New problem with Briggs 16HP Cast Iron

[Rick3410]

I just resolved the magneto issue with this briggs by replacing it with a coil system. Had it running beautiful. Great idle speed and fabulous top end. Had it ready to mow this morning and decided to wait until this afternoon and let the grass dry good. Just went out to mow and it doesn't want to start. Checked the spark and it looks fine. Checked all of the wiring and everything looks good. Turned it over again and it started but only runs at slow speed. If I throttle it up, it stalls. Looking at the points, I see sparks and if I try to adjust them the engine just stalls out. I tried to adjust the carburetor secondary to see if I could bring the engine speed up when throttling but no luck. In fact it runs better when I completely close the secondary adjustment. What could have happened to this thing from sitting a few hours. I can't tell you how great it was running and now, zilch! Help, anybody had this happen? Adjusting the points while it's running is getting me no where.

[mtoney]

Sounds like some crap got into the carb. That being said, my 16hp cast iron single briggs only likes to be started at idle, the you have to carefully throttle up as it will die, espicaly when cold if you come up to fast on the throttle. Once at mid rpm or once warmed up, its fine to throttle up normaly. But it still prefers to be started at idle. Carb is clean as a whistle and it runs flawlessly when mowing or even just sitting there, no surging ect. I do have in inline fuel shut off as it likes to drip gas when the tank is full and it sits for any length of time. Just like some of the old Farmalls or WD45's with updraft carbs! Mike

[Rick3410]

I let it warm up but still cannot throttle it up. Just stalls and runs real rough. Normally I can go to top speed down to slow and back and it doesn't miss a beat. I also have an in line fuel shut off. My carb has just been rebuilt as well.

[Rick3410]

When I can get an engine to idle but can't get it to throttle I think of two things. Fuel and timing. Carb is a new rebuild (less than three months) and points who knows. That's why I was playing around with the points but it doesn't seem to make a difference.

[mtoney]

Mine has had a pointless ignition installed on the engine prior to my ownership, so no points to be bad or out of adjustment. Just a little grey heat sinked electronic gizmo under my points cover. I have no idea of what brand it is. Still uses the standard ignnition coil ect. So mine is probably a carburation issue, but it hasnt been bad enough to deal with. I wonder if you got some bad gas?? Like water or to much ethanol in it? Might try draining the tank and carb, refuel with a different source of gas. Mike

[mtoney]

Also, I have seen a decent looking spark on a spark test light, and with the plug outside the bore, but under compression and at anything above idle, the compression would "blow" the spark off the plug and the tractor wouldnt run. Cause was a failing/weak condensor. swapped it out and it ran like a top. Just an idea!

[Rick3410]

Just swapped the condenser, no change.

[Rick3410]

Just reset the gap on the points and no change. Starts fine at low idle and throttles up a little bit. Too much it just stalls. Running very rough. Turn the carburetor secondary (high idle) valve in all the way and it runs smoother. Any ideas? I gotta get this lawn mowed.

[Ronald Hribar]

Did it backfire at anytime

If so check flywheel key

[Rick3410]

I eliminated the flywheel magneto set up and went to a 12v coil so the flywheel location should not matter.

[Rick3410]

Found a wire location that compressed when the hood was closed. shorted intermittently to ground and was keeping the motor from running full speed. The more throttle, the more vibration, thus the shorting and stalling of the engine. Thanks everybody for your help. Running like a champ again.

[simple_stan]

I would look at the link between the carb and the governor. I chased a problem for hours and found that the throttle shaft was loose. When the governor tried to open the throttle, only the tab on the throttle shaft rotated.

[mtoney]

Awsome, hope you got the grass mowed. Mike

[Rick3410]

Thanks, Mike.