Above Forum Ads



No announcement yet.

2000 Polaris Pro 785 - Warning Long Post (Round 2)

  • Time
  • Show
Clear All
new posts

  • 2000 Polaris Pro 785 - Warning Long Post (Round 2)

    Here's the link to my round 1 build. I figured I should start another thread for round 2 since it deals with different issues.

    Here's how the spring started out. I took it out for the first time this spring drove it across the lake to put it onto the lift when I heard a bang. Lifted the hood and the hull was full of smoke. That cannot be good. I pulled it out of the lake to see what happened. The coupler hose on the PTO pipe stinger had blew, the cooling line from the Jet Works valve had melted and the paint on the collector was starting to turn dark. Wonder what caused that.

    I pulled it all apart looking for a cause and found the ball in my Jet Works valve was completely stuck in the hole. Some water could get around it at very high pressures, but none at low which would explain why it seemed like I had good water coming out of the pissers when I was going across the lake. Ordered the Delrin ball from McMaster-Carr and problem solved. BTW, I have 99 spare balls if you need one.

    Took it to the lake for a weeks vacation. This thing was running perfectly screeming up and down the lake. I was the fastest one out there or at least any of the ones that I came up on. I went to raise the dock out of the water when I noticed my trim nozzel linkage broken. So I pulled that off and MacGyver a piece of plate aluminum in it's place to get me up and going. That was the start of the week.

    I was so worried about my pissers again, I kept an eye on them like a hawk. Needless to say, I didn't notice till I got onto the lift that my bilge pump was running. Luckily I came in because I thought I was running out of gas as I lost power. I am like, now what??? I pull it back out of the lake to see what happened. I started pulling on my cooling lines off the manafold and the first one I pull comes right up. You guessed it, it was the Mag manafold cooling line had come off. Damn! In case you are not familiar with these boats, this fitting is imposible to get to with the exhause in place. So I drain the oil, pulll the tank, drain the fuel, pull the tank and then I removed the PTO exhaust pipe so that I could get my hand on it.

    I put the hose back on the fitting and put everything back together. I pulled the head to see if there was any piston damage. The Mag cylinder had a few dimples on the exhaust side, but the cylinder walls looked perfect. I bumped it over and it seemed to turn okay, but I noticed some small balls of aluminum in the spark plug. That's when I put the head back on and called Jay. He recommended I not run it anymore till I changed out that piston. Thanks Jay for calling me back. I almost gave it a go hoping it was okay. Damn, it's always something with this thing.

    I broke it down today and this is what I found:

    Mag head pipe got really hot, melted the oring and the coupler.

    Piston is toast. Wonder where the bottom half of the piston went on the exhaust side? Also, the top ring was stuck in the groove. Lucky it didn't tear anything up.

    Lucky the jug looks okay. Will just need to go over it with a little muriatic acid to get the little aluminum transfer off.

    I have a new piston kit on the way from Jay and he suggested the crimp style clamps to prevent this from happening again instead of using the worm drive clamps. Here's what he's talking about:

    Now my biggest dilema, with that much material gone off the piston, do I pull the motor and strip it down to see if there is any debris in the case, or just change out the piston and hope all the material exited through the exhaust when it melted. I really don't want to pull the motor again, but I REALLY don't want to start a round 3 thread either. Thoughts?

    Oh, and for those of you who were debating the compression testing in the other thread, I did a compression test before I called Jay just to see how bad off I was. Mag 115, Center 125, PTO 130. The Mag was obviously down, but not super low as you would expect from what that piston looked like.

    FYI, the exhaust couplers can be made from 3-1/2" ID high temp silicone tubing from McMaster-Carr. It's part # 5296K611 and costs $30.02 for a one foot piece. That should be enough for (4) couplers which works out to be $7.51 per each. Not too bad of a deal plus it will match my stinger hoses.
    Last edited by Derwood98; 07-10-2011, 06:12 PM. Reason: Forgot something!

  • #2
    Ouch that SUCKS !!!!!!!
    Your that far atleast pull it and turn it upside down to see if anything falls out and then hit it with an air gun to be sure
    2004 Matrix
    1999 World Finals Moto Marine 785
    2000 virage triple pipe project
    96 hurricane
    03 genisis
    03 msx 140
    04 msx 150 project ?
    92 kawi sc
    99 slh
    2000 pro 1200 triple pipe msd ignition and more


    • #3
      Yes, it does suck indeed. My plan is to tear it down to the crank and inspect everything. Replace all three pistons and rings along with getting the cylinders honed. I want it back to a brand new machine for for the second time around. Something about saving $200 and doing a half assed job just doesn't sit right with me. I found a powder coating place here in the cities who's going to powder coat my complete exhaust system for under $225. Not a bad deal since I spent that the first time around in paint / primer. All I have to do is strip everything again which should be easy and drop them off. I guess there is light at the end of the tunnel since the exhause got burned up on the overheat and the paint is brittle to beginwitth.

      I will post pics as I move forward. Just been really busy with work to get things teared down, but I should or will have it torn back down by the end of this weekend. Stay tuned for more pictures and progress. This will be better than the last build and hopefully will be the last time I have to go through this.


      • #4
        Well, I think I learned a little more about the source this evening. It all started with the ball in my Jet Works valve getting stuck over the winter. Well, guess what, look at what I found on my stinger end of my Mag pipe that had ruptured the connecting hose and melted the cooling hose.

        This pipe had been worked on before, but from what I can see, it is now officially toast. Does anyone have a spare Mag mid pipe they can spare. PLEASE?

        Here's my theory, Jet Works valve balls sticks, overheats stinger, blows connection hose and cooling hose, and the repaired stinger end of the mid pipe blows. Repair cooling hose and connection hose (not knowing the internal damage to the stinger) and ride the machine. Mid pipe doesn't get proper cooling under load at the header end due to the pissing of H2O out the stinger and the header heats up. When the header heats up, the cooling hose slips off and well, the rest is in post number one. Burned paint, burned coupler and oring and melted piston. Damn, what a kick in the balls on this project.

        So, can anyone PLEASE help me out with a used Mag mid pipe? I don't even want to try to repair a repaired pipe. No idea why it was repaired in the first place and it looks pretty bad. That may be where my lost 200 RPM's went?

        I will do a full tear down this weekend of the motor and I will post more, but what a PITA this thing has been. Who knew a $.12 cent ball would cause so much carnage. No wonder Jet Works never returned my call. SOB's.


        • #5
          Contact Keyzbum. He's got a few sets. And maybe Lugs has a few he can spare as well.
          My ski says made in the U.S.A...... Can yours say that???


          • #6
            Thanks Kevin. I sent them both a PM.

            Today I got it torn down to the crank. I will split the case halves tomorrow morning. It's beer time. Looks like Jay was right about it injesting some H2O. Obviously the first piston was distroyed mostly by heat, but the center piston had some grooves in the sides of the piston and the PTO had very slight grooves. That may be normal, but I am going to replace all three anyway.

            Whoever put this thing together last did a fantastic job. Everything came a part easy as pie. That's the nice part of doing something like this yourself and taking the time to replace bad fasteners and what not when putting it back together. Makes it so much less of a battle to do it for the second time. .

            I will know more tomorrow when I split the case halves and I will post up some pics. If the crank is good, I got lucky and can get by with new pistons kits and a hone job. Then it will be a new ski again. The nice part about doing it a second time is that you know where everything goes and what order to disassemble and reassemble. It's also good experience in case Jay ever needs a good service tech.


            • #7
              Finally, some good news. The crank and bearings look perfect. No piston debris in the case and none in any of the exhaust components. Wonder where they went? Looks like it will be pistons and a hone and I will be back in business.


              • #8
                Excellent News..
                2000 785 Pro, 2000 SLX 1200-,1995 SLT 750-


                • #9
                  man that thing is pure secks


                  • #10
                    That's good news.

                    No gritty feeling on any of the bearings right???

                    That debris had to go somewhere...... Hopefully out the exhaust
                    My ski says made in the U.S.A...... Can yours say that???


                    • #11
                      No gritty feeling on any of the bearings. Got lucky on that one. Nothing lookes overheated either. Does this look familiar?

                      Stripped the exhaust AGAIN for powdercoating. TIP: If you go through the work of stripping the pipes, just get them powdercoated! Don't go through the stripping process twice. What a PITA..


                      • #12
                        Found me a Mag pipe. Back in business. Hopefully it will not have any leaks and then off to powercoating. What a money pit this thing has been. Regardless, it sure is fun when it runs right.


                        • #13
                          And the build begins,,,,again.

                          I now have all the parts on hand to put this thing back together again. A HUGE thank you to Jay for getting my cylinders, pistons and rings turned around in record time. They look better then the first time I sent them in to get redone. Hopefully, with the hard lessons I have learned this past few months, this will be the last time I have to post a thread like this again.

                          I know you guys like pictures, so here we go. I will be starting to put it back together tomorrow morning, but here are a few to get started.

                          Newly redone cylinders with pistons and rings

                          Exhaust valves cleaned up and painted, waiting to go in

                          My newly powder coated exhaust and brackets. It looks more orange in the picture, but is a perfect match to the boat. They did an awesome job for pretty cheap.

                          How can a person not like a little head.

                          Even got my water distribution bracket powder coated along with the annodized water distribution bar to match the rest.


                          • #14
                            Damm Darrin, You have a show boat now. Holy smokes, that looks great. I didnt think your ski could get any better looking. damm.. Thats NICE!!!!
                            I know sitting here, you didn't clean the stems on your exhaust valves did you? lol Got ya! Unscrew those caps on them and take a peek at the shafts. I bet they are dirty. Mine were bad.

                            Cant wait to see it all together and running.. man, those jugs look Brandy new. Are you going to paint them also? or powdercoat them?

                            any strainer up front before the jet works valve? Delrin ball in? Remember on my up front strainer I had gook in mine. That strainer prevented that crap from getting to the jetworks valve.. Something to think about anyway.. Seems to work good on mine. Rock on Brother!!

                            I was thinking myself I would take the engine bolts that hold the engine to the mounts and having a machinist drill holes thru the tops of them and safety wire all 4 bolts with stainless wire like they do in aircraft. 2 at a time only.. Iv'e been reading up on how to do it correctly. They would never move then. I had them fall out on my sl750.. basically same as the Pro. When I drop the other motor in, I will do that to mine.. Nice piece of mind knowing they cant fall out again. Good Luck!
                            2000 785 Pro, 2000 SLX 1200-,1995 SLT 750-


                            • #15
                              Yes, Tom, I did take the exhaust valves apart and cleaned them. What, you think this is my first day?? LOL. Okay, made some good progress today. Got the motor assembled, installed, wiring done and pump installed. Tomorrow will be exhaust, water lines, oil and fuel tanks, carbs, priming everything and hopefully if all goes well, I can start it. A few pics of the progress...

                              The dremel does an awesome job of removing the old sealant and gasket material without messing up the surfaces.

                              Was very careful with the tripple bond not to use too much and made sure all of the bearings were well oiled before asm.

                              Checked the ring gap on all the rings. They were all exactly at .015. That's pretty awesome.

                              New 750 pistons and rings went in.

                              Oil pump installed. Used all new crush clamps on all hoses. Will be doing that on every hose going forward.

                              Stator, perfectly alligned on the case halfs mark.

                              Engine ready to be installed, just need to hook up the electrical before I drop it in.

                              Electrical complete, just need to drop it in.

                              Engine is installed, electrical is complete and the pump is installed. The powder coating is a perfect match.

                              More tomorrow.