Help Electrical Questions

I'm fairly sure if you don't touch the magnets in the flywheel, the same amount of power will be generated. Since the stator creates current from magnetic fields moving around the coil, but I'd assume most of the flywheel would contain said magnets.

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I'd say you'd get diminishing returns on a street bike since I believe a lot of stators make less power than needed to run the bike at low rpm and you could end up draining the battery in traffic. If it's a track bike you could definitely afford to play around with it and worst case run it total loss.

Someone correct me if I'm wrong but I'm pretty sure less magnets=less magnetic field=less power so you could measure amperage output from stock and total power consumption by the ecu etc etc and start slowly lightening the flywheel until the power output matched power consumption.

Probably, again, not an expert.

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Re: the bold text, it depends entirely on whether the stator is star wound (also known as y or wye wound) or delta wound.

As far as I know, most bikes use a star wound configuration with the exception of Suzuki. On many Suzukis you will find that they output maximum charge at idle, and taper off as RPM increases.

In contrast, most other bikes won't output full charge voltage at idle especially if the magnets, stator or regulator are a bit sad.

 

There's difference between wye vs. delta winding in low-RPM vs. max-output performance. Trade-offs are delta has more current and lower voltage at low-RPMs while wye gives less current and more voltage.

Here's conversion process from wye-to-delta windings. https://procycle.us/how-to/wye-delta-stator-conversion
Results in more power-output at higher-RPMs, but less output at idle. Typo in conclusion:

"One drawback is that the stock stator will [NOT] produce enough power to charge the battery at idle. The modified stator needs 1800-1900 RPM to get over the break even point."

To reduce 100% max-output of stator, you'd have to shave magnets so they have less mass and weaker magnetic field.

Magnets are segments held in by thin ring on inside. This is very good design. Some bikes have issues with magnets delaminating from flywheel and destroying stator & windings.

While you can reduce stator-output by trimming magnets, it will still be driven at 100% of whatever capacity it has by shunt-circuit RR. There's tables somewhere someone measured with dump-to-ground current (4) going up with RPM while output to recharge battery and power bike (5) remains constant...

 

Sorry, I mis-quoted, no typo:

"One drawback is that the stock stator will produce enough power to charge the battery at idle. The modified stator needs 1800-1900 RPM to get over the break even point."

 

Out of left field, however I do think if you're lucky you may just land on one that fits - what about something from a later model supersport, ones that I am thinking of is GSXR600/750 because I've seen pics of them, however others may be similar.

The GSXR flywheels have a lot of holes in them for weight reduction and consequent reduced inertia.
Perhaps Kawasaki ZX6R might be similar.
Getting weights of different flywheels may be a challenge

You need it to have the same taper, O.D and depth.

Otherwise, cutting yours on a lathe, machining the O.D. down will reduce inertia, the magnets will be brittle, but could be done with a toolpost grinder though.

Does the ZXR250 stator have the ignition triggers on it though?

 

To add to that, if you drill the rivets between the mounting bit and the main rotor, you could transplant a new rotor like from a gixxer onto the ZXR taper. Then just weld it back up, I did it on an FZR flywheel (fairly long story why, not for performance, but it worked great)

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I just had quick google/ebay peek and the supersport 600 ones look to be machined single piece from a casting and significantly weight reduced.
It may all be a case of OH SO CLOSE, or you may land on the correct dimensions quite easily.

Looking at pics of the ZXR250 flywheel - Transplanting the gear, backing and inner section which goes onto the crankshaft may actually be relatively easy (famous last words) - some of the supersport flywheels look really light by comparison, significantly less material

 

Interesting looking at some pics of the ZXR250 flywheel that it's got parts to it that bolt together, you could jettison the charging part of the flywheel assembly and put something there with less weight to give you some mass.

Alternatively, if you've got someone brave enough, you could possibly put it onto a lathe and cut it shorter with an angle grinder thinner - cover everything though for the abrasive grit.

There's probably a sweet spot for you with required inertial mass and rate of engine acceleration.

 

I don't think stator was used for ignition-triggers since early '80s. Even then, it was separate pickup-coil built into stator housing leaving stator with sole task of recharging battery. Since then, most Kawis used external bumps on flywheel for pickup-coils mounted outside of flywheel. Note 2 missing bumps to signal TDC.



I run total-loss ignition-system on my race-bike with stator and magnets completely removed (battery-powered only). Even machine inside of flywheel thinner to save 0.5kg. I just have to make sure not to disturb trigger bumps or pickup-coils on outside.




On ZXR250, pickup coils are on opposite side of engine under clutch-cover. I think it triggers off starter-clutch gear like VFRs. So you can machine flywheel and magnets any which way you want.

 

I regard any aftermarket regulators, even from supposed reputable well known brands, on the same level as the fakes. They are an unknown.

 

Interesting, haven't seen an SH821 model before. I will have to look into those.