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Those numbers are way low for any ski. 120 is a good avg., but will run ok on 110. Anything below that, and it's time for at least a top end. if the numbers are all pretty consistent, chances are the cyl's are in good shape. Get a good gauge and retest. Sounds like the schrader valve is having issues. Be sure you only have one plug out at a time, and make sure you have the plug wires grounded somewhere. If they've been sitting, a carb rebuild is in order. I believe they are they sbnI carbs. Dave will correct me if I'm wrong. lol If you pull the mixture screws, document exactly how many turns from seat each one is for each carb, and don't split the rack if you don't have to.
Yes replace the oil lines and bleed the system. It couldn't hurt to remove the old oil. Just leave the injection system. They are very reliable. You could mix about 1.5oz's per 5 gallons for your first ride just for safety, but after that, straight fuel. Smoke from a 2 stroke is normal, especially when cold.
1 crucial thing to remember, and don't do it wrong. When you run them on the hose, START THE SKI FIRST, AND SHUT THE SKI OFF LAST. turning the water on and off is always, always the middle process (start ski, turn water on, turn water off, couple of quick light revs, turn ski off). Always in that order.
The other thing you need to remember for any 2 stroke that's been sitting is that the crank seals can get old and hard. When this happens, they leak air and can cause a lean condition. The only way to check them is by blocking off the intake, exhaust, and all other excess ports, and applying 6-8 psi of pressure to the crank case. It should hold it for about 15 min. A 1 or 2 psi loss is ok.
Try disconnecting the steering cable at the nozzle and make sure the nozzle is not frozen. If not, just get a new cable. Don't try to save that one.

Alright Dave, what am I missing ?
 

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Schrader on comp gauge. The additional oil is just for one tank. Just mix that amount in a 1 gallon can, add to the tank, and add 4 more gallons of fuel. It should bring the total ratio to around 32:1 for 5 gallons (give or take). This is just for some extra short time protection and should not be done for eveytank of fuel. Just keep the oil tank fuel. Yes the nozzle is at the back.
I use tygon fuel line for oil injection line.
If using a compressor to check seals, you must be very careful. to much pressure will blow them out. Use rubber freeze plugs for everything you can. Just easier.
If seals are leaking, yes engine comes out, crank cases are split, fly wheel, and drive coupling come off. Ya, it's a bitch to do on a Yamaha, but Dave can walk you through the r&r. The actual seal replacement is a breeze. Just have to use three bond 1211 or equivalent between the case halves.
Get a replacement valve off ebay. Prob just a few bucks. While you have it out, might as well replace all the fuel lines with some urethane fuel line. Can get it from sbt and most pwc stores. Blue in color.
Use this site to reference parts.

https://www.partzilla.com/catalog/yamaha/waverunner
 

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You sure it's smoke and not steam ? Smoke will blow away, steam will dissipate, usually fairly quickly. Any of those lines will work for the oil injection, but I doubt you'll need 25' of it. Prob. more like 12' for both ski's. I believe Home depot and Lowes both sell Tygon fuel line by the foot. Make sure you do one line at a time. Can't remember if Yamaha has specific ports off the pump like Kawai does on their triples. The id on the line should be around 3/32. Take a piece with you.
Just reach down and see how pliable the lines are. If they are, you should be good for this season. Should be part of a preseason check every year. Just amke sure they are still secure.
You need to inspect the impellers very carefully. Rocks like that tell me the ski's were abused. I believe there is a filter under a small cover on the side of the jet pump on each ski. You should prob at least back flush it.
 

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Should be the BN44I carbs. Definitively not the BN. Those are from the early PWC years and are easily identifiable by the big round fuel pump.
Just be sure and use the old needle springs if the pop off was good.
 

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The coupler should be torqued. I've never put anything on the threads. Chances of having to go back into the bottom end are minimal unless the top end grenades and breaks a rod or something else that requires the crank to get rebuilt.
 

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Manual said red loctite. If there was a whitish substance in or on the threads, that was loctite. It's going to get a hell of a lot tighter than 25ftlbs from use anyway.
 

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Go with genuine mikuni or wsm kits. No they don't come with seats. You will need to buy them seperate. If you get cheap kits, you get what you pay for. You can kit the kits from sbt and i believe the needle and seats also. Dave will have to get you the other info you need.
 

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The size is on the seat. It's small but it's there. No you cant use compressed air. The pump is for checking the neddle pop off. If you stay with the oem seats and springs you will be ok without it just reuse the springs.
 

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Read the instructions for the kits. The check valve have to be installed correctly as they concaved, and be careful with the little rubber plugs that hold them in. They break easily. I made a tool out of a old torx driver. Just don't use anything that has squared off edges or pointed. Lubing the new one with some oil will help, and also working it from the back side of the pump to finish helps.
Blue line faces up away from the body. Install the plug in the check valve, then install into the body.
Do one carb at a time so you don't get the mixture screws mixed up per carb.
 
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