Can anyone help.......after a Winter layup during when valve clearances were reset , cam timing set, carbs were removed and float chambers removed and cleaned out but carbs not stripped further, on reassembly when engine warms up revs stay high 2-3000 rpm have renewed throttle cable, balanced carbs, mixture screws 3/4 turn out and feel sure throttle is returning to stop but revs stay up. When cold and when running with the tank removed and running on a small independant tank throttle snaps shut very positively. Is there anything in the carbs or pipework that can hold the revs up that I am missing, the bike is an early model EK type with the early model carbs. many thanks Tom
running lean can have the idle hang can be caused by air leak in the boots between the carb body and the engine, having the air mix screws in too far (they should be very close to three turns out as your stopping point - not 3/4 turn), having a plugged/dirty pilot jet, having floats set too low
having the throttle cable improperly routed can have the throttle hang
having the choke cable improperly routed can have the idle hang
I'm not sure what you meant when you said that you "have renewed throttle cable". (Replaced? Lubed? Adjusted?) But if you disconnected it from the carbs at any point, you probably just reconnected it with too little slack. That's OK; it's a tricky adjustment to make ... at the
carburetor end of the cable. Luckily, there is another more accessible adjuster.
--------------------------------------------------------------
IF YOU DIDN'T DETACH THE THROTTLE CABLE FROM THE CARBS,
IGNORE THIS POST AND WORK THROUGH
mjm's LIST OF
POSSIBILITIES.
--------------------------------------------------------------
First, check to see whether the carburetor linkage is touching the upper end of the idle adjust rod (the knob at the lower end sticks down between the carbs). You can check this by
sound:
* With your ear next to the engine/carb area (engine OFF) twist the throttle just a fraction ... ON and then back OFF. You should hear a metallic "tick" from between the carbs as the linkage lands on the adjuster.
* If you're not sure whether you're hearing the "tick", turn the idle adjust knob IN until you do.
* Turn the adjust knob OUT a few turns, until you can no longer hear the "tick", and then a few
more turns.[/list]
Now start the bike. Make sure it's warmed up. If the idle is still high, the throttle cable is probably too tight. To introduce some slack into the cable (after turning the bike OFF):
*Locate the adjuster at the upper end of the cable
(http://www.bbburma.net/MiscFotos/CX7530_0553_ThrottleCableAdjuster.jpg)
* Loosen the lock nut and spin the hex-cross-section adjuster towards the handlebar, doing the "sound test" as you go. When you can hear the "tick" again, start the bike and check the idle. If it's still too high, turn the idle adjust knob OUT some more and introduce some more slack in the cable.[/list]
If you run out of threads at the adjuster before getting the idle to drop to a reasonable level, you have one of two problems:
1) The throttle cable is so tight that you need to reintroduce some slack at the carburetor end.
2) There is a problem in the fuel system itself that results in a lean mixture.
What we do next depends on your results up to this point.
Very many thanks for your help so far, will try out your suggestions this weekend and report back. Thanks again.