Surging engine

Hello All! I have a Gravely 252Z with a 25hp Kawasaki engine. The issue is that the engine runs fine until the mower is engaged, and then the engine will surge and slow, repeatedly; if I don't disengage the mower, the engine will eventually die. If I disengage the mower, the engine will continue to surge and slow for several minutes before eventually running normally. Then, if I engage the mower, it will run for just a little while before the slow/surge cycle repeats. I've been battling this all summer, trying several things to repair it. There is no vacuum in the fuel tanks. So far, I have replaced: the carburetor, the fuel lines, the fuel switch (there are two tanks), the coils, the spark plugs, and the fuel filter. Nothing has fixed it. What's odd is that it only starts surging/slowing when the mower is engaged, but also continues to do it for several minutes after disengaging the mower until it finally settles down. I am at my wits end. Anybody have any suggestions (other than to buy a new lawnmower)?

Have you checked to make sure the fuel pump is pumping good? Also check governor springs and linkages.

Ckn087 said:

Have you checked to make sure the fuel pump is pumping good? Also check governor springs and linkages.

Click to expand...

The fuel pump is fine, but other than just a visual check of the springs controlling the carb valve, I haven't done anything with the governor. Do you think it could be the governor, when it won't surge without the mower engaged? I ran it for over 20 minutes today without the mower engaged, and it didn't hiccup once. Then, as soon as I engaged the mower, it started surging and eventually died.

https://www.google.com/search?q=how...me.0.69i59.27227j0j4&sourceid=chrome&ie=UTF-8

Are you at full throttle when engaging & disengaging PTO clutch? If yes check air gap at PTO clutch 3 places, should be in your operators manual. Set gap to .015 with feeeler gauge.

I wouldn't think so. Check the pto. I hadn't considered that. Most of the time, surging is a fuel related problem from my experience but it could be elsewhere.

Also, make sure all the spindles are spinning freely. Just unhook those plug wires first for safety. If one of the bearings was dragging it could cause that too I would think.

Thanks guys! At least now you've given me some more things to check. Better than being at a dead end!