Motorcycle Repair: Yamaha SR500, yamaha xt500, regulator rectifier

Question
Hi Bill,
I'm wondering what the function of the stator and rotor is on this bike. I've been told that a coil can wear out on the stator resulting in the ignition not advancing causing low power off of idle. I'm an electrical moron. can you explain what this means please.
Regards,
Gordon

Answer
Gordon, I am not a Yamaha expert, but am aware that they had issues with the electrical and ignition systems. Some bikes had points and coils, and the rest had electronic ignitions that apparently had reliability problems. The rotor is to help generate a magnetic field that sweeps across the stator windings to create an AC voltage that is converted to DC through the regulator/rectifier. CDI ignitions use a separate coil that is triggered by the rotor to send a signal to the Control Module, which creates a timed signal to the ignition coil. These pulser coils are subject to heat and vibration that causes them to fail over time.  Here are a lot of links I dug up for you below...

www.electrexusa.com for charging system assistance.

http://www.thumperstuff.com/

http://www.thumperpage.com/articles/sr500faq.html

http://www.siue.edu/~rsutton/SR/

http://www.yamaha-xt500.co.uk/portal.php

Bought a Yamaha SR500 single.  This was barely even capable of 85 mph, and when it was, it really let you know about it.  It was both noisy and vibratory.  And I loved it.  Thump thump thump thump thump.  But it was underpowered for two-up riding with a pack.  And the example I had bought turned out to be a dog.  It kept getting a partial seizure, and I took a while to figure out why it would lose power and stop, only to re-start after 45 minutes of kicking it over.  Also, some delicate electrical coil in the crank-end alternator kept disintegrating and would need to be re-wound

YAMAHA SR500
78-82 499cc 4-str Ohc single, 32bhp, 95mph, 60mpg, 159kg (350lb)Basic thumper in old Brit mode, still made in Japan, with drum front brake. Also 27bhp Jap 400cc version. Classic good looks and cutting edge technology for its time – oil-in-frame (ahem!). A real looker and the reason many people got interested in biking. Old UK models destroyed the piston, camchain and gearbox; vibrated above 70mph and had endemic electrical rot (including the kill switch shorting out) that made kick starting near impossible.

Bill MrHonda Silver