Box Stock

Predator questions/advice

Z

Zach Jaynes

New member
Hey guys, I'm in the process of setting up a predator for my son's jr sportsman champ. I have a brand new motor straight from Harbor Freight. The changes allowed at the track we will be racing are as follows:

remove governor
racing filter
racing header/muffler
top plate/fuel pump

I have been told that switching to a racing filter will affect the air/fuel mixture enough to warrant changing jet size. Is this correct,and if so, what size jet do you recommend starting with? Also, I figure that I may need to put a restrictor plate in as he is a 6 year old rookie driver. What size do you recommend?
Are there any other things that I need to do to a box stock motor? Thanks in advance for any help.
 
Are there not classes specific to his age? If so the class should specify the restrictor size.

If you want to start him and just practice to get seat time just remove the govenor, leave the muffler and filter.
 
This is a new track (karting is just starting to take off in our area) so the kart count is fairly low and they are just running all the kids together for now. As you said, I'm just wanting him to get seat time at this point.
 
Zach not for sure, if its a stock Predator class I don't think you are suppose to change the jet size. But if it was a Clone I would think about a 36 to a 38 would work ok with all the stock parts in the Predator. JMO
 
If you put a filter adapter and a pipe, around a 24 low speed, and a 33 to 35 main.
It would be plenty too fast for a 6 year old rookie. A wiener pipe and stock air box, will still get down pretty good. We run an adult class that way and we are 1/2 to 3/4 a second slower than the fastest clones at our track. Our fastest pro clone has logged mid to high 9's, our fastest predator ( wiener with stock box ) has ran 10.01. My nephew with a big pipe predator ( total kart/ driver weight 245) could play with clones,
You will probably need a restrictor at first, they run better than most anticipate.
 
If using an aftermarket air filter and adapter you will have to increase jet size just to make it run correctly. With an aftermarket air filter and adapter, but with stock muffler I suggest a 35 main jet. If you put a header on it you may need to go a little bigger, maybe a 37. As you are just getting started I suggest the air filter and adapter, removing the governor for sure, and probably use the stock muffler and gas tank. The gas tanks on the predators are a lot better than the tanks on some of the older motors that were prone to cracking around the mount points. A better set of 10.8 lb. valve springs is probably a good change as well. The stock valve springs do not allow a lot of RPM.
 
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