1982 GPz750 New Owner... many questions

Hello everyone. My name is Dave, and just bought a 1982 GPz750. This is my first bike and pretty excited about it. I've built and worked on cars for years so I know motors. I bought this bike off a buddy and it sat in storage for many years then. It ran ok before it got closed up.

Now I've got it, and trying to get it up and running. I can get her idle, but revving kills it, and starts are hard most of the times. Needs starter fluid when doing it. I've cleaned the carbs, have a rebuild kit coming in, and 1 leaks (left side)

Looking it over and looking online, I'm wondering what he did with some of the vac lines and stuff. Firstly, the petcock is nearly nonexistent. There is no switch on it. No clue what position it's in, or if it even has a position. When fuel is in the tank, it does flow out, so I assume it's set to on. But why is the switch taken out?

Secondly, there is no vac line gong to the petcock. Probably has to do with it basically being disabled anyways.

Where is the nipple on the right side of the fuel tank supposed to go?

The 2 middle carbs have vac lines coming off of them but are plugged. Is that ok?

The outside 2 are Teed together to the fuel.

The carbs have filters on each one, so no stock airbox. There is a big vac hose coming from the motor going back right above the carbs. Should I leave that open?

There is a spot right below the carbs, I think it's on the trans that has a spot for a vac line it looks like. Where does that go to?

I'm hoping to get the carbs rebuilt and balanced soon, so hopefully can get those out of the equation.

Please help! And thank you
/D

Pics would help. It sounds like someone has installed an aftermarket petcock, the 82 GPz750 had a vacume operated petcock valve that was tapped into the #2 carb for it's vacume signal.
Thelarge hose coming off the top of the motor is for crankcase ventelation. I would install a small filter on top of that to keep crud out of the engine.
You symptoms indicate the carbs a clogged and need a detailed cleaning.
I would start with a basic tune up, Check and adjust valve clearances if needed, replace spark plugs, change oil and filter, ect.

I am not a GPZ guru but there are some on here that are and can help you, but the very best advice that you should accept is to get yourself a genuine Factory Service Manual (FSM). Many of your questions can and will be answered there and will include diagrams for correct location of things.

Hello, Dave, and WELCOME to KZrider!

For a free service manual download, click this link and scroll down to "The Bible."
kz.bike-night.com/

Good Fortune!

Sounds like the PO has the lines all screwed up. I would not run it until I got them straightened out. Search this site and you will find Patton has posted pictures of the correct routing for carb lines. Ed

The big hose going back from the top of the motor over the carbs sounds like the air inection system to me. Again, if you can throw a picture up it would definitely help. Then the little one on top of the transmission area is a breather, and should just get the little filter on it like baldy mentioned. The air injection system should be removed and blocked off since you have the individual (pod) air filters. There are diagrams around here for that. Holler if you can't find them. Then for the carbs, it sounds like the PO got the lines all messed up. If your petcock is always flowing, should just need a single fuel line to it to keep the carbs full, don't know what he's doing with the others. I'm unfamiliar with the GPZ carbs, so I'm not sure where that line is on them. Each carb should have a little vacuum port at front. Originally, two will have gone to the air injection system, if that's removed, they should just be blocked. If the petcock is manual, not vacuum, then that one also gets blocked, and the last will have always been blocked, and should remain so.

If you throw up some pictures of the area, this site's pretty good at MS paint and photo-chop and someone can probably throw in some callouts for what's what in the picture for you.

Good Fortune!

Another option for the crankcase breather is to route a hose from the breather nipple to exit underneath the bike.



Good Fortune!

Firstly, I appreciate everyone's responses and help!

I will get some pics this weekend and post them up.

I already have "The Bible" but haven't really gone through it thoroughly yet.

According to the pic, the big breather hose is getting deleted and just connecting the 2 parts of the motor together.

Spark plugs and wires are new. Oil does need to be changed for sure.

In the pic above, which 2 carbs are the purple lines going to?

I'll do some more searching around today and take pics tomorrow and get them up. Thanks for the help again

david-b wrote: ...In the pic above, which 2 carbs are the purple lines going to?....

Guessing to the vacuum nipples on the outside carb holders.

As noted in the illustration, any unused vacuum nipple is supposed to be capped/plugged.
Because any unused vacuum nipple not capped/plugged creates a giant air leak. :pinch:

Good Fortune!

I have an 82 GPZ750 that I bought new. It wont even run without the stock air box in place on the stock jets so Id think about seeing what it has in it for jets first after you get the vacuum lines figured out. Stock is 110 main and 37.5 pilots & they wont run with pods like this.

Well the bike did run for awhile. I've seen it running and my buddy I bought it off from was riding it before it went into storage. Was never perfect in my opinion but is probably due to the vacuum lines being screwed up.

I got some pics. Bike is in my shed and altogether right now and been cold so didn't pull it all apart for the pics.

This is the petcock. As you can see, no switch. When gas is in the tank, it flows freely. No vac was hooked up to the petcock.



This one kind of shows the carb vac/fuel lines. The middle 2 have plugged hoses. Fuel goes to the tee between 2 and 3 (I was confused in my previous post). 1 and 4 have vacuum going to them.


This gets a filter? Or plug it?


And lastly this is the big hose coming from the top of the motor which sounds like I completely eliminate


I got my rebuild kit in finally but who knows when that'll all get taken care of. Mat be moving soon so don't want to tear it down and have to move it in pieces.

And lastly, this is the bike...