Flywheel and stator relationship?

[Entoptic]

Long story short. My electrical bandaid was just that, a bandaid. It's now time to replace the stator. As I got into reading, some people mention replacing the flywheel as well. Why is that? What is the relationship between the flywheel and stator? What the hell is the flywheel for anyway?

I'm sure google can explain this but I like to hear it from mechanics cause you guys know your stuff!

Thanks in advance!

 

[afm199]

The stator is a large coil, or series of coils of copper wire. The flywheel has permanent magnets, either embedded or glued to it. When a magnet passes by a length of copper wire, it induces current into it. ( Actually passes at right angles, length way would be worthless). When the coil (rotor) spins, there are many right angle pieces of wire (part of a winding really, not individual) that cut the lines of magnetic force, inducing a current.

You'd pretty much be crazy to replace the rotor unless it has shed a magnet. GSXR's don't have external magnets to shed, I suspect your VFR does. Check the magnets, if all firmly attached don't replace.

 

[RickM]

I have replaced stators on one of my VFR and the VTR. The flywheel was totally fine. Have not heard of Flywheel issues on VFR.

 

[JimE]

You might be thinking of people that have installed a LIGHTENED flywheel. Different matter entirely. Flywheel stores rotational energy as it's major function. Attach a ROTOR to it and spin that around the STATOR to make electricity (conductor, field, relative motion). Yes? So sometimes folks turn down parts of the flywheel (not having to do with the rotor) to shed weight. This allows the motor to spin up faster as there is less mass to get rotating. BUT there are significant trade off's involved. More vibration, a drive train that feels more "snatchy" (or less "smooth" as the case may be), more wear and tear on drive train parts (chain, sprockets, etc..) so this may not be a good thing. Some folks building the M900's like the one I have went back to stock flywheels after installing flatslide carbs because the increased throttle response combined with the lightened flywheel was just too much direct throttle response and they felt a heavier stocker made it more rideable. Lightened flywheels make it easier to get off the line and get out of corners but beware a heavy hand could put that power to the ground too quickly on a corner exit and cause a spin up and slide out. So it really depends on the bike and application. This sort of stuff is what I call "black arts" and is developed by enthusiasts on a trial and error basis in hobby and race shops everywhere. Cool shit. Your best bet is to leverage fellow owners and former racers of your machine to get real world practical experience and information before making changes to make sure your going in the right direction with mods like these.

Does that help?

 

[Papi]

Long story short. My electrical bandaid was just that, a bandaid. It's now time to replace the stator. As I got into reading, some people mention replacing the flywheel as well. Why is that? What is the relationship between the flywheel and stator? What the hell is the flywheel for anyway? I'm sure google can explain this but I like to hear it from mechanics cause you guys know your stuff! Thanks in advance!

Before you do anything:

Have you tested all the phases in AC coming from the stator?
What were the readings at Mfg recomended RPM?

Have you tested the output of the VRR?
Again, what were the readings?

Did you do a diode test on the VRR?

VRR= Voltage Rectifier/Regulator.

I'm doing one in our shop right now. It failed 2 of the 3 tests. In taking it apart, there was discoloration on a phase of the stator coils. Some charring in the connectors due to Salt shorting things out a bit. The VRR also failed to produce correct out DC output.

The <Flywheel> (called a Rotor) as said earlier is typically never replaced. I don't even "lighten" mine for top speed, waste of time. I do inspect it though for anomalies.

Here's a couple pix of stators we are testing. The two together are a brand new one from Kawasaki, the one next to it on the Right is from Ricks. The other pictured in the side cover is the problem unit. I'll be ripping it all out today. The issue for me was I created part of the problem by using to much power. Our electrical consumption is mildly higher than OEM, hence the Rick's HO unit.

On another note, the Rotors (flywheels) weight is attributed to the Iron in the magnets. So even when removing grams of meat off the Rotor (flywheel) itself, you are not really buying anything from a performance perspective. The drag is nominal. The factory for the most part has optimally weighted and balanced the Rotor already.

 

[afm199]

On another note, the Rotors (flywheels) weight is attributed to the Iron in the magnets. So even when removing grams of meat off the Rotor (flywheel) itself, you are not really buying anything from a performance perspective. The drag is nominal. The factory for the most part has optimally weighted and balanced the Rotor already.

A. I totally recommend Ricks stuff.
B. I respectfully disagree with this conclusion. That big chunk of weight on the end of the flywheel stresses the crank every time you shift, and more so on speed shifts and clutch dumps on down shifting. SV650's on the track break cranks all the time, right at the cotter slot where the rotor fits on. This is stopped by lightening the rotors.

 

[Papi]

B. I respectfully disagree with this conclusion. That big chunk of weight on the end of the flywheel stresses the crank every time you shift, and more so on speed shifts and clutch dumps on down shifting. SV650's on the track break cranks all the time, right at the cotter slot where the rotor fits on. This is stopped by lightening the rotors.

You are correct to a point. If you look at my third pic above, you can see that there is very little meat left to be taken out of the rotor. Now with that said, an all battery non-charging system would be possible for my application, but the added weight of the batteries and power consumption required would negate losing the rotor-stator all together. Would my crank spin up faster? Maybe, but we already did that test on the Frough-Hoffman Motor Dyno and discovered no HP gain that was significant or measurable beyond the 240 I'm already putting out on that motor. And since I cant stop the wheel from spinning and blowing the rubber off at 175 now already, it makes no sense.

Again though, your point is valid. It really depends though on how well the manufacturer did their job to use the rotating mass as a gain instead of a hindrance. If that makes sense to ya. On speed shifting, the use of a no lift shift to kill the ignition cycle works really well also.

On your SV example, instead of lightening the rotor, what is the issue with the cranks strength?
Sorry, I have no experience with that motor at all. Please tell me some more detail.

 

[Entoptic]

Such amazing info! Thank you everyone for your input. I did indeed buy a Rick's stator.

Final question - Why is oil going to spill out when I crack the case cover? Also, how much oil is going to come out? Should I drain the oil first?

 

[Papi]

Such amazing info! Thank you everyone for your input. I did indeed buy a Rick's stator.

Final question - Why is oil going to spill out when I crack the case cover? Also, how much oil is going to come out? Should I drain the oil first?

Depends on bike/yr/motor/etc. But there may be a little bit. Put a small pan under it when you remove the cover. It may have a heavy magnet pull, but DO NOT PRY IT OFF (hope that was clear enough).

Anywho, don't let what oil is in there spook you.

---> BUT, a better way to approach this may be to warm the bike up a bit, drain all the oil (like you said above), change the filter, fix your stator, put the cover back on, refill with freshy oil. You get a service out of it, and less oil coming out of the cover. Win-Win.

 

[elskipador]

The <Flywheel> (called a Rotor) as said earlier is typically never replaced. I don't even "lighten" mine for top speed, waste of time. I do inspect it though for anomalies.

theres gains to be had, at least on roadrace bikes with "kit" parts like these.

 

[afm199]

On your SV example, instead of lightening the rotor, what is the issue with the cranks strength?
Sorry, I have no experience with that motor at all. Please tell me some more detail.

The crank has a cotter slot where a cotter pins the rotor to the crank to prevent rotation (which many bikes don't have, the are only bolt held.)

The cotter slot is where cranks break time after time, the entire rotor assembly just ends up floating in the stator case, being rotated by the jagged broken crank end.

 

[Papi]

The crank has a cotter slot where a cotter pins the rotor to the crank to prevent rotation (which many bikes don't have, the are only bolt held.) The cotter slot is where cranks break time after time, the entire rotor assembly just ends up floating in the stator case, being rotated by the jagged broken crank end.

A cotter or woodruff slot?

 

[D'Ecosse]

The other pictured in the side cover is the problem unit.....

If that is the stator you are saying is 'bad' I'd be willing to bet there is nothing wrong with it
Slight - or even heavy - discolouration is nothing - all it means is that zone is getting hotter because there is less oil cooling there and the epoxy coating is just cooking a little.
Also note that adjacent coils are NOT on the same phase.
Pretty typical stuff.

What voltage did you actually measure out of it?
Did it pass or fail an isolation test?

* You said there was some evidence of burning in the connector and from the last pic, looks like some charring of the wires, just after it exits the grommet.

I would say your problem most likely associated with that and not the actual stator itself.
Note that this burning of the wires could be caused by failure of the R/R (although sometimes just starts out as a poor connection that generates ton of heat and gets exacerbated the hotter it gets)

 

[Papi]

That's not charring, its tape and glue from a tape wrap.
It was tested and measured correctly. One phase was not performing to spec.

Your comments are good though, just not for my application.

 

[D'Ecosse]

That's not charring, its tape and glue from a tape wrap. ...

Fair enough (although you did actually state there was burning in the connector) - that stator still looks fine.

... It was tested and measured correctly. One phase was not performing to spec ...

Care to share what tests you did and the actual numbers?

Also:

The issue for me was I created part of the problem by using to much power. Our electrical consumption is mildly higher than OEM, hence the Rick's HO unit.

Sorry, that is not correct (at least regard to output load consumption affecting the stator current)
You don't use any more (or less) current through the stator when you change the bike's system load - if you add more load on the 12V side, the regulator simply shunts less, in response.
But the current generated by the stator remains the same, maxed.
The stator provides current to two parallel paths - the load from the bike, and the shunt load of the R/R.
If you increase the bike load, the shunt load simply goes down; and vice versa - decrease the bike load (i.e. turn off the headlights) and the shunt current goes up.
And for most of the rpm range the stator is already running at max current (at saturation most likely from about 5 or 6K on up) and simply shunting all that excess through the regulator.
i.e the stator current remains the same - max. It's probably running about 30A out of the stator - about half of that to the load and the rest through the Regulator shunt.
That is why a traditional SCR R/R gets hot - not from the current it is feeding the load, but the current it is shunting - SCRs dissipate a lot of heat.
MOSFET R/R's will flow exactly the same amount of current through their MOSFET devices (in shunt) but MOSFETs have incredibly low on-resistance and so dissipate extremely low heat.
The only place a 'high output' stator helps is at low engine rpm - but has the unfortunate consequence that it produces even more unwanted power at higher rpm, therefor your R/R has even more work to do in dissipating that excess.
That is why a Series R/R makes much more sense - then the stator is only producing what the final load demands, not having to shunt additional load through the regulator and dump the power there instead.

Most OEM systems are designed such that there is marginal shunt current at rpm, and the stator generated current is close to the system load;
but almost immediately as the rpm rises the stator will generate more excess capacity and require to be shunted by the R/R.
If your system load is only marginally higher than the standard (you said mildly!) then there should be no need for a high output stator and indeed is more of a detriment if not needed.
Unless the voltage is (significantly) low at idle and does not actually charge the bike until over say 2000 rpm, std is going to be better. Anything beyond that is just being burned by the R/R anyway.

 

[Papi]

Fair enough (although you did actually state there was burning in the connector)

Yes. We had Salt Water (from Bonneville) leech into the stator output mid harness factory connector that is not sealed well which is midspan between the motor plant and the frame. We replaced that with a sealed Deutsch connector.

- that stator still looks fine.

Stator not fine. More below.

Care to share what tests you did and the actual numbers?

Sure, no problem. Let me qualify the answer first. On this (Special) Production Bike we follow some Kawasaki Factory Guidelines and Testing mildly modified for our draw needs. Meaning, we re-calculate the actual power needs (consumption) of this bike based on our custom harness and electrical components attached. Those components are not exactly the same as Consumer Motorcycle Factory Components. Some are Factory, some are not. I think you are under the assumption my needs are from an off the shelf bike. The bike in my example is what we call a Factory "Built" bike. This is a special Factory Production Bike that is highly modified and used for one purpose only, Top Speed.

Now, on the testing method: I have also attached a PDF guideline (for anyone here to use) that steps through a testing method similar to ours. Again, our method follows some factory with a hybrid to our needs.

In direct response to what "our" numbers were, I will tell you the stator in an isolated test without the VRR looped underperformed and failed both Factory and our needs Standards. I wrote the numbers on my hand in the shop as read from my meter, knew they were bad, and there you have it.

As far as the other electrical theory you provided, yes, the modern bikes use a shunted VRR system. I have also used a Series Regulator which basically switches off power from the stator. Compufire makes a nice series unit we used in another application.

 

[Entoptic]

Papi

In the pic of the stator attached to the cover how did you get the star bolts off and what size was it? I am having a hell of a time getting mine off and I don't want to risk stripping the star head. Any suggestions on how to get them loose?

 

[channelcat]

I've used a cordless driver/drill with real light clutch settings a number times. seems to work well. hth
thanks for the flow chart, papi.

 

[Papi]

Papi
In the pic of the stator attached to the cover how did you get the star bolts off and what size was it? I am having a hell of a time getting mine off and I don't want to risk stripping the star head. Any suggestions on how to get them loose?

Those are metric hex caps, 5mm if I recall. I used a short 5mm attached to my snap on cordless impact and they came right out. If you are having trouble, just disconnect the wire harness attached where the stator plugs into your rr or harness and come down to my shop with your new stator as we'll and I'll show you how and also how to put back together correctly.

thanks for the flow chart, papi.

No prob. It's not mine, but we follow the same guidelines to chase down gremlins. I've always found that with simple concise electrical testing, order and patching point A to B, you can get things fixed a lot faster.
.

.

 

[Papi]

Entropic: Postscript to my last;
There may be thread locker on those bolts, not sure if yours has them or not. I have seen it on some bikes, but not always. Shop manual for your bike would spec that. The bolts are generally around 10-14Nm (90-120inlbs -ish), again, depending on the bike. If you don't have an accurate torque wrench, borrow one. Again, follow Mfg. spec and guidelines. Sometimes where heat/cooling is a constant, threadlocker could be used as a safety net to prevent loose bolts from backing out completely and spinning around areas of your motor assembly, like the rotor/stator area. I am NOT recommending or denying you should use it. Read what the Mfg states in the manual.

Mild Rant Warning:
A side note about Threadlocking compounds mentioned above. On a couple of our bikes, the Mfg goes nutty with that stuff sometimes. I have seen it covering entire threads, which isn't needed or correct. The purpose of threadlocker is to add a vibration retardant to the bolts backing out should they loose tension on the joint. It is NOT a glue, it does NOT replace proper Torque of fasteners, it should NOT be your only method of securing fasteners properly.

We use very very little of it, if even at all. Sometimes a tiny drop or two on a stud to reduce mobility of the stud threads backing out, but again, very little. In most cases, we use a medium bond (blue) when we do, almost never high bond (red).

Now I said all this because many times folks will use Red Locktite up the ass on bolts, screws and studs. It's really unnecessary, and again, if the fastener is applied and torqued correctly, you are generally fine. Some caveats exist where threadlocker may be advantageous, but those instances are clearly spelled out in shop manuals most of the time, or understood in adbvance.

/Rant Off.