PlayDate
Well-Known Member
Kevin,
In order to eliminate the choke plate, there is a new enrichment jet that feeds a small reservoir that is cast into the carburetor. You will notice a small 3/16" hole on top of the carb that pulls air into a emulsion tube that mixes with the gas in the reservoir then injects it under the throttle plate.
This opening is then closed by a plunger on the carb after the tks module heats up from applied 12 volts(ignition on) and blocks enrichment fuel. This takes about 8 minutes for the plunger to extend, when the engine is at aprox. 130 deg. This seems consistent with your engine. There are no adjustments to this circuit other than replacing the plunger.
This TKS module is kept warm or closed by a separate circuit using a second water temp switch. So it won't add fuel when the engine is already warm.
You can hear the air intake hole hissing (the noise you identified) before it closes off with a pretty good suction because it's pulling a vacuum from under the closed thottle plate at idle.
I like carb engines for a lot of reasons. The engineering approach they took was to inject more fuel into the engine rather than by "choking" the air supply which is how a normal carb works. It also explains the rich condition that results from this approach for the first 8 minutes or so.
Looks like your friend was right. After talking to a couple other certified gearheads....TKS behaves this way. Some of them told me that the solenoid can go bad which results in the either hard starting or a constant rich condition (air passage never closes).
Hope that helps,
John
In order to eliminate the choke plate, there is a new enrichment jet that feeds a small reservoir that is cast into the carburetor. You will notice a small 3/16" hole on top of the carb that pulls air into a emulsion tube that mixes with the gas in the reservoir then injects it under the throttle plate.
This opening is then closed by a plunger on the carb after the tks module heats up from applied 12 volts(ignition on) and blocks enrichment fuel. This takes about 8 minutes for the plunger to extend, when the engine is at aprox. 130 deg. This seems consistent with your engine. There are no adjustments to this circuit other than replacing the plunger.
This TKS module is kept warm or closed by a separate circuit using a second water temp switch. So it won't add fuel when the engine is already warm.
You can hear the air intake hole hissing (the noise you identified) before it closes off with a pretty good suction because it's pulling a vacuum from under the closed thottle plate at idle.
I like carb engines for a lot of reasons. The engineering approach they took was to inject more fuel into the engine rather than by "choking" the air supply which is how a normal carb works. It also explains the rich condition that results from this approach for the first 8 minutes or so.
Looks like your friend was right. After talking to a couple other certified gearheads....TKS behaves this way. Some of them told me that the solenoid can go bad which results in the either hard starting or a constant rich condition (air passage never closes).
Hope that helps,
John
