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My father bought a Lawnboy model 10324 in about 1999 or 2000. DuraForce 6.5hp. Finally this spring the mower would not start because of no compression. Installed a new short block and transferred parts. Machine ran perfectly, smoothly and with power. Unfortunately I must not have fully tightened the ignition module and a couple weeks ago the module touched the flywheel and the mower, logically, stopped. Installed a new non-oem ignition module (flywheel today will attract and hold a 7/8 inch combo wrench so I think the magnetic field is OK), mower started and ran perfectly for about 10 minutes until it encountered a heavy load, slowed down, backfired and stopped. At this point non-OEM module would not produce a spark consistently so ordered a new OEM ignition module which now consistently sparks bight blue-white after installation and proper gapping. However mower will absolutely, positively refuse to start. Engine has compression, and spark but unless you prime engine 10-15 pumps and keep the choke off can you only get engine to sputter for 3 - 5 seconds and after 5-7 pulls.
Have cleaned carb, cleaned both idle and hi speed jets, re-set needle valve, pulled flywheel to check if key sheared (wasn't). Fuel (non-alcohol) is new, gas oil mix proper. Choke works. Engine fires, a little exhaust smokes white a bit, but mower just won't keep going for more than 3 to 5 seconds. Won't even fire on starting fluid sprayed into plug hole.
At this point I'm suspecting something going on with the reed valve as a result of the backfire but ????
I've always prided my self on being able to start just about any spark ignition engine in the neighborhood, but this one has me at wits end - particularly after it was running so well for so long this summer. It's hard to believe the carb is the issue since the engine ran fine after the first coil replacement until the backfire but ???
Suggestions - other than lots of adult beverages - are welcome. Thanks.

Hello,

I had a similar problem with a Sears (Tanaka) Gamefisher 3.0 outboard, I bought off Craigslist. Turned out to be a crankshaft seal totally out from it's seat. I't's possible the backfire may have damaged the seals, I doubt the reeds were damaged, but that's a possibility too. Check all crankcase seals.

Jeff

jp1961 said:

Hello,

I had a similar problem with a Sears (Tanaka) Gamefisher 3.0 outboard, I bought off Craigslist. Turned out to be a crankshaft seal totally out from it's seat. I't's possible the backfire may have damaged the seals, I doubt the reeds were damaged, but that's a possibility too. Check all crankcase seals.

Jeff

Click to expand...

Bingo!
Crankcase seal was "blown" out by backfire. Was able to re-set and mower started so fast on first pull surprised me.
Simply forgot that air/fuel mix is drawn in through crankcase and that needs to be sealed to create vacuum.

Thanks

Whew, glad I could help. I must admit that outboard gave me fits, as I'm able to get most engines running too. So now my short list of items to check is, spark?, fuel?, crankcase sealed???

Jeff