What I learned ('82 GPz1100 repair)

I've been asked how I'm doing getting my Big Kawi back on the road, and I'm happy to say I just got done riding it 30 minutes ago.

It's a '82 GPz1100, Canadian bike that I'm the 3rd owner of. 37,000 km.

Right after I bought it, I was going to give it it's first spark plug change, and taking out the last plug it broke off clean with the head, and it had to go into the shop, the head off, and the head taken to the machine shop to get out the broken plug.

At that time, it was apparent that the piston rings were rounded, and it could use freshening up, so I had the Wiseco 1136 pistons installed, wich also bumped my compression from 8.9:1 to 10.25:1.

I rode it less that a year, and it started tapping one day, after I had been out exploring redline in top gear - I had my GPS tie wrapped to the speedo, and the speedo was buried at 240kph, but it was optimistic because the GPS put it at 143 mph.

So I took it back into the shop, and one of the cam bolts had broken off, and the other 3 had then stripped out.

So I learned the first thing: Parts are very hard to find for this bike. I scoured the world for a '82 GPz1100 head, and couldn't find the right one, but Rich Tanz was parting out a '84 GPz1100 and he sold me the entire top end for $400.00.

Taking the exhaust studs out he managed to strip out one of the threads, and even though the bike only had 16000 miles on it they did a valve job, and put in all new valves and springs.

When we set the head on the block, and turned it over, the head just rubbed the piston, because the '84 doesn't use a hemi head, it uses a oblong polysperical combustion chamber, like the S1 racer did.

So it was back to Z1 Enterprises, where I got a .040 block spacer, and 2 each .020 gaskets, and after we put those under the block clearances were OK.

I wish I could have simply installed '84 pistons, but Kawasaki changed the wrist pin size on the '83/'84.

The combustion chamber looked just about the same size as the '82, and I was worried I'd have too much or too little compression, but it tested at 160 psi all the way across, with the '84 cams, so I wasn't worried. I've been at the premium pump with it before, so this is nothing new.

The we fired it up, and the fuel pump was leaking fuel. try finding one of these that isn't varnished up. But once again, the same guy I bought the head from had the fuel pump, and it worked OK.

Bike $5000 including shipping.
1st repair; $2000
2nd repair; $1255
Riding the big Kawi - PRICELESS

So I've got about $10k invested in a bike with a high book of less than $4k, but I console myself with the fact that I love the thing, and that there are probably only a handful of these Canadian shipped bikes still in existence with stock DFI. Plus, $10k wouldn't buy me any new bike that I'd like as well, would it?

How's it run? It was running a little rich before, and now I hit the fast idle lever for about 60 seconds and ride away, but the stock DFI is handling the bigger valves, and cam change just fine. It makes gobs of power.

The original '83 GPz1100 road test said it made 8hp less than the '82 at low speeds because of the extra 12 degrees of cam, and an additional 10hp on the top end, but I cant detect any loss of power at low speed, and the powerband now is kind of like a GPz550 - where at 6500-7000 rpms it becomes a monster.

If I was still 20 years old, I'd drop about 4 teeth on the rear sprocket, take the mirrors off and see what it would do, but I'm not into speed and death anymore.

Nice bike! You're a brave man to keep track of the dollars spent on the bike. I must admit, I'm too much of a chicken to keep track of how much $$$ I spend on my bike or my old car. Ed

I know what you mean about the 1982 model...had one new in 1982 and finally found a replacement several years ago.

Your bike looks good!

Thanks - looking at the picture the only giveaway that it's been apart is the shiny block spacer - I should have painted the edge.

Take a small brush and paint it.
Steve

Great looking GPZ1100 there. I too bought a new one in 1982, and even to this day I miss it dearly. It wasn't a great motorcycle reliability wise, but when it was in decent form it was fantastic. I've said it before, but I actually have dreams I still own mine and found it in the back of the garage even 32+ years since I owned it. Good luck with it.

GPzEric wrote: Thanks - looking at the picture the only giveaway that it's been apart is the shiny block spacer - I should have painted the edge.

Don't paint it, it shows you have "custom" engine

GPzEric wrote: Thanks - looking at the picture the only giveaway that it's been apart is the shiny block spacer - I should have painted the edge.

In the original post text body GPzEric also mentioned: Wiseco 1136 pistons installed, wich also bumped my compression from 8.9:1 to 10.25:1.

I'm curious if adding that .060 spacer thickness dropped the compression ratio much?

When I put a very-similar top on my engine last Spring, original Kaw std. size pistons were used, so my cylinder bore diameter was kept at 72.5 mm. compared to GPzEric's bored 74.0 mm. diameter for the Wiseco's.
Another difference is the GPZ cam sprockets were removed for the J-cam sprockets. per a highly respected forum member's recommendation. I sometimes wonder if the engine performance would be much different with the GPZ sprockets, and I'd probably have changed back to find out by now if the engine didn't run so amazingly well. Thanks again to Larry C. and others.

PS. That GPz is one wicked looking machine. :evil:

daveo, I'm not sure as to the exact compression ratio.

The original Hemi head has more volume than the older KZ mtors, which is why if you drop it on a '80 KZ1000 you'll lose two full points.

But the combustion chamber on the '84 head, has the 'squish' zone, 1mm bigger intake valve, and .5 mm bigger exhaust valve, and they are angled just a little different too, so I'm not sure exactly what the chamber volume is. I don't think you could put valves any bigger into a KZ head and still fit.

So I was afraid that either I'd have plug-splitting, detonating compression, or 120 psi of compression, but when it came oout at 160psi I was happy. You also have to consider that the '84 Cams have 300 degrees of duration, so pinging might not be a problem anyway, because at least with cars I've had, the wilder cams had less cylinder pressure at low rpm's.

I'm going to see if I can get my original '82 head repaired, by having the broken bolt removed, and the other threads repaired. A head guru like Larry Cavanaugh can probably port and polish it to where it'll flow just as much as the stock '84 head. Then there's no mystey as to the compression ratio.

Fuel injection?

The stock DFI is working fine - I was afraid the increased airflow might make me have to go to an adjustable fuel pressure regulator, but so far so good. I'm at 3211 ft altitude here, and if I ever moved down to sea level I don't know if it would have enough compensation for that.