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Discussion Starter · #1 ·
Hi all i have a cd 200 which is single coil single carb, but the problem im having is the left plug is clean white and the right plug is sooty like black powder that just wipes off ( not oily )
how can one cylinder run rich and the other lean ?

thanks in advance
Paul
 

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Sensei
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Difference in compression, difference in valve adjustment or sealing, and the directionality of the plug's spark, plug gap, conductivity or resistance of plug caps, defect/bad plug, etc......

Try swapping the plug wire sides and see if it changes.....IF no change, swap sides plugs are in...Post results...
 

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Sort of the same thing last couple times out, I'll swap plug wires and see what the results are also. A lot of variables there I wasn't thinking about. I had it stuck in my head that it must be the carbs. I have a fresh set of plugs so I'll make sure the gap is exactly the same and also swap wires. I have resistor plug caps but the only NGK 8ES the auto parts had was NGKR8ES that shouldn't matter should it?
 

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Sensei
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You are dealing with DOUBLE the resistance, which affects spark propagation timing... Not saying THAT is the problem, (it likely isn't) but it's not helping any......
 

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Sort of the same thing last couple times out, I'll swap plug wires and see what the results are also. A lot of variables there I wasn't thinking about. I had it stuck in my head that it must be the carbs. I have a fresh set of plugs so I'll make sure the gap is exactly the same and also swap wires. I have resistor plug caps but the only NGK 8ES the auto parts had was NGKR8ES that shouldn't matter should it?
You CAN NOT just swap the plug wires on a CB 450 K5 (You CAN, but it won't run)....
Each plugs ignition is separate, and controlled by its own set of points.....
IF you are certain it is timed correctly, your "carb" assumption has some merit.....
But I'd verify point timing first...Static, at idle, and at full advance (3K+)
 

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Sprint, it's a CD200, not a 450....
Regards,
Nigel.
 

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Yes Nigel..(and thank-you for speaking up when you perceived an error)...

The original poster's (Paul's) bike IS a CD200..... My original response was to him, and applies to his bike....

But, member CB450MWL jumped in with a similar circumstance and was going to take THAT advice and swap plug wires on his CB450... (To which it definitely does NOT apply)....
 

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Discussion Starter · #9 ·
hi all thanks for the advice i managed to fit in a compression test which came out at 130 psi in both cylinders - i'll check the valve clearences tonight and then try the plug cap swap to see what happens and i'll post results in the morning
 

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Is there an obstruction in the right hand exhaust?
 

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Thanks 66, I shouldn't have jumped in there like that, sorry. The only timing that I have done is static and it took me a while to get it right but it is or was, I guess it still is but I will recheck.
 

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Discussion Starter · #12 ·
hi all i had a night in the shed and checked compression 130 psi in both cylinders, checked valve clearences all spot on, ran engine for 5 mins then swaped HT leads, made no difference to right cylinder, swapped spark plugs, made no difference, the only thing i can think is that the inlet valve isnt sealing properly and is taking a small fuel charge when its the left cylinders turn, is this a sensible hypothesis ?
 

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Sensei
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Sorry, but no...There are two down strokes during the four stroke cycle...
One is the normal intake stroke, so the intake valve is open anyway.....
The next down stroke for that cylinder is the power stroke... Expanding, burning hot gasses under great pressure fill the cylinder...
If the intake valve (now closed) leaked, those gasses would enter the common intake tract and meet the fresh charge of fuel/air mixture the other cylinder is drawing in at the moment....

To verify or disprove my theory, you would have to run the engine several hundred miles with the plug wires swapped and fresh plugs...Five minutes is not sufficient.......

Mike brought up a valid theory... Is the exhaust pressure out both pipes the same?
 

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Discussion Starter · #14 ·
how do i check the pressure ? i do have aftermarket pipes on it which are much less restrictive than stock
 

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Cup your hands near the pipe's outlets.... compare heat and strength of out-flowing gasses.....Swap hand positions and re-compare (Your strong hand will register slightly differently than your weaker hand.....)...Judge if overall they are the same....
 
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