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Motorcycle Forum / General / Technical / June 2007CM450 carb problems
its an 1984 honda cm450e. it has VB22 carbs (CV) I'm having hesitation/stuttering at about 1/4 to 1/2 throttle. the carbs have been professionally cleaned and synced. the slides move easily in the bore. once past this "stuttering" it runs fine. i just had the carbs apart again to doublecheck and couldn't find any dirt in the jets. these aren't the original carbs for the bike but every jet has been properly sized as per the service manual. what am i missing?? thanks. > its an 1984 honda cm450e. it has VB22 carbs (CV) I'm having > hesitation/stuttering at about 1/4 to 1/2 throttle. the carbs have [quoted text clipped - 4 lines] > has been properly sized as per the service manual. what am i > missing?? thanks. Weak spark. Ed Cregger >> its an 1984 honda cm450e. it has VB22 carbs (CV) I'm having >> hesitation/stuttering at about 1/4 to 1/2 throttle. the carbs have [quoted text clipped - 8 lines] > >Ed Cregger spark fat and blue, new plugs, coils measure fine. >its an 1984 honda cm450e. it has VB22 carbs (CV) I'm having >hesitation/stuttering at about 1/4 to 1/2 throttle. Are the spark plugs all covered with fluffy black soot? If so, your problem is rich idle mixture, caused by: 1. Incorrect idle mixture screw adjustment. If the idle mixture screw is turned out too far, the idle mixture becomes too rich and the inexperienced mechanic turns the master idle knob up to compensate for slow idle RPM. This uncovers the transition ports downstream of the throttle butterfly and the engine get a rich mixture and fires every other stroke, This is called "stuttering" or "8-stroking". 2. Float level set too high. The engine is able to suck fuel out of the float bowls too easily and the engine stutters until the excess gas is cleared out. 3. Float valve sticks, making the float level too high and the idle mixture to rich. >1. Incorrect idle mixture screw adjustment. If the idle mixture screw is >turned out too far, the idle mixture becomes too rich and the inexperienced [quoted text clipped - 8 lines] >3. Float valve sticks, making the float level too high and the idle mixture >to rich checked the plugs, the tips are light gray in color and the insulator is a very light brown. . >checked the plugs, the tips are light gray in color and the insulator >is a very light brown. That indicates that the heat range is correct and the engine is running good. Are there any little little black specks on the insulator nose after hard aceleration, once the engine stops "stuttering" and runs good? Black specks indicate preignition before the actual spark. > >1. Incorrect idle mixture screw adjustment. If the idle mixture screw is >>turned out too far, the idle mixture becomes too rich and the [quoted text clipped - 16 lines] > checked the plugs, the tips are light gray in color and the insulator > is a very light brown. # The plugs will clean up ok if it's only fouling occasionally. You'd need to drive the bike for a while at the throttle opening that's causing the problem and them stop and check plugs. John. |
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