HI need some help with this one. I picked up a lawn mower that looked to be in really good condition, no identifying marks other than VIP on the front but the engine is a fairly common B&S probably 3.5HP. Model 92908 1818 Type 1 Code 79020208 I will post a couple of pics which may help identify it. Started out with no spark and I discovered that the condenser (capacitor) was faulty but just happened to have an electronic ignition on hand, which gave me good (not great) regular spark. Turning the motor over with an electric drill (poring fuel in the carby) I got an occasional fire but certainly not looking like running. Tested the compression only 50psi, so I assumed it was a piston or rings, pulled it apart and found them to be in excellent condition, I removed the top ring and tested it in the bottom and top of the cylinder, it was pretty similar top and bottom with a gap that I thought was probably about right, I didn't measure it but about 3 millimeters. I did discover what I suspect was a burnt exhaust valve. Spent a bit of time on that and managed to get a compression reading of 60 PSI, but no firing or looking like running. Pulled the head off again and spent a lot of time lapping the valves, reassembled and tested not firing and only 50PSI (The earlier reading of 60 is more than likely an anomaly rather than having gone backwards) The head, head gasket, and top of the cylinder appear to be in good condition. There are some vertical scratches in the cylinder which you can feel with your fingernail you can see them in the photo, I have seen worse on engines which still ran. Valve clearance is intake 0.004" exhaust 0.005" Possible places where I have messed up: Cam shaft timing. I just lined up the marks on the camshaft and crankshaft gears with both valves closed and piston at TDC. When I turned the engine over it seemed logical but could have used a little more thought. Valve Lifters, I didn't look at these and just assumed they were both the same. It is possible that the exhaust valve is bent but it did lap in very evenly. I cannot see that the head or cylinder are cracked but I know that on car engines they often use a special chemical to detect this. The head and cylinder do not appear to be warped but I can only test this with a straight edge and think I would be able to see some blow past evidence on the gasket if that was the case.
At this stage I am thinking that the smart thing to do would be to retrieve my electronic ignition and drop the rest at the tip, but reluctant to give up after investing this much time. If anyone has any suggestions, I am happy to try them out, but may not get to it until after Easter.
Wishing you all a Happy and Safe Easter
If I can get a large enough hammer it will run for awhile just trying to get away from me
