gpz transmission

I was talking to a guy today that has a bunch of stock kz/gpz parts layin around he is willing to sell. He has a gpz 1100 trans removed from an 83-84. Will this fit into a kz bottom end, and is it any better than a kz trans? Also, will any modifications be required to make it fit? I thought a j model trans had a wider 2nd gear, is this the same?

not sure on the gearbox sorry but this may be worth saving.
by a famous brit motor builder.

In order of strength...Z1...KZ1000 better....J model better then KZ....GPZ (83-84) strongest tranny from kawasaki. A kz trans out of a mk11 motor has a .030 wider 2nd gear and can take more abuse then a stock KZ can. Main difference between a J and gpz trans is that the gpz trans has bigger 3rd gear sets. I know a guy who used a stock mk11 trans on a mid-8 second bike without problems. Yes, it will take work to fit and work in a KZ motor. I believe you will need to use a J model input shaft so you can use a KZ clutch basket and you will also need to replace a bearing or two. There used to be kits you could buy that had the bearings in them. Go the dragbike.com and do a search. I know it has been covered in there many times. I have been told that a KZ trans is good down to low nines and high 8's. A j model is good to low 8's and a gpz trans has been in the sevens. Good idea to back-cut any trans you use for insurance although a KZ will take quite a beating. For about $2500 you can get a billet trans and for a bit more, Weisemann will sell you a trans that they use in funnybikes.

thanks alot, checked at dragbike.com and found out that they have a tougher 3rd gear with a little more desireable gearing. Also they were undercut from the factory.

jordan wrote:

thanks alot, checked at dragbike.com and found out that they have a tougher 3rd gear with a little more desireable gearing. Also they were undercut from the factory.

i'm reading now but does that go for the j-model and gpz...i know they are the same right??

the factory backcut was only for gpz 83-84. otherwise the j-model and gpz was the same. No backcut but wider 2nd gear.

hey jordan ive never done that conversion myself but all the real fast guy's have done it and after today's dyno performance it looks like i might have to do it my self. my god i love big blocks long time. also lectron carbs so cool. i would definitly grab them if iwere you and if you decide that you can't use them remember i'll be down your way in august.

The 83,84 GPZ had a different tooth profile and different tooth count for 3rd speed to increase its strength.83 and 84 GPZ had alittle factory undercut if I remember correctly.
The J 3rd speed had 21 input and 30 output for a 1.42857 ratio
83-4 GPZ 3rd speed had 19 input and 27 output for 1.42105 ratio
The 83-84 ones are stronger and hard to find
The ratio's round off to 1.42 for both 3rd gear sets
1,2,4 and 5 are the same ratios too-J vs GPZ

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81 thu 84
It is my opinion --the only difference 1 vs the other is the better/stronger 3rd gear in 83 and 84 models

Here's a link to some information about j and gpz trans. on dragbike.com. Might be able to find some help in here.




forums.dragbike.com/forum_posts.asp?TID=...KW=mk11+transmission

unless youre making a truckload of power with a chassis made to hook it up i can think of lots of otherthings on a bike to spend money on that are bigger prioritys

Most of the time when someone is parting an engine, the transmission bits don't go for all that much although shipping is usually pretty high. If I had a go-fast bike, I would be concerned about 2nd gear & shift forks and would very likely buy racing components as they aren't really that expensive. NOTHING is more annoying than popping out of 2nd gear all the time. I don't know how a GPz tranny would compare to aftermarket transmission bits I noted but those and a bit of undercutting are in order for any bike making more than 80-90 hp (real horsepower on a dyno; not an OEM claim).