The International CBX Owners Association

I've rebuilt the carbs on my '81, blew out the slow jets with compressed air & cleaner, sync'd the carbs with CarbTune. The bike idles smooth, revs smooth, but when I try to pull out from a stop, the bike stumbles bad, almost stalls. When I push the choke on 1/2 to 3/4 the way, it will accellerate. Once moving, I can pull off the choke and the bike flies.

Help!

accelerater pump? stock airbox or individual filters?

I'm using the stock airbox with a new filter. I checked the accel pump and it squirts.

If you have individual filters it's easy to remove them and pump the throttle to see if the accelerater pump is working.

vaccum leak ..did you check the intake boots real good

and where you connect vacuum lines to sync the carbs.

dan1995 wrote:vaccum leak ..did you check the intake boots real good

I also vote for vaccum leak.

Thanx to all who reply(ied).

The boots look good. No apparent cracks, very stiff, but not brittle.



Has anyone bypassed the vacuum thing that permits the fuel to flow?



What is the advantage to blocking the idle circuit?

by passing the vaccum to the petcock won't work fuel won't flow without the vaccum , however you could chang to a pingle petcock and do away wilt the vaccum one but remember to always shut the gas off when parked



as far as blocking the idle circuts i'm not sure what you mean ,you can't block them it won't idle

mc-nut wrote:Thanx to all who reply(ied).

The boots look good. No apparent cracks, very stiff, but not brittle.



Has anyone bypassed the vacuum thing that permits the fuel to flow?



What is the advantage to blocking the idle circuit?

mc-nut,



you can try spraying some engine starting fluid at your carb boots. If there is a bad vacuum leak, you will get a noticeable change in idle that will let you know the general area of the leak.

Just because you cleaned the slow jets it doesn't always mean you got the passages unplugged. The only way to know for sure is to blast cleaner through the passages and make sure the cleaner exits the other side of the ciruit, if you did this then the slow idle circuits aren't the problem and you could have a vaccum leak or a stuck slidder.



jb

Oops, I meant to say bypass or block the "air cut valve" instead of idle circuit.



Thanx everyone for your replies.

Ron

Jeff Bennetts wrote:Just because you cleaned the slow jets it doesn't always mean you got the passages unplugged. The only way to know for sure is to blast cleaner through the passages and make sure the cleaner exits the other side of the ciruit, if you did this then the slow idle circuits aren't the problem and you could have a vaccum leak or a stuck slidder.



jb

I ditto Jeffs' suggestion. I found these circuits difficult to test without blocking the primary pickup gallery, both ends, the secondary gallery (pausing to refresh memory back in one).



This is the way I cleaned and tested my carbs. From another post:



"To clean out any blockages in the carb circuits, I poked a bare strand of copper wire to into the small air and/or fuel inlets in each carb body. I used the copper wire because it is thin enough to get into the tiny holes and soft enough not to damage or enlarge the openings. It is also pliable and has the ability to "bend" into angled passageways allowing you to reach further into a circuit. You just put a tiny bend at the very tip of the wire and when you come to a stop point gently rotate and push on the wire to change direction and travel into the circuit a little bit further. It takes some practice, but it works a good deal of time. Starting with carb # 1 and going form 1-6 I methodically applied the below cleaning inspection process.



I started with the idle mixture jet opening into the venturi, I poked the copper wire through it then I shot carb cleaner from the needle side into the hole and watched for the carb fluid jet stream into the venturi. As a finishing touch I blew compressed air through it. Success, one circuit down. Next the tiny brass air jet for the main that sits under the black plastic jet cover at the base of the float chamber. I poked the wire into it, shot some carb cleaner into the opening and watched for the discharge through the main jet float bowl fuel siphon (pickup) shaft. A shot of compressed air into the brass inlet, and two circuits are done. On the side of carb # 1, under the air cutoff valve is the tiny brass air jet for the slow jet circuit. Once again, a poke with the wire, a shot of carb cleaner, discharge through the float bowl slow jet siphon tube, a shot of compressed air into the brass inlet and that makes three circuits clear and operational.



Under/behind the throttle at the base of the venturi are 3 tiny holes. To get at these I needed to make a special tool. I took a single small standard sized staple, I straightened one end, and then I locked the straightened end into an Exacto Knife blade holder leaving angled end exposed. I wedged the throttles open with a rubber plug and I, "GENTLY", poked my makeshift tool down into the three holes paying care not to damage/disfigure the geometry of the holes. In order to test these holes and the circuit(s) that feed them I needed to improvise some plugs to seal off the other large circuit openings. I happened to have a small rubber plug that fit the slow jet siphon pickup, for the two other large openings of the main jet circuit I use the cone shape rubber bumpers that are used in steel door frames to keep the door from banging into the metal frame. The cone part is pushed into a hole in the frame with a little rubber bumper sticking out of the back. The exposed bumper has a hole in the center. I twisted one rubber bumper cone into the main siphon pickup side and on the slide needle side I stuck a chopstick point into the bumper hole and used it to hold the cone in the venturi side slide needle opening. Once the three largest opening were blocked (I left the tiny brass slow air jet open) I shot carb cleaner into the tiny brass air jet for the main. The result was a stream of carb fluid up through the idle mixture opening into the venturi and also three streams from the three tiny openings under/behind the throttle. I covered the idle hole with a finger and re-shot the carb cleaner to double clean/check the three holes, three streams check done. To blow dry/out these holes I attach one of the Mytivac rubber accessories to the air hose nozzle. It looks like a tubular rubber right angled joint. I blew compressed air down into the three holes from the venturi side to blow out the circuits. Circuits four and five done. Carbs 2-6 six were done in a similar manner with the exception that the tiny brass air jet for the slow circuit for those carbs was on top of the carbs, under the float chamber, situated to the side opposite of the main jet.



Last but not least the accelerator pump circuit. On carb #3 float bowl side, the airbox opening side, almost on the edge of the right corner and in line with the fuel line joints, sits the opening for the accelerator pump circuit. This circuit presented a special problem in that the nozzles that spray the fuel into the venturi via this circuit are too small to wire clean. I didn't want to use compressed air to blow them clean because of the risk of jamming something permanently in the nozzles. I poked a single plastic bristle cut from a parts cleaning brush into the opening of the left and right fuel joint tubes as far in as its length would go to clear any blockage near the opening, if any. Next I shot carb cleaner into carb # 3 nozzle and the left and right circuits, there was no resultant spray or even a dribble through any of the nozzles. I had a brainfart and decided to press my lips to the opening and gently blow in the circuit and through the nozzles to get some of the carb clean through them, no resultant spray/dribble appeared. I got another brainfart and pressed lips to the opening and sucked hard. The result was a mouth full of carb cleaner and six clean nozzles all in one shot. Upon reflection I should have use a Mytivac, but I got the nozzles unblocked so a mouth full of cleaner was acceptable. I next sprayed carb cleaner into the center nozzle, left and right circuits with six very nice plumes as the result. Accelerator circuit good to go."

Thanx everyone! Especially the detailed instructions from Retrex.



I think I'll try the wife's new vacuum cleaner (while she is at work) instead of my kisser. I've tasted various carb cleaners over the years, but have never been able to acquire a taste for it.



I plan to work the bike over on Monday 10/9 as I have off from work that day (and the wife has to work). Will let you guys know what happens.



Any suggestions on how to effectively talk your way out of an extreme speeding ticket if I get this bike cookin'?

ask me in a month