GPz1100 building -

Hi Guys -

I want some opinions - please -

My bik Kawi is a '82 GPz1100, with stock DFI, a Kerker pipe with loud baffle, and has a Wiseco 1136cc piston kit in it, making the compression 10.25:1 instead of 8.9:1.

My cam bolts came loose on the exhaust cam, and beat up the head.

I found a complete, low mileage head from a '84 GPz1100, and I dropped it off at the shop today, the only bad thread is one of the exhaust studs looks a little ratty.

After breaking out the caliper, it appears that the intake valves are 1mm bigger, the exhaust valves are .5mm bigger, and the valves are maybe tipped a little straighter. Plus the head isn't a hemi head, like the '82, but have had some re-shaping to them.

I'm a little concerned about the bigger valves clearing the Wiseco pistons, so I'm thinking about using the '82 cams instead of the '84 cams, and keeping the higher mid-range, and having a little less lift.

If I use the '84 cams, I'll have the full power of the '84, but I'm also thinking that Kawasaki Motors made the wrist pins in the '84 bigger for a reason, and I'd better not push it.

I've got both computers, the '82 and '85, and the injectors, etc are exactly the same, so tell me guys, what would you do ?

You have no where the lift needed to contact the pistons.

If that's the case, I'm thinking to use the '84 cams, as the higher displacement and compression would love the added lift and duration of the '84 cams.

You could always put a little modeling clay in the piston valve notches then put the head on with a used head gasket torqued down .
Then turn the motor over by hand a few times and pull the head back off and measure the thickness of the clay in the valve notches with a micrometer,that would give you an idea on the clearances.
Without knowing the specifics of your motor its russian roulette guessing what your clearances are.
Has the cylinder been decked,was the head decked? too many variables.

If you are using the 81/82 pistons with the 83/84 head, they will hit. The 83/84 pistons have different domes. Also the valve angle is different.

don

Nothing has been decked, and running Wiseco pistons makes it a mystery. And I cannot put in '84 pistons because the wrist pins are changed.

Send a pm to larry cav

if you use a 83/84 cylinder head you have to have a piston dome to match since your is a 82 GPZ 1100 inj in the rack assy and not in the head this has the "J" style combustion chamber using the 83/84 head you will be down on compression not to mention valve angles are different your best bet would have been to locate a "J" head and had it redone then painted it black.

gpz1170 wrote: If you are using the 81/82 pistons with the 83/84 head, they will hit. The 83/84 pistons have different domes. Also the valve angle is different.

don

If that's the case, that just thru a money wrench in my plans.
I also was planning on swapping a bathtub head on the "81 I just acquired.
Pretty sure my valve seals are shot. The bathtub head is suppose to have
a 1.5cc smaller chamber. With "83 cams would be a nice upgrade.

..

Well, I guess I'll be the guinea pig, and settle the debate, won't I ?

The '84 valves are sunk just a little deeper in the head, giving them more clearance, and looking at pics of the '84 pistons, they have a dome, just like the Wiseco Pistons, and deeper cutouts for valves, just like the Wiseco pistons.

So I'm going to put it together with the '82 Cams, since they have .8mm less lift than the stock '84 cams, and will help with bottom-end power, and give a little more peace-of-mind as far as clearance.

So I will report back as to how much clearance I have, and how many psi of compression I have.

I didn't start out to build a Frankenmotor, just to preserve a piece of motorcycling history !

Here's a comparison from a '83 magazine - not surprisingly the '83/'84 GPz1100 head looks a lot like the Superbike head, only one plug instead of two.

By PM request I'm going to post something here.

In this situation you have less to worry about using either cam because as cams go they are baby grinds, especially when used with an aftermarket piston. Wiseco pistons tend to have larger valve pockets than OEM cams because they are designed to be used with true performance cams.

The 83-85 head had the included angle angle altered 1 degree on the exhaust side. That amount with the aftermarket pistons and those little cams [either grind] should not be an issue. BUT HERE'S THE SMART MOVE if you were going to attempt this.

Install valves in one cylinder of the 84 head using light springs. Bolt the head on. You don't actually need a degree wheel but it would be best. You do need a dial indicator setup on the bucket. Also, clay up the piston to get piston to head clearance measurement after you take the head back off again.

Bring the piston to about 10 Degrees BTDC. Turn the crank in small [1 degree increments...as closely as you can estimate that if you don't have a D.W.] As you go, push the valve open with a screw driver on the bucket until it touches and read the dial indicator. Keep doing that until you are 10 degrees past TDC. You want at least .040" clearance on the intake and .060" on the exhaust.

That is the most accurate way to tell what is happening with regard to valve travel and clearance. The old method of poking a piece of solder or wire between the valve is at best a guess. The closest point of contact for valves is often at a position other than TDC. The dial indicator is the only tool that lets you track it through the critical range BTDC & ATDC with any real confidence as to what is actually happening.

As long as you're setup you may as well degree the cams at the same time, providing you used the degree wheel.

After removing the head, cut and measure the clay on the piston dome. I've never tried to use anything but the correct piston for that late model chamber when using that head so I can't tell you what the result will be. The chamber is closed up a bunch on the sides so you might have a contact issue there......the clay will tell the tale...

How about some pics of the beat up head? I might be able to fix that. Photos are a must.

If the head is indeed not cost effective to repair there is always the route of calling MTC and getting some pistons from them. That may lead to a bore job though.