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Thread: 1996 670 to 1998 670HO conversion

  1. #1
    Member Bullelkklr's Avatar
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    Default 1996 670 to 1998 670HO conversion

    First - this is not on purpose but rather jus the way that it is working (or not working) out.

    I bought a 1996 Summit that lost a ring and subsequently I hammered the whole motor.

    So I bought a rebuild from out of state. We had some misscomminications and I ended up with a 670 HO motor instead of a regular 670. A newer 1998 or 1999 670X or 670 HO motor.

    Well, the wiring doesn't match up. Initially the builder was going to send me my old stator to put into the 670HO. After thinking about it I asked him to send me his CDI instead. The HO has different timing, compression, pistons, head configuration (and maybe more?) so my thinking is that using the CDI for a regular 670 would not be so smart.

    Does anyone here have exp with trying to do this? Is there anything that I need to worry about besides the CDI unit?

    What does the 2nd electrical port coming off the head do? I think that it is DPM, but my 1996 summit doesn't have the DPM connector coming from the chasis....

    Will I have any problems lining up the clutch to the driven pulley?

    Will I need to re-clutch it? (I put on my old regular 670 clutch).

  2. #2
    Member AKDoug's Avatar
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    I just replied to your other thread. You stock carbs won't work with the HO motor without changing the carb boots on the engine and a complete rejetting of your carbs. Even then I don't know if it will work. If you got H.O. carbs with the motor than they won't fit your airbox. I also do not believe that your CDI will work. You will also have to change the clutching as the H.O. is good for 15-20 hp more than your standard 670.

    How bad was the original motor. My 670 H.O. has swallowed pistons and rings on many occasions and has always came back to life. It's one tough motor.
    Bunny Boots and Bearcats: Utility Sled Mayhem

  3. #3
    Member Bullelkklr's Avatar
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    the original motor was hammered pretty bad. The rotary valve face was scored to about .030 or so. One jug needed about .020 over boring. One of the bearings was froze up. I am past trying to re-work it.

    I will talk to the builder. I am pretty sure that he would send me the carb boots and he said he will swap me CDI's. I would prefer to have the airbox and the 44mm carbs too..but that might be more cost for me. I am leary about jetting the 40mm mics as if I run lean then I could smoke this new rebuild.

    What would need redone to the clutching? I probably should buy new sheaves anyway. Dayum I am going to have more money into this thing that I wanted......right now I am at about 700$.

  4. #4
    Member AKDoug's Avatar
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    I have dug through everything I have and I can't find any info. It's been 10 years since I clutched my machine and I've moved on to other sleds. The info has fallen out of my head and was saved on a computer three computers ago.. I do know that the TRA is super easy to do yourself. Looks like it's time for you to head over to DooTalk and ask around.

    Added on edit...at Doo Talk look up Big John. He's helped dozens of times on my SkiDoo questions several years ago.
    Bunny Boots and Bearcats: Utility Sled Mayhem

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    Member Bullelkklr's Avatar
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    I have a post up there, but no response yet.

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    Member Bullelkklr's Avatar
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    Builder wants me to put my old stator and flywheel on this HO motor. He is pretty confident that it will work for my needs and uses.

    Whatdoyathink???

    BTW - thanks for all of the input on this - this thing is driving me nuckinfutz...

  7. #7
    Member Bullelkklr's Avatar
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    Well - finally all back together. She fires right up, but won't idle or run a steady RPM. I didn' try to adjust the timing at all yet. I don't think it is carbureation...

    It will start after I give it a couple throttle skwirts but then wants to die right out unless I give it a bunch of throttle (which I don't really want to do very much).

    Will get after it tomorrow night and see if I can get it smoothed out.

    Had another question on the primer...it is not flowing any fuel when pumped...the one on my other 96 GT (583) doesn't prime either.

    Primer just isn't pulling any fuel...are they tempermental or do I maybe have a hole in a tubing or something (I do not see any leaks).

  8. #8
    Member Bullelkklr's Avatar
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    I had a vac line on the hac wrong was the primer issue...

    Well it is now a timing issue. 670 non-HO stator/flywheel won't work with the HO crank. Now looking for CDI/DESS/Coils for the HO stator/flywheel assy.

  9. #9
    Member Bullelkklr's Avatar
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    It is actually not a timing issue. The cranks from the 670 and 670HO are exactly the same. I was getting intermittent spark so got a new non-ho CDI and have great spark now, but it still won't idle.

    It starts right up and I can keep it idling pretty good by slowly pumping the primer. I can also keep it running by pumping the throttle but it really likes to open up. It won't idle by itself and it will not maintain a steady RPM.

    I am starting to wonder about the rotary intake timing or maybe low vacuum pressure.

    The carbs from the stock 1996 670 summit fit the 1998 HO 670 motor fine. No issues there. I went through the carbs twice now and they are set to spec for the 96 670 summit. Second time I put in new floats and seats (ouch those little parts add up).

    Anyway - so I want to take it to a 90's knowledgable ski-doo mechanic - not a parts swapping dealer. Any recommendations?

  10. #10
    Member Bullelkklr's Avatar
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    Whew - I got her did last night. She purrs like a kitten and roars like an ***** shot girzly bar now.

    If she will hold up through break in it should be a screamer.

    Thanks for everyone's help!

    Who says that you can't put a 1998 670X into a 1996 S chasis machine utilizing the 1996 electronics.....well, besides everyone on the internet I spose (not here - but most of the snomobile forums on other sites).

    I still might need help with clutching - I haven't ventured there before.

  11. #11
    Member Bullelkklr's Avatar
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    Back on this project here soon - I put about 40 miles on her and lost a head gasket or something...went another 15 or so back to the lodge and when I broke it down I have to do a little honing, new piston and rings and gasket kit...I have the parts and now that snow is falling it is time to put her together in next few weeks....

    Also adding a roll of quarters to the project (to tape behind the throttle during break in)!

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