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Because every lady could use bigger jugs...

  • Thread starter Thread starter makenzie71
  • Start date Start date
M

makenzie71

Guest
...well, these ladies anyway...

1981 GS750E

I'm contemplating bigger power and am looking at my options here. I know that you can bolt an 850 head, jugs, and pistons to the block and go. Can the 1000 or 1100 assemblies bolt up?

Are there fundamental differences between the '79 750 and the '81 750 that would make one a better candidate for this than the other?

I ask the latter because I have both motors to play with.

Lastly, is there a way to add a 6th gear to either engine? I know the later bikes came with six speed trannies...will the gearsets just slide right in or do you have to tweak them?
 
The 850 top end won't fit on an '81 750; they are completely different - one is 8V and the other 16V. The '79 850 and the 8V 750 share cylinder heads and the cylinders and pistons will exchange but that linage stopped in '79.

Regarding adding a 6th gear, I don't think it's possible. The smaller bikes had six speeds but those parts won't hold up to the power of the larger engine even if they fit...which I don't think they do.
 
It would be cheaper

It would be cheaper

to find an 16V 1100E, Making 109 hp out GS750EX 79 hp stock would cost more than getting a reasonable GS1100EX, but then you would end up spending twice again that much to get 135 hp (see my thread on "cheap" performance :lol:.

For cheap "perceived" hp go to the 1/4 throttle mod :D. I did on the GS750EX and it works.

Pos
 
Ok so I would have to slap the jugs on the '79 block...that suits me just find. I could rebuild that motor while I ride.

What if I just bored the 750 out? How far could I go?

What about heads? Do any other heads bolt on to the '79 that would "breath" a little better or would I be better porting my stocker?

Ultimately, my goal is in the 85whp area. If I had a hankering for 130+ I would just pony up and buy a new 1k...
 
Never short yourself because a piston "set" isn't out there...but that's not relevant. If 85whp is realistic going with the 850 top end plus BPU's, then that'll be my goal.

Just confirming:

I would need the 850 jugs and pistons. Jugs bolt to '79 750 block. Pistons fit '79 con rods. '79 750 head ties it all together.
 
Head?

Head?

Hey, I made my '81 750 an 863 using modified GS11 pistons. Only problem was the 13:1 compression. Used 1000 sleeves in the 750 cyl. 1100 cyl will not bolt to the 750 because of the cam chain tunnel being different. Though, You could put aluminum sleeves into the 750 cyl, weld top and bottom, bore them out and then you put larger sleeves from an 1150 and you go 77mm and you 987cc's. Though you might look into a GSXR1100 cyl just mill it down some. And then there is the 750 slingshot/750 Katana cylinder heads if you want a much better"Head".
GREG
 
?

?

Or go through all this work and why not put a GS1100 engine in the frame as it pops right in with minimal mods.
And you always could make that 1500 cc's if you want with off the shelf parts. As why stay with a 2-valver?
G
 
meh more power is enticing but I want it to be a straight bolt on thing...hell, the 850 jugs thing all I have to do is swap in the jugs and the pistons.

As for why sticking with the 2-valve engine?

1st, I have it.
2nd, makes the 850 thing a bolt on...unless there's a way to go about doing it with my '81.
3rd, my '79 has an LP oil cooler kit and I would really like to have an oil cooler (can't find one for my '81)
4th, it allows me to rebuild the engine while still riding.

I can't find any significant reason to make it more interesting to run with modifying the '81 engine over the '79
 
I see someone has the entire 850 top end for sale in the Parts for Sale.

Sounds like you're on your way
 
pick up a set of 550 gears and pull your 750 stuff and see if you can mix and match? you will need the 550's shift drum as well as the gears. if the 550 stuff is wide enough to fit in the case you might have to find some differant bearings that to adapt into the case. But all this is unknown until you can do a side by side comparison.
 
makenzie71 said:
meh more power is enticing but I want it to be a straight bolt on thing...hell, the 850 jugs thing all I have to do is swap in the jugs and the pistons.

As for why sticking with the 2-valve engine?

1st, I have it.
2nd, makes the 850 thing a bolt on...unless there's a way to go about doing it with my '81.
3rd, my '79 has an LP oil cooler kit and I would really like to have an oil cooler (can't find one for my '81)
4th, it allows me to rebuild the engine while still riding.

I can't find any significant reason to make it more interesting to run with modifying the '81 engine over the '79
Click to expand...
If you're trying to increase performance, going from 16v to 8v is the wrong thing to do.

I would bore the 81 engine. Surely you can fit the cooler kit to the 81.
 
Not that I'm aware of...the '81 doesn't have the same block port.
 
for a "cheaper" solution, bore out the 81 barrels and use GSXR 750 pistons, 816 cc. I did also hear somewhere that GPZ 750 Turbo (don't know if they were called that in USA) heads fit, giving fuel injection :) or pop over to oldskoolsuzuki.info and ask in there, if they can't point you in the right direction you're lost :D
 
The 80 and 81 share the same head setup, yes? If so Id like to look into that GZP setup.
 
surplus 6 said:
for a "cheaper" solution, bore out the 81 barrels and use GSXR 750 pistons, 816 cc. I did also hear somewhere that GPZ 750 Turbo (don't know if they were called that in USA) heads fit, giving fuel injection :) or pop over to oldskoolsuzuki.info and ask in there, if they can't point you in the right direction you're lost :D
Click to expand...

Efi is over-rated...but...what year GSXR750 pistons? 816cc sounds cooler than 850cc...I like the wierd numbers.


The GPZ750 Turbos were KZ's here, iirc.
 
or if you want to work on the 2 valve and still ride the 81, here's what a friend of mine did
"I have 810cc wiseco's for a 750 kawasaki turbo in my GS 750, and they give me 848cc instead of 810 because of the longer stroke of the gs."
or another friend did this
"I know you can use Kwak pistons in GS's I have a GS1000 with Kwak 1170 pistons"
 
Last edited:
6 speed thoughts.
On my 79 GS550 racebike, I use the taller 1st gear from a GS400 and the full clutch from a GS750.
The diameters on the shafts are the same so I would not expect issues with bearing sizes.
I have a GS750 here but the main case is still in the frame so I can not get the measurements of the gearbox at this time.
I do have a few 550 and 400 gearboxes and two 550 cases in the shop so I can measure them.
 
That would be cool as hell if you could check the measurements! I won't have 750 measurements to compare to for another month or so but it'll be nice to know.
 
Does anyone know the specifics of why the '85 jugs and pistons won't fit between the 81 head and block?
 
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