TOPIC:

slmjim+Z1BEBE wrote:

MODS - just realized that slmjim posted the wrong OD of the retaining collars in the OP as 50mm. Oops...

They are 40mm.

Please correct or, enable edit & we will do so early AM tomorrow.

Thx.

Good Ridin'
slmjim & Z1BEBE

Done 

Nerdy wrote:

I've been meaning to pull the ancient 4-into-1 off the '81 GPz550. Let me see if that can happen this weekend; if so, I can get some measurements.
 

Thanks Scott.  Perhaps there's a 4-2 system in your GPZ-550's future at a price you can't resist?

Good Ridin'
slmjim & Z1BEBE

slmjim+Z1BEBE wrote:

Thanks Scott.  Perhaps there's a 4-2 system in your GPZ-550's future at a price you can't resist?
 

You read my mind

Regrettably I didn't get into the shop this weekend, but had an idea. Tucked away in the basement are two new-in-box MAC 4-into-1s for the GPz. I can get one of them open and take some detailed measurements.

Okay, I finally made it down to the shop Here are the measurements from the newer of the two MAC pipes:

- the flange diameter at the head (the part that sits on the exhaust gasket) is 38mm

- the outside-to-outside of the 3-4 headers (close to the head) is 119mm

- the inside-to-inside distance between 3-4 is 41mm

- the center-to-center of 3-4 at the flange is 83mm

I did these using a really basic set of Harbor Freight calipers but they should be pretty close. The center-to-center might be a little suspect since I eyeballed the caliper points.

EDIT: let's put slmjim's measurements in here, too

Center-to-center of 1/2 and 3/4 headpipes is ~88mm -  ~3 1/4in.
OD of headpipe collars is. 40mm
OD of collector(s) out is 48mm.
OD of connector pipes is 48mm.

The verdict seems to be that the exhaust in question will not fit a 1981 GPz550. Dang it.