Briggs 18Hp Intek, requires choke under load

Hello All, I'm new to this forum, but after reading some of the posts here (I did search for an answer) you might be able to point me in the right direction. I have a 3 year old Ariens Zero Turn (1844 Zoom) with an 18Hp Briggs Intek with 130 running hours. Great mower, love it, but last fall I started having problems with loss of power and surging under load requiring choke to correct it. I am fairly mechnical so I have treated what I thought could be the cause. I do perform regular maintenance - oil and filter changed every 25 hours, fuel filter and spark plug changed every 50 hours, fuel stabilizer in the fall. In addition I: 1) Verified governor linkages and carb linkages 2) Took carb apart and cleaned thoroughly - resulted in slight improvement. 3) Ordered carb rebuild kit and rebuilt the carb - no further improvement. 4) Replaced Fuel pump - no further improvement. I have again changed filters, plug. This thing starts right up with full choke, without any load, I can back the choke down just fine. I am at a loss.
The service shop is booked for several weeks (and pricey) and I'd like to fix it myself if possible.

I have ordered the service manual from Briggs, should be here next week.

Any ideas would be greatly appreciated. Sorry for the lengthy post. Jan

 

something is still in the carb. by choking you are compensating for a fuel shortage in the fuel/air ratio. check the main jet again. not sure if it's removeable. carbs are an array of very small passages. nowadays i just replace them and move on.

 

Same here, and this is more then likely a emissions carb, barely any adjustments can be done to the idle mix screw. Also make sure that the carb and all is on good and tight.

 

Depending on the amount of varnish build-up (and you likely have considerable build-up, although not visible to the eye) and will need to soak the carburetor in a quality bath cleaner (I like Napa's). Be sure to remove all rubber and most plastic items from the carburetor before doing so. But make sure you soak all critical components. Usually a 20-30 minute soaking will suffice.

 

Thanks for the replies guys. I will take your advice and try soaking again. I'm pretty good at getting the carb on and off, and you are correct, there are few adjustments that can be made to this carb. I really thought that I had done a good job on the cleaning of the carb, but more cleaning definately won't hurt. Just wanted to make sure that there was no other area that I was overlooking.

I'll try soaking it this weekend and let you know how I make out.

Thanks again, Jan

 

I had the same problem with a JD lawn tractor with a 15hp kohler. It was a freind of mines tractor and he said to drain all the gas out of tank. XXXXXXXXXXXXXXX (unsafe wording advice removed by forums monitor). It worked for about a week problem came back so I did it again. It helped for about 20 min. It got so bad I had to have it full choke to drive it back. I looked at fuel filter, its clear and was a few little specks but nothing to plug it. XXXXXXXXXXXXXXX (unsafe wording advice removed by forums monitor) and pulled the hose off the filter and I used the air compressor to blow air back into the tank and a goopy black stuff came out but filter was always clean. Well that was last summer and it ran like a top for months till winter came. If you try this let me know if it helps.

Forum Monitors Note:
Unsafe advice only has been removed from this post.
Rest of the post remains intact.
Word Of Caution:
NEVER use electrical motors around and fuel source in the work area.

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Bear in mind that if you have a leak in the intake system (manifold gaskets, head gasket(s), or, intake valve-train) you will have similar symptoms that you have. I just don't want you to look only at the carburetor - although it is the most likely cause. You mentioned you have already soaked it...in what, specifically?

 

For safety's sake, I guess I have to mention do NOT use any electrical motor around gas, especially a vacuum...even if it's wet/dry. Vacuum motors have brushes. Brushes arc constantly as the motor runs. All it takes it a spark, and with all that gas right under the vacuum motor, and lots of fumes and forced air, a life threatening situation is created.