Topic: '74 CB550 carb 'gurgling'

[Dimitri13]

When I first got this bike, the carbs were so dirty that it wouldn't run except on full choke, and wouldn't run without constant throttle and full choke while cold. But it ran.

Over the weekend, I cleaned and rebuilt the carbs. Right now I'm running open headers until my new exhaust comes in, and pod filters. After reassembling the bike, it wouldn't start, and I could hear gurgling in the carbs. After a few tries, it ran for a second, but sounded like a bubble machine.

The carbs are on stock jets, and stock a/f screw height. I've tried with the floats at stock height, and at the height I got the bike at (about 32mm). With the stock height it just dumped the fuel on the ground after a few kicks.

The electrics work, but I think the battery might be almost dead or underfilled. Could that be a factor?

[luap]

your gonna have to do some rejetting to get it to run right,

[eideteker]

Too lean, backfiring on the intake side?

[Dimitri13]

No backfiring, because no running. I'm going to get it rejetted as soon as my exhaust comes in, so hopefully that'll magically fix everything.

But I thought it'd at least run, but I guess not. (Still kinda new to the inner workings. First bike was a '11 Ninja 250, so no tinkering needed on that, heh).

[Danno]

bud it sounds like you need to put the float height back to stock it should have 38  slow jets and 100 mains but this is for stock resistence in the airflow circuit and the exhaust circuit if you have a foam aftermarket filter (not stock) or a K&N than you need 40 slows and if your exhaust is loose then 105 to 110 mains I have owned a 74 cb 550 for 27 years and can help you with any of your problems and if I can't then there is also two tired who can probably help but burbling is usualy caused by the needles and seats not sealing and flooding the carbs it wont run this way

you need to take each needle out and polish it with 2000 grit sand paper and make sure you polish the sides of the needles too
to polish the seats  in the carbs use a match stick or other small piece of pine and twirl it around and press hard on the seat while you do it till the piece of wood becomes the shape of the seat then put the needles back in but set the float height to stock

the 550 is very sensitive to rust in the tank clean it and or use a paper fuel filter baby powder fine rust particles can make the needles not close and dump fuel on the ground through the overflow tubes

if you have the seats absolutely clean and are sure there is no rust in the fuel and it still dumps fuel then you have a hairline crack in the overflow tube which can be cleaned and soldered or epoxied or replaced but I doubt you will have an easy time of finding them I usualy just clean up the metal and solder it with lead solder rosin core works fine but I have bad luck with acid core it works too well and can plug the tube

lastly the air screws if everything else is correct will be anywhere from a turn to a turn and a half out they may all be a little different as none of the needles are perfect you set them by looking at the plugs after it has been running at idle
white plug means turn the screw in black means out don't turn the screws more than half a turn at a time then run it at idle again and check the plug again I usually turn the screw about a quarter turn at a time in the direction the plug dictates

[Danno]

the 74 cb 550 will never run worth a damn on pod filters I seriously suggest that you get a stock air box for your bike I can get you one if  you need me too
the carbs for the 550 require still undisturbed air ...turbulance in the air flow will make them run inconsistent and like crap
plus the guidelines I gave you for jetting means nothing since for pods you will have to move the mixture needles up by moving each one of their clips down one and even with 45 slows and 120 mains it will still run like crap

if you want the most horsepower and the best ride of your life then unrestrict the intake and the exhaust jet it like i told you earlier and hold on and for more horsepower ask me

[Dimitri13]

Hey Danno, thanks for all the info. First thing I'm going to do is move up to bigger jets, and clean everything out even more thoroughly when I do.
While my bike is sitting, I'll probably do a de-rust and sealant on the tank.
I'll mess around with the air screws too, but I'd like the keep the pods (I'm generally not a form over function kinda guy, but in this case I'd like to make an exception).
If it won't run worth a damn I'll switch back to the airbox.

You said something about unrestricting the airbox and exhaust.. How is that done? Is there a how-to/DIY for it?

[Danno]

I used EVAPO-RUST on my tank with good results just dump two gallons in the tank let it sit over night then close a piece of plastic under the fuel cap to block off the breather in the cap and turn it upside down and let it sit over night again keep rotating the tank night by night till you are happy the rust spots will turn to what looks like spots of galvanizing and you will have no more rust to deal with I am even considering removing my paper filters since they have nothing in them now

to unrestrict the air flow just put an after market foam filter int place of the stock filter or a K&N
you must have an air box for good performance and power making on this motor with the stock carbs if you really want pods find some cv carbs off a cb650 they are not as sensitive to turbulance

to unrestrict the exhaust use any decent aftermarket exhaust like carpy's
or  remove some of the baffle material from the mufflers just enough that it is on the verge of popping but will not any more than that is too loose and will hurt performance not help it

some mufflers have restricter plates in them just make sure the last one is at least 7/8" hole

[Dimitri13]

Alright, sounds good. I should be getting my MAC 4-1 exhaust today. From the posts I've seen, it's a decent one?

CV carbs will probably come later on, but I'll keep it in mind.

Thanks for all your help man. If I was in MI I'd buy you a beer

[Danno]

Mac is good 4 into one is a little restrictive on this bike but it will work may need to cut the baffle in half but try it without cutting first

[Jv550]

+1 airbox over pods. It made a huge difference for my bike...

[Hush]

I had this problem, took me a while to remember what exactly was the cause, now I remember.
My carbs were flooding due to a small piece of fuel line rubber that had become detached and stuck under the float, it caused that carb to dump massive amount of fuel into that cylinder and then because the 650 carbs run across to each other it backed them up too.
Anyway that is what caused my "gurgling".