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Discussion Starter · #1 ·
Hey everyone,

I've got a CB200 - got it from a gal in town that got it from a guy who had it for several years. She did a bit of work on it, but lost interest or ran out of money - who knows. Picked it up for $600 along with a box full of extra/old parts that she replaced. Was not running when I got it.

I cleaned some things up - petcock, carbs, slides, air filters, fuel filters, oil, etc.

I couldn't get good fuel flow to the carbs. I charged the battery overnight and could get the bike started, but it ran SO poorly and super rich. Could only get it started with full choke, then backed it off a bit to let it idle properly. Idled okay - pretty sputtery, backfired a lot when I would rev it. Lots of gray smoke and would sputter out when what little fuel was in the carbs was burned.

Replaced the fuel lines (clear now with clear in-line filters), replaced the fuel (it was a bit yellow - I'll be sealing the tank soon, but seems to not be an issue for now), set the carbs to factory. Set the valve clearance, adjusted/cleaned the points, adjusted the cam chain, new plugs and wires...

After doing all of that, the bike starts right up on the first kick when I pull the throttle a bit. Runs really nice and clean and smooth, but if I let go of the throttle, it dies instantly. Starts right back up like its new, but as soon as I let go of the throttle - dies. Rode it around the block a few times, for about 15 - 20 mins to warm it up (figured the idle speed and mixture screws needed to be set), but would die a lot as i was riding (remember, any time I let go of the throttle - dies). Got it back - engine nice and warm, set the screws to factory start - but I can't even get it to idle to make adjustments. If I'm lightly holding the throttle at about 1300 or 1500 rpms, idle speed screws have no effect, mixture screw has no effect...

I'm completely baffled.

I've re-cleaned the carbs 2 more times (upon the advice of other bike owners) - yes, taken them COMPLETELY APART, soaked for several hours, reassembled, etc. Jets are clean and shiny, floats are set to factory and functioning well. Fuel coming through is clear, filters are not clogged.

When I engage the choke, the bike dies instantly. For a while I thought the bowls were filling too high and flooding the engine - so when air was cut out, too much fuel was being pulled in, and cutting the engine. But bowls/floats are set. Air filters were old, and since I thought it maybe wasn't getting enough air, I took them off and put a pair of pods on - no change, so I took the pods off to try running it open to test - no change.

For a while I thought the throttle needle was set incorrectly and not allowing enough fuel in when the throttle was dis-engaged, but the needle is set to the highest setting.

Is there a chance that having the needle set to the highest (most open) setting would allow too much fuel in and flood the engine??
Is there a chance that my battery is dead enough that it can't keep it going at idle?? If so, why does it take virtually nothing to start it up?

I'm really at a loss of where to look next... any advice would be so helpful!!

If there are any pics you need to help analyze, let me know - I can snap some tomorrow after work sometime.
-W
 

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I've re-cleaned the carbs 2 more times (upon the advice of other bike owners) - yes, taken them COMPLETELY APART, soaked for several hours, reassembled, etc. Jets are clean and shiny, floats are set to factory and functioning well. Fuel coming through is clear, filters are not clogged.
I'd personally suspect the idle circuit being partially blocked, if adjusting the air screws has no effect. Main jet and needle position has no bearing on idling problems.

I subscribe to several magazines devoted to repairing old bikes, and there was an interesting article by Mark Brewin ( a well respected UK bike technician ) in one recently, in which he touched upon carb cleaning. He said that many folks clean their carbs ultrasonically, or soak / boil them in various potions, and end up with shiny carbs that look fabulous, but still don't work properly. Basically, he was saying that these cleaning methods don't always shift stuff that is lurking in the really tiny passageways in some carbs, and that mechanically cleaning, if possible, was the only solution. Guitar wire, that sort of thing.

I can relate to that. I cleaned a set of CL/CB 175 carbs several times in my home ultrasonic bath, they looked great, but failed to respond to the air screws, idle as such being achieved on the throttle stop screws. I swapped these carbs for a newer set of CB200 carbs, bike now idles much better, adjusting the air screws actually has some effect. Ditto my latest CB175, carb adjustment works as expected on that one.

I really ought to dig out my previous carbs, and try cleaning them again using wire.
 

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If you don't have and use one of these, you aren't cleaning the carburetor, other than cosmetically. I ALWAYS verify that a jet/passage is open visually by seeing a wire pass through, before I consider it clean. Be careful not to damage the jets, as I've seen deposits so hard that my ultrasonic cleaner couldn't touch in a couple of days of high heat operation.
 

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yep, carbs not cleaned.
 

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Discussion Starter · #5 ·
pulled the carbs and cleaned them out again tonight... i can see through all the jets, they are cleaner than when they were made new.

Was looking more closely at what my rpms are when it starts up - if I'm revving it to 2000 rpms, it holds nicely. I can get it down to about 1700 rpms at the lowest and it dies. Did TONS of meddling with the mixture/idle speed screws - but they really have minimal, if any, effect on things. I think I'll take the bike for a ride around town tomorrow to warm it up nicely, and I'll spend more time screwing with the idle screws.
 

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pulled the carbs and cleaned them out again tonight... i can see through all the jets, they are cleaner than when they were made new.

Was looking more closely at what my rpms are when it starts up - if I'm revving it to 2000 rpms, it holds nicely. I can get it down to about 1700 rpms at the lowest and it dies. Did TONS of meddling with the mixture/idle speed screws - but they really have minimal, if any, effect on things. I think I'll take the bike for a ride around town tomorrow to warm it up nicely, and I'll spend more time screwing with the idle screws.
Your slow and main jets may be clean , those are the ones that are removable you can see through them, the idle jet is pressed into the carb body its visible from the air filter skide of the carb intake.its passage goes past the idle set screw and ends up under the needle. Im with everyone else its still dirty
 

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There should be a small hole that is visible with the butterfly closed, that is the passage for the idle circuit (FYI, I have never worked on 200 carbs). Spray carb cleaner through it to see if it is clear. A completely clogged passage (sounds like your is) will not allow cleaner to get through and do its job so you might have to run a guitar string or something similar through it.
Not your carb but might be similar.
book.jpg
 

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My most difficult carb issue turned out to be a vacuum leak. If you have a leak nothing you can do with settings will do anything. You need to check all the places where vacuum can leak, starting with the gaskets and connections between the carb and the thing called an insulator (I call it a manifold) and between the manifold and the head. Make sure the surfaces are flat. I found a scrap square foot of granite from a countertop contractor, taped a sheet of fine sandpaper to it and rubbed the contact surfaces against the sandpaper. Make sure the ring gaskets are good or better yet replace them. Tighten them up gently, a little at a time, and maybe use a torque wrench so they are all tightened equally, so you don't warp them. Make sure the gasket under the top cap over the carb has a good gasket. You get the picture.
 
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