750 Twin GPZ 500 carby swap info needed

Oi All. Have a 12/82 Z750LTD Twin. The carbs that are on there have been butchered off something else and the manifolds are home made. Neither work really well. Blackjack tells me that GPZ500 carbs can be adapted to work but I'm unable to find out much info on the particulars. Anyone ?

The spacing on the 750 and 500 is different. Some fabricating would obviously be needed. Different brackets, different fuel pipes, sync linkage would need to be modified, appropriate carb holders would need to be found, etc. Anything is possible with enough effort. It might be simpler to find a good, rebuildable set of 750 carbs and use them...

Actually the spacing is the same mate just the throat sizes are different. It's a common mod on late model 750 twins in the UK . As stock late 750 carbs are super rare out here it was the deal breaker for the bike. Otherwise I'll just make a 2-1 manifold and run a 36mm Amal MkII or something but I really don;t have the spare time to be stuffing around with it.

chopaweeza wrote:

...It's a common mod on late model 750 twins in the UK ...

I'd like to know more about this should you ever have any success... unfortunately I've never heard of it so I don't have anything to offer... but, as usual, I'll pass along what I learn from you...

What I have been able to find out is encouraging. Don who works with Blackjack used ER500 carbs on his chop but as it was an early model had to make new manifolds. They are a simple swap over on late model LTD & CSR models as the carbs are basically the same even the jetting. They even line up on the stock manifold and air box rubbers. Apparently , any GPZ500 , KLE500 or ER500 carb set swap over . But , you have to convert the throttle to a push/pull set up and add a cable operated choke. Rather that use parts that require more work I'll be using the throttle tube and lower throttle case housing off a GPZ750 as these are a straight swap over & give a push/pull set up and the choke lever off a 66' W1 . Probably use GT750 cables for the throttle and make a simple Bowen cable for the choke. As the manifold that are on the bike are bodgy welded up homehand items I'll make a set myself out of steel and use GPZ500 rubbers to attach them . Will hunt up a dynojet kit for the carbs and run pods. No biggie . And I got one piece of info wrong , the throat sizes on the carbs are the same . It's just the set that are on mine are off something else and are very big .

A guy named speedy did it over on Kawasaki twin owners ,, I am sure you can find the write up .. it included pictures , I looked into it when I did Cafe shoe ,, even bought the carbs and controls BUT decided not to do it as the Brake and Clutch lever perches were also going to need to be changed due to the newer controls being larger in Dia.

Yeh. I've had a yarn with him. The reason I'm using the GPZ throttle is it's a straight swap over. Just a case of gutting the existing lower switch block and swapping the guts over to the GPZ one. Did it last night and it took all of 5 minutes so unlike the KLE conversion I don't have to stuff around with wiring or extra cabling. The casings for the GPZ & LTD are basically the same except for the bit at the bottom were either the single or twin cable go in (& the Throttle tube of course). With the choke it's really simple too. Either use an existing seperate choke lever assembly(I'm using a W1 because i already have one) but I could easily use a 60's lawnmower throttle(they look like a 60's choke assembly and work the same) . Cables like the choke cable are super easy to make or I could easily adapt a GPZ/KLE/ER 500 cable to suit . If I had a set of LTD manifolds I could do the entire conversion in 3 hours at a guess. It can be done completely with off the shelf parts , no re-wiring , requiring a couple of screw drivers & a set of needle nose pliers and in limited time frame(ie. an afternoon) . In my case it will take longer as I have to make new manifolds but relatively straight forward none the less.