pump look good
-I don't know what they are called but the cap for the slide in each carb was horrendously dirty... could this cause a rich condition?
-I pulled 1 quart of dirty nast oil out of the air box. My only thought is blowby, but who knows? I do know the carbs sucked in a good amount of dirty oil because there are black streaks thru them.

How I missed a quart of nasty oil in the airbox I do not know, but yeah, seems a little much for blow by on a good running engine... ideas?

[Volker_P]

Oil overfill could cause flooding of the airbox with oil. Afterwards the air filter might be soaked with oil. As you tried without it, seems you have other or additional problems. Dirty oil in the carbs is bad and suspicious. It may block channels, so I propose to blow them through and clean them out with clean fuel or solvent. In case of permanent blow by of that amount, it should smoke at least like a two stroke.
Blowby of that amount would mean quite poor compression, are you sure that the oil level is and always was correct (maybe wrong dip stick?).
Changing from high weight mineral to low weight synthetic oil might be another option to produce your problem.
Or fuel leaking into the engine somehow, possibly from mixing up hoses as you removed the shutoff valve. Have a smell at the oil fill opening to verify.
I could also imagine the head gasket blows through a bit to the camchain tunnel. This would also explain the oil in the airbox. A crack in a cylinder could do the same. A compression check could clarify these points before tearing apart the engine.
I hope it is one of the harmless options.

[5.4L to Freedom]

Well last night I pulled the carbs off and thoroughly cleaned them. I do not know the compression yet however as smooth as the engine ran it definitely doesn't have a major ailment such as cracked cylinder or blown headgasket.

However once I got the carbs all cleaned up and put back on cylinders 2 and 3 died. I tested the cv slides worked beautiful and all the boots between intake and airbox are sealed nice and tight.

I also checekd oil smell and it smells great, talking to the owner she said when she bought it it had way too much oil in it... about 3 quarts to be exact. Where it went in there I do not know... I thought the case only held 4 before overflowing... but ehhh I didnt drain tht oil out of the motor so it could be an exageration.

Anyhow, what does this indicate to yall?

[5.4L to Freedom]

So no ideas why a CV carb would just 'die'? I've checked plugs and everything. I know the carb is clean and all is proper... that I can see. Can a carb sync fix something like this?

[Volker_P]

If slider positions/gaps are optically equal, the engine should run all right. At least mine did and still does that way. Vacuum gauge synchronization is only fine tuning.
Simultaneous failure of 2+3 might be related to an ignition problem. Possibly dependent on temperature.
Do you mean three quarts all in all or really three quarts of oil too much? Because this would mean about twice the usual amount of oil and certainly this will end up in oil at some places where you do not like to have it at all. May even cause severe mechanical damage due to hydraulic effects. I won't be surprised if the alternator or the pulse generators swim in oil now or so. BTW, a good explanation where the oil may has gone.