16 hp Vanguard surging

[cycub]

First post in the Vanguard forum. I'm swapping engines in one of my 1641s because the original engine has almost 1900 hours and can not start the PTO without the engine dying.

I got a 430 hr engine from a 2165. I've got everything hooked up but it is running rough. I thought it was a dirty carb, but I cleaned the bowl and all of the jets. It improved but still is rough. Any chance this could be the governor or it needs adjusting? Or is the carb just still dirty?

The gas should be fine because I didn't have this problem with the old engine.

[Arnie Cunningham]

Sounds like idle mixture is too lean and needs to be richer.

It’s ironic to me because I just got a 2165 back together today as a flipper and it’s running identical at idle only. I ran out of daylight but was going to look into that. Does pulling the choke out a little make it smooth out?

[cycub]

It's hard to tell on the video, but about halfway through I throttled it up to about 1/4 throttle and the surging got worse. I did try to choke it more at idle and it may have helped a little.

[J-Mech]

Well, you state that the old motor wouldn't engage the PTO at idle without dying. That may have in fact been a fuel problem. (Or at least carburation.) The idle circuit in those engines is known to be problematic. Doesn't take much to make them run rough. Most engines use the idle circuit up to about 1800 RPM or so. (Under no load.)

I suggest cleaning the fuel system completely and possibly running new fuel hoses. Did you change the filter? I also suggest cleaning the carb again, and then going through the adjustment procedure. I don't recall if the Vanguard has an adjustable idle jet. If we don't have the Vanguard manual in the tech section, just holler. Pretty sure it got uploaded, but I know we have a copy if it's not posted. Engine sounds to me to be a bit rich.

[cycub]

Thanks Jonathan. I will do those things. I had replaced the filter last fall but I should put on new lines and clean out the tank. The lines are original I'm sure.

It looks like the idle jet isn't adjustable but there is a mix screw.

[J-Mech]

I'm not super familiar with the Vanguard motors. I'm more of a Kohler guy. Shoot Sam Mac a pm. He might tell you a trick, but I'd bet his advice will echo mine as a place to begin.

[Leadslingingdaddy]

As J stated it could be as simple as changing the fuel filter... I always run a larger filter as some are spec'd by Hp.... and make sure you have it on the right way.... check the flow arrow...

[Diesel Doc]

I'll just throw this out as food for thought, since the carb has been off to clean the jets, I think it would a good idea to check the governor adjustment as well. I'm not real familiar with the governor linkage on the VanGuard but a misplaced spring or binding linkage could cause some surging as well. Given that the position of the choke seems to have some minor effect on performance it is most likely fuel related. Another possibility is a vacuum leak. The carb mounting and intake manifold should be inspected to be sure the gaskets are good and the bolts tight. I see no mention of the condition of the ignition system. Bad plugs or wires won't cause a surge but having good spark at the right time is part of overall performance.

[cycub]

Thanks for the additional input guys. I am planning to replace the fuel filter.

Doc, I actually didn't take the carb off the intake manifold to clean. Most of the orifices are accessible from above, so I thought I could do an adequate job with carb cleaner with it in place. Obviously not. After looking at the manual I see that the main jet is only accessible after removing the solenoid. I will have to pull the engine back out of the tractor to get the carb off the manifold and completely disassemble and soak it. Depending how it comes apart i may need to use a new gasket.

The carb had about a half inch of gel in the bottom of the bowl and the solenoid was stuck open so i suspect the main jet may still be dirty because its near the bottom of the bowl.

[J-Mech]

Idle circuit is fed from the main jet... so, yeah, that's likely the issue. Better pull it and clean it. I wouldn't soak it. Unnecessary. I only soak a carb if it has stuff on or in it so bad you can't hardly chisel it off. Or if it was pulled basically from the junk pile. I've rebuilt cast iron Marvel Schebler's that were literally full of rust. Otherwise, disassemble, spray over with carb cleaner. Wear goggles and spray it into the passages. That way you can see where and if it comes out another hole. If you don't see it spray anywhere.... that passage is plugged. Good luck!

[cycub]

Edit: I realize now I should have also taken out the mix screw. I will try that first.

I cleaned the tank and replaced fuel line, fuel filter, and rubber bushings on the tank. I also recleaned the carburetor. It idles fine now after adjusting the mixture screw a little. When I slowly increase the throttle, it surges a little but then evens out. However, above half throttle it surges badly.

Page 12 through 14 in the manual on the forum here lists the carburetor adjustment procedure. It involves using a tachometer to adjust idle mixture screw, the limit screw for the throttle, and bending a tang that the governor spring connects to. Before I buy the tach to do this, I wanted to see if you guys thought that was the best next step. As far as carb goes, the only other thing I could do would be to buy a rebuild kit with new jets. Those run about $50 and I don't think that will solve my problem.

Thanks for the help

[cycub]

Well, I swapped in a different carb I had and followed the adjustment procedure in the manual. It ran good at lower speeds but ran bad at high throttle. I had to do what they call a static governor adjustment in the manual and that fixed the surging at high throttle. I still have two issues. First is when I change the throttle up it takes a few seconds to even out (surges for a few seconds). Second problem is it surges while driving around now. Could this be an electrical or valve adjustment issue or still carburetion? So frustrating.

[J-Mech]

Sounds like carb to me.

[cycub]

I got sick of pulling the engine, cleaning or swapping carbs, and putting the engine back in. I just bought a new carb. Rebuild kits are about half the price of a new carb band don't even include the main jet.

Got the new carb in tonight. Runs good finally. Now I need to replace the PTO switch and a couple wheels on the deck that are worn, grease it up, and it will be ready to mow.