Suzuki 2 Strokes

Just got a set of new Jemco's for my GT380, went to install them and the rear mounts are all off. Are they the right pipes for a 380 or was there a split in the model years for a frame difference?

Try, loosening the 2 bolts on the cylinder flange nearly far out as they will go. Slide exhaust toward front of bike. Run mounting bolt through at rear. Then, tighten the cylinder bolts. Be mindful of torque on cylinder flanges. They sometimes strip, easily. Turn bolts by hand as far as you can, then use a wrench. Ant seize grease on threads, always helps to avoid future problems.

Rear frames changed about 1975 I think. As did 550s and 750s.

Higgspeed has two pipe designs for the GT380 & GT750: early J/K (72 & 73) and late.
They have only one GT550 pipe design.

I’ve seen late-model Higgspeed pipes mounted on a 72 GT380J that used an adapter for the rear mount.
Can provide a pic of the adapter if you want to go that route.

Alan's right - the exhaust mounting points on the frames changed with the L/M models in '74 / 75, to raise the exhausts and give more ground clearance. So factory pipes from J/K models are not a straight bolt-on for later bikes.

You can make a small adapter plate from a piece of plate steel to link the frame to the chamber. Painted black, no-one will notice.

Major hardware stores sell one inch wide by 4 ft long quarter inch aluminum. Easy to drill and cut obviously.

I called Jemco earlier today he seemed unaware of any chassis changes. Seems like that 1.5" you guys mention is what I'm seeing. I hope I can get them to hang well, I don't want to use adapters but recoating the pipes is a bigger pain in the ass at this point.

A pic of the adapter:

Thanks for the tip, I made some temporary straps for them and once the bike is fully assembled I will cut the mounts off and weld on a permanent solution.

First kick resulted in this, pretty annoyed with the fit of the pipes at this point. Can't kick the bike hard or far enough for it to even start to hear them. Something is pretty wrong with this set of pipes or my bike.

Either heat up the kickstart and bend it out a tad, or have a word with Mr. Hammer and get him to slightly adjust the outer surface of the spannie so the kickstart misses it.
Really though, I notice that the outer pipe is on the outside of the rear footrest frame hanger on an earlier pic. Fit it inside if you can, that'll move it inside a bit so the kickstarter misses the pipe.