on page 123 of Yamaha combined service manual it says, Field Resistance 4.8 ohm's @20°C (68°F). I was assuming it was talking about both field coils. so evidently I don't understand what I am doing. It says if the generator is not charging to remove white (A) wire and green (F) wire from dyanamo jumper green connector to E (ground) then put the + led of voltmeter to A (white wire terminal) and the - led to engine, rev engine to 2000 rpm and you should get 14v. I get between 1 and 2, which I thought told me the field coils have an issue and one tests at 4.8 ohms and the other didn't so I thought the other is faulty. So now I am not sure what to try next.

This is what it says to check filed coils. It leaves a lot out for me to interpret any way I want to.

Conductivity Test of Field Coil
Check the continuity between the terminals M,A, and F. If continuity is bad, the field coil is broken.
Check the visible coil connections. If the coil connections are good, then the coil is broken inside and it
should be replaced because repairs are very difficult

KEEP IN MIND, this is for DISCUSSION. I am only stating what I have observed, read and offer this information as subject for review. This subject is certainly worthy of discussion. I welcome corrections where needed.

There are 8 coils. They are wound with magnets in center, ie electromagnetic forces. The light green 12v wire attaches from your starter relay to coil#1. Its at about 11 o'clock, looping like the engine spins in a counter-clockwise direction.

At 12N there is no connection between coil 1 and 8, yes in series as well as the armature. The loops end at 8 and project out about 1 - 2pm on to the lug connector A.  The input power is continued on in series to the brushes, ie armature windings.

When the field coils are sent 12v, an electromagnetic field is created with N/S poles. In this case, a fixed magnetic repelling force that acts on the armature stacks. There are 2 positive brushes at 2pm and 7pm or there about. There are 2 negative at 10 and 4pm. The positive brushes are powered where the #7 coil exists to surface again on lug block. Ever notice that firm wire that loops around from 2pm, horizontally left then down to 7pm? These brushes send power through the commutator, winding coils of armature, thus resulting in another magnetic force. The commutator flips the direction of current, to change armature polarity causing a pushing in one direction from interacting with field coil force.

Even and odd coils are not connected. there are 2 distinct sets that are laid out next to each other and daisy chained by jumping over the one next to it.

counter-clockwise:
large light green 1,3,5,7 large black connector
small green lead 2,4,6,8 small black lead

power to light green goes through "odd" coil #1 comes out at around 2pm on coil #7 on connector.

these were values from my DT125A:(direct from coils)
charge coil 5.8 ohms. My charge worked great. 
start coil: 0.5 ohms. My starter (DT125A) did not work well, I ended up getting an entire field coil and armature while I was at it.

Dirty slots between stacks on armature can weaken how powerful the starter effectiveness is and commutator also.

**************
M=Coil1, power supply from relay (lt green) (the other end is black, believe "A". Yes, A and Coil2 appear connected, but I think for charge purposes possibly not sure on this)
F=Coil2, green lead from charge coil series; Exciter from Regulator; Incr/Decr field strength for output.
A=Coil8, white lead from charge coil series; Raw DC current to the regulator; end of the other series, ie large lug connector from last coil.

So, by "If continuity is bad,...coil is broken". I think bad = open circuit as they describe it as broken.

"Remove A and F, then ground F to E" translated:
Remove starting and ending coil connections, then ground the starting coil or Exciter coil line. Does this imply 0 voltage at battery to get full excitement from coils for testing?

Don't quote me, but I think the starter coils are used as charge coils after starting is done, as the last start coil is connected to the A terminal, or charge out term, but
intial is unpowered in charge mode?? Is this the same as connect F to E? 1 coil going full blast and the other used as needed?

What does all this mean?
Clean it well and look for broken wires. Make sure the brushes are good.

Exciter coils and armature generate power via windings, send it through commutator to brushes to white wire. The brush at 7pm has a hard line that routes vertical next to points then directly right to A terminal.
The brush at 2pm connected to same, as 7pm.

Random things:
*A Honda Accord wheel rotor screw fits those coils. haha, good one.
*make sure battery negative is well grounded. Why not put jumper from battery to lt green wire and
black to head of bike. Skip battery to test.
* is the commutator spinning true? Not warped?
* is the field housing screwed ALL THE WAY down? You know that little slot on top left needs to seat.
* those valleys on armature can cause shorts if dirty, ie weaken output of starter.
* Brush Insulation. Are the brushes secure and not shorting; 2 of them are insulated from surface. Is that surface full of carbon or current conducting material?
* Commutator must be at least 38mm
* Switch at right handle bar uses neutral switch for ground to trigger relay I believe.
* good start with no plug and weak w/compression; brush, ground corrosion, weak battery
* don't go above 1800rpm, because exciters are on max output when input voltage = 0??
* over advanced timing = weak starter. cylinder fire too much before TDC will cause a clockwise force

WOW! that is a lot of info thank you.
these were values from my DT125A:(direct from coils)
charge coil 5.8 ohms. My charge worked great.
start coil: 0.5 ohms. My starter (DT125A) did not work well, I ended up getting an entire field coil and armature while I was at it.

My values on 73 AT3
5.8 ohms, mine doesn't charge
.4 ohms. My starter is very very slow.
Brushes have plenty of wear left and were not shorted. Commutator was not shorted BUT I did not know to check ALL of them. I have not seen any broken wires and need to look at the valleys on the armature closer. when I kick start it it feels as if it has no compression compared to the DT175B, but on the road it does run well just not as strong as the 175.

imgur.com/a/zmV2ETa

Thank you for the write up

I have to agree w/MarkT, read ALL the manuals from bikes with this system on it.
 
Note, 4.8ohms is for a given temp.  Resistance changes w/temp. Yamaha usually references this range, but not in this case. The wire is copper. The change based on temp can be estimated by calculation:

For example @ 90F
R = Ro(1+ 0.004041 *(Temp - 68))
R = 4.8 (1 + 0.004041 * (90-68))

R = 5.2 ohms @ 90F
5.8 ohms might be within your temp calcs for the time/temp when you did it. Not how hot is is outside, but was the bike in a garage and temp was increased, etc?

What was your raw voltage from the Dynamo?
 

Very good point.  When Yamaha shows the temp specs for resistance testing of electrical components it's always 68F as far as I remember.

Also, they used "analog" ohmmeters which can read different than a digital meter for some tests.

Well it is now charging and the starter works! After reading and re-reading and taking more pictures I realized I was interpreting clean the carbon from the mica gap wrong, I thought they were talking about the armature not the commutator and once I realized that and saw the pictures (enlarged) I saw the there were supposed to be lines in between all those commutator segments. once I cleaned them out and shined up the commutator it started charging, the electric starter now works and the the engine stopped turning off when the rpm's get to 6500 with switch in position 2.

thanks for all the info and suggestions to read the manuals and actually pointing out some good manuals to go through. Again thank you to all that commented.

If you have pictures of dirty and clean, that would be nice to check out as a relative reference for what works and doesn't

Well done!   

Well of course I did not take any pictures after I cleaned it as I didn't think that was the issue. But I will get some later today.