flathead runs hot

kartboy63

Member
I have a flathead that runs hot in about 5-6 laps, it gets up to 480, its a SA flathead, It is 80 over, 4.500 rod, stock crank, I run the cyclone carb, the flywheel is a clements small flywheel with the fins at 34* timing, I went down with timing and it didn't help, its a stock head that's been cut for SA with a fire slot and it has stock valves with the 112alt cam.
 

flattop1

Dawg 89
Methanol ?
Jet 62-64 ?
Kart too tight.
 
Sounds like a good build, I am not very familiar with the Cyclone carb, Never ran one my self. But I Have built a lot of engines with the 112 alt and the 3 hp flywheel no problem. Usually when you have too much heat it is running lean. With tillotson just turn the needle out . tune the carb for more fuel or bigger jet. Leave the timing at 34 to 36, I usually set timing at 36. The coil will retard at higher rpms. Sometimes up to 6 degrees.
Of course always If your kart is too tight that will run it hot also.
 

OVALTECH1

Premium User
Nothing was said about the amount of air that is able to get into the blower housing. How open is it?
 
Go up on jet with that carb until the engine can't take any more (ie the engine will cut off at peak rpm = foul the plug due to excess fuel.)
Once is starts cutting off at the end of the straight, either pull two teeth of gear off, or back up a jet size or two until it runs cleanly all the way around the track.


-----
?Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 

OVALTECH1

Premium User
if the exhaust valve is not sealed up perfect it will cause you to have to keep throwing jet to it as well as making your cht go higher than it should....might not be your issue just putting it out there
 
Leaking head gasket will do the same thing.
Check around the #7 head bolt (middle bolt on the left hand side of the engine) especially on large bore sizes for leakage.
 

Nickp

Member
Make sure the piece of sheet metal shroud is on the coil, It helps direct the flywheel air across the cylinder head.
 

kartboy63

Member
Go up on jet with that carb until the engine can't take any more (ie the engine will cut off at peak rpm = foul the plug due to excess fuel.)
Once is starts cutting off at the end of the straight, either pull two teeth of gear off, or back up a jet size or two until it runs cleanly all the way around the track.


-----
?Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
it does stumble a little on the starts but it clears up, but it don't cut out on top end
 

OVALTECH1

Premium User
usually a stumble down low is a lean stumble, these carburetors don’t really have the greatest transition recognition.
 

flattop1

Dawg 89
yea a tube with a couple small holes and a butterfly would work almost as good.
:)
 

OVALTECH1

Premium User
Lol! yeah that pretty much sums it up..
 
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