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Discussion Starter #1
Hello,
I just purchased my first jet skis, a pair of 1999 GP1200s. I'd ridden a few times in the past and had owned a small ski boat in college, but this is new territory for me. They look to be well cared for and one of the skis is good to go, but the second has low compression in one cylinder. That'll be a winter project.

I was able to take the good one out this weekend, and it ran great. There are a few minor adjustments I'll want to make, but I'm really happy with the way it performed. My question though is, how long should I be able to run on a tank of gas. In two hours, I used about 3/4 of a tank. Is that normal? I expected better, but it was a lot of WOT. Like I mentioned, it seems to run like it should. Doesn't seem to be running rich. Let me know what you are getting.
Thanks!!
 

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Pwc's, especially 2 stokes are not known for their mpg, but more for gpm.
The thing that should be looked at asap is the oil injection lines. They should be semi soft, but pliable. if they are not, they need to be replaced asap. when they get hard from age, they become brittle and will break or come off. It is a easy project, and takes very little time and money compared to trashing the engine. If they are still in good shape, I would at least put new zip ties on them.
I would also look at replacing the fuel lines, and rebuilding the carbs. No telling how long it's been since the last rebuild.
Compression should be about 120psi and plugs should be tan to med brown.
 

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+1 for what Rods already covered.
this is a non-power valve unit so you have no worries there.
your fuel consumption at that rate is normal.

Your fuel consumption rate at WOT is around 16/17 gallons per hour.
 

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Discussion Starter #4
Thanks for the input, fellas. I'll be giving both skis a good going over this winter in addition to rebuilding the one with the dead cylinder. From the reading I've done, I suspect an oil feed issue caused the compression problem, so I'll add your suggestions to my to do list.

On a related note, I had considered doing the oil feed block off and just running premix. If my gas mileage is going to stay this poor, I may have to rethink it. I can't carry that many gas cans with me everywhere I ride. Sounds like I'll need to stay close to a marina so I can refill. :tango_face_sad:

Thanks again. I'm sure I'll be back with more questions.
 

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Nice ski's. Where in Missouri ?
I would leave the oil injection. They are very reliable systems. It's normally the oil lines that fail, and that's normally from age.
 

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Welcome to the forum, and I feel your pain. I have two '97 1100 triples, and if I would have ridden them for two hours at a time would have had the same result. Mostly WOT with me too, my wife, she gets much better mileage!

Mine were converted to the premix, and I just keep a couple of bottles that can mix with 5 gallons of gas at a time, so that I always have oil ready. I buy it by the gallon and pour into the bottles and reuse them.

Glad your one ski is running well. I also used to keep a set of plugs and wrench in my skis too, as inevitably, you are out on the water when it starts to run rough. That's why I'm selling those and bought a new 4 stroke, will get a second next year. The older skis are very stable, lots of fun, but she wanted something that didn't have to be messed with. Oh well, guess i'll be putting them on Craigs list tonight...

Have fun!
 

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Personally I'd leave the oil injection in tact. There a variable rate pump. At idle they mix about 200/1 up to 50/1 at wot. Saves oil and fouled plug when running no wake zones. If set and maintained they are pretty much bullet proof.
 

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Discussion Starter #8
Nice ski's. Where in Missouri ?
I would leave the oil injection. They are very reliable systems. It's normally the oil lines that fail, and that's normally from age.
Thanks, they look a little better in the pictures, but I think they've been maintained. Really clean inside and all the pivot points are greased, etc. I'm in Parkville, northwest corner of Kansas City.
 

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Discussion Starter #10
Second noob question. Can I run the engine for extended periods with the cooling system flush connected and water running through the engine? This would allow carb adjustments at home rather than at the lake.
 

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You really need the load on the Motor of being on the water. The best way I've found to do adjustments is to leave ski strapped to the trailer and back it into the water at a low use or unused ramp. That way it's easy to stand beside the ski and make adjustments while on the throttle.
 

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Discussion Starter #12
Good to know, Dave. I'll give that a shot.

A few other questions:

The PO had stowed a stubby phillips screwdriver in the storage compartments of each of my skis. Any ideas what this was for? Is there something that might need adjustment while out on the water?

I started messing with the ski with the bad engine last night. Compression test showed 120 psi on the front and center cylinders, and 100 psi on the rear. I also checked my good ski, and it's 120 across the board. Both skis have about 160 hours on them. Is 120 about where I should be? I didn't find the acceptable range during a quick scan of the owner's and service manuals.

I pulled the carbs and exhaust and was able to get my hands on fuel and oil hoses. Fuel hoses are blue and appear to be in good shape, nice and flexible. Same with the oil hoses, only they're black. Should I go ahead and replace all these since I'm in there? I've heard that the yellow Tygon hose you can get at auto parts stores works well. Thoughts?

Thanks!
 

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Good to know, Dave. I'll give that a shot.

A few other questions:

The PO had stowed a stubby phillips screwdriver in the storage compartments of each of my skis. Any ideas what this was for? Is there something that might need adjustment while out on the water?

I started messing with the ski with the bad engine last night. Compression test showed 120 psi on the front and center cylinders, and 100 psi on the rear. I also checked my good ski, and it's 120 across the board. Both skis have about 160 hours on them. Is 120 about where I should be? I didn't find the acceptable range during a quick scan of the owner's and service manuals.

I pulled the carbs and exhaust and was able to get my hands on fuel and oil hoses. Fuel hoses are blue and appear to be in good shape, nice and flexible. Same with the oil hoses, only they're black. Should I go ahead and replace all these since I'm in there? I've heard that the yellow Tygon hose you can get at auto parts stores works well. Thoughts?

Thanks!
Unknown as to stubby screwdriver?? Only thing I keep with me, as I'm out on an open bay and can be miles off shore is an extra set of plugs and an old dirt bike plug wrench. And orange collapsing paddle.
For 160 hrs your compression is about where it should be. I think a New top end you should be about 130/135 on that unit. Your bad cyl still being at 100, I'd take to be a good sign. Maybe it's not to bad. A local shop should be able to bore it for you or you can do an exchange through WSM performance. Top end exchange with everything, pistons,gasket,cyl,ext... Is about 600/700 bucks. But I'd pull the motor all the way down and replace the crank seals as there probably hard/leaking from age.

The Yamaha fuel line is a high quality rubber and I wouldn't replace them. Just retie them if there loose feeling with new wire ties. I believe I already told you about getting a wire tie gun from Lowe's, HD or electrical supply house. The oil lines, any tygon tubing from small engine repair, auto parts store or SBT will work. Leave it a little long to allow for some shrinkage a be sure to get them tight. you should plan on rebuilding carbs also. Use only mikuni kits.
 

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Discussion Starter #14
This just got a whole lot more interesting...and expensive. I never did find the missing piece of piston, but it clearly bounced around on top for a while. Maybe I need to look in my muffler? I actually suspect it made its way out the hole in the bottom crankcase, and the PO fished it out.

Surprisingly, there's no evident damage to the upper crankcase, the cylinder block or the head. Other than the dings and scratches, the crank and rod look ok too.

So, this is probably a bad idea, but here's my cheap first thought. Take the bottom crankcase and have it welded, and have the cylinders bored. Mic all the crank, rod and crankcase clearances and if they're in spec, get a new top end kit, new seals and gaskets and put it back together. What could go wrong, right?
 

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Yes, the piece/pieces probably went out the exhaust. If it's not in the muffler it's in the water box. The lower case could be welded and ground down and probably be ok. But I don't think I'd trust the crank. It took quite a beating from looks of it. The rod integrity is what I'd be worried about. Would hate to build a motor to throw a rod 15 hrs later.
It may be cheaper for you in the long run to contact "pwcengines" and see what they can do for you. That motor with rebuildable core Is $999. I don't know if they'll do part cores based on damage or not. There motors have a 2 yr no fault warranty. May be able to find core motor on eBay to use if need be. I'd call them though, reading there procedures sounds like they'll work with you on it.
 

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Discussion Starter #17
I want to get some carb kits on order while the machine work is being done on my cylinders, and I'm a little confused. Do my skis have BN44 or Super BN44 carbs? The service manual seems to indicate regular BN, but Super pops up when I search based on model (1999 GP1200). Thanks.
 

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From what I find looking it up by model yr is the sbn44, not the supper sbni. The sbni was used on the power valve motors.
I believe the needle and seat should be 1.2mm, if nobody's changed them. You may want to pull one before you order.
Also make sure each carb goes back where it came from.

And above all pay the extra $$ for true mikuni kits. Not after market no names.
 

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Discussion Starter #19
From what I find looking it up by model yr is the sbn44, not the supper sbni. The sbni was used on the power valve motors.
I believe the needle and seat should be 1.2mm, if nobody's changed them. You may want to pull one before you order.
Also make sure each carb goes back where it came from.

And above all pay the extra $$ for true mikuni kits. Not after market no names.
Thanks, Dave.
 

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Discussion Starter #20
I did a quick search and didn't come up with anything, so I'll ask here. I want to replace my crank seals, so the coupling flange will need to come off. I don't have the special tool shown in the manual, and the crank is out of the engine. Are there tricks to removing this in my situation? i.e. safe way to hold the crank, homemade coupler wrench? I'm assuming this has a right hand thread, but that's just my guess. Thanks.
 
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