I have a 2002 Kawasaki 900STS purchased used last year after a full service was preformed by my neighbor (original owner). The ski ran fine all year and would achieve 51mph with my 6’1” 190lb frame.

A few weeks ago I had it out on a fairly cold day here in Texas. I ran it as hard as it would go and noted speeds around 53…which is 2 mph faster than I had it going last summer on flat water with no wind. I had cleaned the spark plugs off before this ride so I thought it had helped a bit. After 4 miles of flawless running I shut it down for a 5 minute fishing attempt. I fired it up again and once I reached the high 40’s low 50’s (mph) it suddenly bogged down and quickly quit running. I let it sit for about a minute and it fired right up. I headed toward shore and it quit again once I got over 45mph or so. It did this 2 more times as I approached shore so I decided to try running it slower. I stayed a@ or below 35mph and it ran normally so I drove the shoreline 5 miles home with zero problems to note.

Some specific things to throw in there that I discovered after the fact:

1. The tank hit “reserve” on my way home and fuel tank has quite a bit of trash in it.
2. I took the fuel filter off and replaced it with a glass one. When I started it up the next day I could see something that looked a lot like water in the fuel filter.
3. I drained as much fuel out as I could which ended up being close to 5 gallons (was very surprised that the reserve would light up with that much fuel remaining. I did not get the tank completely empty and suspect that I would have missed much of the water if there was any in the tank. I filled it up with 10 gallons of fresh Shell 89 octane with Stabil added at 1oz per 2.5 gallons.
4. Changed out the spark plugs.
5. Installed fresh battery


Items to note for diagnostics:
1. There is no water rooster tail that comes from this unit while driving it (if it is supposed to have one)
2. It is extremely cold blooded when starting for the first time per day all year. I literally have to crank it for about 3 minutes (10 seconds on, 10 seconds off) before it fires. It is almost painful listening to the starter cranking while doing this. After it is running, it is very easy to start after short stops. It fires up in less than 1 second.
3. It runs just fine with no battery connected after the initial startup (just a self-diagnostics attempt).

The new spark plugs did not seem to do anything for the initial startup duration. After I replaced the battery, plugs and fuel I tested it and it failed exactly as before (at high RPMs somewhere around 45mph. It ran fine at 35mph. When I returned to shore I pulled a plug and found that it was quite wet with oil/fuel etc. This seemed odd but could be due to me coasting in at slow speeds???

Question: Is there any merit to a possible choke issue with these symptoms or if the choke was stuck closed wouldn’t it just quit on me even at slow speeds?

Question: Does this sound like a carb issue? It doesn’t seem likely since it does run fine at slower speeds.

Thanks for any help in advance. Summer fishing is upon us and I need to get this boat running!

 

That is a 2-stroke right? My polaris 2 stroke quad had a similar issue and I learned that if a 2 stroke has trouble starting, but eventually does, it is a sign of LOW compression. I replaced the rings and head gasket and it starts up in less than a second hot or cold. Check compression. I hope that is it. If not I hope everyone learned something today. Good luck.

 

You are correct. It is a 2-stroke and I'll bet a shiny nickle that you are right on the money with the compression issue being the original offender. I finally got back up there to the machine last week and took the compression readings (all 3 cylinders plugs out) and only read front=89psi, middle ZERO psi, rear=89psi. Even the two that had compression sure seem low. I think these are supposed to be around 130psi each but have to look that up yet.

Regardless, the rings and head gasket sound like a great start to this mystery. Since that time, I took it out to show a buddy what was going on. It helped a TON to squeeze the throttle in all the way till it started to sputter. Only took 40 seconds or so to get it to cough at me. Then, a few more strokes with the choke pulled all the way out (closed) and she fired. The new problem though (UUUUGGGG!) is that I not only had stabil in the fuel but I also poured a measure of Heat into the tank to try and further dry up any water in the tank. This might have screwed me because within 5 minutes of starting it and breaking loose on the glass smooth lake (max of 40mph instead of the 51 I used to get) it died again. Upon starting it up again it now would crawl slowly up to 30 and just sit there. Even full throttle, which used to kill it, it will just pull off 30mph.

Anyway, after taking the compression readings now I know why (with the dead cylinder). Since the ski will still run, I assume that that middle piston is just pumping up and down but the explosion in the cylinder isn't creating any type of force.

I shut the operation down and am in the process of pulling apart my first ever engine of any sort. (here begins the part where I talk about parts that I don't even know the names of...let alone how to work on it ha!).

I pulled the top cover off of the carb area, then the 3 metal, holey filters that sit inside, then the bottom of that box and there sits the tripple carb unit. I know I have to get a carb kit and rebuild it for sure.

Secondly, I guess I'll be pulling the top off of the piston case and try to figure out how to get everything out of there so I can pull the cylinder head out for someone to inspect and measure to see if it is still within tollerance for the factory pistons. My understanding is that IF it is still within tollerance then I might be able to just get it re-coated or something like that to narrow the space between the piston and the hole. If it is all egg shaped, then I guess I have to find someone to bore out all 3 cylinders and buy an oversized cylinder kit ($350 or so).

The one question I have on that is...do I need to have all 3 cylinders bored out if only the one is bad, or can I just bore that middle one out and put an oversized head in there? My guess is NO because of the size of the explosion being different in that hole when it is all said and done.

I don't care too much about performance personally. I just want to make sure that doing so would not cause more damage in the long run. I only have $800 invested in this 02 so far before these repairs but believe the boat is worth around $2500 or so if it was running well. Hence, I can afford to dump more money in this pit while I learn a BUNCH from the experience.

Does this sound about right so far? Oh yea...I'm sure I'll replace the oil and fuel supply lines as well and since the engine will be out I'll take advantage of that and pull the fuel tank and oil tank to clean the heck out of them.

 

Hi there,

Just thought would let you know that by removing all the plugs you will not get a true reading.

You need to disconnect the leads from the plugs and remove one plug at a time. make sure the you earth the plug leads too as it can cause damage to the CDI system.

when turning the engine over have the throttle wide open, not sure why you do it with WOT but thats what they say anyway.

check this again this way and you will notice a big improvement on the compression readings, they should all be with +/- 5psi of each other.

Cal

 

Glad to see you’re up to the challenge. The first thing your need to do is go here:
https://www.kawasakiepc.com/SystemSe...TOKEN=89696524

This should link to KAWASAKI.COM web page where you can find the part diagram for your boat. This will show you what every part is, and how it goes together. You can also go to babbits.com and look at their parts diagram as well. This is useful when you need to order parts from some Kawasaki parts tech who if they are like mine they ride 4 stroke dirt bikes and don’t even know that Kawasaki makes jet skis.

Also from this web page your compression should be 121 in each cylinder. Crazybass is right about how to test but in your situation 5psi will not help.

When I redid my 1995 750ZXI I pulled the motor. I have pulled the motor now so many times it takes me about an hour. However the first time was about 4. With this being said there are certain ways of doing it. And I guarantee you can do it too.

What you are saying about redoing the head and oversized rings is quite ambitious. All you need to do is pull the head, replace the top gasket (use the parts diagram to order a new one), pull the cylinder wall off (this is one piece for all 3), replace gasket cylinder base, piston ring set (get the same size you took out), Snap ring (you will break one and loose one its inevitable), the bearing small end (it’s the tubular bearings), and if any marks replace the piston pin. Make sure all surfaces where old gaskets were are cleaned very well. Then I used a gasket sealer, it was a blue gasket maker silicone. This helped hold everything into place and it just added more sealing. The 2 stroke engine is very reliant on internal pressures to make everything work. It the pressure is low the carbs won’t pull fuel from the gas tank so it is important to have a good seal.

Also you can rebuild your carbs BUT your machine runs. That means carbs WORK. You can F-with a perfectly good working carb and turn it into a paperweight. If you want to spend the money on a carb rebuild (don’t) but if you have to, rebuild the engine first. Get the compression to 121 in each cylinder, run it on the lake, then come back and mess with the carbs.

Remember ALL engines need 3 things:

FUEL
AIR
SPARK

That’s it folks. In your case you have too much air because it is seeping in around the piston ring during compression. Hence your problem.

I typed this with 2 maybe 3 fingers and they hurt now but I hope this was educational to all. Send me a private message with your phone number or contact info and I will walk you thru the whole process.

PS/Disclamer. I am not a mechanic. At one time I wanted mechanical toys. So I bought them within my budget (which was little to no money and no money was tied up with debit). So if I wanted it, it had to be fixed by me. So after years of self taught right and allot wrong I pass on the right to everyone and what I have seen and done.

 

Ok so the link doesn't work right. Sorry.
Use this:

http://www.kawasaki.com/DefaultFrame...OSEVEHICLE.ASP

babbits:

http://www.babbittsonline.com/pages/...d/default.aspx

 

here is a bit more info for you from http://www.groupk.com/k900-1100.htm

If you got some money to spend speak to these guys. Kawasaki Jetski Gurus

PISTON CLEARANCE - The original factory piston clearance setup of both machines is generally very good. Over long term use, we have found significantly more piston skirt collapsing on the Kawasaki 900 than the 1100. In either case, bore wear and piston skirt inspection should be done seasonally on triples that experience long term high rpm use. On any high output recreational packages, we recommend set-up clearances of preferably .003" and no more than .004". Engines intended for moderate recreational use can easily live with .004"-.005" set-up. Piston clearance inspection is available on request, and cylinder boring (using pistons furnished by you or us) is available in oversizes of .020"and .040". In any case, all ported cylinders are honed by Group K before return shipment.

BIG BORE CONVERSIONS - Kawasaki -- As of this writing, we still consider big bore modifications to be a questionably good idea for the Kawasaki 900s. The stock sleeves in the 900 are so thin on the exhaust side of the cylinder that boring the existing sleeve is risky business. We looked into big bore sleeve kits until we learned that Kawasaki was releasing the 1100. When we learned that the 1100 had substantially longer rods (a great benefit), we figured a big bore 900 would probably have excessive piston wear problems unless the rods were lengthened. By the time you install longer rods and a sleeved/ported top end, you could afford the 1100.

And to the question about fixing the middle cylinder only, I would do them all while its apart.

 

Are there any free resources out there where I can find the torque values for the different bolts on my 900 STS?

Thanks to all of you thus far on getting this pig up and running again. Still pretty stoked seeing it sitting in parts in my garage.

Greg3c: So When I took the cylinder head off, there was a very thin metal gasket (assumed to be the head gasket) but there was no sealant whatsoever to keep it in place. I found this stuff at autozone called "Liquid gasket" for about $15 for a cheese wiz type tube. I'm wondering if I can use that to seal the head gasket better? If so, do I squeeze out a line of it on both sides of the gasket and then put the head cover back in place to torque down? Damn this stuff is interesting for some reason??? ha!

Anyway, I am going to:

#1 get the middle (offending) carb cleaned out
#2 get the middle cylinder wall bored out (if possible)
#3 buy an oversized piston to replace it with along with all of the rings, bearings etc...


One particular thing that is stumping me at the moment is the crank-case oil. When I pulled the middle piston off of the piston arm I noticed that there was a measure of engine oil (not 2 stroke oil) down in the piston arm well. There was not very much but it was there. It was pretty burnt looking but in the other 2 piston wells it was nice and clean brownish clearish like standard 10W30 looking oil. I see on top of the motor that there is a plastic looking bolt so I removed it. Inside is clearly the place where I have to do oil changes periodically. I have no idea what type of oil to use (30 weight?) or how much to use. Does it seem odd that I would have had visible oil in that piston oil well...or is it quite probable that the place who did the last service would have poured a bit down each well to let it slosh around on the piston arms just to keep them extra lubed? Shoots...for all I know there should have been an inch or 2 of oil down there instead of just an amount that was about as thick as the side of a quarter or two.

Thoughts?

 

Here are the specifications from the Kawasaki web site:
General Specifications
Engine
Engine Type 2-stroke, 3-cylinder, Reed valve, Water cooled
Displacement 891 cc
Bore x Stroke 73.0 x 71.0 mm
Compression Ratio 5.5:1
Ignition System DC-CDI
Lubrication System Oil injection
Carburetor Keihin, CDCV 38-29 X 3

Starting Electric
Drive System
Coupling Direct drive from engine
Jet Pump: Type Axial flow, single stage
Thrust 732 lb.
Steering Steerable nozzle
Braking Water Drag

Hull
Length 3,100 mm (122 inch)
Width 1,170 mm (46.1 inch)
Height 1050 mm (41.3 inch)
Dry Weight 278 kg (613 lb.)
Fuel Tank Capacity 53 liters (14 gal.)
Load Capacity 496 lb.

Model Identification
Year & Model ‘02 JT900-B4:JET SKI 900 STS
Color
Jet White (8C)
HIN Range KAW20001✓102 —
Engine No. Range JH900AE000001 —
Engine No. Location Top front reed valve housing cover

Tuning Specifications
Spark Plug NGK BR9ES
—Gap 0.7-0.8 mm
Ignition Timing 15° BTDC @ 1250 rpm~25°BTDC @ 3000 rpm
Carburetor
Idle Speed 1,250
100 rpm (in water)
Compression Pressure 121 psi

 

The maunal that I have for the 1100 shows:
head cap nuts at:
29 N-m (3.0 kg-m, 22ft-lb)

The cap nuts at the bottom are:
34 N-m (3.5 kg-m, 25ft-lb)