Glowing Pipe

[james1]

Hi Guys,

This is my first post on this board. I'll get right to the point. I had to replace the magneto and headgasket on a Briggs 12.5 horse motor. It was night when I fired it up to make sure everything was working. After a minute or so, the exhaust pipe started glowing bright orange until the point it reached the muffler! I couldn't believe how hot it looked. There is usually a metal baffle over the exhaust so I have never been able to see the pipe coming right off the cylinder. I don't think the timing is off since it looked like the piston was TDC at the correct flywheel position. It this glowing pipe normal? I don't want to melt my valve etc. Thanks!

 

[SteveD2]

No, that's definately not normal. Maybe it's running too lean?

 

[mrchecker]

It's not unusual for the exhaust to glow at night. When I've run small engines at night I've seen this. On my Dad's 8 HP B&S generator, the whole muffler is orange under load. As long as you can't see it glow in the daytime, don't sweat it. Like ZmOz said, it may be running lean. Is the mixture adjustable or is this a new commie carb?

 

[Brett Miller]

Normally this is caused by the timing being retarded. The spark fires too late and fuel is burned in the exhaust. You may want to try another magneto and check the flywheel key.

 

[blano]

A stuck choke or a overly rich mixture will also cause the exhaust to glow on a four cycle motor like the ones found in lawnmowers.

 

[james1]

Thanks guys. The carb may be the culprit. It was allowing gas to flow down into the oil pan. Found out the hard way when the mower was belching black smoke after a long period of non-use. The oil about 30% gas, but boy the cylider was sure clean! I cleaned the carb pretty thouroughly, but will try adjusting the mixture since I may have messed it up. If it still glows afte that, I will assume it is somewhat normal. I will double check the timing, but I don't know how it could be off since I never touched the flywheel.

 

[Bill Kapaun]

I've never seen too rich of a mixture cause a small engine muffler to get red hot. Maybe it will in a Cat Convertor as found on a car..
A dull glow while in the dark may be somewhat normal, but it shouldn't be a "bright" glow.
Typical sign of a too lean mix.

 

[blano]

Bill, Its actually quit common on four cycle dirt bikes and other small four cycle motors. The rich mixture can not be all burnt in the combustion chamber so the excess is burnt in the exhaust causing the glow. FWIW I have also seen gen set engines have glowing pieps under normal operating conditions.

 

[pfgslg]

If your Kohler has a diaphram fuel pump, the leaky diaphram will let gas into crankcase. This condition WILL TAKE OUT your rod and crankshaft.