Jetting a 1982 GPz750

Hi, I just bought a 1982 GPz750. It came with carburetors but they aren't installed on the bike. It has a mac 4 into 1 header and 4 individual air cleaners(k&n style) rather than the original air box. The carburetors came off a KZ1000 from what I was told and are supposedly the same as the original except for the pilot jets. I guess the air cleaners and the header would affect the jetting too though. I'm new to working on motorcycles and could use all the help I can get. How do I figure out the size of Jets I need? Thanks.

Looking at your pic, the carbs are similar, but not identical.

The GPz750 carbs have curved bottoms on the slides, not straight like the ones on the set you have, so if you were I, I would start with 37.5 pilot jets, Canadian Jet needles in the middle position, and 125 Main jets, and see how she runs.

That's the setup I'm running on my '82, but for my main jets, which are #115 since I'm running the stock air box.

If you have the air box, I recommend running it.

BTW - I have a couple of extra sets of pilot jets you can have for the cost of postage if you need them - sorry - but no main jets that size.

Hey Eric, thanks for your response. Here's where I'm at now:
I installed the carbs and all I get is a big backfire and nothing else. The first two carbs from the left have a little gas dripping out the front. I was told it might be the float needles. So what I think i'm going to do is take them back off and go through them, clean them up and check the floats. It doesn't seem too hard thanks to youtube and the internet in general. As for the airbox, it didn't come with it{I paid 750.00 for the bike) and from what I've seen online, they're pretty expensive for me right now.

That's very generous to offer the jets, I can Paypal you the postage or send me your snail mail address and i'll send it to you. If you have a line on an airbox i would be interested to know.

Does your bike have an aftermarket header? I can't wait to get this beast running, summers gonna be over before you know it.

Thanks again for the help. Marty

P.S. How can I tell what the model of my carbs are?

I'm running stock exhaust - and I'm no BS34 Guru - but there are some here that may chime in.

My bike still has an occasional lean stumble, and I'm thinking about going the DYNOJET kit - but it doesn't happen enough that I'm concerned - at least not yet.

Drop me a PM if you need little parts - I've got a little stash.

Ive been running stock jets & needles with 3 turns out on the mixture screws on my 82 GPZ750 since it was new. It has the stock airbox and an old RC Engineering 4-1 that I bought in 1982

Another question. I have my carbs apart and there is a metal cover where the pilot jet is suppose to be. Can someone help?
Another thing, I got new float needle assemblies and they didn't have the little screen filter like i had on the old ones. Do I need that filter?

The metal cover is to keep you from dicking with the mixture screws. You need to carefully drill a hole in them and pop them out. Be careful you don't go too deep!
You can reuse the little screens or do what I did and run a fuel filter from the tank.

Thanks a lot. Yeah I was sort figuring out about that cover. Now I know how to get them out. I finally just went ahead and got a rebuild kit. I'll just store anything I don't need. I do have a filter so I guess I can ditch the screens( I lost one anyway, think it blue off the table and fell between the slats in our deck). Thanks again.

I've been reading (here) that if your carbs have the metal covers over them, that you need to put them back gain after you clean the carbs, because those carbs pull the fuel for the pilot jet from the main jet passage.

Hopefully a BS34 guru will chime in here -

Yeah, I read the same thing. I plan on replacing them.