Z750 E1 from 1980 I want more grunt ;)

Hi since I am new to this forum I will start by introducing me and my bike.
I am from Sweden and have recently bought my first motorcycle which is a Kawasaki Z750 E1 from 1980.
(I belive this is the same as a KZ750)

The thing is that I for now have the slowest bike among those I know.
And this will simply not stand
My goal is set at a 100hk and everything over is a bonus.
And this I say without any real experience working on a motorcycle engine
(although very experienced with car engines)

So I wonder what is the most sensible way to go about it?
I am thinking about replacing the whole engine to an early GPZ 750 but on the other hand I don't know what differs from a KZ750 and a GPZ 750 other than a increase in horsepower.
What is most cost effective to replace the whole engine or just take the goodies from different engines and put together a monster?

I will have a bit to go to reach my goal even if I replace the whole engine I mean.
IF I even find a engine in decent shape here in Sweden (new laws regarding junkyards have forced the majority I knew about to close and the prices on the others to go sky high in used parts)

But back to the matter of chasing horsepower.
I am interested of knowing what you think I should do?
Replacing the whole engine or just take parts here and there and another thing where do I find performance parts for these engines?

Best regards Hemmek

The 1980 KZ750-E1 came with 74 hp. The 1981 750 GpZ came with 78 hp. Not a big difference. When stock and running as new, either will run the quarter mile in the 12's and will run at a top speed of a bit over 125mph. That's fast for bikes of that generation. If your bike is "the slowest bike among those I know" there are one of two problems. Either A, your bike is not running as it should (maybe someone put on pod filters; or otherwise modified it; maybe it needs a tune-up; maybe previous owners didn't change the oil and the engine is tired?) Or B; it is running fine, but you are expecting the bike to perform like new bikes that are lighter and more powerful than your 34 year old machine.

If you expect to bump your bike up to 100 horsepower be prepared to pour a LOT of money into it. Gaining 25 hp on a KZ750 is not something that can be done cheaply. However, assuming you are serious and are willing to pony up the bucks - you can give your KZ750 enough power to whip even the newest, fastest, macho machine so badly that its owner will go home whimpering like a little girl who stubbed her toe. Just follow the example set by these folks (see link). Talk about GRUNT! You can far exceed 200 horsepower (not a typo) and go 200+ mph. It only takes commitment and money. Ed

www.750turbo.com/forum/viewtopic.php?f=9...377&p=120771#p120771

The problem is that.
A buddy of mine (newer bikes) has his limit at 100hk (will simply not buy anything under that)
And the worst problem, my father has a Suzuki gsx 1100 from the 80's.
and to make matters worse it is supposedly tuned from a previos owner. (I desperately want to outrun him :evil: )
And that sucker is supposed to have 100hk in it's original state.

I have installed KN filters on mine (no it does not run right just yet) Since the rubbers that connected to the original airfilter box where shot.
Of course when I get it to run right and have done about everything else I want to the bike I will get it jetted in a dyno.

So you say I will have to shell out some serious dough?
Hmm sometimes I miss tuning cars since it normaly aint a great deal to get another 20 hk (HP sorry) out of them.
Was kinda hoping I would get by on a new camshaft and some porting. mabey a set of carbs.

Do you know what the OEM bottom end and piston will take before breakdown?

I recon I would (if the bottom end will allow it)
Stage 1, better cams
Stage 2, porting and possible bigger valves (of course I would get a professional to do that)
Stage 3, (if necessary) bigger carbs

Since I don't have a great deal of experience working with motorcycle engines I don't even know where these modifications would get me, or for that matter how much I can do to an air cooled engine before engine heat is starting to be a problem.

Since I am reckoning I could get to the 100hp limit without forced induction (don't have a clue to be honest)
I would probably mill the head to get a higher compression ratio.

An alternative to milling the head is of course to increase the swept area (boring out the cylinders :evil: )
The big question is witch direction is the most cost effective.

And furthermore where do I get performance parts?
Seems to be none existing to my engine

Hemmek wrote: Hi since I am new to this forum I will start by introducing me and my bike.
I am from Sweden and have recently bought my first motorcycle which is a Kawasaki Z750 E1 from 1980.
(I belive this is the same as a KZ750)

The thing is that I for now have the slowest bike among those I know.
And this will simply not stand
My goal is set at a 100hk and everything over is a bonus.
And this I say without any real experience working on a motorcycle engine
(although very experienced with car engines)

So I wonder what is the most sensible way to go about it?

Buy a different motorcycle.

Hemmek wrote: The problem is that.
A buddy of mine (newer bikes) has his limit at 100hk (will simply not buy anything under that)
And the worst problem, my father has a Suzuki gsx 1100 from the 80's.

You could buy a GPZ 1100 from the early 80's. It was the first production bike to clock a quarter mile under 11 seconds (10.88) in purely stock trim. It put out about 108 HP stock.


www.vintagemotorcyclesonline.com/feature...01-kawasaki-gpz-1100

The bottom end of the KZ750 is extremely strong. I doubt you would ever over power it. Ed

Step 1) get yourself a repair manual for your bike

Step 2) perform all maintenance on the bike that is covered in the manual

Step 3) learn to ride the bike and then learn to ride it with 'enthusiasm'.

Then you will be ready for step 4) engine and chassis upgrades.
Broken bones and/or a bike in pieces is not that fun.100 h.p. at the crank is easy
100 h.p. at the wheel is a little more difficult.

.

Hemmek wrote: The problem is that.
A buddy of mine (newer bikes) has his limit at 100hk (will simply not buy anything under that)
And the worst problem, my father has a Suzuki gsx 1100 from the 80's.
and to make matters worse it is supposedly tuned from a previos owner. (I desperately want to outrun him :evil: )
And that sucker is supposed to have 100hk in it's original state.

I have installed KN filters on mine (no it does not run right just yet) Since the rubbers that connected to the original airfilter box where shot.
Of course when I get it to run right and have done about everything else I want to the bike I will get it jetted in a dyno.

So you say I will have to shell out some serious dough?
Hmm sometimes I miss tuning cars since it normaly aint a great deal to get another 20 hk (HP sorry) out of them.
Was kinda hoping I would get by on a new camshaft and some porting. mabey a set of carbs.

Do you know what the OEM bottom end and piston will take before breakdown?

Buy a newer bike and save yourself the heartbreak and expense..... You're not going to touch a GSXR1100 with an old 750 Kawasaki without serious expenditures.

Hemmek wrote: I recon I would (if the bottom end will allow it)
Stage 1, better cams
Stage 2, porting and possible bigger valves (of course I would get a professional to do that)
Stage 3, (if necessary) bigger carbs
......

There's a Wiseco 810 piston kit you could install, but I think you'll have to do the other stuff on your list & then some to take advantage of the extra ccs (see links below). For cooling you can install an oil cooler - I think you'd need a GPz750 oil pan for the oil lines.

I guess you'd also need to get a different ignition system (a Dyna S or something?) & an aftermarket 4-1 exhaust. The aftermarket exhaust saves some weight & you can get rid of the center stand. Also, you could swap the front end from a Suzuki - I think that saves weight(?)(I don't recall what models) & there may be a Suzuki swing arm for the 750. I've never heard of doing this, but you might be able to save a little more weight by adapting a plastic seat to the bike? .... I'm guessing the KZ seat is heavy.

Here's a couple of topics: KZR - wiseco 810cc kit? ... KZR - power increases?

Thank you for your advice, i have come to my senses a bit regarding this build though.
I know im boring as fuck now

But for now i will do a stage 1 tune up imho.
Meaning.
Light port job (smooth out the ports and remove obvious flow restrictors )
Stage 1 camshaft
And Heavy modifications to the exhaust, (i have a restrictive 4-1 system today)

After that i don't belive it will be cost effective to do more to that enginge.
Next step is probalby to replace the whole Engine, i hope i will be able to find a used turbo Engine here in Sweden.
Or at the very least a gpz 1000, and start over from there. :evil:

Know i just wonder where i could get hold of performance cams?
Any other basic uppgrades you can Think of?

Just did the final Dyno run today on my GPz750 racer, Wiseco 810cc kit, pod filters and free flowing exhaust ... drumroll ... 77,89HP at the rear wheel, so about 90+BHP. Hope this helps settle the matter. Pic of the printout attached