Derestricting variators.

Wolf Wizard /

So. I have heard a lot about doing this so your variated moped can get a little more torque and go a little faster. I was wondering how this is done? I am working on a variated engine at the moment and well, Who dose not like a little more torque and power?



Re: Derestricting variators.

[Radium City] kyle k $ /

what is it and why don't u look in the wiki?

Re: Derestricting variators.

What is "this"?

Also what engine are you working on...

Re: Derestricting variators.

Wolf Wizard /

A minarelli c2.

and I could not find anything in the wiki.

Re: Derestricting variators.


there is not much info these super rare engines. There is a mod but you don't need it yet. You would need it kitted to see a bigger differeance.

the belt doesn't ride all the way up to the top of the cheeks on vario. so you must lathe some material off to get the belt to go high up on the cheeks of the vario. Easy mod, but you'll need to focus on getting it apart, witch is not easy sometimes. No force it either you will bent the pulleys/cheeks. (edited)

Re: Derestricting variators.

you can do some measurements to confirm that your variator is living up to its full potential. do these in the correct order.

1 - figure out what belt most people use with it, or if the stock one looks good use that. measure the width at the bottom of the belt, the smallest parallel leg of the trapezoid that makes up the cross section of the belt. This is the 'range' of the belt. It's a good idea to check if the angle of the cheeks matches the angle at the side of your belt. I'll let you figure out how to do that. Also a good idea to check that the diameter of the weights is at least the width of the belt.

2 - this should match how much of the shaft is exposed between the two cheeks of the front variator at maximum spread. same for the rear variator, but you'll need to pry it open to measure. actually the 'range' should be a little greater than this measurement, by maybe 2-3mm so that the belt makes contact on the cheeks rather than on the shaft.

3 - determine if the diameter of the cheeks matches the range of the belt. check this by pressing in the movable face of the front variator with your fingers (engine off, duh), and wrapping the belt around it and observing where it sits. if the outer edge of the belt is flush with or up to 3mm higher than the outer edge of the variator, the belt is well matched. If it sits inside the variator, you could use a wider belt, but would also need to increase the measurements in item #2. If it rides higher than 2-3mm, then the front pulley isn't big enough. on the rear, if the belt is flush or 2-3mm higher than the outer edge of the pulley when the pulley just begins to open (so that the contra spring can apply enough force on the belt so that it doesn't slip during takeoff), then the rear pulley is of the correct diameter, provided it opens enough to accommodate the range of the belt as in item #2. Keep in mind the shaft diameters of the front and rear variators are likely to be different, so you can't exactly just compare the diameter of the rear pulley to the diameter of the front. You could, though, use your geometry skills to determine the correct diameter rather than going through this test.

4 - determine if the full range is actually used. provided that the rear pulley is of the proper diameter and you can pry it open to accommodate the full range of the belt, then it's fine, and you can install the belt and rev the engine on the stand to see if the front pulley is restricted. if the belt doesn't sit where you determined it would in item #3 on the front pulley, then it is restricted. no much use doing this test if you've determined that the rear pulley is restricted, because if one pulley is restricted then the whole system is, and you wouldn't know if the front is fine if the rear isn't.

so yeah, if all of these check out (which they rarely do on a stock bike), you can make full use of the variator. get to tuning. if not, get creative with grinding stuff in the rear variator, shims in the front, notches or windows, belt widths, etc. or determine if it's worth it to do all the work, because it probably isn't. Maybe you can do enough modifications to use a belt with a wider range.

an example i'm familiar with is the pa50-ii/hobbit drivetrain. the stock belt has a smaller range / is slightly less wide than a bx-40 belt. the front pulley opens wide enough for the stock belt, but could open wider for a bx-40. the rear pulley doesn't open wide enough for either, and is of too small a diameter for either. the rear pulley also doesn't close fully. the front pulley has about the right diameter, but the stock weights don't spread the cheeks enough to use the full range, which is why people window or notch the front variator, which can increase the travel to the limit. tjt or derbi variators don't need notching to achieve this limit. so with easy mods the front variator can match the range of the belt, but there aren't any easy mods to get the rear pulley to a larger diameter or open further, so most people live with it. oh, I guess there are some rivets you can grind off the inside of the rear pulley to allow it to close a bit more, but not a whole lot. motomatic did a build where they welded extra material on the cheeks of the rear variator and turned it in a lathe.

hope that helps.

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