[RideoutKSC]

I have a 20hp V-twin Briggs and Stratton that has been giving me problems ever since I bought it as a project back in April.

I have replaced the governor, a gear in the transaxle and most recently rebuilt the carburetor but have had one problem this entire time.

The left cylinder exhaust header glows red. The right cylinder exhaust seems to run cool and pops occasionally. From low to mid throttle the engine runs smooth, but anything otherwise and it pops (from the right side only).

I tried adjusting the valves but nothing changed and I'm not sure if I did it correctly. Assuming I DID adjust the valves correctly, do you think there could be other issues at play here?

Thanks in advance,
Mike

 

[Bill Kapaun]

Some of them have different size carb jets from one cylinder to the next.
Possibly swapped?

Download the IPL for your engine from the Briggs site and see if yours is one of them.

I'dalso examine valve travel to make sure they move the same amount. (flat cam lobe?)
Since you have to remove the valve covers to do this, you might as well look for a blown head gasket.
One at a time, remove one valve cover, have a rag handy and start the engine.
Look for a "mist" blowing out in the gasket area near the push rods.

 

[RideoutKSC]

Thanks Bill!

I actually saw some mist coming from the RIGHT side of the engine when I ran it at full throttle. Would a side-effect of a blown head gasket be popping and a cooler exhaust temperature in that cylinder?

 

[DonF]

Yes you need fuel, fire, air and compression for it to operate. Missing any one of the four can cause it not to.

 

[Bill Kapaun]

When under load, the "good" cylinder has to work harder and will thus run hotter.
I'd expect the "bad" cylinder to run cooler, since proper combustion may not be taking place. I'd expect that to be somewhat variable, depending on how low the compression is.
Between the two?????

Also, if combustion isn't taking place, you may have unburned fuel getting discharged into the exhaust system where it ignites.

 

[RideoutKSC]

I decided to take the heads off tonight. I found fuel residue in the right side intake took and intake runner on the cylinder head. I think I'll lash the valves and clean the carbon off. Should I do anything else?

By the way, I'll be using this machine to remove snow this winter and tow a dump trailer full of fire wood so I need it running absolute TOPS! Ideas/ Advice appreciated!

Here's what they looked like...

 

[RideoutKSC]

UPDATE: The right side cylinder (the one that ran cooler) had a ton of carbon built up around one of the valves. I've spent over an hour cleaning it up and have ordered new cylinder head gaskets.

The valves seem to be sealed nicely, as I could pool cleaner in the combustion chamber while cleaning the heads without any leak down. Do you all have any thoughts on that?

 

[rscurtis]

I don't see anything wrong with those heads. You still have another problem, maybe a bad coil, or if it has a two-barrel carburetor, one side is not delivering fuel. Carbon in the intake could also indicate a bad exhaust cam on that cylinder.

 

[Bill Kapaun]

You tore things apart maybe a bit prematurely.
My next suggestion would have been to check the amount of valve travel between the 2 cylinders to check for a bad cam lobe.
Some of these eat cams and you'll get a valve that barely moves.

 

[Walt 2002]

I can send you a Service Manual for the engine IF you like, address below, put in proper format and remind me, engine model number and what you want.

Walt Conner
wconner5 at frontier dot com

 

[RideoutKSC]

I swapped in new head gaskets and rebuilt the carb. It runs MUCH better with no popping and a nice and even idle speed. I adjusted the valves but did not measure valve travel. I had to chip the carbon off with a wooden chopstick. There is still a difference in exhaust gas temps but it seems to be less of an issue so I'll run a compression test soon. I'm guessing it could be a bad cam since other parts inside the engine were junk when I bought it.

 

[RideoutKSC]

I performed a compression test this morning before work.

Left side = 160
Right side = 120

New Head Gasket and adjusted valves. Looks like I'll measure the valve travel next. I'm thinking possible issues include...

bad valve(s)
bad cam lobe

Am I right? Could there be more?