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    Re: Small Engine CVT's
    #21
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    When running they get up to 3".
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    Re: Small Engine CVT's
    #22
    Keeper of the Asylum K-fab's Avatar
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    Take into account that the secondary (driven, rear) will open up and get wider as the belt moves inwards. Make sure thereís nothing that it can expand into and rub on like a frame brace that you have holding the trans....
    Experience speaking.

    There should, somewhere, be a chart that shows center to center distance for the clutches and belt length for those distances.

    Cannot stress enough how important getting the clutches aligned - the trans input shaft and engine crank shaft MUST be parallel. I use straight edges clamped to the back side of each clutch in a vertical orientation and facing forward from the rear of the car, the two straight edges should line up perfectly.

    Look at the light between the two edges - as you move your point of view left and right, the light should disappear as your view orientation aligns the edges. If the light between the visual is tapered at all, the clutches are twisted in orientation.
    Does that make sense? There is a section in the Deztaz II build where Iíve documented this procedure.



    Same goes from looking down at the system with the straight edges clamped in a horizontal position. There will be an offset between the two straight edges but the must be parallel.

    CVTs also have an offset (when using the back sides of the clutches as the datum lines). As the front clutch closes the rear opens and the belt will travel inwards towards the engine and trans. Instead of trying to find/use offset data I use a straight edge with a square that allows you to put the straight edge perpendicularly through the primary clutch and show you where the secondary needs to be (in offset). Basically itís using the straight edge to mimic the belt.

    See how much they look offset? The front, being wider and the rear narrow makes is look funny:



    If I lay a squared to the front clutch's outer edges, straight edge through the opening where the belt rests, it'll drop perfectly between the two sheaths of the secondary.



    Does any of that make sense?

    Oh, then you get to deal with center to center too - that should have been known from the second paragraph of this post.

    Iíll hunt around and see if I can find pix to explain. - they may be on www.Yellowdogracing.com under either of the Deztaz builds.
    Last edited by K-fab; 11-13-2019 at 02:02 PM.
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    Re: Small Engine CVT's
    #23
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    Woah, thanks K-fab. I kinda understand it, so If I got a strip of metal or wood and had the same width at the bottom of the clutches (thinnest part of belt) and clamped it down to get alignment, and use a square against the clutches to get offset, but why do you need offset on the clutches? if you said I must've missed that part. And chain length, 420 chain with about 8" sprocket to sprocket, around 16-20" of chain, would that last? or does it need to be longer? And can you run a Disc brake on that jackshaft, with the driven clutch and drive sprocket without any problems?

    Thx
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    Re: Small Engine CVT's
    #24
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    Quote Originally Posted by JagerDanger View Post
    When running they get up to 3".
    Is that on both clutches (Driver and Driven) or just the Rear?

    Thx
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    Re: Small Engine CVT's
    #25
    Keeper of the Asylum K-fab's Avatar
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    Quote Originally Posted by PanDa_ View Post
    Woah, thanks K-fab. I kinda understand it, so If I got a strip of metal or wood and had the same width at the bottom of the clutches (thinnest part of belt) and clamped it down to get alignment, and use a square against the clutches to get offset, but why do you need offset on the clutches?
    The offset is required because one clutch (primary) is "open" and the other (secondary) is "closed" while at rest. You can see this offset in the pic below - the left side of the primary is offset to the left relative to the secondary.

    When the engine RPM starts moving up the primary starts closing, pulling the belt into the secondary, causing it to open. That offset will change as this occurs.

    You're looking from primary back to secondary in this pic. As the primary closes, pulling the secondary open, that straight edge would move to the left (in the pic)




    if you said I must've missed that part. And chain length, 420 chain with about 8" sprocket to sprocket, around 16-20" of chain, would that last? or does it need to be longer?
    No clue on this chain stuff - is that coming off of the secondary's shaft or??? Is the secondary driving a chain setup that drives the rear axle?

    And can you run a Disc brake on that jackshaft, with the driven clutch and drive sprocket without any problems?

    Thx
    Yes you can - but try to go as large in diameter as possible - the heat they can build can be impressive - it's turning a lot faster and is geared through the drive train than the axle where the brake would normally be so it sees more load. My first Deztaz (1500ish lbs) would turn the secondary shaft brake rotor red hot - and was eventually ditched for twin rotors on the axle - I am very abusive to brakes, though. On the stadium lights (650ish lbs), the little single rotor worked fantastically - could still get it hot but nothing bad.
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    Re: Small Engine CVT's
    #26
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    Ah ok, I understand now, thx. The last pic, looks to be from the Raptor? Cvt's get complicated, almost makes bike engine gearboxes / manual's easier, but Cvt is well worth it. So I need to offset the secondary to when the front is full closed and rear full open, they are still aligned. I'll most likely need help again when I try to align them, but then I'll have pictures so it won't/shouldn't be as bad.

    Thx
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    Re: Small Engine CVT's
    #27
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    sorry for the hijack but...
    K, I see a 4 pro clutch on the floor, is that what you are going to end up with?
    I'm looking at a new clutch for the 670 pilot and that is one I have my eye on
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    Re: Small Engine CVT's
    #28
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    Your fine Kuma, this one? and are you talking about 670 predator or a different 670 motor?
    Pro4PrimaryCVTClutch.PNG
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    Re: Small Engine CVT's
    #29
    Keeper of the Asylum K-fab's Avatar
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    Quote Originally Posted by Kuma View Post
    sorry for the hijack but...
    K, I see a 4 pro clutch on the floor, is that what you are going to end up with?
    I'm looking at a new clutch for the 670 pilot and that is one I have my eye on
    That was on the old Deztaz.
    I’ll be running the stock Yamaha primary that came with the engine.
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    Re: Small Engine CVT's
    #30
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    Quote Originally Posted by PanDa_ View Post
    And chain length, 420 chain with about 8" sprocket to sprocket, around 16-20" of chain, would that last? or does it need to be longer? And can you run a Disc brake on that jackshaft, with the driven clutch and drive sprocket without any problems?
    As far as a brake rotor on the jackshaft goes, it can definitely be done, but keep in mind that if you have a failure in your driveline between your jackshaft and wheels (such as the chain breaking/falling off) then you no longer have rear brakes. Ask me how I know.

    For the chain length, I pulled this from Gizmology:
    "Center distance should not be less than 1.5 times the diameter of the larger sprocket, nor less than 30 times the chain pitch, and should not exceed 60 times the chain pitch."

    Another note they make about making sure your chain has enough wrap on the front sprocket so it doesn't skip teeth:
    "The chain should wrap at least 120į around the drive sprocket, which requires a ratio of no more than 3.5 to 1; for greater ratios, an idler sprocket may be required to increase wrap angle."

    I hope that helps
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