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Author Topic: Oly Heat  (Read 781 times)

cgg17

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Oly Heat
« on: March 18, 2017, 01:56:25 AM »
Hello all,
We have been blessed with snow from the snow gods and it has been here since Tuesday. It will probably be un-ridable by Sunday though...
Anyway, when I ride my 1968 Olympic (Rotax 247) it gets really hot after about 10-15 minutes and then bogs mid range. It will idle fine and run full throttle no problem, but mid range there is a big bog. I noticed there is a small leak around the head, I was told it requires no head gasket to run (cast iron jug, aluminum head with bolts not studs). I have the jets turned out twice as much as the manual says they should be, and it till is giving me problems. I cleaned the carb, resealed the engine over the summer, and now its still giving me crap. Tried the spray on the seal and doesn't make any difference. Any ideas would go a long way in getting this running correctly.
-Chris
1981 Ski Doo Everest L/C Electro
1968 Ski Doo Olympic 250
PETT No. 117

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    EricR

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    Re: Oly Heat
    « Reply #1 on: March 18, 2017, 02:15:05 AM »
    I wonder if in fact the problem is not the engine but the secondary clutch either not backshifting right, or upshifting too quickly? 

    My experience is those carb needle settings are just a guideline, yours will vary with temparature and sticky snow makes it run hotter, more load to pull through.

    How bout some pics?
    I scatter them from the midwest to south of the Mason Dixon

    oldsledz

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    Re: Oly Heat
    « Reply #2 on: March 18, 2017, 04:35:11 AM »
    Maybe the muffler is plugged up some what , or maybe a mouse nest in the fan housing?

    2muchfun

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    Re: Oly Heat
    « Reply #3 on: March 18, 2017, 09:37:47 AM »
    68 250/247 should have a head gasket. I believe the a 67 does not.

    Desmo878

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    Re: Oly Heat
    « Reply #4 on: March 18, 2017, 11:53:11 AM »
    I noticed there is a small leak around the head

    I don't know about the head gasket, or running hot, but this ain't good under any circumstances. Dis-assemble & inspect. I agree as well that it could be the clutching. Check to make sure the secondary returns properly, if that got hung up, would do what you are describing. Just happened to me.
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    skidoonut3

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    Re: Oly Heat
    « Reply #5 on: March 18, 2017, 01:10:19 PM »
    My guess mouse nest so no air circulation either in the engine or muffler.

    cgg17

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    Re: Oly Heat
    « Reply #6 on: March 18, 2017, 02:54:08 PM »
    Muffler is clear, no nest in the shroud, I can get pics of the leak later and I will remove the head tonight. It has excellent compression, about 135 pounds, so that's why I questioned the head gasket. Ill try not to run it today, Ill ride my other sled before the snow melts.
    1981 Ski Doo Everest L/C Electro
    1968 Ski Doo Olympic 250
    PETT No. 117

    thefoolsbro

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    Re: Oly Heat
    « Reply #7 on: March 18, 2017, 04:34:40 PM »
    I thought I had a head gasket leak on my 372 JLO, after closer inspection I found the sealing surface
    of the head to spark plug had a small chunk out of it, and was leaking right there. seems when it was
    overheated/burned a piston I too the plug out while it was too hot and it stuck to the head a little. Had
    to put a new head on. that was for the leak, not overheat though.
    1970 moto-ski 375 (372 jlo) most original vintage winner 1st  Hale show
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    T-Dub13

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    Re: Oly Heat
    « Reply #8 on: March 21, 2017, 01:13:30 AM »
    Those motors had a pretty bad combustion chamber design in the head.  If you're not running a head gasket and should be, then the higher-than-stock compression ratio may be getting you into trouble on a warm day.  Remember, fuel isn't what it used to be either!
    My 335 always ran boggy on warm days.  And it didn't respond to twiddling the tilly screws, just ran so hot, I could use the glowing red header to light my way home since I lost the cowl.   :o ;D
    Valves are for Toilets...

    ricardo

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    Re: Oly Heat
    « Reply #9 on: March 21, 2017, 02:15:10 PM »
    I took a look in my 68 parts book to check on a head gasket. 68 model year did not use a head gasket in the 247. Re-check ign timing. 150-170 btdc. In thousandths. Try to get as close to .170 as you can. Be sure to advance timing fully when checking timing. I have had these rotax motors run hot when timing is off. There is an actual service bulletin from 1968 to do this. Rick

    cgg17

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    Re: Oly Heat
    « Reply #10 on: March 22, 2017, 05:55:22 PM »
    Thanks for all of the advice, I have been couch ridden sick the past two days and now the snow is all gone too... Ill work on this later on.
    « Last Edit: March 22, 2017, 10:37:52 PM by cgg17 »
    1981 Ski Doo Everest L/C Electro
    1968 Ski Doo Olympic 250
    PETT No. 117

    skidog59

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    Re: Oly Heat
    « Reply #11 on: April 05, 2017, 03:14:54 AM »
    i'll second ignition timing.  do it right with a dial indicator and take your time. remember full advanced cam when setting. Timing is often overlooked on these old sleds and its very important.