Intek twin 24hp OHV engine surges only when hot

[Chucksrt]

this started happening about two years ago so I replaced the carb and it seemed to clear up for a bit but started happening again. I also recently replaced the spark plugs and it seemed to run really well (higher reving) then it just acted up again. The kicker is that the mower runs fine until it is completely warmed up. Once it is hot the surging starts. If I cool the engine down by either letting it cool naturally or even if I hose it down, it will run smooth. I can't seem to figure this thing out. Any info on what to check next would be greatly appreciated.
Chuck

 

[Scrubcadet10]

NEVER spray cold water on a hot engine.... It can be bad for electrical components and metals don't really like being taking from One extreme to the other, (hot to cold)

Surging is caused by a lean fuel mix ratio, meaning there is either TOO MUCH AIR in the mixture or NOT ENOUGH FUEL in the mixture.... This could be the result of a leaking carburetor/intake gasket or even a cracked intake pipe (manifold).. Or if the fuel line falling apart internally bits and pieces can flow into the carb and plug things up blocking fuel.
Post the engine model numbers so we can see what particular set up you have, should be stamped into the Overhead valve cover at the front of the engine.

 

[Chucksrt]

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!!!

NEVER spray cold water on a hot engine.... It can be bad for electrical components and metals don't really like being taking from One extreme to the other, (hot to cold)

Surging is caused by a lean fuel mix ratio, meaning there is either TOO MUCH AIR in the mixture or NOT ENOUGH FUEL in the mixture.... This could be the result of a leaking carburetor/intake gasket or even a cracked intake pipe (manifold).. Or if the fuel line falling apart internally bits and pieces can flow into the carb and plug things up blocking fuel.
Post the engine model numbers so we can see what particular set up you have, should be stamped into the Overhead valve cover at the front of the engine.

 

[bertsmobile1]

You have an air leak
get a trigger pack
Fill it with WD 40 or similar
Start the engine then spray the engine with the WD 40 till it runs different or starts to blow smoke
The last spot you sprayed should be where the leak is.

 

[Chucksrt]

I sprayed starting fluid around the carb and the idle didn't change. This only happens when the engine is fully warmed up (HOT!). Otherwise it runs great. I can run it for roughly 10 to 20 minutes before the engine starts to surge. Just before it surges, you can hear the rpm drop slightly as if it was laboring to run. Thats also when I tried cooling it down with a hose to see if it affected it and sure enough it did. The engine ran better and stopped surging until it got hot again.

You have an air leak
get a trigger pack
Fill it with WD 40 or similar
Start the engine then spray the engine with the WD 40 till it runs different or starts to blow smoke
The last spot you sprayed should be where the leak is.

 

[bertsmobile1]

Yep. the engine gets hot and the crack opens up .
Spray cans do not cut the mustard and are highly likely to ignite
Do you think you will look sexy with no eyebrows ?

 

[Mower King]

Yep. the engine gets hot and the crack opens up .
Spray cans do not cut the mustard and are highly likely to ignite
Do you think you will look sexy with no eyebrows ?

I always cringe, and laugh at the same time when someone says they use starting fluid for trying to find an air leak or prime a carb......that sh*t will blow your a** up!

 

[Hammermechanicman]

Did the engine run better when you cooled the carb? Or the crankcase? How hot is the ambient temp? Have you checked for clogged cylinder fins? When it starts surging how hot is the carb to the touch?You might try to fabricate a heat sheild for the carb and see if that helps. What spark plugs are you using?

 

[Chucksrt]

It runs better after I cool the crankcase. The weather has been in the mid 90's recently. I haven't been able to tell how hot the carb is getting. I will have to remove the covers and run it to check. The engine is pretty clean. I don't see and built up debris. The spark plugs came from craftsman and are a Briggs and straten plug. As far as heat shields go, it has them installed from the factory. Oddly enough, after I replaced the spark plugs (not long ago) it seemed to run great!!! It may have even reved higher. But something happened and it reverted back to its normal running condition. It was weird. I actually pulled the plugs to inspect them but they were fine.

Did the engine run better when you cooled the carb? Or the crankcase? How hot is the ambient temp? Have you checked for clogged cylinder fins? When it starts surging how hot is the carb to the touch?You might try to fabricate a heat sheild for the carb and see if that helps. What spark plugs are you using?

 

[Scrubcadet10]

did you notice the color of the spark plug ends?