1979 Kz750

[EthanKZ750]

Hey everyone its been a while since ive been on. I just got my 1979 kz750 b4 running today after a 6 month rebuild. I bored it 50 over, matching pistons, new valves, new jug, new head, only thing left original is the cams. I bought the head off ebay and its in great shape. the only difference is that this head has to port holes on top of the engine, almost right behind the front/top motormounts. If i plug them (they make a terrible racket left open) the engine dies. Any thoughts? I want to plug them, its just too loud for me and i would hate to have to rebuild the top-end again. I believe this came off a 1980 or 81 750.

[DrKayak]

You are talking about ports in the valve cover, like a hose would connect to? That is vapor recovery, polution control "feature" added to the newer bikes. I would use your old valve cover (if it fits) or I think you can plug them.

[MFolks]

Some riders use a hose between the ports at the fittings, others use a block off plate like this:KZ Zone - Billet Stuff

[EthanKZ750]

This is on the head, not the valve cover.

[StarGate]

A good picture of the hole's in question wouldn't hurt.

[EthanKZ750]

ill try and do that soon

[steell]

You have a head off a 82-83 (84 in Canada) 750 twin.

Those holes are used to inject fresh air into the exhaust to reduce emissions.

I'm using a 82 motor in my 79 750 twin with the 79 cam cover, and I assume that's what you want to do. It's real simple, plug them with epoxy, like JB Weld or Plastic Steel, etc. I did mine over a year ago with no problems so far.

Now if the engine dies when you plug those holes, there is way to much restriction in the exhaust, like maybe the muffler(s) are plugged.


Oh yeah, just for info, the 80 750G doesn't use that system, and there wasn't a 81 750 twin (at least in US and Canada).

[EthanKZ750]

thanks steell, i wasnt sure on the model.