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Thread: low compression

  1. #1
    freedom04's Avatar
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    low compression

    alright guys, bad news for me.. i put a new well (reman) engine from sbt, for my 2004 polaris freedom. installed it, everything ran great, until i put it in the water yesterday. i put it in the water, started it up, ran awesome in the water at first, no leaks, no vibration, seriously ran the best it ever did. so i got on it, idled around for about 5 mins or so, still no problems, so i put about a quarter throttle, ran great, got it up on a plane, ran good, so i turned back around, headed for the dock and while i was idling back, it just shut off completely on me. tried stating back back up but wouldn't go. so i got home, took the jet pump off to see if something got in it or anything but nothing. so then i decided to check spark,, i have great spark. i also just put a fresh new battery on it and it's reading 12.38 volts. so then came compression test.. get ready.... i only have 79PSI !! i guess its time to send it back to SBT? i have a warranty on it. anyone have any input on what happened/ what i should do?
    P.S everything is brand new, fuel line, carb rebuilt and tested pop off, brand new plugs.

    What would make the compression go that low that quick??

    Thanks


  2. #2
    Click avatar for tech links/info K447's Avatar
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    Do not take the sealed/painted engine apart if you intend to send it back to SBT for warranty.

    Inspect the oiling system. Did you prime the oil hose(s) after reinstalling the engine? New oil filter?

    Oil pump correctly reinstalled, engaged with plastic drive cap on crankshaft snout?

    Did you add any pre-mix oil into the fuel tank?

    If you remove the intake manifold and reed cages you can look into the crankcase. Look for signs of oil being present.

    If you have a borescope you can inspect through the spark plug holes. Look for clues. Scars on the cylinder walls? Signs of water inside?

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  4. #3
    freedom04's Avatar
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    Quote Originally Posted by K447 View Post
    Do not take the sealed/painted engine apart if you intend to send it back to SBT for warranty.

    Inspect the oiling system. Did you prime the oil hose(s) after reinstalling the engine? New oil filter?

    Oil pump correctly reinstalled, engaged with plastic drive cap on crankshaft snout?

    Did you add any pre-mix oil into the fuel tank?

    If you remove the intake manifold and reed cages you can look into the crankcase. Look for signs of oil being present.

    If you have a borescope you can inspect through the spark plug holes. Look for clues. Scars on the cylinder walls? Signs of water inside?

    I actually switched to premix.
    i put 32:1 for break in. so i took the plastic drive cap off the crankshaft.
    I also have a snake camera, i looked in there but could not see any problems with the cylinder walls or pistons. all looked brand new.

    Hm im really stuck.

    and yes i know not to take apart anything on the engine, don't want to void my warranty.

  5. #4
    freedom04's Avatar
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    Quote Originally Posted by K447 View Post
    Do not take the sealed/painted engine apart if you intend to send it back to SBT for warranty.

    Inspect the oiling system. Did you prime the oil hose(s) after reinstalling the engine? New oil filter?

    Oil pump correctly reinstalled, engaged with plastic drive cap on crankshaft snout?

    Did you add any pre-mix oil into the fuel tank?

    If you remove the intake manifold and reed cages you can look into the crankcase. Look for signs of oil being present.

    If you have a borescope you can inspect through the spark plug holes. Look for clues. Scars on the cylinder walls? Signs of water inside?
    keith, compression should be around 150 for a rebuilt engine shouldn't it? i'm just confused what could of went wrong. i put brand new gaskets on everything. not sure what happened, but i'm not sure what 79psi in each cylinder means. and just to let you know, it was exactly even in each cylinder.

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    Click avatar for tech links/info K447's Avatar
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    Did you test compression of the rebuilt engine prior to running it?

    Throttle held wide open, strong battery, both spark plugs out?

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  8. #6
    freedom04's Avatar
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    Quote Originally Posted by K447 View Post
    Did you test compression of the rebuilt engine prior to running it?

    Throttle held wide open, strong battery, both spark plugs out?
    no i didn't check the compression when i received the engine, i honestly didn't think anything would be wrong, since i think SBT engines go through a compression test prior to them shipping it to me. but i did check it last night while the engine was hot and got 79 exactly, then checked it while cold this morning and got 79 also on each cylinder. battery is ver strong it's brand new and checked voltage and it's at 12.38 exactly.

    this is just making my head explode haha.

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    shawndak07's Avatar
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    Wow! SBT Reman strikes again!!! I remember reading a lot in 2010 on how crappy the SBT motors were and ended up buying a used motor from a older machine.

    Interested in why you went to premix on this machine? The oil pump on these motors are pretty strong.

    Check your spark plugs are the pure white, tan, brown or black? Metal shavings?

    Get a battery minder charger to bring your battery back to life while you wait. A good battery base voltage for a battery should be 12.6 +

    Also turn it over with the spark plugs out, see if water blows out. Had a gasket go bad in a old 650 and water got into the piston head. Funny i repaired it with black RTV silicone and it lasted many years until I sold it. I was 16 don't judge haha

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    Quote Originally Posted by shawndak07 View Post
    Wow! SBT Reman strikes again!!! I remember reading a lot in 2010 on how crappy the SBT motors were and ended up buying a used motor from a older machine.

    Interested in why you went to premix on this machine? The oil pump on these motors are pretty strong.

    Check your spark plugs are the pure white, tan, brown or black? Metal shavings?

    Get a battery minder charger to bring your battery back to life while you wait. A good battery base voltage for a battery should be 12.6 +
    from what i heard SBT is pretty good, but now i'm maybe starting to think otherwise. But also from what i heard SBT engines go through a leak down test plus compression and it must be within OEM spec. they also keep records for each engine from as soon as the core gets there to when it leaves for your house. Not sure if i just have bad luck. but they will send me notes on what they find and see what happened with it.

    I switched to pre-mix because it's just a piece of mind for myself, yes it's a lot more expensive because of buying more oil, and yes a little more work, but i'd rather just stick to pre-mix. i have the gas at 32:1 ratio, it has a blueish tint to it so i know it's getting plenty plus smokes a pretty decent amount but once it was broken in, i was planning on switching to 40:1 but looks like now i have to wait for another engine to get here to start my season.

    plugs are perfect, nice tan maybe a little darker because of all the oil that's in there.

    I'm not sure if i mentioned this, but it did crank over this morning and started but sounded like complete S**t. it also didn't have enough compression to pull the fuel through the fuel pump on the carb as much so it's not getting that much fuel.

    I plan on starting taking it out tomorrow, and once it's out, i will call SBT and send it back over there.

  11. #9
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    Quote Originally Posted by shawndak07 View Post
    Wow! SBT Reman strikes again!!! I remember reading a lot in 2010 on how crappy the SBT motors were and ended up buying a used motor from a older machine.

    Interested in why you went to premix on this machine? The oil pump on these motors are pretty strong.

    Check your spark plugs are the pure white, tan, brown or black? Metal shavings?

    Get a battery minder charger to bring your battery back to life while you wait. A good battery base voltage for a battery should be 12.6 +

    Also turn it over with the spark plugs out, see if water blows out. Had a gasket go bad in a old 650 and water got into the piston head. Funny i repaired it with black RTV silicone and it lasted many years until I sold it. I was 16 don't judge haha
    no water in engine,
    also i bought a battery maintainer the day i bought the battery and has been on it ever since.

  12. #10
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    i will for sure keep this thread updated and update what they find when i send it to them.

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