1981 Kawasaki GPz550: Restoration

[Nessism]

Oh man Steve, you're killing me! That's the nicest looking parts I've seen in a while! Damn shame to tear that thing apart! A man's gotta do what a man's gotta do though.

[SVSooke]

Oh man Steve, you're killing me! That's the nicest looking parts I've seen in a while! Damn shame to tear that thing apart! A man's gotta do what a man's gotta do though.

+1 To nice for one of my projects

[Greg65]

Some must die so that others may live.......

As a 17 year old I used to drool over a neighbours Gpz 550, it's been great reading your thread, even though it has been painful at times. You will get there, keep us all informed when you can.

A strong cup of tea works wonders over here at these moments.

Cheers,
Greg

[srsupertrap]

Been busy like everyone else but making good progress. The KZ550 donor which I got for $400 looks much better on the outside, Gas tank is totally rusted inside, carbs the same, chain seized solid. PO lived on a road base country road. A field mouse made a nest in the airbox, ate or chewed up the air filter and used the rear frame tubes for a crap pile. The fork are soaked in oil but the fork tubes are good



Another smelly view


Last week before getting serious about dismantling, I checked the compression by running cables from the Tacoma. The girl still has life in her. 150 psi across cylinder 1-4 with oil squirted into cylinder #2. Check out the plugs above.



I had fun dismantling the cylinder head because pretty sure this motor has never been apart. The I & E valve lash were still set to the loose side and every cam bearing bolt snapped loose. Here is what the lash & shim sizes look like. I suspect Kawasaki set the valve lash right in the middle of the range of 2.00 to 3.00mm. I am tempted to use this head considering its condition. Lap the valves, change the valve springs and then replace the valve stem seals it should be tight.

KZ550 Valve Clearance
Date: 4/16/17	Cyl 1	Cyl 2	Cyl 3	Cyl 4
In .004-.008	0.008	0.006	0.008	0.008
Shim	2.60	2.60	2.50	2.50
Ex .006-.01	0.007	0.008	0.007	0.007
Shim	2.45	2.60	2.55	2.60
Compression (Psi)	150	120*	145	150
* 150 with oil

[srsupertrap]

I cut the chain off yesterday with a bolt cutter which caused problems today removing the clutch hub nut today. I pm'd Gearhead13 and he reminded me to use the rear brake to remove the clutch hub nut (Doh!). I used a crow bar wedged between the foot peg bolt to hold the inner clutch hub stationary. The Harbor Freight impact worked as advertised which brings me to the donor. Dr. Steve the donor has been anesthetized . . . I want your crank

[rphillips]

I was disappointed with the 1st picture, didn't look like a donor bike. Impressed with next pictures, does look like a donor. Hope things go a lot better this time.

[Nessism]

Coming right along Steve. Good work.

Using the head would be very tempting. I'd look at it closely to see if the seats and valves are truly as good as the compression numbers suggest. On my 750 head the seats were uneven for width, presumably from the factory, so that had to be cleaned up even though the engine was low mileage. Don't assume anything...

[Big T]

Steve,

Hope you're swapping out the primary chain and starter clutch also, while you have the two motors apart

[srsupertrap]

Im surprised that did not bust your crankcases or do some other sort of horrible damage.
Did you dind all the bits in the oilpan? Are these parts still available?

Good question, here is the extent of the damage to the upper case. I will examine it closer but hoping for the best & plan to increase the radius. I want to keep this crankcase since its a survivor (S/N 000030 or maybe its 25). I did fish out most of the shattered cylinder liner parts and will be splitting the crankcase halves this weekend.

PS: Free boat anchor inside, you pay shipping & handling

[srsupertrap]

Steve,

Hope you're swapping out the primary chain and starter clutch also, while you have the two motors apart

Good approach Big T, I agree 100% and will add oil pump & secondary shaft & clutch hub too if they are the same. Here are the KZ550 entrails.

Other progress: Just pulled the trigger on a EBay Wiseco K615 & cylinder assembly from an 550LTD. The KZ550 parts bike has the angular fins which are not period correct.

[Nessism]

I'd take all the guts you can and move them over. With only 6300 miles on that engine the internals should be in great condition.

[srsupertrap]

Last week, I shipped a used KZ550 cylinder with a brand new Wiseco K615 BB kit to APE to have the cylinders bored. Corey, I finally followed your advice . I only later learned from Rapid Ray that Carolina Cycle does great work as well but with faster turns. Oh well.

After carefully numbering all the plain crank bearings, I have transferred the KZ550 crank bearing with 6300 miles to the GPz550 engine cases. It looks like the crankcase internals from the KZ550 are identical to the GPz550 too . . . so everything may be ported over.

I am struggling with what to do with the original GPz550 cylinder head which has had two valve jobs, the #1 NGK spark insulator breaking which required replacing both valves in cylinder #1 and the latest start up issue in March 2017 were the valves may have kissed piston #1 as the connecting rod let loose. Great history . . .



The easy solution is to use the 83 KZ550 cylinder head which is unmolested from the factory and still retains the original valve shims. This head could be easily freshened up with a valve job, port cleaning, new valve springs and valve stem seals and out last me. This 83 KZ550 came with CV carbs which also allows me to slip the Mikuni Flatslides TM27 directly into the stock boots, see below.



This solution is appealing because the carburetor adapters the PO had machined (81GPz550 & Many 80-83 KZ550 came equipped with TK22 Slides) are not spaced correctly. For example, most Suzuki GS carbs are spaced 77-93-77mm. When the carb spacing is incorrect the only thing to give is the carb boot. Installing the above carbs in the original GPz550 cylinder head is a feat of strength requiring heat gun prep and JB penetrating oil. Just more evidence the PO did his best.

My only reservation is the 83KZ550 cylinder head has a different casting and looks different than the 81 GPz550. The cylinder fins are not rounded but instead angled at 45 degrees. I know I would hear the comment its got the wrong cylinder head . . . thoughts?

[Nessism]

Steve,
You should plastigauge the crank bearings after moving the bearing shells and crank over into your cases. I think the cases have bearing size codes stamped into the cases somewhere too so you may want to investigate that detail. Bottom line is that different cases take different size bearings so don't take anything for granted.

I'd use that new head. As you say, it's factory fresh and should clean up like new very easily. The fact that the carbs will fit up better is a bonus as well as you know. As for the valve springs, I'd compare the springs that came in your engine to try to figure out if they are HD type to match the cams or just stock.

Looks like you are doing a nice job. Keep going...

[Cipher]

eventually you'll want to put some Zephyr plastics on the bike.
HAHAHAHAHAHA

[MaurieG]

Morning Steve. Terrible luck with the motor, but it looks like you've hit paydirt with the donor bike. Might look tatty, but take what you need and hide it in a corner. I can guarantee you'll need to re-visit!