[dziebell]

Hello All,

I am putting the finishing touches on my CB360 build, and I started it again for the first time last night. I kicked it over a few times and it fired right up, however, the engine raced up to a high RPM immediately and I had to kill the engine before it over-revved. The motor is stock and ran fine prior to teardown. I swapped the stock airbox for a pair of velocity stacks, and the exhaust is a aftermarket 2-into-1 MAC setup, which was on the bike already before I started the build.

The throttle is functioning properly- closing completely and opening completely without binding in the cables. I turned out the idle mixture knob to it's outmost setting and tried again, but still the same thing. The bike is running the factory jets, which seemed to be fine with the MAC prior to teardown. I assumed I would have to up-jet it for the stacks, but I wanted to leave the jets stock for the first start to get a baseline, and then tune as needed. I thoroughly cleaned and closely inspected the carbs during the build, and reassembled without changing any of the mixture screws from what they were before I tore the bike apart.

Does anybody have any ideas why the bike would race up so high immediately after starting? Floats are set to spec, and there are not any leaks from what I can tell in the rubber boots between the head and the carbs. Would I have to change the mixture screw settings for the pods? Any suggestions are greatly appreciated!

 

[delineator]

by throttle closing completely, do you mean at the bars or at the carb? if not at the carb, try adjusting the linkage screws so that your throttle plates can close more.

 

[dziebell]

Meaning that my throttle opens and closes freely and with full motion at the bars and at the linkeage on the carbs. I did change out the throttle to an aftermarket one, so perhaps it changed the amount that it pulls/pushes. Definitely worth looking closer at tonight, thanks!

 

[delineator]

if you didnt mess with them, the throttle plate on each carb will have an idle adjustment screw that if your cables are too tight, these screws will no longer be resting on the body of the carb. loosen up the cables until those screws sit down again and it may be as simple as that. and then there is all the fun of balancing them and getting the mix right through the complete rev range!

here is a basic diagram:
Carburetor Adjustment

picture on the left is the adjustment screws that may be "floating". picture on the right is how to make your cable effectively longer or shorter.

 

[dziebell]

Turns out that with the new throttle that I had installed, the pull throttle cable was about a 1/4" short, causing the throttle to remain partially open even when the throttle grip was completely closed. I ended up removing a nut and washer where the cable attaches to the carb, and that gave me just enough slack allow the throttle to close completely. My throttle now opens and closes fully. THanks for the help!

 

[delineator]

no problem, glad it was as simple as that.