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  1. #1
    Junior Member meechee's Avatar
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    1970 Ruppster > Fix old JLO vs. New Engine

    I would love to have the old one working but I just have no idea how to work on them. The guy I bought it from knows alot more than I do about these and he couldn't get it to work consistently.
    At 14 HP, I bet the JLO really makes it haul ass.

    Another thing - once I get it running, I would hate for it to break down 3 miles from camp. I know so little about these 2 stroke engines that it could be a minor fix and I wouldn't know how to fix it.

    So I just thought the safe bet would be to put a new engine in there.

    I'd appreciate any input. Hopefully I get some input from both sides > those of you who've fixed the JLO and those who've swapped the engine for a new one.

    I'd like to compare three things> cost, man hours, and results.

    Results> power/ speed & reliability out in dirt country

    Thanx

  2. #2
    gumpit's Avatar
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    I think you know the answer. And I would do the same thing. Drop a new engine on it and GO...................... Unless it is a restored piece and in a museum. I don't see any reason to go all original... Just my opinion... Randy

  3. #3
    Junior Member meechee's Avatar
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    Oh, and what would you replace it with?

    I just want to make sure I avoid any problems. Like buying a new engine that doesn't end up working in the ruppster for one reason or another.

  4. #4
    shoe's Avatar
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    to install a newer engine you will most likey have to fabricate some new stuff to get it to fit , the chances of you finding a drop in engine are slim at best ,,, Maybe you need to find someone willing to help you out in this ? Or maybe this is a bigger project than you actually thought it would be ,, Not a bad looking old Ruppster really

  5. #5
    Hangin with Neck and GTO The Restore Kid's Avatar
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    Quote Originally Posted by jesse8931 View Post
    you will need new crank seals and and a carb rebuild at the very least
    That is what goes wrong in every snowmobile engine... IT MAY just be as simple as the carb needs torn down cleaned out and reassembled readjusted, it MAY have a fuel pump that is not working properly, although I don't believe those machines use a fuel pump... I would say START with a simple carburetor rebuild... If that doesn't fix the motor, it is PROBABLY your crank seals.. two cycle engines suck the fuel air mixture into the crankcase on the up stroke, then forces it into the cylinder on the down stroke.. 38 year old snowmobile engines have a tendency to leak around the crank seals from wear and USUALLY dry rt from sitting.. If they are bad the engine will never run right.. You'll have to shoot gas into it to prime it, THEN keep it running a fairly good speed or it will lose vacuum and die.. ..If the guy is a 2 stroke expert and can't make it run he probably never went very deep in the motor... I would say look into a rebuild (refurbish) on the motor.. It probably does not need rings and bored and EVERYthing.. just fix whats wrong with it.. You could take the motor to a reputable small engine place, and get an IN WRITING estimate of what they will charge to get the engine back to reliable and good running.. Crank seals and carb kits are cheap... You MAY have the engine redone for less than the cost of a new one.....
    HOWEVER I think running a NEW 4 stroke motor is a great idea too.. No oil to mix at EVERY fill up.. quieter, more dependable.. I would butcher the machine as LITTLE AS POSSIBLE doing a motor swap and DEFINITELY KEEP your original motor on a shelf with the piston rolled to top dead, spark plug in it, all the little holes and passage ways sealed off... and just leave it parked where it is safe, and run a new Briggs I/C 11 horse in it's place.. Problem solved..

  6. #6
    Senior Member quiklids's Avatar
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    We had JLO's in both of our Ski-Daddler snowmobiles...'when' the recoils were working, we always had trouble starting 'em. My Dad really expanded my vocabulary with those engines...

  7. #7
    Senior Member oldyeller's Avatar
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    I used to own a 1972 artic cat snowmobile with a 340 JLO motor..I have owned a lot of snowmobiles over the years and I think that JLO was probably the most frustrating engine to keep running I have ever experienced...

  8. #8
    Senior Member oldyeller's Avatar
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    Quote Originally Posted by quiklids View Post
    We had JLO's in both of our Ski-Daddler snowmobiles...'when' the recoils were working, we always had trouble starting 'em. My Dad really expanded my vocabulary with those engines...
    We had a couple of those as well..My dad and uncle were dealers for a short while..

  9. #9
    Senior Member quiklids's Avatar
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    Here's a restored one with a 372 JLO-



    Last edited by quiklids; 03-01-2010 at 04:45 PM.

  10. #10
    Senior Member
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    i dont know what size jlo you have but i know they can be fun to get parts for some of them , unless someone started making parts again. i have a 292 in a sled , work on it for a week for a 10 min ride . they can be good motors but also kinda of picky . good places to start looking for problems the carb the gaskets and the seals . check the points and coil . mine wasnt too bad but it did like eating top end gaskets , mine also got the strange run problems before it got shelved . it would start fine idle great ,till you touched the throttle the it went wide out and would not come back down to idle you had to kill it and restart it . if there is a shop that work on snow cats they would be your bet bet i would thinnk for fixing it .
    JLO =Japanese left overs

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