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Discussion Starter · #1 ·
My 79 CX500C starts right up and I can take right off with the choke out. But if I push it back in, the bike will hesitate then finally take off. It will do this for a few miles then it seems to work itself out. It does great at around 70mph, then I can feel the bike to begin to hesitate at lower speeds. Can't really run the bike with the choke out all the time. Any idea what I can do? I've rebuilt the carbs, put new air filter in. It also pops during deceleration. Please help.
 

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I'm not the expert here but I'm pretty sure that your carbs are not COMPLETELY clean...possible didn't get all the jets done quite 100 % and that's quite common....sometimes it takes a couple tries to get them right as much of a pain in the ass as it is.



As for your popping on deceleration that's typically indicating that you need new air cut off valves.



Are you also sure that your plug wires and boots are ok ?...they can cause nightmares too.
 

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Discussion Starter · #3 ·
I put all new jets in the carbs, so I hope that's not the problem.
 

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Discussion Starter · #5 ·
I inspected the plug wires and had the boot apart and it all looks fine. The carbs probably need synched. Is there an easy way to do that?
 

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With the bike idling, spray some carb cleaner around where the carbs connect to the motor, the boots, etc. Could have an air leak. If you do, the idle will change when you hit the spot with the cleaner.
 

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Unfortunately, new jets seldom cure a carb problem. They really never wear out and can easily be cleaned. But those dang passageways under the jets and throughout the carb do get clogged and need to be cleaned out. A ultrasonic cleaner is the most effective for this, but soaking in Pine Sol, boiling in vinegar solution, regular carb cleaner and other home brew mixtures may also work. In any event, you need to visually verify that when you squirt carb cleaner in a hole, that it comes out a different place. Then completely blow out all the passageways with 100 PSI compressed air.



Sometimes it takes several tries to get them clean, but that may be the only solution to the problem. I would recommend getting Larry's carb cleaning book and reading and following his procedures.
 

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Sounds like your low speed circuit is too lean. How many turns out are your idle enrichment screws? The starting point is 21/2. If more than that is needed then what everyone has said about more cleaning may be where you are at.
 

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Your jets are clean, but did you remove and thoroughly clean the emulsion tubes? If not, then the jet-like small passages in them are likely partially occluded. Even a commercail ultrasonic unit (with a typical solution of, say, Simple Green), will not thoroughly clear petrified petroleum gum varnishes from these. There are plenty more of these small orifices throughout the carb. See Larry posts and cut-away diagram of the carbs. Good Luck!
 

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Discussion Starter · #11 ·
Looks like I'll have to take them apart and do a better job cleaning them. Thank for all your help!
 

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I'm not sure if you mean the bike likes to be richened up (choked) to run right...





I'm going to guess it's the crankcase airbox breather. Maybe not clogged or obstructed, maybe just not connected? If I understand the issue, it sounds like its sucking 2 much air to me.



Jasonh has mentioned a good way to look for air leaks. I'd at least check this before more carb surgery
 

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Discussion Starter · #13 ·
I will check for air leaks. Otherwise the bike runs great! I ride to to work everyday. 30 miles each way. I haven't driven my car to work in over three week since we haven't had any rain. What's nice about this bike, my son has an '81 CB750, his friend has an '97 Valcun, both are not currently running. My '79 CX500 is running great and really hasn't given me much problems. I'd just like to get it running a little better. I'll let you know if I find any air leaks.
 

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Discussion Starter · #14 ·
I'm not sure if you mean the bike likes to be richened up (choked) to run right...





I'm going to guess it's the crankcase airbox breather. Maybe not clogged or obstructed, maybe just not connected? If I understand the issue, it sounds like its sucking 2 much air to me.



Jasonh has mentioned a good way to look for air leaks. I'd at least check this before more carb surgery


It does seem like the bike likes to be richened up (choked) to run right. How would I check to see if its the airbox breather?
 

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You should be able to visually check the crankcase breather hose, just make sure it is clear and connected. I'm not sure that a clogged crankcase breather will cause your symptoms tho. Did you put the same number jets in when you replaced them? And as Phil mentioned, make sure the large number jet goes into the brass hex fitting.



If you have a minor varnish build-up, adding Seafoam to the tank may eventually dissolve some deposits. It certainly would not hurt to try that for a tank or two. Are your black rubber plugs in the float bowl secure? The spraying of carb cleaner that was mentioned my also point to an area that is sucking air. It doesn't take much to upset these carbs, so check everything carefully.
 

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Hi I'm new to the forum. I just pulled my bike out of storage after not being able to ride for about 5 years. I've got this same problem. I pulled the carbs and cleaned the jets...three times! It seems to be running better on the left cylinder than the right one.



Just wondering if you figured this one out. I'm starting to get a little frustrated!



Thanks!



-Matt

1980 CX500D
 

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You have cleaned the jets, but have you removed the emulsion tubes under the jets? And all the little passage ways that lead thru the carb? I would recommend getting Larry's carb book and investing in a ultrasonic cleaner. That may be the only way to get the crud out of some of these carbs.



And welcome to the forum.
 

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You have cleaned the jets, but have you removed the emulsion tubes under the jets? And all the little passage ways that lead thru the carb? I would recommend getting Larry's carb book and investing in a ultrasonic cleaner. That may be the only way to get the crud out of some of these carbs.



And welcome to the forum.


I pulled all the brass parts out and cleaned them using this as a guide. http://globalcxglvtwins.hostingdelivered.com/viewtopic.php?f=19&t=32



I didn't have any jet drill bits to clean out every air passage but I'm sure there is no obstruction in any of the brass parts. Maybe I'll have to break down and buy the ultrasonic cleaner and start from scratch.
 

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If you followed Larry's advice in that thread, you shouldn't be having any problems. But there may still be some crud in the internal passageways that didn't come out. I don't know a safe way other than ultrasonic to clean these out. Some use a dilute CLR to break up deposits, but you have to be careful with that stuff. I have tried boiling them in a 50/50 vinegar-water mixture on a gas grill for ten minutes and then rinsing them out. That seemed to work for me, but I don't know if I even had any blockage to start with.



Keep us informed of what you find.
 
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