Headwork Winter Project

[sss r1]

Originally Posted by im2fast2furious

I bought a yec generator for my 08 r1 recently. Once I had it, I started to think about how a standard rotor could possible be modified to the same or even better for the road guy somewhere in between. I have been looking at 2 different ways of doing this both will mean machining the magnets. Just wondering has anyone ever tried this or heard of being done?

yec rotor uses neodymium magnets, which are much stronger and more expensive then whats used in stock rotor .

why do you want to machine the magnets ? is it for weight saving ?
it will hurt generator power output , and depends on what you do exactly , you can totally fook up the magnetic field .

[4yamahas]

Just wanted to bump a good post . This thread strated out with some misleading cam timing information and even a link to a Muzzy article that was bass ackwards . Hard to believe that article is still on their site 7 years later un corrected .
There are also some very nice measuring tools out now and can be seen in the YEC Tools manual . Also some different and interesting methods of measuring .
This thread is packed with great info if you take the time to wade through it . Would be impossible to find anything again without writing down the page or post number .
Thanks to everyone that put this great information here . I love this stuff .

Originally Posted by max the lion

Hey Crash, here's some stuff I used when I did mine, all on here if you do a search for it, bit confusing but worth getting your head around it.

I have mine at 109' inlet and 100' exhaust at present just a guide for you.

Intake Cam Measurement Example (taken @ .040" lift)


(9* BTDC + 45*ABDC + 180) /2 - 9* = 108*

If you advance the cam it starts to open earlier (and closes earlier)

(11* BTDC + 43* ABDC + 180)/2 - 11* = 106*

The lower # means the intake valve will open and close earlier which will increase cylinder pressure for more low end/midrange power. The higher # means the opposite.

108* = retard cam (top end)
106* = advance cam (bottom end)


Exhaust Cam Measurement Example (taken @ .040" lift)


(45* BBDC + 12* ATDC + 180)/2 - 12* = 106.5*

If you retard the cam it starts to open later (and closes later)

(43* BBDC + 14* ATDC + 180)/2 - 14* = 104.5*

The higher # means the cam will open and close earlier which will reduce pumping losses to help with top end power. The lower # means the opposite.

106.5* = advance cam (top end)
104.5* = retard cam (bottom end)

To understand if a cam is being advanced or retarded look at the opening # for the intake cam and the closing # for the exhaust cam.

In the examples above the intake cam @108* l.c. opens and 9* BTDC and @ 106* l.c. opens at 11* BTDC, so the cam @106* opens 2* earlier than the cam @ 108* so you would say you have advanced the cam 2* @ 106*.

For the exhaust cam @ 106.5* l.c. closes at 12* ATDC and @ 104.5* l.c. it closes at 14* ATDC so the cam @ 104.5* closes 2* later than the cam @ 106.5* so you would say you have retarded the cam 2* @ 104.5*.

Cam Overlap

If you take the higher l.c. #'s, for the intake @ 108* the cam opens 9* BTDC and the exhaust @ 106.5* closes 12* ATDC for an overlap of 21*.

If you take the lower l.c. #'s for the intake @ 106* the cam opens 11* BTDC and the exhaust @ 104.5* closes 14* ATDC for an overlap of 25*

The lower overlap produced by the higher l.c. #'s will generally produce more top end power while the greater overlap produced by the lower l.c. #'s will generally produce more low/midrange power.

Piston to Valve Clearance

Advancing the intake cam (lower l.c.#) will cause the valve to get closer to the piston as it approaches and goes past TDC as the cam lobe is starting to ramp up the valve motion on the intake stroke. It should be checked at 5* increments BTDC and ATDC.

Retarding the exhaust cam ( lower l.c.#) will cause the the valve to get closer to the piston as it approaches and goes past TDC as the cam lobe is ramping down the valve motion on the exhaust stroke. It should be checked at 5* increments BTDC and ATDC.

From Chuck Graves re: p to v clearance

" Your piston to valve clearance will be relative to the rpm, valve springs, retainers, type of valves, type of cam. The stock springs with stock valves, stock cam and 11600 rpm you will need to have .050 intake @ 10*, .090 exhaust @ 10*. Just for a comparison if you use our 49 grind cam or our 194 grind 2003 cam @ 13500 rpm our springs and stock valves you can set the intake .040" @ 10* and the exhaust .076 @ 10*. If you used a similar cam with stock springs @ 11600 you will need to set the intake .080 @ 10* and a bigger exhaust (like the Yosh or YEC) .120 @ 10*. What does all this mean you ask? Well the best advice I can
give you is to make sure what you are assembling has been tested and will not cause you problems because if you hit the valves then you will be very upset with the outcome, replacement parts are not cheap.

I have had customers question the fact that we require the use of our springs with our cam. This is why - we have tested and know what works. This is why the cams are only available through us. We have also had questions why no exhaust cam. For the same reasons. Just for the record this is the same setup that we race with the FX bikes ridden by Damon Buckmaster, Jamie Hacking and Aaron Gobert (in the example
above)."

[im2fast2furious]

Originally Posted by sss r1

yec rotor uses neodymium magnets, which are much stronger and more expensive then whats used in stock rotor .

why do you want to machine the magnets ? is it for weight saving ?
it will hurt generator power output , and depends on what you do exactly , you can totally fook up the magnetic field .

Just saw your post dude. No weight saving is not the aim here.it would be nice if the magnets were easily machined, then I could take a skim off them and rely on the inverse sq law to decrease the power of the rotor.
I think you are mistaken there sss r1. The magnets look the same not only that but the yec rotor magnets are not as strong. The stock rotor magnets feel twice as strong probably due to there size in comparision.

[im2fast2furious]

sss r1. I have a few questions for you that I am not 100% sure of the answers. How does a shorter rotor magnet with a say the same power, effect the out put from the coils do you think.
2)what do you think a lower emf from the magnets will do to the voltage of the generator?

[BSR-1]

Originally Posted by 4yamahas

Just wanted to bump a good post . This thread strated out with some misleading cam timing information and even a link to a Muzzy article that was bass ackwards . Hard to believe that article is still on their site 7 years later un corrected .
There are also some very nice measuring tools out now and can be seen in the YEC Tools manual . Also some different and interesting methods of measuring .
This thread is packed with great info if you take the time to wade through it . Would be impossible to find anything again without writing down the page or post number .
Thanks to everyone that put this great information here . I love this stuff .

Very nice repost! I didn't realize Max was so smart!

[sss r1]

Originally Posted by im2fast2furious

Just saw your post dude. No weight saving is not the aim here.it would be nice if the magnets were easily machined, then I could take a skim off them and rely on the inverse sq law to decrease the power of the rotor.
I think you are mistaken there sss r1. The magnets look the same not only that but the yec rotor magnets are not as strong. The stock rotor magnets feel twice as strong probably due to there size in comparision.

Originally Posted by im2fast2furious

sss r1. I have a few questions for you that I am not 100% sure of the answers. How does a shorter rotor magnet with a say the same power, effect the out put from the coils do you think.
2)what do you think a lower emf from the magnets will do to the voltage of the generator?

i dont know , maybe what i saw wasnt yec rotor , but it was definately different magnets (chrome colored neodymium).

if you use weaker magnets (or smaller), it will lower power output .
if this is your goal , you can also unwind few turns from the stator coils and get lower voltage .
i didnt understand what are you trying to do .

[BSR-1]

Originally Posted by sss r1

i dont know , maybe what i saw wasnt yec rotor , but it was definately different magnets (chrome colored neodymium).

if you use weaker magnets (or smaller), it will lower power output .
if this is your goal , you can also unwind few turns from the stator coils and get lower voltage .
i didnt understand what are you trying to do .

I don't understand either.
Are you trying to lower output so that there will be less HP lost from electrical production?

If that's the case, how about running a total loss system?

[4yamahas]

It is a shame this thead died . I found a couple of 2 stroke threads just like it that are still going strong . Some of the guys in them built Aprillia MotoGP 125 and 250 motors and are pissed at Dorna for killing the 2 stroke , and are telling all . Google searches will bring up Jan Thiel and Frits overmars . One site is French and the 2 part thread starts in french but switches to English . Another is on Kiwibiker.nz works engine tuner . This stuff ties into standup jetski porting for me , and make me want a 2 stroke track bike .

[BSR-1]

Originally Posted by 4yamahas

It is a shame this thead died . I found a couple of 2 stroke threads just like it that are still going strong . Some of the guys in them built Aprillia MotoGP 125 and 250 motors and are pissed at Dorna for killing the 2 stroke , and are telling all . Google searches will bring up Jan Thiel and Frits overmars . One site is French and the 2 part thread starts in french but switches to English . Another is on Kiwibiker.nz works engine tuner . This stuff ties into standup jetski porting for me , and make me want a 2 stroke track bike .

It is a shame, this is one of the greatest threads of all time!

The 2 stroke stuff sounds interesting. I have (somewhere) the Yamaha Factory porting specs (including very detailed pipes) for all of the late 60's early 70's bikes right up to just before RD's.

Thanks for bringing a little life to this thread. All of the "important" people used to check in here.