how many magnets do you really need?

I am on a mission to remove weight from my motobecanes

rotating assembly.

I am going to be drilling my variator cheek and am going to turn some metal off of the flywheel.

I also am wondering if I could take 2 magnets out of the flywheel - would it still generate spark or would that screw up the sine wave too much?

I have never really put much thought to it but I have a spare flywheel that is butt ugly to try it on.

Anyone try this before?

Re: how many magnets do you really need?

I have to be the one to ask... you're running a variated bike. A bike that's designed to very carefully maintain engine rpm over a wide speed range. Light rotating assemblies help when your motor is changing rpm wildly. On most motobecames... they aren't.

So what's the point? I'd do it on a puch ;-)

Re: how many magnets do you really need?

yeah.....

My varplus is set up light and any weight I can remove will help to improve its hook up and get me into my pipes powerband quicker.

Re: how many magnets do you really need?

Not to mention helping acceleration all around.

When I installed the varplus with its lighter moving cheek I could feel a difference in the feel of the bike, it feels more responsive and snappier. I think I could remove a little less than a pound maybe a little more.

Re: how many magnets do you really need?

seems like it'd be easier to take a big shit and get the same results. then, for even better results, go on a diet.

Re: how many magnets do you really need?

If you really want to save weight, why not just go on a diet or ride barefoot

Re: how many magnets do you really need?

wow

Re: how many magnets do you really need?

the don't seem to understand you paul.

Re: how many magnets do you really need?

They never do.

Until I blow by them...

Re: how many magnets do you really need?

you mean blow-up by them right?

Re: how many magnets do you really need?

If you don't need lights you could run one magnet but you would need to balance the other side. With one magnet you can replace the points with a TCI unit for pointless ignition

Re: how many magnets do you really need?

why?

Re: how many magnets do you really need?

stevew thank you.

Re: how many magnets do you really need?

do it man. rather than just remove whole magnets tho just remove alot of material from the magneto, make it similar to a peugeot or puch magneto.

lighter cranks will help the moby out ALOT. mobys are soooo excessively heavy on the crank its ridiculous. they are so heavy that they often will snap cranks at higher speeds cuz they rn't balanced perf.

every little bit helps. I removed my clutch completely from the crank and have the lightest variator u can get and its one of the hardest ripping mopeds ever. I haven't met a moped yet that can out accelerate it, tops out even with a gila puch at 18x36 and gets 70mpg.

skinny light ass wheels, light ass frame, light as rider, light ass motor, hella light transmission, light magneto + lots of power

Re: how many magnets do you really need?

If you're having trouble getting into your pipes powerband, you need to look at your variators weighting scheme, not your flywheel weight. If your variator were tuned right... you should be riding your powerband throughout the variator's ratio range.

Fix the problem, don't modify the rest of the bike to get around the problem ;-)

Re: how many magnets do you really need?

Hmm... in theory you could run one magnet, but in practice what would happen is it would leave you with very weak spark. The magnets go around the outside North South North South, so as it sits on the end of a coil it pushes electrons from one side and pulls them from the other, as the flywheel turns it changes the poles and thus creates your AC output. But since it changes sines 4 times a rotation since it has 4 magnets, if you remove 2 of them on opposite sides then you will have a balanced but weak spark due to it not flipping as fast and only either pulling or pushing, not both; or you can remove two from one side so that the coil still flips but only once per revolution, and you better hope that it is at the same time the HT coil is charging otherwise it won't spark at all, while also being very out of balance.

My suggestion, if you don't care about lights then remove the whole damn flywheel, leave the points, and replace the coil that powers the points with a battery on the frame. use a 6V battery and run it. The points will still open and control the spark and you won't have any flywheel weight at all. Although you have to keep the battery charged, but if it's just for blasting and not daily riding who cares. Run the lights off the battery too if you want.

Re: how many magnets do you really need?

I do have a bunch of thunder power lipos for my planes...

Re: how many magnets do you really need?

Well I can now say that an av7 requires all four magnets to run.

Too bad it was a lot of weight removed.

Re: how many magnets do you really need?

what configuration did you take out?

Re: how many magnets do you really need?

One time, Creature Heather thought her bike seized, but in reality, a magnet fell off and got jammed in the magneto. She just ran three and it ran fine. I'm surprised yours didn't run with two, guess that was too much. shame...

Re: how many magnets do you really need?

Maybe if you ran those two magnets 90 degrees from where they are it would run. You need to go no further than understanding the construction of lawnmower or weedwacker ignition to educate yourself

Re: how many magnets do you really need?

on those old single magnet systems they typically don't have points, at least not in the case of old Briggs and Stratton engines. They run by letting the field build up and allowing it to collapse since there are no more magnets fueling it. While on a points system the points cut the circuit off at the peak of the primary coil output. Also a motobecane system is more advanced in design due to having three coils with a common ground (AC wye windings) that are all 90 degree's out of phase and two of which are 6v while on is 12, they can do some weird things when not balanced right. more complicated than you think.

Re: how many magnets do you really need?

Not having messed with Mobys I have to defer to the very experienced Jesse. How about afixing a more common primary moped coil like Bosch Puch in the magneto and thus only requiring one magnet. This is under the assumption that Moby magnets have a similar strength as Bosch. There has been three iterations of mower ignition. The pointless, the points and the transistorized TCI unit that simply replaces the points.

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account