Wisconsin AEH Over Revving

[SteveL]

Hello everyone, I have a confusing situation here. When I first got this engine a month ago it would start, and as I pulled the choke off and turned in the needle valve it would start to scream, running close to or over 3600 rpm. So I took the carb apart and found the butterfly screws were gone, and it was basically running wide open in all throttle positions. So I replaced the screws and put the carb back together.

At this time I also hooked up the governor. I set it so the plunger inside the engine would just be able to push the governor lever enough to close the throttle down to idle (when running and flyweights are spinning). I figured once I had it idling smooth and I would try some different springs from the governor lever to the throttle control, and see which works best under load at 3200 rpm.

I haven't got this far yet, because it still screams. The weird part is, if I turn down the idle, it speeds up! If I try opening the throttle it will bog down and try to stall. I've checked to make sure that I didn't install the butterfly backwards, it's not. This engine actually revs higher as you close the throttle. And I can't get to the point of actually closing the throttle completely, it just starts reving to high as I turn the idle screw down. And yes I've triple checked to make sure I am turning the idle screw down (counterclockwise). This doesn't make any sense to me, and I'm worried its gonna blow up if I keep playing with it. I pulled the carb off for a 3rd time tonight to make sure the butterfly valve is still there, and opening properly. Sure enough it is, but the engine still acts like its running WOT at idle.

Anyone have any ideas??? I am at a loss.

Thankyou in advance. --Steve--

[grub54891]

Major vacume leak?make sure all the gaskets are in place, including the head gasket, I've seen em run funny with a blown headgasket....

[SteveL]

It has a ton of compression so head gasket seems unlikely, but it's a possibility. Carb to intake might be leaking tho, I'll have to take a better look at it. Thanks for the suggestion.

--Steve--

[SteveL]

I checked it out this afternoon. No vacuum leaks I can find on the head gasket or the carb-intake one. I looked at throttle plate again, everything looks A-1. It operates smoothly with out any binding. Had it running again, and this time I was able to fully close the throttle. As I closed it by hand, it would rev higher and higher until the throttle plate completely closes. Then it would just stall. Opening it a little would result in it revving up as high as ever, and slowly closing it would do the same until I completely closed it. When its running trying to open the throttle makes it bog down, and I hear a lot of poping in the muffler, like unburnt gas igniting. Anyone run into this kind of problem before? I figure it must have some major carb issues. However I have no idea what to look for. It is a Zenith carb, with the updraft L shape to it.

Thanks for any input

[MoRo]

Sounds like a major air lead to me. Is there enought play in the throttle shaft to allow a lot of air to be sucked in that way?? I'd check it from stem to stern, as it were. I'm sure that your problem will be the last thing you check. Always is!

[SteveL]

Well it's running fine now. After tearing the carb apart, cleaning it out, cleaning out the needle valve assembly which was pretty rusty and crusty, adding new gaskets again, it started right away and purred like a kitten. A very loud kitten at that.

Thanks all,

--Steve--