TOPIC:

But wait. Won't the throttle shaft only have vacuum on the intake side?

Thinking out loud; 2 ways to replace t-shaft seal 1) remove plates to remove shaft. Then concern with re-installing plates perfectly aligned and staking new screws. 2) grind-off the swaged end of shaft at linkage arm then "Tac" arm back on with mig ?

Slide a verrrry thin o'ring over linkage arm and have it fit between inside of arm and shaft boss. The problem with this is the need for the shaft to traverse slightly in order for the plates to fit the venturi-bore perfectly when closed. I measured the shaft end play to be .022" with the throttle open.

No conclusion here. Any light-bulbs ?

I would agree that there's a pressure differential across the shaft from one side of the throttle plate to the other but at all throttle positions including wide open throttle there will always be a vacuum inside of the carb compared to the outside atmospheric side which will always be trying to pull air into the carb past that throttle shaft/bore. Otherwise it wouldn't be able to pull gas out of the float bowl at wide open throttle. Makes sense??

I agree with you and Bruce that the leakage past the throttle shaft seal is negligible and usually the idle circuit is richened slightly to compensate for the leakage unless the leakage is such that there's not enough fuel flow in the idle circuit to compensate. That's why when I was at Chrysler, we had to check the throttle shaft clearance and replace the throttle shaft bushings if the wear was too much. (There was no seals on those shafts)

I'm thinking in this case Kawasaki put the seals in there to act more like wipers to keep dirt out of this area since they didn't fit the carbs with hardened bushings for the throttle shaft to turn in. They just bored the carb body and anodized the shaft.

I filed the staked end of the throttle plate screws off then removed the throttle plates. When I put it all back together, I'll do as Trike Builder suggests and red Loctite them back in. If down the road I need to remove them a little heat will destroy the Loctite and they'll come out easily. I probably did 30 carbs at Chrysler and never had a problem with the alignment or screws coming out.

scotch wrote: But wait. Won't the throttle shaft only have vacuum on the intake side?

Thinking out loud; 2 ways to replace t-shaft seal 1) remove plates to remove shaft. Then concern with re-installing plates perfectly aligned and staking new screws. 2) grind-off the swaged end of shaft at linkage arm then "Tac" arm back on with mig ?

Slide a verrrry thin o'ring over linkage arm and have it fit between inside of arm and shaft boss. The problem with this is the need for the shaft to traverse slightly in order for the plates to fit the venturi-bore perfectly when closed. I measured the shaft end play to be .022" with the throttle open.

No conclusion here. Any light-bulbs ?

From this burned-out bulb:

Yes, there would be vacuum only on the intake (engine) side. And, that vacuum is pretty strong, so it stands to reason why the plating is worn off just one side of the shaft.

Mig'ing it back on MIGHT cause too much heat on the new seal! Restaking the butterly screws or Loctite'ing them would be so much easier and safer.

An o-ring between the lever and the body would cause extra drag on the movement, too. Might slow down the return movement.

Kawboy wrote: I would agree that there's a pressure differential across the shaft from one side of the throttle plate to the other but at all throttle positions including wide open throttle there will always be a vacuum inside of the carb compared to the outside atmospheric side which will always be trying to pull air into the carb past that throttle shaft/bore. Otherwise it wouldn't be able to pull gas out of the float bowl at wide open throttle. Makes sense??

I agree with you and Bruce that the leakage past the throttle shaft seal is negligible and usually the idle circuit is richened slightly to compensate for the leakage unless the leakage is such that there's not enough fuel flow in the idle circuit to compensate. That's why when I was at Chrysler, we had to check the throttle shaft clearance and replace the throttle shaft bushings if the wear was too much. (There was no seals on those shafts)

I'm thinking in this case Kawasaki put the seals in there to act more like wipers to keep dirt out of this area since they didn't fit the carbs with hardened bushings for the throttle shaft to turn in. They just bored the carb body and anodized the shaft.

What I was saying is that only half of the area around the shaft, when there is leakage, is actually contributing to unwanted air getting into the engine, especially at idle, where it is most critical.

Wow ! My dry sense of humor evoked quite a discussion. The anodizing being worn off the shaft is likely as much from the asymmetric force applied by the return spring as the force of vacuum. It sounds however that a consensus may be leaning toward just leaving the shaft and seal as is as long as there is no lateral movement and providing settings will hold.

Just curious: Do you "Injected" guys have equivalent issues and problems ?
I know carbs - I know nothing about "Injection".