EFI to Carb conversion

I've been looking through the old posts on the forum for some answers but so far no dice. Hoping someone can help...

I've got a 1980 kz1000 g1 Classic, the American fuel injected model from 1980. Converting her to Mikuni VM28 carbs (without the accelerator pump). I'm new to fuel injection and new to these carbs. I don't have the carbs on hand yet and I'm waiting for a manual to arrive in the mail. A couple questions...

Do I need to run these carbs without the fuel pump and fuel pressure regulator, or do they need to stay in the fuel circuit somehow? I'm thinking of just letting the carbs run on a gravity feed and plugging the fuel return line to the gas tank, but not sure if this is correct.

Also, there are what appear to be vacuum lines running from the fuel injector holder to an "air flow valve" then to the front camshaft covers, as well as a larger line which runs from the air filter can. What are these for? I'll be running pods and doing away with the airbox and air filter can...want to make sure these vacuum lines aren't essential with a carb setup.

Aphex

On the GPz1100 it is quite a common modification, I think all you need is a fuel tap -that might be in the wrong place for carbs. There are tap/carb clearance issues with some GPz tanks. I guess the vacuum lines could be used for a vacuum opertated fuel tap or blanked off.

You can run Mikunis VM28 directly by gravity feed. Block the fuel return line at the tank.

The hoses coming out of the fuel injection throttle body are vacuum hoses that are used to open the "clean air system valve". The larger ones feeds air from the airbox to this valve.

You can remove all that but remember to block the 2 reed valve ports at the valve cover.

By the way, why do you want to get rid of the fuel injection? Any problems?

Besides various parts being obsolete, the early fuel injected systems had problems. The VM 26's will do and are cheaper. They do a good job but everyone wanted the 29's or bigger. I have a set of VM 28's and they worked well with my 1015 overbore. The problem with these are the outside adjusters. More difficult to keep in sync. The 26's are inside the tops and stay put better. Pics would be helpful.
Steve

Like undiablo mentioned, you can block off the 2 ports for the reed valves on the valve cover, by simply

attaching a hose from 1 , 2 the other
Pete

aphex wrote: I've been looking through the old posts on the forum for some answers but so far no dice. Hoping someone can help...

I've got a 1980 kz1000 g1 Classic, the American fuel injected model from 1980. Converting her to Mikuni VM28 carbs (without the accelerator pump). I'm new to fuel injection and new to these carbs. I don't have the carbs on hand yet and I'm waiting for a manual to arrive in the mail. A couple questions...

Do I need to run these carbs without the fuel pump and fuel pressure regulator, or do they need to stay in the fuel circuit somehow? I'm thinking of just letting the carbs run on a gravity feed and plugging the fuel return line to the gas tank, but not sure if this is correct.

Also, there are what appear to be vacuum lines running from the fuel injector holder to an "air flow valve" then to the front camshaft covers, as well as a larger line which runs from the air filter can. What are these for? I'll be running pods and doing away with the airbox and air filter can...want to make sure these vacuum lines aren't essential with a carb setup.

Aphex

Don't forget that the FI units mount directly to the head and that these ports must also be closed/epoxied shut. I have seen both approaches...epoxy and large threaded bolts .

Thanks to everyone for the response and advice!

I bought this bike from a guy who says "it just died one day while idling in the garage." He wasn't into wrenching on things so had no idea what the problem was, and didn't want to bother fixing it when shops told him they'd put carbs on it but wouldn't touch the FI. He said before the machine shut down it ran like a dream, he wouldn't have had second thoughts about taking it all the way to Florida.

Right at 10,000 miles on the odometer and I'm inclined to believe it because the bike looks very well cared for and completely stock, as far as I can tell. I haven't gone through the FI components but I suspect it's the classic computer fail so common with this model (although I've learned that sometimes on these bikes it can be something simpler to fix). My plan is to put to carbs on her, fire it up and see how she sounds. If it runs well (I think it will) then I'll ride it daily and meanwhile go through the FI components, see what I discover. I don't want to alter anything permanently in the conversion to carbs process, that way I can always put the FI back on if it turns out not to be the computer, or I find a replacement computer and feel like taking the gamble of buying it.

if a gravity feed works well for the carb setup then I'll definitely go that route, simplify things that way. Found some good 28's at a very good price, gonna run pods instead of hunting down an airbox because I want to get her on the road asap.

I came across some posts that mentioned using clevis pins and holding plates to plug the injection ports- I like this idea. Simple, quick, not permanent. My main concern here is that the injection port hole will disrupt air/fuel flow at the intake if it isn't blocked off smoothly on the inside (where the injection port meets the main intake port). I'm thinking after I put in a clevis pin maybe I could fill the bottom of the injection port with high-temp rtv sealant and smooth it out to match the intake port wall....does this sound feasible?

What exactly is this "clean air system"? I don't understand....why send air from the airbox to the camshaft area? I'll probably do like you guys have suggested and block these reed valves off, but I'm still curious what it's all about.

I'll post pics soon as I can.

The system injects air into the exhaust valve ports after the valve to burn off excess fuel while in the exhaust pipes.. As for silicon, you'd be better off with a bolt or something if I understand you right.
Pics would help.
Steve

I have a 1982 GPZ1100 that I am in the midst of doing the swingarm swap out that I have been planning for over 2 years. The upper shock mount is going where the fuel pump used to be, The more I look at it, the more, I am thinking the best course of action for the interim is to remove the injection system and put in a set of carbs. Will KZ1100 carbs (Mikuni bs34's) bolt right up to my stock air box?

I had put pods on it to make room for this swap under the seat and it ran poorly. I think where I have located the upper shock mount will allow me put the full stock air box back in and I need the real estate in the tail for the battery... Any input would be appreciated.