I type with two fingers and usually have to backspace 50% of what I have already typed. So here is the general idea.

All 4 cylinders need to have the same strength. To do this, the best way is to measure the vacuum on each intake between the carb and engine. In theory, this will cause each cylinder to have the same fuel intake if all else is even. The butterflies on each carb is adjusted to achieved this balance.

OK, lets say one or more cylinders are week. This would be the ones with the highest vacuum readings because the butterfly for that carb is to far closed and in return cause a higher reading because less air/fuel mixture is filling the intake. For those week cylinders, they will be running lean and hot.

The butterflies that are to far open make for a strong and rich burn and have low vacuum readings because they let more air/fuel mixture in to
lower the vacuum level in the intake.

On some out of whack bikes, the rich mixture is not all burned and fills the head pipe where it is lit by the hot lean cylinders and the bike pops. The popping is what is heard when the mixture explodes and occupies more room when expanded. This expansion causes a blockage and stops more spent gasses from leaving the engine and this in return hurts performance.

When the carbs are way out of whack, the strong cylinders are pulling the week ones and the engine shakes or blubbers. The engine fires every other time it comes to TDC with a 4 stroke. The other times the opposite cylinder on the crank fires while at TDC. So every 180 degrees, on a 4 cylinder with 2 pairs each 180 degrees out on the crank, the engine get a strong or week fire and the engine shakes due to the unbalance.

The strong cylinders are acting like the throttle is open and the week ones are as if you are backing off the throttle, much like engine breaking. This is why you get uneven idle. Cold starts are hard because not all cylinders are working strong and the week ones are to lean for the cold start. When taking off from a dead stop, the strong cylinders are not only trying to move the bike but also dragging the week ones causing loss of power. The week cylinder are doing noting but robbing power at low speed RPMs.

If you take the bike out and run it at full throttle, all cylinders will be pulling hard and you may not feel that they are out of whack. It is mostly when you are going through town at low speeds and the bike starts to surge and hop that you know they are really whacked out.

When you adjust your valves you are either tightening or loosing them. This in turn changes their timing as they will open sooner or later and that will effect the vacuum in the intake. So if you adjust your valves, it's a good idea to check the sync of the carbs after.

When installing a 4-1 header, they work by creating a free supercharge, by pulling spent gasses out of other cylinders. This loss of restriction causes less back pressure and in some cases cause the carbs to go out of sync as well.

EDIT: There was a lot of back spacing going on there. (I even had to do backspacing on the freaking edit)

 

Thanks TimbucTwo. I didn't even have a vague understanding of how carbs functioned, even in principle. That gave a little more insight.
Here is an update to those offering help:
I have the fairings off now and am looking at it.
I filled up the coolant tank, and tried starting it up:
After a few seconds (15-20, which has always been normal for this bike, for me anyway)
It started up. As it warmed up, I sprayed just a little starter fluid near the air intake, which gave a little power surge to help it warm up. As it did, I was also able to turn the (choke?) **** counterclockwise a bit to let the bike idle at a lower rpm.
After a few revs of the throttle it seems to be somewhat responsive again, like it used to be, but every now and then it still pops, which I'm sure is due to the wacked out carb balance that TimbucTwo is describing.
I think I will proceed by trying to address the imbalanced carbs.
I think this thread is now firmly off topic, and I will follow up in the appropriate forum category next time.
Thanks all,
Nick

 

Nick, off topic off smopic, who cares as long as we get results. That's what forums are for.

I am currently sitting in a hotel room in Kansas after working a 12.5 hour shift (6:30PM-7:00AM) with a 1 hr drive on each end. I would describe the working principles of carbs but, I don't think so at this time as the Merlot is flowing at a steady rate.

I can't remember if you said what kind of pipe was on the bike. An open or less restricted pipe would not have the standard back pressure and cause some popping at idle but, it is still a good idea to look at the carb sync.

Good news to hear that she is running. Non-running bikes are the devils work.

 

Alright guys, I'm back.
I had bought a 4-guage carb synch tool off of amazon.com for about 70-80 bucks, using that, spent about 2 hours continually hand-pumping the fuel pump vacuum with my mightyvac, so that the engine would continue to run, while making tons and tons of tiny changes so that all of the needles would align.
Convinced that it was all done, put the bike back together and started...
No real change in situation.
I plan on taking apart the carbs again (for the third time) and giving it one more shot at paying extra careful attention. I think I will also take pictures along the way and ask questions about things.
I toyed with the idea of saying "eff it" and take it to a mechanic to fix it, but after a few calls to find out labor rates, I'd easily end up spending upwards of 300-400 dollars for a "6-hour carb clean job" @ about $85 an hour This one place (mungenast motorsports) told me 699 PER HOUR for labor.
If I can't get this horrible situation figured out soon, this bike will live the rest of its days with a tarp over it, only to later be carted away, while I go ahead and try to find a newer bike.
Holy crap! I've spent so much money on a bike that doesn't run properly lately: carb synch tool, stator, 3 regulator/rectifiers, that I don't know what to do!
It has been more maintenance than my girlfriend that I live with, who also has two kids from a previous relationship.
Bah, there goes my ranting again.
Anyway, I'm hoping to get around to spend time taking apart the carbs completely this time.
My fear is that there is something wrong or that needs replacement/repair that will cost me MORE money, and I may be better off getting a newer bike.
Anyway, I'll post again, after I do what I can

 

I haven't been reading the 18 page previous topic, but... have you made sure that there is a 100% good ground connection from the battery to the frame/engine, from the frame to the coils, and from the plugs to the engine?
I'm no expert on bikes or carbs, but I've learned from several cars that a bad ground cable is very likely the reason for a bad start and sh!tty running engine, and some people have applied teflon tape to their plugs' thread...
You could also check all other ground connections you can find in the wiring loom.

My 2cts. about selling or keeping the bike... if you like another bike better, and think you can afford it after a bit of saving up money, stop investing in this bike.
Sell it (after trying to fix it without putting money in it, a running bike sells for more money) and put the money aside for the replacement.
If you're a bit like me, and by the tone of your posts you probably are, you've put so much effort/time/money in this bike without yielding satisfying results, that you've probably lost your confidence in this bike by now; I myself would not be able to fully appreciate it anymore, even when it's running fine.
You're just spending your time on the bike trying not to think of 'what else will break now?'.
With me, this feeling will not wear off, I've sold a few cars in good working order that have given me this feeling, but only one broke down (in an expensive way I might ad) within weeks.
Decide for yourself, how much do you like this bike, or do you feel you want something new/newer?

 

Hi 93 cbr, When I bought my bike it wasn't running and the carbs were hanging off so I attached them and tried to start her. It would start but was making all the noises you mentioned and had no power, so I took the carbs off and cleaned them. The jets were blocked and needed cleaning out and I suspect this is maybe your problem.

Did you take the jets out and check them when you them apart?

 

Checking back on this thread again and in reading down through it the only other issue
that might be of major concern would torn and or perished carb diaphragms !

Just thinking out loud !

 

With the carbs, you will get much better at taking them apart and putting them back together with time. I bet I can do it in less than 2 hours now and I have only been riding a hurricane for 2 months

I fyou crack them open and put them back together and get the bike to run again, you are most probably doing everything properly. The things to check in the carb are the little jets and tubes. Force carb cleaner through all the little holes you can find, and the 'jets' are the brass tube/pipes kinda sticking our of the bode (the dangle into the carb bowl.

You should be able to unscrew these with a flat screw driver and look through them. pike a bit of fishing line or a small needle through and spray the cleaner through them. also, one of the tubes will have cross-drilled holes. I dunno what they do but I poke things through them too...

then check the black rubber thing. it shouldn't have any holes. this is what seals off the 2 chambers to make the vacuum in the carb do it's bit. depending on engine speed the vacuum pulls the black slider up and down and moves the tapered needle in and out of it's jet (this is the main jet I think). As the needle tapers, the whole gets bigger and the air flowing through the carb pulls more fuel into the engine. So make sure the slide is clean (and slides freely) and the needle is straight and clean.

The last thing is the idle mixture adjustment. My knowledge of this is even worse than my general knowledge of the rest. I can't quite remember where this lives in the CBR carb, but it s basically a spring screw that screws into a tiny passage that allows fuel to get sucked into the airflow, bypassing the main jet. you can take it out and spray cleaner through the hole and make sure the tip of the screw is clean (it has to seal the hole).

To reinstall the idle screw, screw it all the way in (just seat the screw, not tight) then screw it out 2.5 turns or so. You can count the turns-to-seated before you un-install them if you remember...

once you put it all back together you can be confident you have a functional set of carbs, then you can put them in and try to tune it.

If you didn't touch the synch screws, then you should be able to start it as is, if not bench synch them to get them pretty close. (that's the drill bit under the butterfly thing.)you just need to set them so that each butterfly is open the same amount.

Once you get it running the 2 things you can change are the idle mixture screws and the synch screws. to synch you use the gauge (it should have instructions) for the idle mixture, I once read you should let the bike warm up, and then turn them a bit each way and listen for the idle to rise or fall. Find the point where the idle is the highest on each carb, then set the idle back down to 1000 (with the idle adjust ****) and then tweak the screws again. I guess the best mixture is where the idle is the highest...

Sorry this post turned out to be a bit of a brain dump. I started of just wanting to give cleaning tips then kinda talked about the inner workings and didn;t really get either right. I blame the fact that I am at work and keep getting interrupted by things I am being paid to do...

Stupid work.

I'm with the others though, a bike like this needs love, you need to be able to give it a bit more time than, say. a 2009 model bike. If you have the money and are lacking in time then upgrading would be easier.

By the sounds of things you should be able to get this one working well easily enough, parts are easily shipped to you from wherever if needed, and on the plus side you learn all sorts of crap about mechanical stuff!

Tim.

 

The tubes Tim is talking about are "emulsion tubes"
Nice write up Tim

Simple answer
Jets aren't functioning correctly, I think.
I'd buy a can of Wynns injector cleaner and run it through the bikes fuel system, in maybe half a tank of gas.
If it's still making strange noises, do a full strip and clean of the jets.
Then sync them again.
MAKE SURE ALL THE CLAMPS ON THE INTAKES TO THE ENGINE ARE LEAK PROOF

Let's hope you find it before we get to 18 pages again
A bit like reading "War and Peace" esp when the answer was in the first 2 pages