Box Stock

Isolator plate cheating

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fasttommy

Member
I think someone in our class is cheating. There engine seams to not want to idle but fast as hell on track. I think there getting extra air in behind isolate plate . Maybe no gasket or trick machine work IDK. Does that sound right
 
First thing that happens when someone is faster, accuse them of cheating. Introducing air after the carburetor is not a reliable way of making power.
 
Then fuel is most likely best place to start. Only way I can see getting consistent gains by messing with the isolator would be to make a small gap or something like that where the amount of air coming in is somewhat controlled at least. I have seen guys cut a notch in the isolator plate or the metal gasket between airbox and carb when there is no tech on those items. Not wanting to idle fan simply be a really rich carb setup also, which is usually how the stock engines run best. I bet you are getting beat by a legal motor, setup and tires instead someone cheating....that is usually the case. Great tires will be 3-4 tenths or more faster than good tires, and there is absolutely such thing as great tires or perfect tires when racing dirt
 
I think he meant filing a notch in it to allow air in. I can see it being an advantage but would more than likely have to go up on jet size.
 
So often the one of the first diagnostics given for poor running engines, or lack of power is check for intake leaks. Now we are hearing want to make more power, file notches in the intake spacer. Air leaks after the carburetor venturi will be virtually impossible to tune for. Any gain would be very narrow in range, all other RPM ranges would suffer, it would be a fluke at best.
 
I know that some are filing or machining the little grove off of the isolator plates, they are slick on both sides, if you don't need them why are they there at all
 
They are there to provide atmospheric pressure to the float bowl. Does the rule package not state a minimum thickness for the plate?
 
Sucking air on a unrestricted engine won't give the advantage you think.. Like said tough to tune for and likely not going to benefit a measureable amount.. NOW on a smaller restrictor plate engine the above statement isn't so true..

Its really very easy tech to catch anyone sucking air in the intake system... Bring out a can of LEAK Finder.. aka WD 40
Crank engine and allow to idle,, spray all around the front of carb,,isolator and intake port.. If engine speeds up its wrong / illegal.. Turn the light off and go home.. I don't even have to show them the hole or bypass..
 
My point was, in a all stock class, you wouldn't be able to simply file a notch in it and outrun everyone. He would have to go up on jets, which would be easily caught in tech if they check the engines. Generally, if they are cheating. It's not just one lil trick that they are doing. It's a chain reaction. U do one thing, it will require u to so else. So it's not hard to catch them in tech. Guess I should have explained.
 
kartboy63 said:
not in SA
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That is because some reroute the bowl vent in the SA carbs. Usually done to carbs with a big throttle bore so that you can port match the isolator to the carb and head without having to worry about cutting into the grooves in the isolator. The grooves are filled with epoxy.
 
fasttommy said:
I think someone in our class is cheating. There engine seams to not want to idle but fast as hell on track. I think there getting extra air in behind isolate plate . Maybe no gasket or trick machine work IDK. Does that sound right
Click to expand...

Seldom........if ever.....are kart races run at idle speed.
Our karts would not idle at all......no throttle, no run. The carbs were tuned for acceleration to WOT.
One of our class competitors took great pride in achieving as smooth pit idle as possible........we praised his talent and encouraged him to continue to seek perfection. :)
 
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