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  1. #1

    GTX 4 tec Engine Advice

    I have a 2002 GTX 4 tec which I have just bought (75hours). The guy I bought it from said the engine had "blown" but did not know anything else. I rolled the dice and paid him the $1000 he wanted for it. I now have it home and have stripped it down. I now have the engine out and apart. The timing chain had snapped and the exhaust Valve Rockers for number 2 cylinder are broken in two. I have found one piece of the broken timing chain but not the other. The crank case is a little scored where the chain bunched up but looks OK.
    Obviously timing chain rockers etc all need replacing, but I have also found that the oil pumps (Both) have scoring marks, and the cam shaft has some slight blue marks on it? Is this normal, or has it been overheated? Also do the oil pumps need replacing? Pictures attached. Any help appreciated, I have never rebuilt a four stroke before, but have done plenty of two strokes.
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  2. #2
    The most interesting man in the world. Nils888's Avatar
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    Quote Originally Posted by sx4tec View Post
    I have a 2002 GTX 4 tec which I have just bought (75hours). The guy I bought it from said the engine had "blown" but did not know anything else. I rolled the dice and paid him the $1000 he wanted for it. I now have it home and have stripped it down. I now have the engine out and apart. The timing chain had snapped and the exhaust Valve Rockers for number 2 cylinder are broken in two. I have found one piece of the broken timing chain but not the other. The crank case is a little scored where the chain bunched up but looks OK.
    Obviously timing chain rockers etc all need replacing, but I have also found that the oil pumps (Both) have scoring marks, and the cam shaft has some slight blue marks on it? Is this normal, or has it been overheated? Also do the oil pumps need replacing? Pictures attached. Any help appreciated, I have never rebuilt a four stroke before, but have done plenty of two strokes.
    I would replace oil pump gears and covers.
    If I were you I would take the rest of the engine apart and look at the bearings.

  3. #3
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by Nils888 View Post
    I would replace oil pump gears and covers.
    If I were you I would take the rest of the engine apart and look at the bearings.
    +1

    The bluing on the cam is normal so nothing to worry about there.

    Chances are your bearings are fine but split the cases anyway just to verify and look for the missing piece of timing chain.

  4. #4
    Thanks for the advice.
    I have already split the case and cannot find the missing chain link anywhere. Attached picture shows bottom bearing and damage to case from the chain, I think the case should be repairable, and the bearings don't look that worn? I have no idea where the missing chain link went! Do you mean just change the pump covers or the casings as well?
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  5. #5
    thompsdw's Avatar
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    IDK - those oil pumps look pretty normal to me. I have torn apart 3 of these engines now and they all seem to be scarred to some degree. How deep are the marks?

  6. #6
    i would agree on oil pump and cover change. bearings look ok dealer's choice to replace given the hours and how extensive of a rebuild you want to do. if you can't find the rest of the chain, there aren't too many places it can hide. maybe whoever looked at the ski to determine the engine was shot took it out.

    any metal shavings anywhere? if there are make sure you clear out the oil passages throughout the motor.

  7. #7
    Finally finished rebuilding the engine. Ended up changing 4 valves, all oil pumps, chain and guides. Started up first time, and I ran it yesterday for the first time on the lake. Runs smooth and goes well. The only question I have is how hot should I expect it to get under normal running? I ran it for about 5 minutes in the lake on the trailer, there was no leaks and all seamed fine. Topped off the coolant and checked the oil, all good. Launched and ran for about 30 minutes some low speed some high but never flat out. ( I figured I would take it easy for the first few hours ).

    When I came back in you could feel the heat from the engine through the seat, and when I lifted the seat the exhaust seemed hot to me. I have only ever run two strokes before, but the exhaust seemed hotter than I would have expected. You could not have touched the manifold or J pipe, is this normal? I have no over temp alarms or codes and the engine still runs fine, oil level is good and clean, coolant level dropped an inch, but suspect finally getting the last of the air out.I am just curious as too what is normal on 4 strokes, and don't want to cause any damage after a winters work and $$$. I still don't know what caused the damage it had when I bought it, and don't want it to have been overheating and it still does it!

  8. #8
    Richieb's Avatar
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    Sounds like you did it all ok to me. The J pipe will feel just a little warm, and the heat under the seat is the scourge of the SC and force-feeding it air.

    The alarm would go off if the water box was empty, which is fed from the J pipe.

    All good.

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