Hard starting Briggs & Stratton 3.0 hp lawnmower engine

[muzician21]

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.

[HLS]

Look, I didnt study this as well as I should have. BS engines with solid state ignition normally start pretty well.

I suspect you might be having fuel delivery problems. I have rebuilt the "carburetors" on some BS implements we have here several times.

In these cases, I have to take the fuel tank off, wash it well with water, and then carefully dry it. Then, I remove the carburetor, clean it, and put it back together with a new diaphragm. This is important. Just a carburetor job is not enough.

Ignition may have to be followed up as well.

Let us know how you are proceeding. I have had only one BS engine really disappoint me, and that was because the casting was make of parmesan cheese.

[m6onz5a]

try a quirt of starting fluid in the carb. Will it start any faster? I too think it's a fuel delivery issue if it'll start quicker on the starting fluid.

Does it have a choke setting?

You can also see if the solid state unit is adjustable. Maybe the gap is too far apart.

[Vic Smith]

Not familiar with this particular engine, but it sounds like a gas delivery/mixture problem. Choking can be real critical with these. This is the first year I've had no problem starting my 2-cycle weedwacker because I've learned the primer bulb needs to be pumped up hard, the exact choke setting it likes, and that it has to be unchoked immediately upon firing. Only took me 5 years, but I've got it starting in 3 pulls. I'd start by maybe looking in the carb for wetness, and trying 3 to 5 pulls at different choke settings. But you have to let it dry out between tries so you're not confusing the issue. Once you know what works, you're all set. Until it doesn't work any more. That's what I like about the Honda I have on my Craftsman.

3 horse I think, 4-cycle. It starts first pull after sitting all winter. Every time for about 6 years now. Original plug. And I never drain the gas or use a gas additive on anything. Not saying don't, just that I don't bother.

--Vic

[pheeh.zero]

If this is an older Briggs without a primer...they make an after--- market primer on a replacement gas cap. Stens.com should have it (they used to). It makes starting a snap.

[Fat Moe]

Sounds like it's time to do a little work on the carburetor. Put a new diaphragm in it if it the older type that uses those. As the motors age it's worth while to make a priming port in the air cleaner, drill a hole you can plug after starting and spray some carb cleaner in it to start it. Also check the valve clearances (those easy spin engine valve clearances are pretty critical for easy starting) and a good spark plug. Would help if you posted the engine model number. On newer ones with primer bulbs and bowl/float it's common for the main jet to get clogged over winter.

[Brandon McCombs]

[snip]

I had a mower given to me recently by a co-worker. It uses a B&S engine. I had to take the carb apart and clean out the main jet because he hadn't used it in years. The mower would not stay running unless I did that however, it *would* start up still on the first or second try if primed properly. It would also continue running if a 2nd person was available to continue priming it. I don't know anything about mowers but if the OP's mower takes that long to start could it still be an issue of a dirty/clogged carb? I'm just comparing what you said to what I recently experienced.

[Ashton Crusher]

Does it have one of those push ball primer gizmos? I've got a BS with one, it's about 5 years old now. Supposedly it takes 3 to 4 pushes of the ball to prime it. But that has never worked. It takes 13 pushes, and has since it was new, to get it primed. then it starts on the first pull and runs just fine.

[jim]

muzician21 wrote: Now it takes probably 20 pulls or more and

The issue is that the engine needs a rich mixture to start when cold. There are several different ways that the engine (carb) could be designed to do that. In your case it probably has a choke. If it was the original 30 year old engine the choke would probably be part of the throttle control. The procedure for starting the engine would be to set the throttle to the start position and then when the engine started you would move the throttle control lever to the run position. On this design the throttle cable was mechanically linked to the choke plate. Sometime in the 80's they changed that to an automatic choke where a spring closed the choke plate and then a diaphragm used engine vacuum to pull the choke open once it started. On newer engines there is also the system that eliminates the choke completely and replaced it with a primer bulb where you pump a little gas (others have described the process).

So the first thing you need to do is identify which method it uses to deliver extra gas on cold starts and then figure out why it is not working as designed.

-jim

[ransley]

A motor that old may be worn out and not have enough compression to start easily or have good power. Have you tried starting fluid. Electonic ignition modules eventualy fail, hard starting was my first sign of mine failing. If you have ever hit anything and stalled the mower the flywheel key could be bent throwing off timing. At that age it could be many things.

[pheeh.zero]

Part no.125-492

[Stormin Mormon]

Several things could be the issue.

• Sometimes the gasket between the carb and the engine body dries out. Or people neglect to replace it. Pull the carb, and make sure it has a gasket. A very little bit of Permatex #2B Non Hardening gasket sealer will be a big help. If the gasket isn't there, put a little permatex on the carb to engine matching surfaces.

• Only buy new gasoline, of a trusted name brand. Pay the couple extra cents and get good brand. In the western NY area, Mobil and Hess are good.

• If the spark plug is Champion, try a different brand. They had bad sparkplugs in the past.

• Like the guys say, try a squirt of ether on the air cleaner filter before starting. If that helps, you likely have fuel supply problems.

• A trace of water in the fuel tank will cause this kind of problem.

• If the gap between the flywheel and the ignition coil is too great, the spark will be weak. Normal air gap is about the thickness of the cardboard they use for spark plug boxes.

Please let us know how things work out. If you get it going, or not. Either way, please write again. That way, we can learn also.

[JP]

I have found that a lot of times the muffler is plugged. I have got some good byes because of a plugged muffler.

[Stormin Mormon]

Sorry you had to say good bye to a mower, just cause the muffler is clogged. Many of them have half inch pipe thread, and replace rather easily.

[Joe]

If the engine plant is in Milwaukee, they probably used cheddar.

Joe

[Ulysses]

As Stormin suggested I agree you should check the "air gap" on the ignition coil even though it sounds like a fuel problem. I remove the ignition coil every few years and clean the edges and magnet on the flywheel with sandpaper and coat it with a little oil or vaseline or whatever. This helps keep down the rust. I generally use three thicknesses of printer paper to adjust the air gap. Check the spark plug connector and clean out any corrosion and squeeze it a bit with pliers to ensure good contact. Sometimes the spring for the governor will get a bit stretched and can be shortened to where it just barely has tension with the engine off. Try holding the throttle all the way closed while it's running and adjust the idle speed to where it seems about right. If it's too low it may be hard to start. Also, if the throttle/choke cable has slipped it can cause the choke to be on or off when you want it the other way. Removing the head might be in order to--scrape off the carbon deposits and clean the valve seats being careful not do damage the seats. I have had success many times simply by putting some high-temp silicone on the old head gasket and reusing it.

My old B&S lawnmower sounds very similar to yours but it's only 23 years old. My experience with these engines is that as long as the piston is still attached to the crankshaft they can be made to mow lawns. I was having a lot of trouble with mine in the past with hard starting and I even turned the engine sideways so I could pull the rope from the side. This arrangement also eliminated some problems with the cable moving out of adjustment as it eliminated the 90 degree turn in the cable. Also, check to be sure the blade is tight. These things need it to maintain momentum.

[Oren]

Plenty of good advise for the OP, so far. I would start with a new plug with a hotter heat-range. Putting a "hot plug" in one mower was a solution for me.

Some pre-gapped plugs are not accurate and should always be checked , before install.

[The Daring Dufas]

I've worked on a lot of standby generators with small engines and one of the problems with older engines that have accumulated a lot of hours is valve seat wear. The valve recedes into the head decreasing clearance at the end of the valve stem. You can actually heat up such an engine with a propane torch and the expansion of the metal parts will allow it to start easily. If you can adjust the valve clearance, I do believe your engine will start easily again.

TDD

[clare]

Put some "sea foam" in the tank to clear out the jets and see what happens. If it has adjustable jets try setting 1/4 turn richer to see if it helps. Definitely sounds like it is starting too lean.

[Stormin Mormon]

On the early Briggs, that means pulling the head, and then using special equipment to get the spring ends back on.