This guy's pretty good at that.
Small Engine Technical Forum
Briggs & Stratton 11 HP, runs for 20 seconds and dies Postby Dave T » Sun Jun 05, 2011 7:57 pm Briggs and Stratton, 11 HP (From a Murray riding lawnmower) Model 28V707-1116-E1 Vertical shaft Nikki Carb I use my riding mower through December, start up again in March, so I do not winterize even though I should for just the couple of months. I usually leave gas in it, unstabilized, but have learned over the past month that leaving old gas in equipment is a really bad idea and even worse idea with all the ethanol in gas these days. This is going to be kind of long, but I want to share what I have done, step by step. Symptoms at start of season: 1) No gas in tank - surprising, since I had not drained it. Made me wonder how it could have evaporated. 2) Oil looked fine on the dipstick, clear but the viscosity seemed off and I was expecting the oil to be darker. 3) Refueled, attempted to start (electric start). Hard cranking, fired, ran for 20 seconds quit. Tried to crank again, would not fire again at all. 4) Took apart air filter housing, dusty as expected, shook that off, but more alarming, the bottom third of air filter appeared wet from either oil or gas or some mixture. 5) Looked at the top of the mower deck blade housing, and found a disconcerting puddle of oil or gas or both that seemed to have leaked down possibly along the vertical shaft, or maybe from outside the engine and through the frame. 6) Fuel filter and spark plug are new from July 2009. Decide to buy new ones. 7) Grass is growing. End of weekend one. Weekend two: 1) Try new spark plug, attempt to start. Same thing as before. Ran for 20 seconds then quit. Tried to crank again, would not fire again at all. 2) Begin a lot of online reading, get the engine manual pdf, parts list pdf, and buy the B&S Repair Manual and B&S Small Engine Care & Repair books. 3) Buy some carb cleaner. 4) Grass continues to grow. End of weekend two. Weekend three: 1) Squirt some carb cleaner in the carb. 2) Attempt to start, 20 seconds and quits again. (This is the definition of insanity). 3) Start to panic over height of grass. [INTERMISSION: Pull out my Craftsman Self Propelled mower, which I haven't started in five years (ever since I got the riding lawnmower) and which I did not drain the gas out of when I quit using it. Bad, bad. Add fuel, prime the bulb five times, and pull the cord. Nothing. Pull the cord again, and it fires right up, and I mow the front yard. Ignored for five years, starts on the second pull. Go figure. Too bad women are not like this. END OF INTERMISSION.] End of weekend three. Weekend four was spent digging for more information - figure I am going to have to deal with the carburetor. Weekend five: Mow the entire yard with the Craftsman Self Propelled mower. Back to the riding mower's B&S 11 HP 28V707: 1) Took the top housing off, cleaning out a few leaves from around the screen, flywheel and top of the block. Not as much dirt as I had expected to find in there. 2) Took the air filter housing off. 3) Muffler cover also had to come off to get the carb off. 4) Then got the carb off. (Nikki model) 5) Took bowl off, some loose debris in the bottom, but otherwise the carb looked fairly clean. 6) Float looked OK, but I haven't taken it off and checked whether it has a hole in it or not. 7) Also, haven't looked at the inlet in detail. 8) Blew air through a lot of the carb, without completely disassembling it yet. 9) New SYMPTOM: with the carb off, I stuck my finger in the valve intake area and was surprised to feel a huge puddle of gas. This led me to stop and think, and do more reading. Found the perr website Memorial Day weekend. End of weekend five. Weekend six: (Decide not to reassemble anything yet. Leave the carb off. Going to investigate the oil situation.) 1) Decide to change the oil, as I read that if the oil was too full, perhaps some of these symptoms could have been caused. 2) I have on hand a 32 ounce measuring funnel (which can be closed off for measuring) and a 20 ounce cup. Engine oil capacity is supposed to be 48 oz, so I am all set to drain and measure just how much is in there. 3) Loosen drain plug with wrench, then remove the rest of the way by hand. 4) All [censored] breaks loose. I quickly fill the 20 oz cup, and this stuff is coming out way too fast, and my 32 oz funnel is rapidly filling up too. And in all the excitement, I've lost track of where I put (or dropped) the drain plug. 5) With the funnel in one hand, and full cup sitting on the ground, I decide to put the thumb of my free hand into the drain hole. 6) Then I sit there and think for a few minutes. This is not oil. This is gas mixed with oil. And lots of it. Continue to think for a few minutes. [For the record, I should add that I really know how to cuss and practiced some this afternoon.] 7) I decide I need a third hand, but there is no one around to help. Funnel remains in one hand. Thumb of other hand remains in drain hole. Still thinking. 8) Decide that if I can reach up in there with my "funnel hand", I can put the thumb of my "funnel hand" in the drain hole, thus freeing up the thumb (and hand) currently stopping up the drain hole. 9) Switch thumbs. With free hand, grab empty gas can, get gas can cap off, and dump contents of funnel into empty spare gas can. Get drain plug put back into the drain. Dump the other 20 oz cup into the spare gas can. Free both hands. 10) Now that some sense of order had been restored, I opened up the drain again and got even more oil/gas mixture out. I gave up on measuring, but I estimate that I got 60 to maybe 70 ounces of this stuff out. Put drain plug back in. 11) Quit for the day. Clean up the mess. Go back to thinking. 12) So, New SYMPTOM: Definitely have gas mixing with the oil in the crankcase. That brings me to where I am now, typing this foolishness up in the Forum. One other symptom of note: The governor spring/links over to the carburetor looked fine on disassembly, and the engine did not hunt and surge last year. However, I do know the throttle linkage needed adjusting. It would go into the choke position for starting, and open up for full throttle, but I didn't have much of any variation from low to full throttle. I've gotten a lot of dirt out from spring and foam cover which might have been causing the throttle linkage to not work right. So, my questions: 1) Could this all be caused by some malfunction of the carburetor? 2) Do I possibly have some blown gasket which caused the gas/oil mix? 3) Any recommended steps in trying to put things back together and testing it? (Currently, everything is disassembled, no gas, no oil, no carb, no air filter, no housing cover, fuel line disconnected. My thoughts are: 1) Going to clean the carb more thoroughly, including taking the float off the hinge, going to make sure the float doesn't have any holes, and will look at the inlet nozzle more closely. 2) My major concern is about this oil/gas mixing and what is going on deeper in the engine. I guess I could reassemble everything, add new oil, new gas, and see what happens when I try to start it again. Will that hurt anything? At worst, I guess I could wind up with gas mixing in the oil again, and would have to drain it all out again. Any help would be greatly appreciated. Girlfriend has already started asking me how much money I have spent on the two repair books. Not to mention six weekends of off and on tinkering. Thanks, Dave T. My first post on here. Hope I followed the rules OK. Dave T Posts: 2 Joined: Tue May 31, 2011 12:14 pm * Private message * E-mail Dave T