You can extend any swingarm of any year Tecate.
But, the 86/87 3-wheeler and the 87/88 4-wheelers have ALUMINUM Swingarms. Of course, the welding required is different than steel.
The 84/85 3-wheelers have steel swingarms.
In either case (and I can weld), I would have it professionally welded. And the more you add to it, the harder turning becomes. On the 84/85, I definitely recommend a +2" extension. It still turns great but It helps keep the front end down. 84/85 Tecates have a very short rear end.
The 86/87 I like the stock, but wouldn't mind having a +2 on it also. The 4 wheeler needs help in the width department more than the length. It's a 2 wheeling SOB in stock form.
:-D
1986 Tecate
1984 Tecate
1985 Tri-Z
1986 ATC350X
1985 ATC250R (2)
1985 ATC125M (2)
1982 ATC70 - Original Owner
175 TriMoto Frame with Pro-Tec Rear Suspension
3-Wheelin' since '82