[Matt Gibson]

Got the zeta going on a school today. first time ive had it out properly since i bought it.

 its a briggs v twin 18hp petrol and its hunting on idle. ive had a play with the screw next to the carb, seems to sort it but when i turn the screw it stops huntin but starts backfiring (popping) on idle instead. im assuming its a fuel problem dont knpw where to start on these petrol machines.

any ideas? Everything is working fine when the trigger is pulled. machine runs fine under load.

[Kenny83]

Hunting as in water hunting? making the engine rev up and down? If so that's a leak in your high pressure side....
Also try taking your return pipe out of the bucket and let it ldle and see what happens... reason being if your return pipe is to close to your suction pipe then it can suck in air from the return pipe, also making it hunt or go up and down on revs.... this is because when you first put your return pipe into your source tank it has air in it (because it has not yet been in water), this air can circulate back round into the suction filter and keep circulating around the high pressure side.

If none of those work then you need to start looking at your throttle governing spring etc

[Matt Gibson]

Hi mate,

No the water isnt hunting its the actual engine thats hunting. as i said, i have played with the screw on the carb amd it does fix it but if i screw the screw in to stop the hunting then it starts to backfire and i cant adjust the revs. if i unscrew the screw, i can lower the revs but it hunts on idle. ive got it set somewhere in between.

[G O Cleaning]

Matt as lee has said, if you have a small high pressure hose leak it can cause engine to hunt, mine was doing it yesterday from the roof I could see tiny spray from one of connectors 

[Matt Gibson]

Mike,

Ive checked all the hp side of things. no leaks anywhere. The hunting is more like the engine side of things, a fuel thing im thinking. its not the leak kind of hunting where the system is having to constantly re-pressurize because of the leak. if that makes sense.

[G O Cleaning]

In that case good luck

[Len Gribble]

Matt

I don’t know your machine but check the air filter 1st don’t twiddle with screws.

http://www4.briggsandstratton.com/miscpdfs/RNT/Carburetion_Troubleshooting_Detail_Reference_Guide.pdf

This ones good http://www.youtube.com/watch?v=NRhc08AeL88

[chris scott]

Clean the pilot jet and the emulsion tube out with carb clean and/or compressed air.Possibily a build up of varnish if it's being unused a while.

[Matt Gibson]

Thanks Len, some good info there.

Chris, no idea what your talking about   

[Roger Oakley]

Matt

If it is any use I had the same problem earlier this year with a Honda engine, in the had the carb changed and problem sorted.

[chris scott]

Thanks Len, some good info there.

Chris, no idea what your talking about   

Search here http://www.vanguardengines.com/service-support/operators-manuals/ for the carb emulsion tube and pilot jet.
I would do it for you but you will need to send me the engine serial number.

[Ged]

look behind the throttle cable linkage you might find a very fine retaining spring is broken. i am not a tech guy but i spotted this one on mine a couple of years ago and this sorted it spring is very fine and hard to see. just worth a look.

[Len Gribble]

Matt

Hope you sorted it out

The more expensive option is crankcase back pressure (leak in a seal) which causes idle problems ok a ½ to full revs

[Matt Gibson]

Thanks guys for all the replies, After a chat with Lee kenny the other day, ive had a look over it, checked all the springs, seems fine, no change when i touch the springs, the seem to be doing their job properly.

Len,

Its only hunting when the machine is on tick over. when i pull the trigger, and the machine is under load its fine, runs fine, no hunting.

If its on tick over, and i adjust the revs, it still hunts.

I havent had time to take it to a local guy, but itll be going to an engineer the first chance i get.

Cheers again guys.

[Len Gribble]

Matt

When I say back pressure, I mean vacuum or lack of it at tick over; fuel is dragged into the cylinder via the carb. Compression test is different

Let us know what the problem was

[Matt Gibson]

Just thought id update for any future issues anyone has with these engines, as i know there are a few floating around now.

Finally got off I disagree (just noticed that when you type "my A S S" it turns it into "i Disagree) and paid to have the Zeta fixed, Took it to a local Briggs dealer and it was the carb/all fuel lines etc that were just coked up. It has a hood over the engine and a tailgate on the trailer, and whoever had it before me/before them used to run it with the hood down and tailgate up so the exhaust fumes were just circulating back into the machine. caked the whole thing up. The more it got caked up, the more fuel it had to run to compensate for the lack of air and it just kept getting worse.

They cleaned the carb and some air sensors/line and did a service.

Thought id give it a whirl while i had it hooked up so did the inlaws drive. only a small one car, the flow was awesome  

Also added a nice little anti freeze feed to it to keep it from freezing up while its stored and added a pressure gauge to one of the spare ports via a quick release fitting so i can pop it on and off when i want. Pressure is good, although it does spike quite a bit when you release the trigger.. oh well  

Chris scott got closest i think. Well done mate, you dont wint FA  

[chris scott]

That will pi55 Carl off...Chris "boring" scott is right again.

[Matt Gibson]

Boring people are usually smart, hence - right. That's why they are boring. 

[BDCS]

So to sum it up your saying he's smart and boring but able to diagnose a blocked pilot jet whilst chucking in a few technical terms to confuse the uneducated.

To prevent this in future look to fit an inline filter

[Matt Gibson]

I never attached my previous statement to any one particular individual 

And it wasnt that the engine sucked up bad fuel or anything an inline fuel filter would have solved, it was because the fair filter got clogged up with exhaust fumes, restricting the air, which caused overfueling fr long periods which caused a heap of unburnt fuel or something similar. I dont know, i only clean patios.