I saved this from another site (the old Thumper Page message board I believe) and is the most in-depth article on doing this yourself. IF you are on your game, one could do this pretty easy. If you are off your game..........good luck ;D------------------------------------------------------------------------------------
Everything(?) you ever wanted to know about rewinding a stator.
To rewind your own coil you don't necessarily need to be a fool, but as you can see in this text, it is a benefit...
I haven't seen the stator of a new SR if there are much differences or changes in colors of the wires. This text tells how to handle a -79 SR stator. Of course the ignition energy is still made by coils in the newer bikes and repairing them is similar.
Here comes your chance.
1) Find a resistance meter and learn how to use it so that you know what the results mean.
2) Before removing the stator make sure there is a failure in it.
Check the plug, even a just bought one. Do this without the plug and the cap. If nothing is wrong, the spark can even by an easy kick jump 5-10mm in the air from the high-tension wire to the frame of the engine. Use NGK B6 ES, it is a sure one and trying others you obviously waste money because their heat range is not wide enough for your single. If still no spark, let the ignition coil be checked by a professional. The CDI box cannot be checked, you check it by finding that all the other parts are working.
To check the stator, find the block connector where the five wires coming out of the stator case are connected to the connector that leads to the cdi box. Measuring can be done without disconnecting anything. Measure the colored wires as follows:
Between:
White/green and black 90 ohms
White/red and black 16 ohms
Red and brown 5 ohms
Brown and black 330 ohms, the most obvious failure coil with lots of thin wire giving charge to the ignition by low speed
Red and black - 335 ohms. Here are the 330 and 5-ohm coils in series giving charge to the ignition by high speed. You will see the same difference as above in this measuring result if the biggest coil is broken. Note that according to all manuals the range is large: by each coil plus or minus 30%.
If any of the results is out of the given range or if it obviously will soon be, you must do rewinding. I'll tell you here how to handle the biggest and most difficult 330 coil. Though if the failure is in some other one, the principle is the same: Find the diameter of the copper wire, the demanded resistance and replace the broken wire with new. With the smaller coils the work is a piece of cake compared to this one.
Rewinding
1) After removing the flywheel (absolutely only with the certain tool !) and the stator you can easily guess which one is the 330 coil. It is the biggest one located on a special flat place with covered iron walls both sides of it. Remove the three screws and separate the plate and the stator. Don't remove too much parts, only what's necessary. I separated all the wires and also the plate and stator from each other, but I think it is possible to do the rewinding removing only the broken parts and disconnecting only the necessary joints.
2) Carefully find the wires going out of the coil and the case. Find also the 5 ohm coil, it is located later thinking in the direction of rotation of the flywheel and there are a couple of energy coils between these two. The energy coils have nothing to do with the ignition, they are made of thick wire and they are a part of the three phase system.(energy to lights, battery and so on) You don't need to dig everything up, it is enough to find the important joints and the ends of the wires. It is good to make markings on the wires to make it easy to find them by reconnecting them. When you measure, you must be sure that you really are measuring the right wire and the current cannot be going some other way between the measuring points. If the meter shows 0,00 you have a short cut or a good wire with a very very low resistance between the measuring points.
3)Find the place where the thinnest coil wire is jointed to the wire that leads to the 5 ohm coil, the 5 ohm coil is wound with 0.25 mm wire. Using the resistance meter find out which wires are connected to which colors going to the cdi box. Note that thicker uncolored wire is used between the coils and between the coils and the colored wires. Find the ends of them.
4)Use a chisel to cut the bad coil and remove it. Use a file to remove all the sharp edges that should damage the thin wire. In the end there should be only the T-figured iron hearth of the damaged coil left.
5)Find some special heat resistant wide tape (you can find it only by a professional) and cover the iron hearth with it. In the middle of the hearth you can use this hard one and on the outer end and on the bottom you can use soft plastic tape. The traditional transparent Sajp-tape (used and sold in markets) is good and heat resistant. Carefully cover the iron hearth thoroughly but avoid using too much tape: later you will see how important every millimeter is in this small space.
6)Find the wire, 0,15 mm diameter for the big coil and 0,25 for the 5 ohm coil if it happens to be broken. I hope you find a professional who is willing to cooperate with you. You need the whole roll because it must carefully be wound straight from the roll to the coil. Buying it only the needed 300 meters is not possible; it will get tangled, damaged and cut. I could borrow the roll from my acquaintance who has several times helped me in my difficulties with electric motors. He is not interested in making more stator coils because he has enough work with electric engines.
7) Find a piece of thin plastic pipe, the one they use with spray CRC bottles is good. It is got to be about 10 cm long. It is a special tool to do the winding; the wire must go through the pipe due to the figure of the iron heart of the stator from which the hearth of the 330 ohm coil cannot be separated. Metal pipes are forbidden, they will cause damage to the wire.
8)Find a long 6 mm screw and a couple of nuts and fix them to one of the holes in the stator frame. You need the screw to avoid damaging the stator when fixing it to a vice. Fix the stator to a vice in a position that the coil, you are making, points to you.
9) Set the roll of wire standing upright on the floor below the stator so that the wire comes out easily. You must not try to pull it out circulating whole the heavy roll, because the wire will stretch and be damaged.
10)Thread the wire through the plastic pipe and cut off all that is bent or scraped. All the wire that goes into the coil must be unmoved and undamaged.
11)Scrape some of the varnish with a knife from the end of the wire so that you can see clear copper. Joint the end of the wire to the ground with tin, there is a special place for it between the frame of the stator and the plate, beside the big coil.
NOTE 1):The black wire, that leads to the block connector, is a common ground. It is connected to the frame with a screw and you don't need to ground the coils straight to the black wire. They are grounded to the frame of the stator. NOTE 2) The 5 ohm coil is not grounded. It is in series with the 330 coil between brown and red wires. The wire that comes out FROM TOP of the 330 coil is connected to the wire that GOES INTO THE MIDDLE of the 5 ohm coil and it must also be connected to the wire that later turns to brown.
12)Find out in which direction the 5 ohm coil is wound (clockwise or counterclockwise) and wind the bigger one in the same way. I am not sure of does it really matter if they are made in opposite directions but I AM SURE that the bike runs fine when they are wound in the same direction. I don't need to kick my SR anymore, hand is enough...
13) Start winding with the plastic pipe and avoid scraping, stretching and bending the wire. Keep it tight (moderately) and make the windings parallel. If they begin to go across each other you will loose space and the demanded resistance is not reached in the end. If you manage to cut the wire, joint it with tin, cover with tape and leave the joint outside the coil fixing it with silicone and varnish in the end. Patiently and carefully fill the space with the thin wire. Adding the special heat resisting varnish or epoxy glue ones or twice in the middle of the coil is good and will make it more solid and insulate it.
14) When the space is full, (totally and well done) cut the wire and measure between the frame and the end of the wire. If you didn't reach 330 ohms, don't worry. Mine has 290 and is working fine. The limit 30% means that 240 ohms already makes the bike run. Ignition advances will work and the spark will be strong.
15) Connect the wires with tin as follows:
The wire going into the middle of the big coil is already grounded in the beginning. Connect the wire coming out of the big coil to the wire going into the middle of the small coil and connect these together to the wire that later comes out of the stator and turns to brown. Connect the wire coming out of the small coil to the wire that later turns to red. It is good to use the special cover, the soft pipe, familiar from coils, on the wires and joints in places where the wires would be without cover.
16) Measure one more time between the terminals and compare to the original values. If everything is OK and the joints are well done, fix the wires and joints with silicone to make them resist vibration and to insulate them. Use silicone or epoxy glue also on the four corners of the big coil to fix the outer windings to each other.
16) Let the whole stator swim in the varnish for some time and after drying install it back, adjust the timing with a xenon light lamp. There is not much adjusting to do, only some by the high speed impulse coil using the long holes in its frame. After installing the flywheel and the connector there should be a strong spark. If no, try another cdi.
Good luck
