Are GT550 expansion chambers specific to model years?

[jabcb]

I’ve noticed that there are GT750 pipes for J/K model years & L-B model years.
Same is true for GT380s.

But I haven’t seen any model year specific GT550 pipes.
Does that mean the aftermarket pipes fit all years?

I noticed the mounting link on the Jemco pipes in the pic below is adjustable.
Does that allow these pipes to fit all years?
Pic is from: viewtopic.php?f=5&t=5989

[Coyote]

I would assume that to be a yes, but I'd certainly ask before acting. I do know the the only difference in the early and later pipes is the rear mounting point location..
So that's what it looks like, but it might be compensation for inaccuracy in manufacture. But my guess is they fit both. I have no real experience, but I remember reading that the mounting point varied about 1 1/2 inches.

[Craig380]

I can't speak for the 550, but on the 380 the exhaust mounts on the LMAB models were about 1.5" forward (so the pipes could be mounted higher for better clearance). However stock J/K pipes WILL fit LMAB bikes, you just need to make up a small steel adapter plate that is drilled for the two mounting points.

I have a pic which shows this, I'll try and remember to upload tomorrow.

That adjustable mounting link in the picture is probably on the chamber for the centre cylinder - that is the awkward one to fit, as it has to fit around the centre stand lugs, swingarm and brake torque arm, and it's a bitch to fit properly if the mounting link is fixed. Ask me how I know this

[Alan H]

That adjustable mounting link in the picture is probably on the chamber for the centre cylinder - that is the awkward one to fit, as it has to fit around the centre stand lugs, swingarm and brake torque arm, and it's a bitch to fit properly if the mounting link is fixed. Ask me how I know this

How do you know this?

[jabcb]

Starting from the only difference being the rear exhaust mount, have two examples:
RedZone, a 1975 GT550:


The yellow bomb, my 1972 GT550 project bike:


Both mounts are at about the same height as the kickstart shaft.
The distance from the kickstart shaft to exhaust mount centerlines is quite close.
Roughly 12-1/4” for the 1975 & roughly 12-1/2” for the 1972.

The Jemco 3-into-1 has a joint between the header & exhaust that allows for some alignment differences.
Perhaps one pipe design will work for J/K & L-B model years.

When I have time & the weather cooperates, I’ll have to get these bikes out for a closer look.

I didn't check for side to side differences & will have to look into that.
But if cut the center stand bracket off, that perhaps it doesn't matter.

[Craig380]

How do you know this?

Heh, I eventually realised that four hands were needed to do it properly. So I used to force my son to hold the pipe in place while I swore and tried to get the bolt through the mounting holes. Fun and games

[jabcb]

The Jemco 3-into-1 doesn’t have the adjustable mount.
Here are some pics.

[jabcb]

An answer via a bit of luck with a different Google search …

Video of the Jemco 3-into-1 on a 1972 GT550
https://youtu.be/klM5hD__tfM