81 gpz1100 - EFI - To keep or not to keep

I have been searching for an 81 GPZ1100 to do a project with. Either a restore or another ELR-like bike.

My question is... is it worth trying to save the EFI? I would like to convert to carbs, since the EFI on the target bike is not working and my understanding is they never worked all that well, even when they do work.

Input welcome:)

My take is this...the really early FI was troublesome...by really early I mean 1980-1981 vintage...by 1982, Kawasaki started figuring things out and it is slightly less prone to failure. That said, the failure rate on really early FI was high enough on the KZ1000G models, that Kawasaki itself recommended replacement with carbs. So, if you have functioning FI on any early models, leave it alone until such time as it does fail (and it may not)...functioning FI on an early KZ1000G/H/KZ1100B1/2 is becoming a rarity. Another consideration on the KZ1100B1...if you find one and convert to carbs, you'll also have to move the petcock on the tank to accommodate the carbs or replace the tank with a KZ1100B2 tank. If you find a KZ1100B2 and convert to carbs, there is no tank issue.

you could run the standard hardware on a megasquirt ecu, Im just not sure on if the first efi gpz has a throttle position sensor which you would need for the ms ecu.
Have a look here :-

msefi.com

The 80/81 EFI was a problem in more ways than one. First of all these systems had the injectors mounted directly on the head. This caused injector overheating and eventually failure. Also there was no TPS on the throttle bodies. The system used an air flow sensor instead. This leaves you with a double problem when converting. Plus the poor positioning of the petcock. First of all the cylinder head is garbage. You must plug up the injector ports by having plugs made that go all the way into the ports. The better choice is to get a standard "J" head and replace the one you have. Now you can get rid of all the garbage that goes with the injection system. The ECU is only particular to the 80/81 injection systems and not usable on the 82 and up bikes. Now you can use a set of "J" stile carbs. They work very well. Also as mentioned the petcock will hit the top of the carburetors. You must move the petcock. The simplest way i have found was to plug the hole where the petcock goes and install the new petcock where the fuel bypass valve goes on the other side. This is at least ALL what I have done. Now I have come full circle and am mounting a 83 fuel injection system on the bike once I have all the components.

OK - this is a new project on the line.

Otto, thanks for the input... first hand experience is the best

Any input on me getting lined-up would be great. So far I my thoughts are... input requested.

• to convert to carbs I need an 1100 J head. A 1000J would not work.
• would a "P" model J head work, since the cop bikes seem to be numerous, this should be an ez find
• I was thinking Mikuni RS carbs, should be no issues, especially if I punch it out while apart.
• moving petcock... I can see the plug on the existing one, but I would need to reinforce the point where I tap the new one.

ANY "J" head would work 1000 or 1100 1981-2005-P24. I get tremendous power from my BS34s which are a bit modified and would be equivalent to about 32mm smoothbores, without giving up efficiency and millage. If you want to drag race the bike than CV carbs would not be as good. Because I wanted to keep stock sleeves, I punched mine to 1150. 1137 and 1175 are off the shelf available sizes where I did not want the overheating problems of the 1175. I paid about double for my pistons to get the extra .5mm which I think wound up being a bit of a waste for an extra 15cc. Wit good porting on the bike like I have it can either be a arm pulling screamer or a 175MPH hype-bike. I chose the latter. The head I chose was a 84 GPZ head which flows more than a standard "J" head, but they are hard to come by and when you do they can be quite expensive just for the stock head. Here is a link to my build.

kzrider.com/index.php?option=com_kunena&...w&catid=11&id=169462

Here are some pictures on how I converted the petcocks. This first picture is of what used to be the return check valve fitting which I re-tapped and installed a low profile elbow. I than went with a Pingle valve supplying a double filter. The valve is totally unsupported and is just inline.

On the other side I just tapped the inside of the existing valve nipple and installed a pipe plug with a little non hardening sealant.

Here is another picture of the fuel supply from the other side.

I like the new petcock set-up. Simple and quick.

My only thought would be that on hard acceleration, or when you run it low on gas in the tank, you'll starve it. I have this problem, although very minor, on a CBX that has the petcock set pretty forward from the factory.

I've been running it like that for two years like that now and not once have I experienced that problem. The petcock is almost at the identical position front to back but just on the other side of the bike. it is much farther forward on your Honda. Looking at the picture on the Honda it looks like it is in the front half of the tank. On mine it is about 30% from the rear.

If you study the pictures i posted you will see that the elbow is just over the back part of the diaphragm housing. If you take a look at the side picture of the bike that will show you where it places it on the tank, in relationship to the carburetors.

Ahhh - I see the positioning now. and why you used that. I was thinking, just cut down the original petcock location and tap it... but no need;)

Yeah - I have a CBX that I have been working on, so I don't put much fuel in the tank... and one day I could figure out why it was acting up when hammering the throttle through the gears... only to realize I was starving it.

BTW, Otto, I have been following your build - very nice, seems like you da man... from engine and carb rebuild to paint. You make us wannabees with more vision then ability jealous:laugh: