Puffs of smoke at shutdown of old Briggs?

[JHZR2]

The old Briggs engine in my second Snapper started after 5-10 pulls after sitting for five years. It runs well, consistently.

When I shut it down, sliding the throttle lever to “stop”, it takes a few seconds, and puffs 2-3 little puffs of smoke before it shuts down.

I’ve done nothing to this besides put some gumout pea additive in the tank.

But was curious what this might be pointing to in terms of an issue. The engine doesn’t smoke or give signs of oil use or anything else.

 

[Soft Cars]

Is that a throttle kill or an ignition kill? If it's a throttle kill which basically chokes the engine by taking the air away, I'd say it's running rich for a couple of seconds until it runs out of air. Did you ever give me the engine numbers off that? They should be on the flywheel cover somewhere.

 

[JHZR2]

Is that a throttle kill or an ignition kill? If it's a throttle kill which basically chokes the engine by taking the air away, I'd say it's running rich for a couple of seconds until it runs out of air. Did you ever give me the engine numbers off that? They should be on the flywheel cover somewhere.

Can’t say I did.

This is one of two that I now have. I think this one is older. The other has a B&S max engine.

This one is:

I don’t think it’s an ignition kill, it’s entirely associated with the throttle cable you can see in the photo.

 

[Soft Cars]

I'm seeing 110902 3911-01 84022502

Is that correct?

Sometimes there will be a wire coming from the ignition coil going to a plate on the throttle cable. You push the throttle lever far enough, it grounds out the ignition coil. I'll go look at my parts list. I'll be able to tell you in a minute.

 

[Soft Cars]

It does have an ignition kill. The kill wire from the ignition coil gets held in place by the spring loaded leaf spring in reference number 621.

 

[JHZR2]

It does have an ignition kill. The kill wire from the ignition coil gets held in place by the spring loaded leaf spring in reference number 621.



View attachment 178928

Thanks. Ill have to look more tomorrow.

I know that there is no movement/action at all from the fast setting to the choke/start setting. I would think that something woukd be obvious but the control wire doesn’t move at all.

I’ll look at the stop end of the travel as well tomorrow.

So essentially, the thought is ignition kill, some fuel still is coming in, runs rich, no spark, partial combustion, mess… and I’d assume potential fuel dilution in the oil. My other mowers and small engines don’t do this puff.

 

[JHZR2]

I'm seeing 110902 3911-01 84022502

Is that correct?

The number is correct…

 

[Soft Cars]

I know that there is no movement/action at all from the fast setting to the choke/start setting. I would think that something woukd be obvious but the control wire doesn’t move at all.

No movement from what; the throttle lever and throttle cable? Those two have to be oiled all the time. You need to get oil down in between the throttle cable and its outer sheath on both ends of the cable. If you oil the cable, the cable will carry the oil into the sheath when you move the throttle lever; hopefully.

 

[Gyro Gearloose]

I have a 13 year old briggs on a toro mower that does same thing. It runs great and doesnt burn oil but when i let go of the kill handle it puffs blue smoke while coasting down. Odd thing is the spark plug and piston face are totally dry.

 

[fantastic]

Yeah, as noted It's either not grounding out or the needle in the carb is allowing fuel past it until it runs out of fuel. That would be a carb rebuild or new one if they're still available.

 

[billt460]

Cleaned up and restored, I'll bet that baby would be worth something. Is it a cast deck?

 

[Lubener]

Make sure the air filter is clear and the plug is burning cleanly. If its running rich enough to create smoke, the plug should show it. I don't think there's a problem with the kill switch since the engine stops as you indicated. However, I have had where grass accumulates and affects the operation of the leaf switch to kill the engine.

Could also be a small amount of oil being consumed. I wouldn't worry about it if it doesn't consume much oil. Using a straight SAE 30 oil might help.

 

[Soft Cars]

My little McLane edger with its1968 Briggs & Stratton used burn oil while it was running. For that I installed a hard chrome piston ring set. That sure did the trick. Compression went way up and no more oil burning. Kit came in a box with 8 piston rings. I was confused about that so I took the piston and its connecting rod to a pro shop to ask the guy there in which order the rings went on. The guy at the counter took the piston back to the mechanic while I stood there waiting at the counter. A couple of minutes later the piston comes back with its rings installed. That was very nice of them. I made sure I drew a diagram of the rings orientation before I installed the piston and its connecting rod into the cylinder.

 

[MSCH]

better question is " does it matter"?

 

[JHZR2]

No movement from what; the throttle lever and throttle cable? Those two have to be oiled all the time. You need to get oil down in between the throttle cable and its outer sheath on both ends of the cable. If you oil the cable, the cable will carry the oil into the sheath when you move the throttle lever; hopefully.

The cable slides fine. It’s the adjusted range. The control goes from start, fast, slow, stop. The range of motion is fast, slow, stop. In other words, when I push past fast, no noticeable change in the cable or position is observed. It may be running choked when in fastest speed, or not choked at all…

 

[JHZR2]

better question is " does it matter"?

Sure, it may not. The thing runs well and will run better after I do some servicing on it. But I’m still interested in the cause.

Make sure the air filter is clear and the plug is burning cleanly. If its running rich enough to create smoke, the plug should show it. I don't think there's a problem with the kill switch since the engine stops as you indicated. However, I have had where grass accumulates and affects the operation of the leaf switch to kill the engine.

Could also be a small amount of oil being consumed. I wouldn't worry about it if it doesn't consume much oil. Using a straight SAE 30 oil might help.

It’s only two or three puffs at shutdown. Nothing any other time that I can tell. Maybe it does burn a bit, we will see… I need to pull the plug.

 

[JHZR2]

Cleaned up and restored, I'll bet that baby would be worth something. Is it a cast deck?

Rust free steel deck.

 

[MSCH]

Sure, it may not. The thing runs well and will run better after I do some servicing on it. But I’m still interested in the cause.



It’s only two or three puffs at shutdown. Nothing any other time that I can tell. Maybe it does burn a bit, we will see… I need to pull the plug.

well, it is an old flathead Briggs and as you said it sat for 5 years or more... things don't have alot of compression to start with and they do spin down when they shut off due to lowing compression and the flywheel effect of the mower blades

it is quite possible it has always been that way, which doesn't help you but it is one of those things that might be difficult to fix...

approaching the necessity of pulling the rope 5 to 10 times to start it... don't know if it is modern enough to have the " electronic" ignition or still has points.... but you could clean the carb and fuel tank, clean the air filter and stick a new spark plug in it to begin with...

and before you try starting it give it a whiff of starting fluid and give it a pull just to see if it will kick over like that... if it does then you sort of know it is something to do with fuel or the actual process of sucking the correct mixture into the combustion chamber.. hope this helps, didn't mean to be a smart ass..

 

[Egg_Head]

I had the exact mower for years and yes mine did the same thing. Looking at that picture, I still know how that handle feels in my hands when pushing it. That deck design is legendary. I eventually replaced the wheels, motor, plastic intake and bagger.

 

[JHZR2]

well, it is an old flathead Briggs and as you said it sat for 5 years or more... things don't have alot of compression to start with and they do spin down when they shut off due to lowing compression and the flywheel effect of the mower blades

it is quite possible it has always been that way, which doesn't help you but it is one of those things that might be difficult to fix...

approaching the necessity of pulling the rope 5 to 10 times to start it... don't know if it is modern enough to have the " electronic" ignition or still has points.... but you could clean the carb and fuel tank, clean the air filter and stick a new spark plug in it to begin with...

and before you try starting it give it a whiff of starting fluid and give it a pull just to see if it will kick over like that... if it does then you sort of know it is something to do with fuel or the actual process of sucking the correct mixture into the combustion chamber.. hope this helps, didn't mean to be a smart ass..

Oh it starts super easy now. I do think there’s something not quite right about the recoil or clutch, as it will sometimes make a bit of a screeching sound once the engine starts and the pull cord is being drawn back in…. But that’s another issue.

It started with a bunch of pills when first brought back to life. Probably because gas needed to be drawn in.

Otherwise starts fine, choke or not.

It has a “system 2” box on the engine, for electronic ignition, and the top says magnetotron or something like that. So I think it has a modern-ish ignition.