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  1. #1
    Policeman's Avatar
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    Exhaust bolts broken on Jug.

    I am in need of some advice. I am not a total dunce when it comes to the two stroke engine but new enough that I am not sure how to handle this issue.

    I did my pre-check on a ski prior to taking it out on the water the other day and it appeared fine. Its a 2001 Polaris Virage 700 carb engine. I allowed my daughter to ride it and she creeps on the water. Guessing the throttle never reached 50% with her on it. I noticed while riding beside her that the bilge pump was really pumping water and I stopped her to find that the drain cocks were open. I closed them and checked that the water did not get up to the engine. It was fine so we drained the hull using the pump and off she went. About an hour later, I noticed that the pump is still occasionally pumping water. Not a lot but enough to be noticeable.

    We trailered the ski and I was looking it over today. I found a busted bolt head laying in the hull of the ski. I identified it as belonging to the exhaust manifold and checked them. I was missing TWO bolts on the front jug. From the looks of the the bolt I found, I would say its sheared off inside the jug.

    So first question would be what happened? Did water get inside the engine to cause this or was it a back fire that may have blown it out. Or is it something that Im not thinking of that may have happened.

    Secondly, how should I do the repair? Should I remove the front jug and tap out the broken bolt or replace the jug with another that I have on a scrap engine?
    As a forewarning, I have never worked on a 2 stroke engine internally accept for the stator change on a reman engine.

    So would greatly appreciate some input on how difficult of a job this is going to be; if I can handle it and what is the best course of action. To my knowledge, the engine is running fine at this point.

    Thanks in advance.

    Brad
    Last edited by Policeman; 06-28-2014 at 01:03 PM.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Do you know if this engine was repaired by someone previously, who may have removed and reinstalled the cylinder?

    When these engines are bolted together there is an important step where the cylinders are aligned with the exhaust manifold prior to torquing down the cylinder base bolts. If this step is omitted then the cylinder and exhaust manifold mating faces can be slightly misaligned which puts stress on everything.

  3. #3
    Policeman's Avatar
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    I really don't know K. I purchased this ski for next to nothing so I didn't ask a lot of questions. ($300)
    I had to fix the hole in the hull and its ran great since then.

    Could you educate me on how to check for this or fix it?

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Policeman View Post
    I really don't know K. I purchased this ski for next to nothing so I didn't ask a lot of questions. ($300)
    I had to fix the hole in the hull and its ran great since then.

    Could you educate me on how to check for this or fix it?
    Normally when the engine is being assembled, the cylinders are positioned and the cylinder base nuts are just barely snugged down, almost still loose.

    Then the naked exhaust manifold is installed, no sealant or gaskets. All mating metal surfaces must be clean and free of burrs. The exhaust manifold bolts are torqued, while making sure the cylinder bases stay snug to the crankcase. This ensures that the mating surfaces or the cylinders and the exhaust manifold are in perfect agreement. Then the cylinder base nuts are further tightened and torqued to spec.

    Now the exhaust manifold is removed. When doing the final install with the exhaust manifold (using sealant or gaskets, depending in the engine) you can be sure the exhaust manifold will mate up properly with the cylinders.

    Whether you can get the broken bolts out will depend on how badly they are stuck in there. A machine shop can almost certainly get the stubs out, for a fee.

  5. #5
    Policeman's Avatar
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    Thanks K.
    So do you believe this is something I can handle on my own? Would it be a mistake to swap the jug off the other engine and replace the jug with it or should I have a machine shop simply remove the bolts and replace with the original jug?

    Should I consider replacing the piston while I am under there? Any other pointers you might have for me?

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Policeman View Post
    Thanks K.
    So do you believe this is something I can handle on my own? Would it be a mistake to swap the jug off the other engine and replace the jug with it or should I have a machine shop simply remove the bolts and replace with the original jug?

    Should I consider replacing the piston while I am under there? Any other pointers you might have for me?
    It all depends on the details of your particular cylinders. Piston plus rings plus cylinder = compression.

    Worn cylinder, worn rings, suspect piston. Any one of these suggests starting with a fresh piston and new rings. Overbore the cylinder if needed to bring it into spec and also match the required piston clearances.

    Only a careful inspection and comparison can say which cylinder is in better shape. If neither cylinder is usable as is​ then it is probably easier to get a new piston and rings and have the 'spare' cylinder bored and honed to match the new (probably oversized) piston.

  7. #7
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    Thank you K. You are always so very helpful!

    Brad

  8. #8
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    Click image for larger version. 

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    This is the cylinder walls of the jug that I would like to use. Does this look acceptable for a replacement? I was concerned about the wear marks inside.

  9. #9
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    SBT cylinder swap is good. I got cylinders off eBay under $100, but still had to machine them one was 82mm the other 81mm neither listing said that they were previously machined. Had to get a 82.5mm kit due to that so just be aware if you buy from ebay. You could resleeve them or bore your self.

    on another note I'm putting my jugs on my ski. Where can I read the procedure for the exhaust mounting when I reinstall them?

  10. #10
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    Quote Originally Posted by Policeman View Post
    Click image for larger version. 

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    This is the cylinder walls of the jug that I would like to use. Does this look acceptable for a replacement? I was concerned about the wear marks inside.
    I dont like the wear marks or the rust. Why cant you use the old one? The pieces should come out once the manifold is off.

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