How do i rebuild a 1995 polaris 750 jetski engine?

Answer 1

Before you start the process of tear down please read this from beginning to end several times so you do not miss anything. Yes guys that's you because I myself sometimes think as a guy that I do not need instructions when I really do. Without knowing what model Polaris jet ski I am dealing with here I will do my best to answer this starting with removal of the engine from the hull. Rebuilding a Polaris jetski motor is a fairly easy process if your willing to get dirty and you have some mechanical experience. I am explaining here how to do a complete tear down of the whole motor. If all you have is low compression on one cylinder then just tear down that one cylinder and go back up with new rings, and a new piston if needed. First of all remove the exhaust pipe from the motor. This may be made easier if you first spray break free fluid like my favorite- PB blaster or wd-40. These bolts will sometimes be difficult to remove after being in place for so long. I recommend using swivel sockects for this procedure and buying extra extensions for your 3/8 drive ratchet. You will find this will make removing this exhaust and motor so much easier. Depending on what jetski this motor is in will determine how hard this process is. Once the exhaust is removed and laying to the side inside the hull, begin loosening the hose behind the exhaust pipe so the pipe can be maneuvered out of the way. Now find the motor mount bolts and loosen them completely. Next make sure you cut your wiring harness. (I recommend finding a plug at your local auto parts store and attaching to these wires so that if you ever have to remove the motor again all you will have to do is unplug- this makes for such a nice install in the future) At this point look around and make sure you have disconnected the fuel lines from your carbs, and anything else that can prevent you from removing the motor from the hull. Me personally, I would use a cherry picker for removing the motor from the hull with cargo straps around the motor or if your motor has a lifting eye use it in conjunction with the cherry picker. Once you have the motor out start disassembling. I will stop here and tell you junior and novice mechanics one thing that will cause you to fail if you do not follow my advice- always always bag your hardware from each part and attach to the part with a zip tie and also label the bag of hardware with a sharpie pen just in case the bag becomes seperated from the part. I don't know how many people have disassembled these motors and then given up because they either lost hardware or just threw it in one big coffee can hoping they could remember later where it goes. This is also a good point in the process to make a list of broken parts or broken or missing hardware that you will need for the build process. Start at the top by removing the carbs and setting to the side. Next remove the individual heads from the "jugs" or cylinders. Remove your intake and reed cages from the cylinders. Next remove the individual jugs from the engine cases, slowly working them off the pistons and rings. At this point take the time to inspect your individual pistons and rings. Make a note of how they look, etc. I sometimes reuse my pistons if the jugs are still within tolerance. Make sure before you reuse a piston to clean it well and polish it with emory cloth. Find a local machinist who can help you measure such wear of pistons in conjunction with the cylinder they came out of. I have reused rings before but only in a pinch when I was trying to get a ski back on the water quick on a holiday weekend. Rings are cheaply purchased through different dealers on the internet. You are now down to the point that you should have all your intakes removed, jugs or cylinders removed, and be down to your engine cases. These engines are "spilt case" as in two part engine cases. Your pistons are still attached to your rods so now remove them. If you look in the side of each piston you will see a round hole with a metal pin installed. If you look closely you will also see a ring clip that keeps that metal pin in place. These rings are on both sides of the pin. You only need to remove one from each piston. Using a socket or another item of the same diameter of the pin drive it out from the side you did not remove a clip from. Be careful to save these pins with the piston they came out of along with the needle bearings that will fall out of the piston once the pin is removed. Keep the ring clip, pin, and needle bearing with the piston in case you decide to reuse. Once all the pistons have been removed you can now check play in your rods. Grab the rod and wiggle up and down and side to side. You should have hardly any slop at all. Also if your crank is good you should be able to rotate it easily. If you end up having slop and rough rotation you may need to have your crank rebuilt or have to buy a rebuilt one on exchange. Do your research or contact me to find the most affordable place to get this done because it can be expensive. Ok let's assume at this point that you now have a good crank, engine cases are in good shape, and you have replaced all broken parts, hardware, and have had your cylinders honed in a good cross hatch hone by a machine shop or by using a hone and doing it yourself. Very easy with a drill motor and a stone hone bought at most auto parts stores. Stop here and please clean put your hull so you can have a nice clean install when you go back together. I will usually spray degreaser in the hull and let sit. Then I will use a scrub brush and some elbow grease to really scrub it good. Next get a pitcher of hot water and some good liquid dish soap and your shop vac. Pour some soap in on the problem areas, add a little water and scrub. Pour some fresh water in and then vac it out. Repeat until it is as clean as you want it. Ok back to the engine-make sure all your parts are very clean. Lay out the parts on clean rags and start the build process. Have fresh gaskets ready to go. If your motor had the original metal gaskets I would reuse them if at all possible. First spray them with perm tech copper gasket spray and let it dry well. I usually use case sealant on the engine cases. Look for a case sealant called 1211 super bond. Or go to a parts house and ask for silicone case sealant for engines. Apply the sealant and then sit your crank in the bottom case half being careful to line up the pins where they fit in your cases. Look at all this before hand and what I am saying will make total sense to you. Next carefully set your top case half on and make sure the cases fit together nicely. DO NOT FORCE THEM TO FIT!!! These cases will break because they are sand cast alluminum and brittle by nature so be careful and gentle. Once you have them together correctly tighten all the hardware and your bottom end is complete. I highly recommend buying a manual even in digital format so you know the correct torques for each fastener. Borrow or rent the correct torque wrenches and do the job right. Yes you can build a motor without torque wrenches but the torque values are there for a reason. Abide by them!! Next install your individual pistons as they match up with the cylinders. Install your rings on your pistons. I always stop here and dribble a decent amount of two cycle oil down in the cases and work it around a bit by turning the crank which should spin freely. This oil could keep the motor from freezing up upon cold start the first time. Yes its gonna smoke like crazy at start up. I would much rather have a lot of smoke than have to tear it down and start over. At this point stop and stuff rags or something like that around each opening in the engine cases where your rods come through. This will save headache if your drop hardware or one of the little ring clips. Now start installing your cylinders one at a time on the correct piston. Torque all your cylinders as you go. Install your exhaust intake and your reed cage and intake for your carbs. Install your heads and torque properly by correct factory torque specs, install your bed plate (of course this could have been done back when you just assembled your cases with the new crank). Put your carbs onm drop the motor back in your hull, bolt your bed plate to your motor mounts and hook up the wiring, and all the fuel lines. Here is a word to the wise Polaris engine builder- look at the reason why you had to rebuild your motor and correct the problem before re installing your motor. Polaris jetskis usually have engine problems because of the fuel systems. I always rebuild my carbs on any Polaris jetski before I run a rebuilt motor, I also replace fuel lines even if they look good. Why you say? Because the fuel lines break down over time and the pieces of the line end up in the tank and carbs and cause all kinds of problems. Your carbs lose there factory settings due to the previous owner messing with settings etc etc. Next thing you know the motor is running lean and a piston has a hole in it. Also make sure you replace the lines inside your fuel tank- called pickup lines. These lines have little filters on the end, clean these well and reuse. Next upgrade your fuel pump with a triple outlet pump. A very cheap but effective upgrade. This will keep the fuel distribution perfect. Next check the function of your fuel selector switch on the side of your ski. It may need to be taken apart and cleaned very well. Use vasseline on the little o rings and replace if needed. Last but not the least of words to the wise- go premix!! Get rid of that oil injection system and install what is known as a oil block off plate where the little oil pump goes on the side of the motor. Do this before you reinstall the motor. Check your starter and Bendix also before you reinstall the motor. Much easier to replace out of the hull than when in the hull. I really hope this write up helps a lot of people. If anything this knowledge can save you a lot of money. For a basic short block of the Polaris 750 three cylinder motor with a one year warranty is $700. A 1200cc motor can run you around $1600. So you can easily see how doing your own work can save you allot of grocery money for your families table. Take your time, think the process through before you start on any one part, do it right the first time. Even if you do this process over the period of several days it does not matter as long as it is done right. My first motor took me two weeks of a little work here and a liitle work there as I had time. This of course was after I had all my parts in and was ready to build. Now I tear down and build motors in literally a few hours if I have the parts on hand. I bought a ski last week with a bad motor and had it out of the ski, torn down in less than an hour with a little help from a friend. We replaced a bad piston, cleaned up all the parts and had it back together that evening and on the lake running just fine. So good luck to you. Feel free to ask me any questions. I will do my best to help everyone.