Weird Problem with Carb?

[Fstued]

I can move the acceleration lever on my carburetor at the carb and not see any increase in my RPMs. This doesn't happen all the time just every once in awhile. Very strange. Then in a bit the RPMs will kick in. To continue with the problem I can be in gear and moving forward at maybe 1200 rpm at 3 or 4 kph. Then I increase the rpm to 15 or 1600 rpm and there is no speed increase. I am guessing the clutch is slipping so I tightened it one notch and no change.
I rebuilt the engine last year and have 38 hrs on it. It was running fine just a few days before. Any one have any guesses on this conundrum
Thanks

[JOHN COOKSON]

Is the prop clean? Or maybe there is some garbage wrapped around it. Also is the stuffing box running hot while in gear? This would indicate the packing is to tight.
Try shifting into forward by hand using the lever on side of the trany. Maybe the trany is not fully in forward because the linkage is not adjusted correctly. or the trany nay need an adjustment.

TRUE GRIT

[Administrator]

In neutral, if you crank the throttle up sharply, does the engine RPM respond dramatically?

Try putting it in reverse and giving the engine a healthy shot of power. We have picked up a clump of grass which produced the symptoms you describe. A quick burst of power in reverse threw off the grass, and everything returned to normal. Years ago, it was an old tee-shirt. That one forced me over the side to remedy the problem.

HTH.

Bill

[sdemore]

Does it act the same in neutral?

[joe_db]

Have you got a helper, taken the flame arrestor off, and figured out if there is an actual mechanical issue with the throttle plate not moving correctly?

[Fstued]

I'll check the prop to make sure it is clean. I also remove the flame arrestor and check the carb throttle and make sure the linkage is working properly on the mechanical workings in the carburator. I really don't want to remove the carb. Thanks everyone

[JOHN COOKSON]

Check the control cables.
Take the trany control cable off and then shift into forward with both the cable and the lever on the side of the trany. See if the cable position is correct when both the control lever and trany lever are in forward.
When you are "messing' with the carburetor you are probably moving the control cable not the throttle butterfly.
Most of the time problems like this happen because the ends of the cable are not fixed down securely.*

TRUE GRIT

*Edit: Make that the ends of the outer cover not being fixed down securely.

[joe_db]

If the clamp that holds the cable onto the carb gets loose, the outer jacket can move instead of the inner cable that moves the throttle plate. Something to check
No that this happened to me.......that you know of

[Fstued]

Thanks for all the suggestions

I tightened the forward gear 2 notches and it seemed to do the trick. But I am concerned that the stuffing gland nut may be a touch to tight it was awfully warm down there after my test motor. It didn't seem to be dripping at all. So I think I'll give it a slight turn just a few degrees and see if I can get sa drip a minute or less
Thanks for all the help
Stu

[JOHN COOKSON]

It is important that the packing not be so tight that it generates so much heat that the shaft becomes scored. The packing gland should run at the same temp as the surrounding water.

TRUE GRIT

[ndutton]

Have you got a helper, taken the flame arrestor off, and figured out if there is an actual mechanical issue with the throttle plate not moving correctly?

I'll also remove the flame arrestor and check the carb throttle and make sure the linkage is working properly on the mechanical workings in the carburetor. I really don't want to remove the carb.

You can see the throttle butterfly by removing the flame arrestor? I don't know how. The choke, yes but not the throttle.

[joe_db]

D'oh! Of course you are right. You need to unbolt the carb and let it drop a few inches. The view is in from the top

[Bratina]

These two items point firmly to the packing gland binding up due to being massively over-tightened. Loosen it up substantially until it's dripping a few times a minute, then test the engine. If the symptoms go away then we've found our smoking gun.

Then in a bit the RPMs will kick in.


I tightened the forward gear 2 notches and it seemed to do the trick. But I am concerned that the stuffing gland nut may be a touch to tight it was awfully warm down there after my test motor. It didn't seem to be dripping at all.