A question of rotors????

Dangermouse

Dangermouse

XS650 Enthusiast
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Hi everyone,
rotor on bike.jpg
new rotor.jpg

the saga continues with the charging fault on my 79 SG.
Firstly thanks to Bushyeyed1 for the stator. unfortunately made no difference. mine is marked LD115 - 07B
don't know if there is a difference to the one you sent as it is marked LD115 - 07. Have left the one you sent me on.
I came across a rotor on ebay very cheap, so i bought it, supposed to have come off a SE.
however appears different slightly. 1st pic is the one on my bike at the mo. Can anyone tell me if it is okay to fit. difference i can see is the "omega" looking extra part on my rotor.
Hope someone can help. Oh and it is measuring 5.4, mine on the bike is measuring 3.5
Thanks
 
Calling your bike a 1979 G model is misleading. G models were 1980, 1979 would be an F model. Your bike can't be both. It's particularly important to know in your case because from '79 to '80 was a big change year. The 1980 model got completely new carbs (BS34s), a factory electronic ignition, and a slightly different charging system. Some of this info applies directly to the question you've just asked.

The 1st pic of the mounted rotor shows a 1980 or later rotor with the embedded magnet that fires the factory electronic ignition. The 2nd pic of the unmounted rotor shows a 1979 or older rotor without the magnet. If you do have a 1980 model with factory electronic ignition, this 2nd rotor won't work. Well, more correctly, the factory ignition won't work without the pick-up magnet to fire it. If you do have a 1980 model but have changed the factory ignition to something else like a Boyer, or changed back to the old points system, then you could use this rotor.

It appears the description of your "new" rotor was correct. An SE model would be a 1978 and it would have this older style of rotor without the embedded magnet.
 
Dangermouse said:
had this before and was explained, my bad, it is a 1980 sg. so basically you are saying the rotor won't work on mine. looking like I will have to bite the bullet and get mine fixed. cant locate one here in the UK
Click to expand...
Well, if you can't get it rewound, I have one ready to go here.
Shipping would be pretty steep. PM me if you're interested and maybe we can haggle out a deal.

IMG_20200322_202503.jpg
 
It won't work if you have the factory electronic ignition. It will power the charging system, just not signal and trigger the ignition. But, a working charging system doesn't do much good on a bike with no ignition that won't run.
 
You have said in a previous thread you are only getting just over 8 volts at the brushes, this needs to be resolved before you can start to eliminate the rotor and stator, i suggest you disconnect the battery and wire directly to the brushes and then do the slap test to see if it improves, then go through your loom piece by piece cleaning and ensuring conductivity throughout, after all these are 40 years old, similar problems on mine all sorted now.
 
Thanks for the info all, Thanks for the offer Jim, however experience taught me with shipping and import duties it is better to have things done in the UK if i can.
 
Although 3.5 ohms isn't ideal for your rotor, it may still work if you fix the voltage feed problem.
 
Dangermouse said:
let the learning curve begin. will look at the connections .
Click to expand...
Back at the link I gave you... go back to comment #3. It's a copy of the troubleshooting guide in Tech... with a few of my pointers and videos added. Comment #2 is the basics of how a charging system works. Good luck.
 
I DM, if you do decide to get it rewound talk to Marcus at Rex’s Speedshop, he rewinds a lot of rotors for older bikes, I know a lot of UK members of the SR500 forum and also the XT500 forum have had their rotors rewound by him and have been very happy, not sure if he will do an XS one but worth a try, and if not he may be able to tell you where to go to ge tit done properly.
 
@Dangermouse Jim does good work on his rewound rotors. I am sorry if you bought an extra stator. Maybe you find someone that can use it in the UK. Never hurts to have an extra one laying around though. I made the same mistake as you when I had an issue with my charging system. I got the rotor for the older bike without the magnet. Luckily Jim was able to hook me up with one of his rewound rotors.
 
Dangermouse said:
The saga has ended..... Just received my rewound rotor back from Rex's speed shop , fitted to bike and hey presto ...14.25 volts across the battery..
Dancing and whooping followed with a huge grin on my face.....just want to ride it now.
Click to expand...
Glad you got it charging again!!
If you don't mind me asking, what's a rewind cost on your side of the pond?
 

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