350 throttle problem

Throttle to engine speed response problem. With engine running, throttle in the first notch (low speed) I move it slowly to increase speed. It does not respond until you get to the 9th notch…in continuing to increase speed it does increase speed at every notch until you get to the high speed last notch. (Engine Off) I removed the side plate of the governor and adjusted stop screws per manual. I re-set both screws by several turns to get it to the specs. I then watched the movement of the “arms” in correlation with the throttle linkage…beginning at low end notch one and moving one notch at a time to increase speed. The linkage moved slightly each time the throttle moved one notch for the first five notches…from there on the movement was more noticeable all the way to the top end (notch 20). Engine Running, throttle on first notch I slowly advance to increase speed and get no increase until I get to notch 9…I then slowly continue advancing to full throttle and the engine responds accordingly. Then I rapidly (1 to 2 seconds) lower the throttle to notch 3 and the engine continues to run fast for approx 15 seconds and then the engine drops to idle speed in such a way that it dies. With engine running and throttle on notch 1 I rapidly move to notch 9 and the engine takes about 3 to 4 seconds to respond. The trials were repeated several times and no change in behavior.Ideas???Thanx

First thing I notice off the bat, the idle speed screw on the carburetor should be set so the engine will not die at idle. It should not be set so low that the engine dies.

You will never get true linear throttle response, so the "notch 9" deal is a red herring. Maybe fixing the slop in the throttle linkages will help this? The lack of governor response is something that definitely needs repair. Unfortunately I am the wrong one to ask about that...

Are the weights and springs intact in the governor? Does everything move freely?

My 350 doesn't respond till your almost halfway either. I just use it as it does not affect operation. Just assumed that's the way it is and have never thought about it.

Casey in SD

Your problem lies with worn parts. Starting with ALL the linkage and all the way down into the gov. Rebuild repair all the linkage and then ya get into the Gov. And once inside you will find that the spring has a bunch of slop in the holes of the arms inside , there is suppose to be hardened bushing in them big holes and NO slop . This past summer i rebuilt a friends 400 and he could not believe how much better it runs now. His kid was running my S/MTA and said how fast it responded to the throttle and he wished the 400 did that a few ours later and a quick trip to the machine shop to rebush the inside gov. arms it now only move one notch before something happens.

(quoted from post at 13:24:58 11/01/12) Your problem lies with worn parts. Starting with ALL the linkage and all the way down into the gov. Rebuild repair all the linkage and then ya get into the Gov. And once inside you will find that the spring has a bunch of slop in the holes of the arms inside , there is suppose to be hardened bushing in them big holes and NO slop . This past summer i rebuilt a friends 400 and he could not believe how much better it runs now. His kid was running my S/MTA and said how fast it responded to the throttle and he wished the 400 did that a few ours later and a quick trip to the machine shop to rebush the inside gov. arms it now only move one notch before something happens.

Click to expand...

I've been into a few where those holes were severely worn, to the point the spring was almost ready to break through. I welded the hole shut and then drilled a new hole, which fixed the problem, but I like the idea of the hardened bushings even better.

You can use bearing bronze or a harder steel and PRESS them in with .0015-0025 interference fit , Drill the hole a little bigger then the dia. of the spring wire then champer both side so that the spring is riding on about half the total thickness of the bushing and also allows for ease of getting the spring in the holes . Doing this cures idling down problems and also make the gov. work like it should .

On mine it is the roll pin at the throttle lever. Can't get it out and don't want to beat on it to hard or will break something.