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Hard starting Briggs & Stratton 3.0 hp lawnmower engine
On Sat, 23 May 2009 16:30:46 -0700 (PDT), muzician21 wrote:
Have a B&S on a 70's era Snapper 21" pusher with an aluminum deck. I believe the engine is probably 10 years newer than the rest of the mower. Maybe 10 years ago I took it to a repair shop who installed a solid state unit to replace the points. Even with the solid state ignition it was never one-pull start, but as I recall it usually started with probably 3 - 5 pulls. Now it takes probably 20 pulls or more and monkeying with the throttle. Once it fires it runs like a clock, runs up and down the speed range fine. It's also easier to re-start once it's been running - though still not one pull. Doesn't seem to use an inordinate amount of oil, no discernible smoke out the exhaust. It gets what I'd call moderate use. I'm in central Florida so it gets run bi-weekly or so during the rainy months, not at all during the months of what passes for a winter down here. I'm mechanically inclined but not well-versed on the theory of this kind of engine. I've had it broken down far enough to remove and flush the gas tank, change the points when it had points, replace the pull rope. I've change the spark plug of course. I know it should start much easier than it does. Any suggestions where to look, what to tweak? There isn't that much to it from what I can see, so it shouldn't be that difficult. I believe this mower has a lot of life left in it. Thanks for all input. It certainly seems that there's a fuel problem when cold, since you say the engine runs fine once started. A couple of suggestions, with apologies if they're not relevant due to the layout of your particular engine:- 1) Remove the air cleaner and see if you can look into the carburettor's air intake pipe. Normally there will be a spring-loaded butterfly valve, which is closed when the throttle is in the "start" position. If there's any obstruction preventing this butterfly valve plate from closing properly it can allow too much air to enter in the start position, so the start mixture isn't rich enough. 2) If the carburettor has a priming bulb (which you push to prime the engine), give it two or three pushes while you're looking into the intake pipe, and confirm that raw fuel is being squirted in there. My mower starts first pull, but only since I realised that it takes a little time for the raw fuel squirted in by the primer bulb, to evaporate. These days I normally give the bulb four pushes, take the cap off the gas tank, and then fill the tank from my fuel can. By the time I've done this and replaced the cap, the raw fuel has mostly evaporated, and the engine draws in vapour instead of liquid fuel, to start on the first pull. Cheers, John S (follow-up set to rec.autos.tech, where I saw your post) |
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