81 gpz 1100 questions.....more power?

Just found out this: Stock 81 GPZ head. Wiseco pistons #K1136. 425M07400. 2913XC.

That's all I have.

K1136 compression ratio is advertised at 10.25:1, so that is a good number for what you want out of the engine. Your crank is likely the stock 17 mm wrist pin '81 GPz. There are numerous small and inexpensive performance upgrades you can make as time and budget permit. But, as I said before, you should get your crank built up properly, first.

You could re-work your stock "hemi" GPz / J model head, but it has no real performance advantage over a common / stock Plain-Jane '81 and up KZ1000J / LTD/ CSR / P (police bike) or '81-'83 KZ1100 shaft drive head, so I would consider removing your stock GPz EFI head and sticking it on a shelf as a spare, and sending a less rare standard head or, if you are lucky enough to find one, a '83-'84 GPz1100, '84KZ1100R, or '84-'85 ZN1100LTD head, which are the best performance potential stock heads for these engines (biggest stock valves, best chamber shape, largest ports), down to Larry C. However, if you are going for bottom end and mid-range, the standard head prepped / ported by Cavanaugh will work just fine, maybe even better, for what you want. Follow his plan and you should get what you want.

Another thing to consider is playing with the chain and sprockets (final drive gear ratio)....if you are just looking for a punchier "feel" at low to medium speeds and not a boost in power / torque all over, just adding a few teeth to the rear sprocket might give you those results.....

But like my sig. says - speed costs money....how fast do you want to go?

(just a little perspective from the other side of the counter - when I worked building V-8 car racing engines for a living (more like a starving) years ago, I got out of the business when I thought I was going to beat the living daylights out of the next person that came through the front door and said "I want XXX horsepower, but I don't have any money so I can't spend more than $XXX.XX dollars....)

Well, I see I have lot to think about.

I would spend $2000 I guess for more torque and power.
Looking for that "roll on wheelie" power the ama superbikes had in the early 80's. 3rd gear wheel lifts always feels nice.
I had an insane Spencer rep years ago that had that type of power...almost scary.

Maybe 10- 20hp more hp could do what I want?.
It does lift the front end sometimes at the top of first and 2nd but only just.
On the 1/8 drags the other day I did 7.580 seconds at 96mph...but I didn't really know how to launch very well.
I was using racing fuel too.

So that's the power it has right now. It's ok but not that"holly shit" type of power.

I will think about this a bit and get a better idea of what I want before I waste an engine tuner/builders time.
Wasn't expecting of planing to do anything to the crank though., I could pull off the head but don't want to get much more into it than that.
The wife would have my left nut in a vise if I do too much to it.

The head could be easily mailed off and a new beefed up and (better one) could return without much trouble,
But motor parts all over my wood shop might not go over well with the wife.

Steve

A ZRX would fit your power needs. If you're not overly attached to this bike you might want to sell it and buy a ZRX. I've had two ZRX's and I sold both of them because I was concerned I might get arrested for extreme speeding.

You're kidding right?

Maybe I'm just too close to this bike, but I would never sell it.
And I would be surprised if a ZRX would be very much faster. Don't see many of those either.

Don't get me wrong, this bike hauls ass the way it is, but it's not super scary fast, that's all



.

Yeah, the newer perf. bikes are way improved over the old stuff. My newest litre bikes absolutely run onion rings around a stock KZ in any contest of speed, and even those are considered "obsolete" compared to stuff like Panagale's, S1000RR's and R1M's....just think - they have to dial back the power by using electronics or those bikes would be uncontrollable at WOT. I know that going full power WOT in the first two gears on my R1 results in one of two things - an endo wheelie, or shopping for a replacement tire for the one that just disappeared into a sudden smelly fog bank....

I just happen to despise wrenching on liquid cooled motorcycle engines, and like the grunty old school feeling / noise / look of an 80's torquey beast....

Coast Steve wrote: You're kidding right?

Maybe I'm just too close to this bike, but I would never sell it.
And I would be surprised if a ZRX would be very much faster. Don't see many of those either.

Don't get me wrong, this bike hauls ass the way it is, but it's not super scary fast, that's all

.

And it looks way nicer IMHO!

Kray-Z wrote:

Coast Steve wrote: You're kidding right?

Maybe I'm just too close to this bike, but I would never sell it.
And I would be surprised if a ZRX would be very much faster. Don't see many of those either.

Don't get me wrong, this bike hauls ass the way it is, but it's not super scary fast, that's all

.

And it looks way nicer IMHO!

+1000000000000000 Newer bikes, while they do everything better, lack soul....

You know boys, Funny you should say that.

A few months back I had $14,000 in the bank after selling my race car, and I soon found myself at the bike shop
(funny how that happened).

Looked at pretty much all they had, ...and they had lots. But they all seemed to look the same after a bit of time there.

So, I decided to go back to what I remember in the early 80's (and never had the money for).
A big classic AMA superbike replica.
It was this S1 Lawson Rep or the 900-1100F Spencer Rep. Always liked the big Green Kawasaki's though.
It cost me REAL money though but I still love it.
Just as much as a brand new sportbike I think.

The old bikes do have like you say "soul" whereas the new stuff all seemed like clones but in different colors and sizes.
And sure, they all had wicked wind tunnel looks and traction control stuff everywhere. But they didn't grab me.

Now the ZRX was pretty cool when it came out and at the time I did want one pretty bad.
But It didn't get me excited the way the early 80's bikes made me feel.

And I wasn't digin it's water cooled engine made to look like it was air cooled with little fins... And the oil cooler was actually a rad...

I guess I'm old school and proud of it. :dry:
Give me tube frames and dual shocks all the way!

Right Eddie?.......Freddie?..........Anyone?

I like the old bikes too. My youngest bike is an '85 RZ350 and the oldest is a '73 H1. Also have a '75 H2 and it's a blast to ride. The ZRX is in another league when it comes to speed.

Kapahulu wrote: The ZRX is in another league when it comes to speed.

Not ALWAYS!!!!

This was the deciding factor for me between buying a GPz1100 or a GS1100 to modify the hell out of.....

Cool little vid, Thanks for that.