Need some help with an old B&S engine. Never experienced this before.

[kentuckydiesel]

Don't know if this should fall under "large equipment", but I need to see if you guys can think of anything I haven't.

I have an old Dayton generator bought by my grandfather in the 70's. Has very few hours on it.

I'm am having the strangest problem.
I can go out, open the fuel bowl valve, pull the rope, and it will fire up/run smooth on the first pull.
Problem is, it will run strong and smooth for 15 seconds or so, then die like an ignition switch was turned off...but it doesn't have an ignition switch. It was one of the old style that had a tab you stepped on to ground the plug. If I try to restart it right away, it might pop once, then nothing unless I leave it alone for a few minutes, then starts and runs for another 15 seconds.

I have taken the carb apart and cleaned it, checked/gapped the points (they are like new), and tried a different condenser, same thing. Polished up the magnets on the flywheel along with the legs of the magneto, same thing.
I finally decided it must be the old magneto breaking down and quitting after 15 seconds, so I got a brand new B&S magneto...same thing. I then thought that the wire to the points might be bad, so I wired in a replacement straight from the mag to the points...same thing.

I know what you're thinking...ignition system must be working...has to be in the carb. Well, when it shuts off, I cant even keep it running with a spray of ether straight down the throat of the carb....and if I take the screw out of the bottom of the carb right after it dies, fuel drains out...so I have fuel.

I have never seen anything like this. Is there any possibility that something in the generator side is backfeeding and throwing off the magnetism of the flywheel? I know, I'm reaching here. BTW, the gen side does produce electricity. I have tried plugging in a big halogen light set and firing it up...they burn bright for that 15 seconds until the engine dies.

At this point, any ideas would be a big help!

Thanks,
Phillip

 

[Walt41]

Before you get any grey hair over it, clean up the valves. Sounds like a hanger.

 

[kentuckydiesel]

Before you get any grey hair over it, clean up the valves. Sounds like a hanger.

Hmm...didn't know the B&S had problems with this. Is it a similar problem to the old Kohler engines? Do the B&S need Marvel Mystery oil to keep valves lubed like the Kohler's do?

Thanks!

-Phillip

 

[kentuckydiesel]

BTW, here is the IPL if specific model number helps.
http://bsintek.basco.com/BriggsDocumentDisplay/18mqvGXAnfBhU7y.pdf

Thanks,
Phillip

 

[LegDeLimber]

If you can, try turning the engine backwards
before you crank it (engine cold) and then try back turning it
right after the engine quits again.
Notice if it feels different.

you need turn the engine backwards because of the compression release
bleeding off pressure when turned in normal running direction.

just to be sure of things, check to see if the spark will jump a 1/4" gap
at cranking speed.
an old magneto like that should throw an audible, FAT blue spark at cranking speed.

(was mainly idiots under push mowers and their lawyers, that killed that easy sparking for us)

that big wallop of current was a large part why those old motors would would still run ,even when burning bad amounts of oil.

also look at the throttle linkage to see if the throttle is sticking open
or problems with choke postion.

can't recall all of the varietys of those throttle positioners on the gensets.
just trying to think of all the things that may need attention on an old
unit like that.
But if throttle control is sticking or pulling it open too quick,
could give trouble with starting
(holding throttle open, wont draw fuel well at cranking speed)
or opening to soon... etc.

 

[Walt41]

Hmm...didn't know the B&S had problems with this. Is it a similar problem to the old Kohler engines? Do the B&S need Marvel Mystery oil to keep valves lubed like the Kohler's do?

Thanks!

-Phillip

I've done literally hundreds of them, I pull the valves and chuck them in a drill and clean them on a scotchbrite pad, polish the seats and call it good. Any excess carbon can be remove with a soft wire wheel on a drill and a shop vac, don't get rough in there, scratches are not good.

 

[kentuckydiesel]

Okay will try that stuff.

Throttle position/governer is just as it should be and choke is a simple lever bolted directly to the choke butterfly shaft.


Thanks,
Phillip

 

[Walt41]

I know you probably did this already but did you try a different plug?

 

[kentuckydiesel]

I know you probably did this already but did you try a different plug?

Funny you ask. I'm almost positive I did...but I was thinking about it last night and can't remember for sure. I've been working on so many things lately that. That is one of the things I will check this evening along with the other things suggested.

Thanks,
Phillip

 

[CalTreeEquip]

Yes, replace the plugs. Also, since its on a generator, if you have then gen on when the engine is trying to warm up, that can kill it. Had that problem with an old welder I do believe. Switch the gen off then see what happens.

 

[kentuckydiesel]

Found the problem! Took the carb apart again and fount that the goofy 45degree carb nozzle tube had developed a crack. Got a new one and it runs like a top. Extremely odd that this caused the problem, but it's fixed!


-Phillip

 

[LegDeLimber]

Good to see you got it fixed.

Used to see those old updrafts with bent brass, fairly regularly.
People would try to force the bottom off the carb without removing them
and it didn't work.

...usually looked like a butter knife and worn out pliers were used to dismantle the carb
and a major overhaul kit for one was pricy,
when you had to replace all the damaged bits.

funny how much stuff I've forgotten and these threads bring some of it back.
just wish it came back to me at the beginning, instead afterwards.