First project bike: GPz 900

[RomSpaceKnight]

Priming oil pump would have been a good idea. My KZ manual says to do it. Did you measure piston bores?

[JuniperBug]

Yes, I did. There are some tiny scratches, but the bore sizes are almost as new.

[ZX750E1]

Planning any modifications along the way? Here are a few Japanese eye candy tuning spots for the GPZ 900:

http://a-magic.com/works/kawasaki.htm
http://www.spec-hiroshima.com/
http://www.motofac.co.jp/custom/custom.html

[Ericthejet]

The last time I did a rebuild on a bike I picked up a tube of "lubriplate". It comes in an oversized toothpaste tube, with a blue cap. Be liberal with this engine re-assy lube, FYI. Also, be prepared to dump the oil in the engine after you run it up to temp the first time and then reinstall some good stuff.
I actually just got back from a quick ride.

[r2kool4u]

Ncie bike hope you get it running good.

[sk61]

It has been great sharing your rebuild experience with us. I am in the process of removing year(s) of what looks like teenage abuse to my 85' 900. Eventually, I would like to tackle a top end overhaul but for now, I have more than enough work to do. Give me a pm on what part of Canada you live in. Perhaps we are neighbours!

[JuniperBug]

Hey sk61, nice to see another Canadian with a GPZ. We're not quite neighbours though, I'm in Montreal. Good luck with your 900, I'm sure I'll run into you on the forums.

[arobsum]

do you have to prime the oil pump on bikes? i know that on some cars you do...just a thought. good luck!

[killer9a2]

i have got alot of parts for this bike. let me know if u need anything. don't let the skinny tires fool u they still will run with the new bikes with good tires and alittle work. mines got cams, 38 flatslides, ignition advancer,muzzy pipe,one tooth down on the front sprocket. got a big bore kit for it just never put it in still new in the box

[JuniperBug]

Thanks very much, killer. I'll keep it in mind.

I've made very little progress on the bike. I discovered that I'd accidentally left out the small washer at the bottom of one of the inner valve springs (it must have come out of place while I was messing with getting the valve keepers into place). So I had to remove the intake cam again. Luckily, the first spring I took off happened to be the one whose washer was missing, so it was a relatively painless process.

I still don't know what to do about my low compression, and haven't been able to get my hands on a compressor for a leakdown test. In the coming weeks I'm planning on bolting the engine into the frame and seeing if I can get it to run. I'm hoping on a miracle that all it needs is to be run in a bit to get oil circulating and the rings to seat. And if not, at least I'll have a better idea of what kind of shape the engine's in. It's winter and I'm out of ideas/resources, so I figure it's worth a shot.

Edit:

I forgot to mention that while doing my compression test, I decided to pour some oil in through the spark plug holes. Compression went up considerably - I believe all cylinders are ranging between 90-110 PSI now. Considering my cylinders looked good and I've got brand new factory rings in there (double checked for orientation), my belief/hope is that the rings just need to seat and the engine needs to start circulating oil to get a proper seal. Cranking with the starter has not circulated any oil at all yet, at least not enough to get to the head and that's the main reason I want to try to run the thing.

[JuniperBug]

I put everything back together again. It was a no go; couldn't even get the motor to fire, despite having good spark and fuel. The intake valves were leaking so badly in cylinder #3 that I could feel the pressure coming back out of the carburator on the compression stroke. So I took it all apart again.

My valves were sealing terribly. After no less (and possibly more) than 8 hours of valve lapping, they now pass the varsol test. Ideally I would have replaced or at least ground the valves, but finances didn't allow replacing them (would have cost hundreds) and when I went to a bike shop to ask about valve grinding, the service department didn't know what I was talking about and suggested I find a shop that modifies motorcycles (?!). I had access to an automotive valve grinder, but it wouldn't accept valves as small as mine. The intake valves have so little margin that it may not have been a good idea anyway. So it's not perfect, but it looks fairly leak-tight.

This weekend I plan on reinstalling the valve springs and getting the head back on the block. I'll post results when the time comes.

[JuniperBug]

Update: I finally gave in and sent out the head and block to the machine shop. Things will be honed, ground and machined, as well as new intake valves lapped in. After that, I'll finally be able to see what else is wrong with the bike (I'm not optimistic enough to believe it's going to run as soon as I put it together).

Here's a pic I finally scanned into my computer from when the bike was still largely intact. Anyone see this paint scheme before?

[r2kool4u]

Yeah Gold and Black

[JG6_oddball]

Originally Posted by elr658

Even at Marcus Dairy where 5000 bikes show up every Sunday. I love the Champagne color on the Canada model. We didn't get that here.

I was just about to say.."never saw a gold GPZ BEFORE" now I know why cant wait to see it back together...I almost bought a 85 ninja 900 last week...wound up with a 81 virago 920 in great shape except the starter a WELL known problem.

[Kgillers3]

Saw that its been a while since you have posted a thread and was wondering if you happened to get your bike goin? I myself am a new ninja owner. I bought a 84 GPZ 900. Its a project for sure. When I got my friend who I bought it from said that he believed the head gasket was out of it. It was overheating and oil in the water. We dumped the oil and inspected the findings, the oil looked as if the bike had been left out through a winter and had gotten rained on quite a bit. It was overheating because the thermostat was bad. However we will find out this weekend if the head gasket is bad. There was also a dissapointing find in the oil filter. My buddy believes it was metal (as do I) while his brother and father think some other kind of debris. I will probably end up just getting my endorsement on it if the head gasket isn't bad and then parking it to start fully tearing it apart. I will however probably buy another bike in the mean time. So what about you. Have you gotten yours back together? And I was also curious to see how much money it cost you for parts and work done on the bike, to get a good estimate on what i'm in for.

[JuniperBug]

Wow, you have excellent timing. I just fired my bike up today basically for the first time in well over a half a year. I decided to stop worrying about the low compression. I've done all I can reasonably do (and spend - in fact I surprassed that limit a while ago) in terms of freshening up the motor: new rings, top end job, cylinder honing. So I chucked the compression gauge for now, and decided just to put the thing together and see what happens. I was pretty much planning on being disappointed and getting rid of the thing because I have to move it out of the garage it's sitting in in a few weeks anyway.

So for the hell of it, I took the carbs apart and cleaned them up. Everything looked good, but considering the bike's been sitting for 6 years, it was definitely necessary. Drained the 6 year-old gas out of the tank. It still looked clean, so I put it in the car. =P No signs of rust in the tank. Hmm, pretty good. Went through the hassle of installing the carbs and airbox (45 minutes just to hook up the throttle cable!) and installed the exhaust and cooling system.

The last time I checked, I was reading 130 PSI compression, which is at the very low end of the usable range. But when I tried to fire it up, it started easily, settled into a very smooth idle, and responded to the throttle instantly. I have to admit, hearing the bike rev to 8,000 RPM felt good after all this time! Unfortunately, due to various coolant leaks I have to take care of, I didn't get to take it for a spin around the block to see how much power it's producing. But judging by how well it runs, I'm optimistic that my compression and power will be good once I run it a while and let the new parts bed in.

I still have tons left to do on the bike - lots of wiring is brittle and needs to be replaced. My dampers in the fork seem to be seized. And tons of leaks from the cooling system that need to be sorted out. So far I've focused almost solely on the engine, and I have about $1500 into the bike. If I got it running properly today, I'm fairly certain I wouldn't be able to sell it for that much.

About $600 of that was head work. Rings and a gasket kit were a couple of hundred bucks. I bought a used head off ebay to scavenge for parts - I had cams and rockers that needed to be replaced. That was another $200 or so. Unfortunately, bike parts are very expensive. I went into my project knowing it wouldn't make sense from a financial perspective; it would have been much cheaper and easier to buy a well-running bike than to fix up this one. But I got the bike for free and wanted the challenge of learning how to tear down a motor, and I have hundreds of hours of learning behind me now, but still no bike to ride.

It's a cool thing to do and a unique bike to have, and I enjoy taking my time on it, but as I said, if you need this to make sense financially for you, you're going to be disappointed. Having another bike to ride while having this one to tinker with when you feel like it sure sounds like fun. Learning to ride on a mechanically suspect bike probably wouldn't be a good idea. Focus on learning one new thing at a time

Good luck to you on whatever you decide to do.

[dinoSnake]

Check ALL the valve seats - the GPz has a known issue of the seats sinking due to seat softness.

HELP...Trying to learn about my bike! - Sportbikes.net

This is a somewhat "common" cause of low compression on these engines.

You may want to see if the heads need the oil pipe refit - it is a debatable change that Kawasaki made; some people think it just redirects oil from the intake to the exhaust valves, moving the problem from one place back to the other. But it might be worth looking into.

If you still have the leak as noted in the OP check your O rings in the coolant manifolds - they are a pain to seat I hear.

[oldbenz85]

Hey
How did you make out with your rebuild.... I will be rebuilding my motor this winter

east coast canada

[JuniperBug]

Unfortunately for the last few months I haven't had anywhere to work on the bike. Next month it'll be sitting in a new garage, and I'm itching to get back to it. As I said in my lengthy last post, it seems that the engine is now healthy. I just need to attend to a myriad of leaks. Some are very obvious things that I already have parts for: the o-ring in the thermostat housing, loose coolant hoses, old copper oil line o-rings, badly leaking exhaust gaskets. Once those are sorted, I still expect to have more leaks to attend to, but it might be rideable.

The last time I transported the bike by trailer, tying it down and compressing the suspension seemed to be enough to get the dampers unseized. Or maybe I blew them out altogether. Either way, things move freely now. =P

Check back for more progress in the next month or two. And I'm definitely overdue to take some decent pictures of the thing once it's back together again.

[85900a2]

Good luck with finishing it. I just bought a 85 myself. It supposedly ran before being parked. I bought it in pieces and am getting close to firing it up to see just what I'm in for. Hopefully it won't be too bad, but I share your skepticism that it won't be that easy.

Stephen