Coopz I have a Matrix. I've had a lot of nitro buggies/cars in my time and it was without doubt a real ***** to get running sometimes. A pullstarter on a bigblock high compression motor is a bad thing to begin with (CEN electric starters should be included!). I stripped mine of the 5th tank. A Good starter box that I've had for 10 years was revived and it made things a lot lot better. After 5-10 tanks the motor losens up a fair bit and becomes easier to fire up.

Cen need to include PROPER information with the buggy on engine settings, thje online stuff seems to cater more for the road cars.

I was pulling my hair out in frustration as well the other month, ditch the pullstart and buy a good starter box. If it still fails to run properly ask CEN for a replacement engine.