B&S engine won’t start!

[Kurtatron]

7.8hp B&S engine won’t start. It is separated from a broken generator.

Spark plug shows spark when removed, braced against valve cover, and engine spun.

Compression test cold shows 60psi.

After trying to start the thing with fresh E-0 gas to no avail, I emptied carb and now tried to start with starter fluid. I can’t get this thing to fire once!

What I do get is a literal fire outside the intake where the starting fluid has ignited on the filter housing. I’m stumped here.

I did install a new coil, since old one wasn’t firing. It looked different than the OEM one, but the engine RAN fine with the new coil in the summer.

I had cranked the thing for 20 minutes with starting fluid at different choke settings and didn’t get a single fire. I got a few pops of unburnt fuel bursting out the exhaust but that’s it!

I can’t figure this out!

 

[Spring Break '92]

If you own anything with a small carbureted engine, 98% of the time it's a carburetor problem. I just went through this last weekend right in front of the ice storm. The smallest - and I mean, the teeniest tiniest little piece of debris in a jet can make it not start or run poorly. If you don't need this generator right away, order another one on Amazon. Either way, get some carb and choke cleaner and always keep some on-hand. Remove the carb take everything out, keeping track of what went where and which way it was oriented.

Spray every part on the inside and outside, and you can even spray some in a glass jar or bowl to soak the parts that meter fuel. Now, get a thin sewing needle, a heavy piece of stiff fishing line, a twist tie with the plastic removed, anything that will fit inside the carb jet holes and all other holes, to clear them out. Be mindful not to get carb and choke spray on any gaskets or rubber o-rings, it will eat them away.

It's a good idea with a generator to have two carburetors - one for the generator and one for the shelf that has been cleaned (and possibly rebuilt) to swap out, and keep them in rotation. Then this situation is easily remedied. Whatever you do though, if you don't plan on starting it up again within a week or so, shut the motor down by cutting the fuel off and starve the engine to make sure no fuel sits in the carb. And also you may want to drain the title bit of fuel left in the carb bowl.

 

[Kurtatron]

If you own anything with a small carbureted engine, 98% of the time it's a carburetor problem. I just went through this last weekend right in front of the ice storm. The smallest - and I mean, the teeniest tiniest little piece of debris in a jet can make it not start or run poorly. If you don't need this generator right away, order another one on Amazon. Either way, get some carb and choke cleaner and always keep some on-hand. Remove the carb take everything out, keeping track of what went where and which way it was oriented.

Spray every part on the inside and outside, and you can even spray some in a glass jar or bowl to soak the parts that meter fuel. Now, get a thin sewing needle, a heavy piece of stiff fishing line, a twist tie with the plastic removed, anything that will fit inside the carb jet holes and all other holes, to clear them out. Be mindful not to get carb and choke spray on any gaskets or rubber o-rings, it will eat them away.

It's a good idea with a generator to have two carburetors - one for the generator and one for the shelf that has been cleaned (and possibly rebuilt) to swap out, and keep them in rotation. Then this situation is easily remedied. Whatever you do though, if you don't plan on starting it up again within a week or so, shut the motor down by cutting the fuel off and starve the engine to make sure no fuel sits in the carb. And also you may want to drain the title bit of fuel left in the carb bowl.

Did you read my post? I tried with the carb empty on starter fluid. Should fire with carburetor fluid. It does not.

 

[spasm3]

Not firing with carb spray makes me think sheared keyway and its out of time.

 

[Dborch41]

Backfiring through the carb can be a valve issue, even with good compression. Also, make sure your new coil isn't installed 180° out, in other words the side that should be facing the engine is instead turned outward. I'd check that first.

 

[Dave Sherman]

Agree with spasm3. If you've got compression and spark, and it won't go even with some spray shot in the carb, then I'd go with being out of time, possibly the flywheel key sheared. OR, just occurred to me, since you say you replaced the coil, did you get it mounted the right way? Won't work if it's upside down.

 

[zrxkawboy]

Compression sounds low, unless this engine has some type of decompression system for starting.

 

[spasm3]

Not firing with carb spray makes me think sheared keyway and its out of time.

Backfiring through the carb can be a valve issue, even with good compression. Also, make sure your new coil isn't installed 180° out, in other words the side that should be facing the engine is instead turned outward. I'd check that first.

Compression sounds low, unless this engine has some type of decompression system for starting.

Thinking about this more, I would pull the valve covers and make sure all the valves are moving.
I seem to remember B@S having some bad camshafts maybe with a decompression system.

60 psi sounds low for compression.


Google briggs and stratton bad camshafts and see if you can match up model numbers , see if yours is included, or if it's not an issue with your model number.

Do you know how the generator failed?
If the generator head seized suddenly , it could be a sheared keyway.

 

[The_Eric]

60psi is pretty normal for engines with a compression release mechanism.

I agree that you should check the flywheel key and it wouldn't hurt to check the valvetrain either.

 

[grasscutter]

An inline spark tester is a good way to eliminate one of the variables fast.

Even if it's a fuel delivery issue, the engine should "bark off" with fuel in the combustion chamber.

If the engine has compression release, you can spin the engine over fast enough with a drill to overcome the compression release.

https://www.amazon.com/Lisle-20610-Inline-Spark-Tester/dp/B0002STSC6

 

[Kurtatron]

An inline spark tester is a good way to eliminate one of the variables fast.

Even if it's a fuel delivery issue, the engine should "bark off" with fuel in the combustion chamber.

If the engine has compression release, you can spin the engine over fast enough with a drill to overcome the compression release.

https://www.amazon.com/Lisle-20610-Inline-Spark-Tester/dp/B0002STSC6

I used a timing light to verify I’m getting spark when I pull start it.

 

[PontiacHO]

Flywheel key doesn’t have to be total sheared to allow for incorrect timing. Get the cover off and most likely you can see if the flywheel keyway is not perfectly aligned with crankshaft keyway.

 

[mk378]

It probably needs the flywheel effect of the generator rotor to run. The flywheel on the engine alone is not heavy enough. Push mowers are the same way, it simply won't start with the blade removed.

Also it's hard to get much rpm from a starter cord without the engine bolted to something substantial.

 

[Kurtatron]

Flywheel key doesn’t have to be total sheared to allow for incorrect timing. Get the cover off and most likely you can see if the flywheel keyway is not perfectly aligned with crankshaft keyway.

Is this bad?

 

[Kurtatron]

It probably needs the flywheel effect of the generator rotor to run. The flywheel on the engine alone is not heavy enough. Push mowers are the same way, it simply won't start with the blade removed.

Also it's hard to get much rpm from a starter cord without the engine bolted to something substantial.

No, I had it running in the summer without the generator.

 

[mk378]

With the flywheel cover off probe in the cylinder and check that the magnets pass under the coil about 10 degrees before the piston reaches top dead center.

 

[2strokeNorthstar]

Checked the exhaust? I had one that wouldn't fire and made no sense. Exhaust was plugged. Removed, blew out someone's nest and fired right up

 

[fantastic]

Is this bad?

View attachment 322329

View attachment 322330

I don't see the key...lol
The flywheel should pop off if you look at some YT video tricks. Basically a screwdriver pressing up while you lightly hit the crankshaft top w/the bold on it still.

 

[grasscutter]

I used a timing light to verify I’m getting spark when I pull start it.

If you're getting spark the next step is to pull the spark plug to see if it's wet with fuel.

 

[Kurtatron]

I am wondering if my spark is too weak. I watched a video about strong vs weak spark. I thought any spark would be good enough, but that’s not true. The video showed that a strong spark is nearly as bright as an LED. My spark is barely noticeable.