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Discussion Starter #1
Had issues with the B&S Vanguard on the Pro-16 running rough, surging, etc. When it does this when the PTO is engaged, the 50" deck mounted to the A-frame goes into a weird oscillation until I take it out of Hi or Low, at which point you can hear the engine surging to a cadence. I replaced the fuel filter after cutting about half the back yard when it started to act up. Wanted to get into the carb. but wasn't sure if these are intended to be adjusted. Anyone have experience with these that can offer a remedy?
 

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An engine running to lean usually is the cause of surging, may be slow fuel flow or partially plugged carb.

Dan 2N :howdy:
 

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Discussion Starter #3
Looks like the idle mixture valves are buried under the air cleaner assembly. Each cylinder needs to be set separately. Could be running too lean. Seems to be a stupid setup, as the air cleaner assembly has to be put back on before you can start the engine and put a tach. on it. :dunno:
 

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The Nikki carbs are pretty bullet proof but they can clog just like any other carb. Take the top off, clean the bowl, take out the idle mix screw and give it a shot of compressed air and reassemble and all should be well after adjusting the idle mix.
 

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Looks like the idle mixture valves are buried under the air cleaner assembly. Each cylinder needs to be set separately. Could be running too lean. Seems to be a stupid setup, as the air cleaner assembly has to be put back on before you can start the engine and put a tach. on it. :dunno:
I am lost, is the carb a 2 barrel, or does it have twin carbs, or how do the cylinders get set separately? :dunno:

I would love to see pics!! :fing32:

:wwp:
 

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Discussion Starter #7
Yes, I believe it is a 2-barrel carb. after reading the manual last night. I'm not familiar with what it is exactly, nor have I played with it yet. Seems to not have much adjustability (like a Kohler single). I will tear into it today and post back.
 

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While they don't mention it, the idle mix is adjustable but it requires a little work to get there. Sometimes there is a cap over the screw and sometimes the idle mix screw is recessed in a hole that is covered by a welch plug. If that Briggs is on a Gravely two wheeler, it is just a little difficult to get the top off but not impossible. Remember that the goal is to remove the top of the carb and to remove the idle mixture screw, not remove the carb unless absolutely necessary.

Be careful when removing the screw. If I recall correctly they made the thing so that if the plastic cap over the top of the screw is destroyed, there is no way to turn the screw. Mine was already cracked and damaged when I got it and I was lucky to get the screw out. I had to make and press on a special non-limiting cap.

Good luck

Richard
 

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Discussion Starter #9
Took the air cleaner assembly off and exposed the carb. It was pretty furry to say the least. Blew the thing with compressed air to expose any screws I could find. I only found two visible screws. One looked like an idle adjust screw (low rpm) and the other looked to be a needle of some sort. It is straight out the back on the bottom. I took note of the setting and backed it out. Shot carb. cleaner in the opening, cleaned the needle and reassembled to the preset (9 turns I believe). Not sure what jet it was, but it got cleaned.

I could have removed the top off the carb, but decided not to.

It seem to run a little better, esp. at idle. I'll know more the next time I mow.
 

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Adjust the idle mix for highest RPM and that is as good as it gets.
 

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Discussion Starter #11 (Edited)
I was probably mistaken about the whole "double barrel" bit above. Also, when I measured my "9 turns" above, it was not in the conventional manner from lightly bottomed out. Rather, I took note of the full number of turns to back it out and returned it to that point.

Also, my idle mixture screw appears to be missing the "limiter cap" shown in the manual. Too bad they don't offer a starting point setting for this in turns. Otherwise, how does one figure it out?
 

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Since the starting point is arbitrary I almost never bother counting turns. When all is said and done if you can adjust the idle mix too lean (surging or hunting) and too rich (rough running) then that means that the idle circuit is likely working correctly. Adjusting for highest and smoothest idle is all that really matters and that is how every carb should be adjusted.
 

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Discussion Starter #13
I put my digital tach on it and it is spot-on 1300rpm at idle, so that much, I believe, is correct.
 

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Sounds good to me.
 

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Discussion Starter #15
Any idea what would be good replacement engine for that machine? I know the Vanguards are still being made, but not sure if so in those crank dimensions.
 

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How about a 20 hp Briggs? Nearly the same size and a bit more power.

If you think that changing engines is going to solve your carb issues, I would venture to say no. Run AV100 fuel if you want to reduce your clogged carb issues.
 

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The more I hear about how intricate/finicky these Vanguard engines are, the less inclined I become to obtain one. I hope you get this problem knocked out RedRider.
 

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Discussion Starter #18 (Edited)
Just under 700 hours and I believe it is in need of a rebuild, but don't know of anyone local that would/could do it. Smokes when throttling up, esp. after PTO is engaged. Replacement may be my best option. AV gas is not readily available here that I know of.

On the Vanguards, I was actually thinking something slightly smaller, like 13.5 hp Honda or a Kohler M12 (if you can still get them). This engine is really overkill for a walkbehind IMHO. If I had one of those later 16-G riders 2000-2004 with the Vanguard, I imagine I would not be a happy camper at all. On the flip side, I used the 5665 to cut the extra acre today and it is a pleasure to use.
 

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The more I hear about how intricate/finicky these Vanguard engines are, the less inclined I become to obtain one. I hope you get this problem knocked out RedRider.
Mine has been rock solid. It had been neglected when I got it but got it cleaned and now it starts every time.

I don't know what to say about the smoking. What are you using for oil?
 

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Like any new generation OHV engine, the Vanguard has a learning curve. While not dead simple like the old K series Kohlers, it isn't a 40 valve Audi V-8 either.

If you don't like the tractor, trade it off for a Pro12. Someone would love to have that Pro16 and will spend the time to fix it even if it needs an overhaul.
 
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