Topic: another cb550 carb question

[brianincc]

New guy here. I just picked up a 1975 cb550k with a little over 3k on the odometer.last time it was registered was 1980. I've cleaned the tank and the carbs. When I first got the bike I could only get it to run sparingly with the choke on,the second I tried to turn the choke off it would die.  I pulled the carbs cleaned them and bench synced them using the 1/8" drill bit method,set all my floats to 22mm. Now It fires right up and idles at about 1200 with the choke on. After it warms up and I try to take the choke off rpms climb to about 6000 and wont come down. I'm a bit stumped. I have looked for an air leak around the intake and found none. I am also running the stock airbox. Any help would be appreciated.

[reddyvv]

First, check to see if the slides close when you back out the idle screw. If you back out the idle screw and the linkage stop doesn't follow it, it means that you bench synced it with the idle screw screwed in too far so you don't have enough adjustment range.

Second, did you clean out the emulsion tubes? Also, the carb housing where the idle jets screw in is a larger diameter than the jet so there is an emulsion tube like effect there too. Make sure that area is cleaned out as well with an appropriate diameter drill bit.

[brianincc]

Thanks for the help. I didn't clean the emulsion tubes and I set the slide height from the wrong side of the carb.I pulled one emulsion tube and it was completely blocked. I will clean the rest tomorrow and see what happens. Noob mistake. II've made a few of those so far.
One more question. Do I need a fuel filter on both lines out of the tank?

[dave500]

the factory fuel filter in the fuel tap is plenty,unless you fill up at real #$%*ty stations with real #$%*ty fuel all the time?

[brianincc]

well, the problem persists.I pulled the carbs completely apart again and cleaned the emulsion tubes. I dont know how it was running at all. re synced the carbs and got her back together. It runs much much smoother but still does the same thing. It will run fine on the choke until it loads up but the second I turn the choke off the rpms climb up to about 6000 and never come down. runs very smooth however with no sputtering or popping at those rpms. The slides are closed, Im at a loss at what could cause this. throttle return spring is working fine.

[Kenzo1979]

This may sound like a stupid question, but are you sure you are pulling the choke OFF when the idle climbs to 6K and not in fact putting it ON?  Been known to happen, just sayin'.

[brianincc]

I feel like a dummy. Evidently I did have an air leak that wasn't showing up using carb cleaner around the intake boots. I pulled the tank and cranked down on all the clamps and BOOM
Runs like a champ. Fires off at a bump of the starter and idles smooth. Thanks for the help.

[Duanob]

There are also o-rings between the intakes and the head that over 30 or 40 years can get brittle and crack. But I'm sure you've replaced them as you've had the carbs off.

[fdbrat]

I love a happy ending