View Full Version : Briggs and Stratton IC 20HP Problem

05-19-2007, 08:50 PM
Hi, I am having some trouble with my Briggs and Stratton engine. It will only run on full choke, and does a little backfiring as well when not running full throttle. I have tried everything. It is a 1999 Model 406777, Type 0115 V twin IC 20HP engine. It feels like it simply is not getting gas.
Here is what I have done:
1). Cleaned the carburetor - completely dissassembled the thing and cleaned it thoroughly. I don't think this particular carb has any fuel/air adjustments. I did find the nozzle gasket was swollen and blocking gas from getting out of the fuel bowl. I replaced the gaskets in the carb. The jet in the fuel bowl had some blockage and I cleaned that out as well. I am sure I have the carb clean.
2). New fuel pump and the little vacuum hose that connects to it. The vacuum hose had a small crack in it.
3). Tune up - plugs, fuel filter, air filter, flushed the lines, valve adjustment (they were a little loose @ about .008). The spark plugs did not look too bad when I replaced them.

It will run off full choke once hot, but has no power and runs very rough. I had read that the key for the flywheel on some Briggs motors gets loose or sheared and can cause this. I havent taken that apart yet.

Can anyone give me an idea or suggestions???

Thanks Alot,

05-19-2007, 10:09 PM
As you can see below there are two different size main jets, You didn't by chance get them mixed up ?

What method did you use to clean the carb. ?


05-19-2007, 10:25 PM
Thanks Rob, maybe I am missing something. From what I could tell, it only had one main jet (at least I thought it was). The one I found is at the bottom of the fuel bowl and screws into where the fuel cutoff switch mounts. I did not see any other jets anywhere. Am I wrong here? I have to admit, I have never seen a main jet there before. But I didn't see any other place they could be.

I soaked the fuel bowl in Yamaha carb cleaner. I used it when I worked in a bike shop a few years ago and it works well. Non-corrosive cleaner and can really get the junk out. I cleaned all of the passages with carb cleaner and then blew them out with air. I inspected every single part and made sure the carb cleaner was coming out of the other side of where it went in. (that is how I found the bad gasket). There was a small clog inside the tubes that run inside the nozzle. Some carb cleaner fixed that as well.

So, If I missed the mains (2?), then that is most likely the problem. Please let me know if I did and where they are. LOL.

Thanks for the quick reply.


Bill Kapaun
05-19-2007, 10:53 PM
Rob- I'm not sure but I think you might have gotten the engine #'s transposed or something???
The IPL that seems correct to me is MS-2986. that manual doesn't list a 117A , just a 117.
I always thought the A,B etc. was just for a different type number (usually) and on occasion, a slightly different model#.

05-19-2007, 11:09 PM
Marty, Bill,

The jets are under part reference # 135 fuel transfer tube, Thats the reason for the double "O" ring to divide the two passages through the center of the tube.

Marty, The part you thought to be the main jet on the fuel cut-off solenoid is only the seat for the plunger pin.

This is from the parts description page;

117 791501 Jet-Main (Standard) (Left)(Nikki) Used After Code Date 04080300
117A 791502 Jet-Main (Standard) (Right)(Nikki) Used After Code Date 04080300

Again, Make sure not to get them mixed up.

05-19-2007, 11:21 PM
Thanks Rob. I will check that first thing in the morning. I will make sure not to get them backwards. That has to be where the problem lies.


05-19-2007, 11:25 PM
Bill, I down-loaded MS-2986 and it's the same pic I posted. http://www.gtr-game.com/forums/style_emoticons/default/dunno.gif

Think about it.....It is a two barrel carb. right ? From my Ole automotive days all two barrel carbs. had two main jets, One for each barrel.

I use my dealer's sites for parts look-up instead of down-loading PDF's.

Bill Kapaun
05-20-2007, 12:38 AM
I figured out why the difference-
The manual I downloaded is a 4 year older version! Apparently it needed some "corrections"!
I was downloading from a non Briggs source!
I spent a whole night downloading everything they had. Now they're ALL suspect!:cry:


05-21-2007, 10:24 PM
I finally got it. The fuel shutoff wasn't working (plunger), bad connections. The thing would still run, but only on choke. I started fiddling with it and the engine improved. I cleaned it up, it makes good contact now and opens as soon as the ignition is turned on. Problem solved.

I appreciate the help. I did figure out I have the old style carb with only one main jet which is mounted to the seat for the plunger. Wierd. I pulled the carb apart again, but there is nothing under the fuel transfer but the brass tubes that extend into the main body.