I Need help adjusting carb on 2160 Cub Cadet

[Altair 4]

Last summer, I had to install a replacement engine on my Cub. The new engine, the same as the original - a B&S 16 hp Vanguard, ran very well for about ten hours. Then it developed a "vrruumm - vrruumm" idle, where the idle speed is hunting up and down. This occurs at any throttle setting and can only be eliminated by pulling out the choke about 1/2 way. I'm guessing that one of the carb jets is obstructed.

I've tried a number of carb cleaners including several doses of Seafoam in the gas tank. No improvement was noted.

So. I'm reaching the point where I need to manually try and adjust the needle valves to clear the debris. Bt I'm not sure exactly where these are - are they capped? Are the caps easily removed? Any suggestions on locating the jets on this thing would be appreciated. I'll post a picture later.

 

[OldMachinist]

Most likly the debris is in the main jet. This is the brass screw on the bottom of the fuel bowl on the carb with a 1/2" hex. Turn off the fuel and remove the screw and soak it in carb cleaner. Don't use anything sharp or hard to clean out the jet holes it will change the jetting. There is a cross hole that intersects the hole in the middle of the screw that clogs up. Take the fuel bowl off and clean it also. This should take care of it. When your not going to use the mower for longer than a couple of weeks turn the fuel off and run it till it dies to drain the carb and you shouldn't have this problem again. The fuel today with alcohol in it absorbs a lot of mosture and goes bad real fast.

 

[Altair 4]

I had a chance, between rain and my schedule, to take a better look at my carb. I'm trying to understand what I'm getting into following your instructions.

Here are some pictures of my Nikki carb:
Left side:

Right side:

Right rear quarter view:

Lower right side (with brass cap):

Is the main jet hidden under the brass plug in the final picture? Thanks for your continued help!

 

[OldMachinist]

I'll have to go out and look at a Nikki carb I have out in the shed. The carb I described above is different. I'll get back to you a little later today.

 

[Altair 4]

You are the man! Thanks for your help - I'd like to get this solved, but I need good directions before I screw it up worse than it already is. I'd say right now that I only have about 12 hp available, which isn't much for a 46 in deck.

If I can't fix it, it will have to go into the shop and I don't relish that idea - the cost alone for pickup/delivery is going to make me cringe!

 

[OldMachinist]

Okay the carb I have is a little older but the same basic design. There is a large plug on mine where your fuel shut off solonoid is that the main jet is behind.

Your best bet is to take the carb off and work on it in a flat pan. Take the shut off out and remove the top of the carb. Lift out the floats if it has them. Some of the newer carbs don't have floats. Then start spraying carb cleaner thru all the ports and jets. As you can see I havn't cleaned this carb since I took it off and there is a lot of junk in the bowl.

 

[Eagleview]

Might pay to have a look at the govenor spring , make sure it's still hooked up etc .