New Owner - 1981 GPZ, KZ1100GP, KZ1100-B1

Hello:

I became the proud owner of a 1981 GPZ 1100 yesterday. It is my second one, as I had owned one in the mid-late eighties before regretfully selling it. Reliving my youth, another mid-life crisis, whatever label.

The new one is a great find. I bought it from the original owner, it came with a factory service manual, and only has 16,300 miles on it. Paint, seat and rubber components are in great condition. Came with a Kerker exhaust, but I also got the stock one, and it's in good shape.

The last owner was a good owner, but not too mechanically-inclined. He took it to the dealer on occasion for routine work, and at one point, put a new RKO o-ring chain on it, and would winterize it with Stabil.

The bike was last tagged in '08, but the owner said that it really wasn't ridden that year too much.

It ran, but according to old posts, it suffers from the same malady that someone else had... It would start and idle rough, and stumble all over itself, till RPM's got above 3.5K, then take off. I rode it home at highway speeds 65- 75 MPH, and occasionally it would miss. The gas in it smelled extremely stale.

When I got home, I let it cool, then took off all of the plastic, drained the gas tank, removed the chain (soaked it in kerosene), and gave it a much needed bath.

One bad thing happened while disassembling it, and I hope that someone can steer me towards an easy fix... When I broke the oil drain plug loose to drain the old black stuff in the engine, it broke free easily, but when I backed it out, it was rough going. And I've worked on enough cars and bikes to know what that was going to turn into. The internal threads in the engine came out with the drain plug!

Outside of the aforementioned stripped threads in the drain plug hole, the bike is in great shape. The front fork seals leak, an easy fix, and although the brakes work all right, the brake fluid in the reserviors is the color of molasses, so the whole brake system needs to be flushed out and refilled with new fluid.

Since I am going to be going over it well, I was wondering if you guys can provide some advice on how to tackle the stripped drain plug hole and the engine running so bad. Just to let you know, I plan on keeping the bike stock, so the fuel injection is going to stay on it. The way I see it, and with the low miles and knowledge of the bike's history, that I can get it running all right with the EFI on it. I figure a good cleaning of the fuel system and air box parts, new gas and filter, SeaFoam or equivalent, a synch of the throttle valves, and cleaning and checking the ignition pick up and timing advancer should be good steps in the right direction.

One last thing, where are some of the best places to buy parts from online?

Thanks in advance, and I look forward to your responses.

Marty

With all of the bad fuel sitting in the system over the years, you very well may have fuel injectors with a terrible spray pattern, leaking, dripping. There are on the bike services, but nothing like pulling them, replacing the filters & O-rings, having them put on a ultra sonic cleaning machine, and test bench for flow/ cc delivered.
Also throttle position sensors are know for trouble on most EFI systems, as they are a variable resistor/ potentiometer.
The drain plug could be fixed with a oversize self tapping plug, or you could use a tap to thread for an oversize, with pan on or off. Off would be a good Idea, makes sure no filings are left in the motor, also an Inspection/ cleaning.
For the moment, the Factory Maintenance would be a good start, valve adjust/ compression test/ check for vacuum leaks/ lube the advancer, if still mechanical on that model/ and adjust clutch push rod, etc etc.
Try Z1 for parts, they are highly recommended by I believe all members here. A+++

I built this one from a 81 KZ1000-M (CSR) and a LOT of eBay Parts. :laugh:

Nice bikes! My dad had a couple of GPZ 1100's and I loved those bikes. they are getting so expensive now I doubt I'll ever get one.

nice bike.looks really clean. sucks about the drain plug but,shouldnt be to bad of a fix.

Hello Marty...I'm partial to the early GPz's myself...and I currently have a 1982 GPz1100 to replace the one I purchased new in 1982 and sold in 1988 I also have a 1982 GPz750R1 undergoing perennial refit.

You pretty much have the potential avenues figured out for exploring remedies to your troubles...however, it sounds like when you removed the drain plug, and you pulled out the 'threads', you actually pulled out a poor helicoil job, too! Remove your pipes and your oilpan and retap with something like Time-Sert (google it). Can be a bit pricey but they work...and you can do it yourself. As for running poorly, the 1980/1981 FI was notorious, as you well know, for that. But, it looks as though you can explore possible fixes...the ultimate fix being, of course, switching to carbs.

Guys,

Thanks for the info and comments about my find.

Just got back from bouncing around at a couple of auto parts stores, looking at a fix for the drain plug.

Seems the only fix for the drain plug the parts stores had was from a company called Dorman. It's basically a larger plug with a self-tapping thread that expands the existing hole to fit it. Problem was, that the drain plug on the GPZ is an M20 thread and Dorman doesn't have a fix for that size. They do for an M22 though. They also had one for a 3/4" drain plug that is approximately an M20, but I had the guy behind the counter measure the major thread on it, and it was around 22-23 millimeters. At this time I'm reluctant to try that, because if it didn't go well, I'd be in a deeper hole than I am now.

Another option for fixing the drain plug hole that I've seen is something called Time-Sert, and they (Time-Sert) stock a fix for an M20. It looks a lot more involved than the Dorman fix, and much more money. To do it right, it looks like the best way to fix my problem, but to do install the Time-Sert properly, I need to pull the sump plate that the drain plug hole is in. If I'm going to do that, I may as well see if there's enough material around the old hole for the next size drain plug, and simply drill out the old damaged threads and re-tap to the new, larger thread drain plug. I'm just a little leary of either snapping off one of the small screws (or pulling the threads out of the engine case like what happened with the drain plug) that hold the sump plate on, or damaging one of the exhaust studs while taking off the exhaust system, which looks like it has to come off of the bike to access and remove the sump plate.

I need to step back and think it over a little.

Marty

No eBay APP ID and/or Cert ID defined in Kunena configurationheres a cheap way too...welcome..

Trianglelaguna:

Yes, definitely another option worth considering. Now, if I can just get those little sump screws and exhaust studs/nuts out without further damaging things.

Marty

And here is the simplest solution of all...check eBay for a new used oil pan (check www.kawasaki.com to see which models cross-list)...

The exhaust studs are M8(up from M6 on the earlier engines)so they should come off easy. To ease removal, spray them with some PB Blaster a few days before wrenching.

Marty,

You got a great bike. I used to own a 1983 ELR. Bought brand new in 1985 and sold in 1989. At that time Ninja's were the thing and I think nobody knew the ELR would become such a collectible. Used to see 4 or 5 of them around Honolulu, now they're all gone.

Enjoy your GPZ, the problems will get sorted out.

Aloha, Mike