Old 8hp Briggs and Stratton stalls regularly

[gpburdell]

Here is a picture of my engine, it is a basic old 8HP pull start engine. I don't think it has a valve cover to take off and measure, I think I'd have to take the head off to get to the valves. There don't appear to be any points, just a coil next to the flywheel that has two wires, one is the spark plug wire, one is the wire you ground to kill the engine.

Fish, I don't mind checking the valve clearances, is there a way to do that on this type of engine without pulling the head off? It doesn't seem to be a gradual problem as it's heating up, it funs fine and then all of a sudden dies.

Upupandaway, it dies after 5-10 minutes and then dies every 1-2 minutes after that when you re-start it. It runs completely smooth until it dies and when it dies it mostly sounds like you turned the key off. Every now and then it will start to die and then recover and run a couple more minutes before dying. I have put an ignition light on it and watched it when it dies and the light shows good ignition as it's stalling.

I'll get some starter fluid and try spraying that in when it stalls and see if it fires.

 

[slomo]

it is a basic old 8HP pull start engine. I don't think it has a valve cover to take off and measure, I think I'd have to take the head off to get to the valves. There don't appear to be any points, just a coil next to the flywheel that has two wires, one is the spark plug wire, one is the wire you ground to kill the engine.

Basic Briggs magneto sounds like. Pull the small kill wire. Should drain the tank dry if it's good. That coil needs to be LOAD TESTED to rule it out. As in a PET-4000. Look it up on youtube. Not some Christmas light inline waste of time ignition wire checker. All electrical circuits require load testing. As in full amp draw for that circuit.

checking the valve clearances, is there a way to do that on this type of engine without pulling the head off?

Yes, there is a breather cover with two screws vertically that hold it on. Under that are your valve springs and keepers. That is where you check the gap. Use a new gasket when done and DON'T OVER TORQUE the screws when you reinstall the breather. Gentle snug is all you need.

You've missed something. Easy as that.

You claim to have checked everything and still doesn't run. Most likely a fuel issue. Again, that fuel tank has to be SPOTLESS inside. Carb as well.

Make a video and post it on youtube. Show us what you are working with.

 

[Rivets]

Looks to me like that engine will have a points and condenser ignition system. Go, where does the second wire go, under the flywheel or to a ground connection? Either way I’m thinking you may have a coil with either a hot open or hot short, which causes lose of spark when the coil gets hot.
Slomo, why do you keep recommending that a DIY guy spend $40.00 on a spark tester that they will use once maybe twice. I’ve been at this for a lot of years and have yet to see where that tool has a location in my tool box. Inline tester is much cheaper and easier to understand for the average guy.

 

[bertsmobile1]

And to get to the valve chest you need to remove the carburettor because it is right behind it

 

[gpburdell]

Sorry if I misspoke, didn't mean to imply I'd checked everything or it would be fixed, lol. I've only checked the basic things that I knew to do and am trying to figure out what else to check. I've flushed and cleaned out the fuel tank again. Thank you for the tip on the valves, I'll take that cover off and see what the valves look like. I'll work on it this weekend and report back what I find.

 

[Fish]

Sorry if I misspoke, didn't mean to imply I'd checked everything or it would be fixed, lol. I've only checked the basic things that I knew to do and am trying to figure out what else to check. I've flushed and cleaned out the fuel tank again. Thank you for the tip on the valves, I'll take that cover off and see what the valves look like. I'll work on it this weekend and report back what I find.

If you have the top off, snap a pic of the flywheel/coil area. The last set of numbers on the stamped model numbers is the date code. If it starts with the numbers 83/84 or less, then it has points, as that looks like the original coil. You may still get a flash on your ignition tester, as you would on a spark plug.

Checking the valve lash on these is more involved than with an OHV model, you might watch a youtube video of it or 2. I may do a video of it someday, as most of the youtubers don't do a good valve service, but it will give you a general idea.

 

[Fish]

From the looks of the air filter, it is an older engine with points, so I would look there first. The points are under the flywheel, so generally it is much easier to just snip the wire to the points, and bolt on a new electronic coil, so no need to pull the flywheel.
On a Snapper, getting to the valve cover is not the easiest thing either. But a check of the clearances is definitely a good diagnostic step.
I stress doing testing before just buying parts, as I hate wasting money.

So take a pic of the top of the engine with the starter off, so we know for sure if you have points, as it may have had the electronic kit installed on the old coil.

 

[gpburdell]

I forgot to include that last code. This engine is a model 190702, type 2130-01, code 85010810. The date code is 85 so sounds like it isn't points. The owner manual that came with the engine shows both a foam filter and cartridge so this must be right about the time they changed over. The valve clearance is 0.004 intake and 0.008 exhaust. The spec says it should be 5-7 on intake 9-11 on exhaust so it's just a tiny bit out of spec. I did not remove the head to get the piston in exactly the right position so possible I'm off a bit.

I cleaned the gas tank out again and I also discovered you can buy a whole carburetor for $26 so decided to try that since it wasn't expensive. That did not completely fix the issue but did change the behavior. It now tries to stall every couple of minutes but catches itself and recovers. I'm going to re-examine the fuel supply. I've also never taken the head off the mower, should I go ahead and do that and clean all the carbon out? I can tell from cleaning the spark plug there is definitely some build up in there.

 

[bertsmobile1]

85 will be points
Atom patiented the Hall Effect Trigger in 1966 ( from memory )
Although B & S could have installed them for a 50¢ royalty per unit they decided to wait till the patient expired which would have been 1996 if I got the 66 patent date correct .

 

[slomo]

Slomo, why do you keep recommending that a DIY guy spend $40.00 on a spark tester that they will use once maybe twice. I’ve been at this for a lot of years and have yet to see where that tool has a location in my tool box. Inline tester is much cheaper and easier to understand for the average guy.

Right tool for the job. They are $70.00 now. Better to see the full capabillity of the coil compared to a light which doesn't show the condition of the coil. Brown spark or nice blue purple spark. You can't tell much using the Christmas lights you guys use. Most people are fooled when the dome light works but the car won't start. Average guy doesn't need to be working on a lawn mower. Usually create more problems for themself.