Any
questions, comments or corrections, please e-mail me. The reason for replacing the ignition on my 78 Yamaha SR500 was very simple, the ignition stopped sparking. After troubleshooting the system, I found the ignition part of the stator had an open circuit in one of the coils. I had heard that SR’s that had been in storage for a while were prone to stator failure. I don't know if this is true or not, but mine fit the profile. My SR had been in storage for about 6 or 7 years. I went to my local Yamaha dealer and he quoted me a price of $650 for a new stator. I looked around for a place to rewind the stator, the only place I could find was in Grand Junction, CO. and he wanted $150. I would have to send him the core to be rewound and returned, about 3 weeks with shipping. I later found out that Denny Burg in CA. has rewound stators, at least they are listed on his parts sheet. I ruled out one from a salvage yard on the chance I would be getting another aged stator. Another reason I decided against the stock electronic ignition was the anemic spark it generates. If I spend that much money I want to improve the situation not just replace it.
I looked around for other options. I couldn't find a system that would work with the existing pulser coil. The major problem was the lack of spark advance with the flywheel triggered ignition. All the units with electronic advance would not work because the pulser coil triggering with every rotation of the crankshaft. The aftermarket system would see this as double the rpm of the engine giving an advance curve twice as steep as required. The only other option was to get the control pulse to happen every other revolution of the crankshaft. I was informed by Michael Moore at EuroSpares that the XT/TT 500 engine used a point controlled magneto or energy transfer ignition system and that I may be able to use the clutch cover and point drive off of one of these bikes. I opted for this modification.
I got my XT/TT 500 parts from Outpost Motorcyle Salvage in Rosebud, MO. I paid a premium price and received very poor service and only a portion of my parts. After 3 calls and 2 shipment of parts I finally gave up and bought the thrust washers from the Yamaha shop. I thought I would support a relatively local business and get my parts a little quicker. Well I guess it's true "no good deed goes unpunished". I won't make the Outpost mistake again.
Installation of the XT/TT clutch cover requires some reworking of the inner engine case. The casting for the SR and XT/TT are the same but the SR case is not drilled for the point drive shaft. Michael Moore suggested removing the engine and putting it in a mill to drill and ream the hole. After looking over the situation I figured it was a simple inline boring operation. I could leave the engine in the frame and use the new XT/TT clutch cover and some drill bushing to align and drill the hole. It's a fairly simple operation, install the new clutch cover, insert the drill bushings, step drill the hole and ream to size and then a spotfacer to adjust end play. The hardest part was finding a 9mm reamer. If you don't have access to a lathe you will need to have the drill bushings made.
The stock coil cannot be used with any of the aftermarket ignitions I looked at, the reason is the common connection of the coil (common to both primary and secondary windings) is grounded to the core of the coil which is mounted to the frame. In the aftermarket systems the common or positive (+) terminal is connected to the battery. To use this coil it would have to be insulated from the frame and ground. Another reason the coil won't work is the low resistance of the primary windings. RITA and Boyer require coil resistance of 3-4 ohms to operate properly, the resistance of the primary of the stock coil is .98 ohms.
These system are complete unit, they use there own electronic pick-up to replace the points and the advance is controlled electronically in the unit thus replacing the mechanical advance (governor in Yamaha terms). They all require an external coil, at extra cost, and are powered by a 12 volt battery. I was going to include some posting I received from Brit-Iron on the RITA vs Boyer systems but they were lost in a computer crash a work. Each system has there supporter and detractors, price versus preceived quality. One person said you can buy 2 Boyers for the price of a RITA and keep one for a spare. I'll let you decide.
Lucas RITA System
EuroSpares sells the Lucas RITA electronic ignition system. To use the RITA system I would have to modify the points housing on the XT/TT 500 clutch cover to accept a RITA electronic pickup. The reluctor, the part that fits on the point shaft in place of the point cam and mechanical advance, must be bored out to fit the point shaft and is another modification required of the RITA system. The RITA system, originally intended for a BSA single, has electronic advance, so the governor (mechanical advance) and points plate are not used. The major problem with this approach is expense the RITA system cost $270 plus a new coil for another $63. You can get the unit for $210 if you do the machining yourself.
Boyer System
I also looked at the Boyer Electronic Ignition for BSA singles, I was not sure of how the reluctor was made and if it could be bore out safely. The Boyer system cost about $83 on sale from British Only, normally $99. The Boyer also requires a new coil, I didn't price a coil.
Dynatek Systems
If they have one that works they are keeping to themselves, I could not find the SR or any singles listed in supplier catalogs.
I also looked at spark amplifiers systems. This type of system does not have electronic advance, the mechanical advance and points must be used. Basically all these systems do is increase the voltage to the primary of the coil from 12 volts to about 375 volts and use a semiconductor to control his increased voltage. The semiconductor is triggered by the points. In this way the semiconductor handles all the current instead of the points and with the higher voltage into the primary a higher voltage across the secondary and spark plug. MSD figures show 40,000 volts at the plug with .3 amps through the points as opposed to 21,000 to 24,000 volts and between 3 and 4 amps through the points for standard battery and coil ignitions. That a 90-92.5% reduction in current, and current is what burns and pits the points. The only draw back to points that remain is wear of the cam follower. You still have to check the point gap periodically, but the contacts should last indefinitely.
MSD makes the MC 2 system for motorcycle drag racers, it had all kinds of neat stuff, adjustable two stage rev limiter, air shifter signal output and all kinds of stuff I couldn't use. The cost was also very expensive, around $330 retail, on sale at Star Racing for $260 plus that ever present need for a new coil. The feature I did like about the MSD ignition was the multi spark feature, at lower rpm the plug fire multiple time not just once like most systems.
By now I getting a little worried, as Michael Moore wrote me when he gave me the price for RITA system, welcome to the world of motorcycle modification, or something like that. One day I took my wife to Wal-Mart to do some shopping. No, I didn’t find a replacement ignition system for the SR sitting on the shelf in the Automotive Department, but I did find a magazine/catalog titled “Street & Strip” from Summit Racing a custom car and drag racing supplier. As I am looking through the pages I see a listing of MSD ignitions, well look at that a multi-spark unit for $70 and a coil for $28. I wonder if it will work on a single? I bought the magazine and the next day e-mailed the tech department at MSD, great company but slooow on the e-mail tech line. MSD said if it had a set of points it would work. I mailed off my order form a week later I had the MSD 5 Ignition with a Blaster 2 coil. I now have a light show going on at the end of my spark plug. There is one other problem with the MSD 5, it is rather large for a motorcycle. Since I had removed the air box several years ago space was no problem. The MSD 5 measures 8"L x 3 1/2"W x 2 1/4" H.
MSD also makes an igniton system called the Blaster it is a little smaller physically (6"L x 3 1/2"W x 1 3/4"H) than the MSD 5 but does not have multi-spark. It is also $6 more expensive. I opted for the MSD 5 but you may want to give the Blaster a look if you are cramped for space.
Any
questions, comments or corrections, please e-mail me. 
Ron
Sutton's Home Page