Prestige help

[Angry Bear 90]

Ok guys, I’m working on a 2014 Prestige with the 27hp Briggs Commercial engine. (Machine #2691181, Engine #49T877-0011-G1)

I’m kinda lost on this one. I don’t think the right side cylinder is doing it’s share. I have spark. I even swapped coils from side to side, with no change. It doesn’t run at full rpm, and when you kick the deck on, it almost dies, but then comes back up. Real boggy while mowing. But what’s odd is that if I take the RH plug wire off, there’s no change in engine performance. If I take the LH wire off, it starts surging and running poorly. So the RH cylinder must be doing SOMETHING, otherwise it would just die when I take the LH wire off. I’ve been through the carb. It was pretty clean. New spark plugs gapped to .030. Compression at 150 on both cylinders. The machine only has  212 hours. I don’t see any chewed wires or anything. Anyone have any ideas?  

[LMichaels 57]

What triggers the coils on that engine? Do they fire in unison (IOW is it a waste spark system) or individually? If it's a waste spark system than it is most likely not ignition. What is the fuel delivery system on that engine? Perhaps the issue is there. Again though if it's a common carburetor  than odds are the issue is not there.

[Angry Bear 90]

Individual coils fired by the magnets on the flywheel. Twin barrel Nikki carburetor (p/n 799511)

[SmilinSam 3,621]

Just throwing rocks in the dark...but have you checked the valve clearances? assuming they are adjustable.

 

[Angry Bear 90]

I have not. But that’s gonna have to be my next move I think. Assuming they are adjustable, like you said. 

[LMichaels 57]

If it was valve clearance the compression would be off. My guess is the carb especially if the cylinders are fed individually from each "barrel" of the it. I am hedging only because I have no knowledge of that particular engine and am going from automotive knowledge more than anything

[Cityboy 0]

2007 Legacy XL with the same engine I had to replace the coils with a retrofit system. It had acted up for some time, and did not get better. Coil kit fixed it. Still going strong! Good luck.

[Angry Bear 90]

51 minutes ago, Cityboy said:

2007 Legacy XL with the same engine I had to replace the coils with a retrofit system. It had acted up for some time, and did not get better. Coil kit fixed it. Still going strong! Good luck.

Right, but if it were a coil issue, it should have followed the coil when I swapped the coils from side to side, right?

[Ronald Hribar 70]

Simplicity has a diode for each coil

they are on the ground wire

you can disconnect the wires off each coil

and see how it runs

you can still stop with the key

as the fuel solenoid will stop motor

but Briggs motors need valve adjustments frequently

[Angry Bear 90]

2 hours ago, Ronald Hribar said:

Simplicity has a diode for each coil

they are on the ground wire

you can disconnect the wires off each coil

and see how it runs

you can still stop with the key

as the fuel solenoid will stop motor

but Briggs motors need valve adjustments frequently

I’ve disconnected the plug wires while running. The RH cylinder wire makes no difference. The LH cylinder wire removed, it will start to run poorly, but not die. I visually checked for spark on both cylinders also. 

Edited July 5, 2018 by Angry Bear

[Angry Bear 90]

Valve clearance spec is .004”-.006”. Intake is at .005”, exhaust is at .004”. So I’m not seeing a problem there. 

[Angry Bear 90]

Sprayed all gaskets and pertinent intake areas with carb cleaner while running to check for intake leaks, since a Briggs tech told me to try that. Nothing. Ordered all new carb and intake gaskets to be safe and gonna go through the carb again just in case I missed something. 

[PhanDad 3,248]

Definitely a head scratcher problem.

 

[Angry Bear 90]

On 7/6/2018 at 8:02 PM, PhanDad said:

Definitely a head scratcher problem.

 

Yeah. I’ve done everything that I know to check. The only thing that I don’t know for sure is that it’s getting ENOUGH fuel in that RH cylinder. So that’s why I’m gonna go through the carb a second time.