Hi all, I have a garden machinery sales/repair shop in the UK and I have a real head scratcher of a problem!
I have an MTD Lawnflite ride on mower in for repair with a Briggs 21 series 13.5hp vertical OHV engine. It cranks, but "jams" at the compression stroke.
I've seen this plenty of times before, the battery was in good condition, but the cables from the manufacturer were only just big enough to carry the current needed to crank the engine when they were new, so after years of being out in the open the corrosion sets in and the resistance of the cables increases, causing slow cranking.
I replaced the battery to solenoid cable, the battery earth cable and the starter solenoid and the problem seemed cured, but after a few days of perfect starting it happened again.
I checked and adjusted the valve clearances, it happened again.
So I stripped the starter motor, cleaned it and rebuilt it, it happened again.
Checked and cleaned all terminals, earths, connections etc... still did it one in ten cranks.
So the only cable left in the starting system was the one from the solenoid to the starter which tested fine with my multimeter. I only got a 0.3v drop under load which is easily acceptable. But I changed it anyway and then I only had 0.2v drop with the new cable. It then seemed to be fixed. I kept it at my shop for about 5 days starting it morning and night numerous times to try and get it to fail but it was perfect.
So I call the customer, he comes to see it and it fires up no problem. Later that day I'm about to load it into the back of my van to deliver it back to him and... yep you guessed it!
So I'm open to any ideas or stories of things you guys may have experienced! The compression release is working whenever I feel for it so I'm pretty stumped!
Sounds like an intermittent sticking flyweight on the compression release on the camshaft. Sounds like time to pull the engine and install a new camshaft. If you go through the trouble of pulling the engine to inspect the cam, just replace it to eliminate the potential of an ongoing issue.
