Intek twin 24hp OHV engine surges only when hot

[Hammermechanicman]

Most likely the problem is boiling gas in the carb and making the engine surge. Changing the plug heat range will not make the engine run cooler but you need to match the spark plug heat range to the cylinder temperature the engine is running at. Spark plug electrodes need to run in the self cleaning temperature range which is approx 950 degrees F. If running too hot you can get preignition. If the engine is running on the verge of boiling gas in the carb the RC14YC plug may be too hot and need to run the RC12YC for the plug to operate in the proper range. Looking at the plug will tell you about what temp it has been running at.

 

[Mower King]

That number isn't on the plugs!. Here is a pic. Do you know what the gap should be set to?
Thanks Chuck

Spark plug gap is .030

 

[bertsmobile1]

Chuck.
Start the engine and run it till it starts surging .
Slowly choke the engine
If the surging continues then you have an air leak after the carb venturi tube
If the surging stops then you have a fuel supply problem
I am yet to see a spark plug causing surging

 

[Hammermechanicman]

Plugs won't cause surging but i have seen them run hot enough to cause pre ignition that makes the engine run very rough.

 

[Fish]

When it starts acting up, partially close the choke and see if it runs better.

If it still runs poorly,

Try adjusting the valves after it cools completely, one of them might have too little clearance.

 

[Chucksrt]

I attached a picture of the plug earlier. Here it is again. It looks really clean. I tan take a better pic of the electrode if needed

Most likely the problem is boiling gas in the carb and making the engine surge. Changing the plug heat range will not make the engine run cooler but you need to match the spark plug heat range to the cylinder temperature the engine is running at. Spark plug electrodes need to run in the self cleaning temperature range which is approx 950 degrees F. If running too hot you can get preignition. If the engine is running on the verge of boiling gas in the carb the RC14YC plug may be too hot and need to run the RC12YC for the plug to operate in the proper range. Looking at the plug will tell you about what temp it has been running at.

 

[wrldtvlr]

I attached a picture of the plug earlier. Here it is again. It looks really clean. I tan take a better pic of the electrode if needed

The parts of interest are the center electrode, side electrode and tip insulator. I'm no engine guy, but from what I can see there's no carbon buildup on the plug (which would indicate the plug was too cold), and the insulator and electrodes aren't burnt (plug too hot). Check the gap, but to me it looks fine.

 

[StarTech]

I sprayed water on it as a test to see if it would affect the surging issue, and it did. I just think that its really odd that it only surges when it is fully warmed up (hot). I attached a pic of the label that you mentioned. Thanks again for for your help!!!

That is the emission label and is of no help. On one ofthe valve cover should be the model, type, and date code stamped into it.

You may have a leaking head gasket or bad ignition coil since cooling the crankcase changing the engine operations.

 

[Hammermechanicman]

I attached a picture of the plug earlier. Here it is again. It looks really clean. I tan take a better pic of the electrode if needed

A pic of the center electrode is what i was looking for. If the white insulator is a tan color the plug is runnig the right temp. If the insulator is white and the ground electrode is pitted or looks like it was sand blasted the plug is running too hot.

 

[Chucksrt]

A pic of the center electrode is what i was looking for. If the white insulator is a tan color the plug is runnig the right temp. If the insulator is white and the ground electrode is pitted or looks like it was sand blasted the plug is running too hot.

The plugs are newer and when i pulled them for the kast pic that i did submit they still looked new. I can take a better pic if needed. It stopped surging when I completely removed the front hood assembly. Not sure if the black painted hood was heating up and or if the engine was heat soaked from the cover being installed? But I ran it for over an hour without the hood and it ran great.