My buddy just bought a 1987 Tecate-4. I need some info on
who makes pipes for them, shops that know how to tweak
those motors real good, how hard would it be to drop a KX500
motor in it, and are the Tecate motors the exact same as
the dirtbike motor of the same year or are they different??
If they are different, can a KX250 cylinder be put on a
Tecate-4 bottom end??

 

i used to own a tecate with a 2000 KX cylinder on it. The KX's run a 72mm stroke with slightly smaller piston(tecate runs 70mm stroke) so for it to work properly you can use a 86 or 87 KX crank and rod. You have to use the head off of the KX cause it is shaped differently due to not having the extra water jacket like the tecate ingine does. I had a LA sleeve big bore 300 kit in it with a good port job and was putting out around 65HP. But before you go getting into more power the tecates suspension barely handles the power it has now so different shocks,swing arm(+1 or 2), and longer +3 A arms should be the first investment on the bike.