Bought a new rotor the other day

jussumguy

jussumguy

XS650 Addict
Messages
355
Reaction score
205
Points
43
Location
reedley, ca
IMG_4603.JPG
I have an '83 with stock style charging system. I have modified it with radio shack rectifiers and the Chrysler regulator.
When I first got the bike in 2012 it wasn't charging due to the regulator thing. I think the rotor was shot too so I replaced it with one I had laying around.
It charged great for years, in fact so good that I let the battery run out of acid. Since then I put a new battery and all was well.
Coming home the other night I noticed I wasn't getting all 14 volts like normal. This bike has worked so well over the years that it is obvious when it isn't feeling good .
I took it all apart and checked the brushes and connections and stator. Everything looked fine until I checked the resistance of the rotor. So long story short I shopped around and found Race Tech sells rotors for a little less than $95 delivered. Hoping it was made in San Diego I purchased one on amazon. It looks a little rough and dirty like early harbor freight stuff used to be.
I'm going to try it out and report back how it fares if anyone is interested.

Thanks for reading!
 
IMG_4604.JPG

The back side looks like it was cleaned up with a 4" sanding wheel. The taper is machined a little rough compared with the origional. The ignition magnet looks roughly in the right spot. Hope the old girl isn't disappointed with me...
 
Sounds about right clean the tapered bore with strong solvent to get the varnish overspray off. You will probably need to file the keyway slot a bit so the rotor fully seats. That was my experience.
 
Very interested to see results. Wondering about "runout" as it seats onto the taper. Should be interesting. My rotor took a dump recently so I'm researching and stalking this sight for any info. Hope it works for you.
 
A racetech rotor was the in the "runout" video I did and that runout thread.
 
Seems to me it matters greatly if there's no timing mark on it - after installing it, how would you ensure that total advance at 3000 rpm does not exceed 40 deg BTDC? The Racetech rotor I bought 3 years ago did have a timing mark, but apparently not quite in the same place as the original OEM rotor. I strongly urge anyone replacing their original rotor to do a TDC test with a piston stop and degree wheel to verify a timing mark if there is one or to create one if there isn't. On a TCI-equipped bike, use the degree wheel to also create a 40 deg BTDC mark somewhere on the left side cover.
 
The one pictured on their web site looks very nice - new, clean, very shiny, and it has a timing mark. Yours looks like a refurb honestly. Now, if it was a $10 part, I'd probably just shrug my shoulders and go with it, but a $100 part? I'd be on the phone complaining, mostly about the lack of a timing mark. How does one check/set timing, valves, etc. without one? Sure, you can do the piston stop - degree wheel routine but the whole point of having a mark is so you don't have to do that.
 
I think most people buy parts, put parts on , live with it.
I guess if it pings I'll back the timing off a little.
If it wobbles I will be disappointed
If I burn a piston I'll be really disappointed
Come to think, I'm really not in that big a hurry to get it going. I'll send a message and see if they respond.
 
How are you going to know where to set the timing in the first place without a mark?
 
5twins said:
How are you going to know where to set the timing in the first place without a mark?
Click to expand...


Old style two stroke tuning comes to mind, with a dial gauge down the plug hole. Myself, I wouldn't install that rotor, looks like a used part that somehow got put into a new part box. If I was looking for a rotor today, I would only consider Rick's or a tested used OEM, just going on my actual experience.

Scott
 
You know, I make the mistake of not considering how much time and effort I put into my old bikes. I have always paid very little for them because they are at a dismantlers yard or well on their way to the dump. I think I should have more consideration for myself. This thing is a cheap copy of a 650 rotor, I think I'll box it up and send it back. If I ruin the crank or grenade the motor I'm not sure what would become of this bike
 
jussumguy said:
I think most people buy parts, put parts on , live with it.
I guess if it pings I'll back the timing off a little.
If it wobbles I will be disappointed
If I burn a piston I'll be really disappointed
Come to think, I'm really not in that big a hurry to get it going. I'll send a message and see if they respond.
Click to expand...
I'm sure you're right about just putting new parts on and running with it - in a more perfect world, we ought to be able to do that every time. All I can say is that on a part like a rotor where correct angular spacing among the key way, the magnet and the timing mark are critical for "plug and play" installation with on-spec ignition timing, my timing mark showed 4 degree ahead of TDC when pistons were at true TDC. Full advance at 36 degrees may be no big deal/risk; but if the error went the other way, full advance at 44 might be much more serious.
 
xjwmx said:
Who's this Rick?
Click to expand...

https://ricksmotorsportelectrics.com/New-Yamaha-Rotor-41_400

Rick's Motorsports, this is a new '75 rotor, they also offer a core exchange for rebuilds. They can be found on ebay and Amazon, but probably without a warranty. I get Rick's rotors locally for less money without a warranty because the seller knows that I will install it right and not blame the rotor for problems caused by other components. The guy that I buy them from will not sell to me unless I can prove to him that the rotor I am replacing is bad, he does the same with other parts, I have won the argument every time. Believe me, you would not mess with Pat, he is built like an oak tree. I once saw his helper come into the shop with his head all bloody. The helper said, "you didn't have to beat me up". Pat said, " you should have done it the way I told you to". I didn't ask any questions.

Scott
 
Last edited:
jussumguy said:
So...how much cheaper? They were $150 on their site. You gonna share the favor to a couple 650 bros? Hmmm
Click to expand...

I get new Rick's rotors for Honda DOHC CB750's for $140 without a warranty. That's local to me, add shipping to that, and I don't know if Pat ships parts. These Honda rotors are almost identical to the early XS rotors, I've read that they may be interchangeable, I don't know that for sure. I haven't asked Pat if he has them for the XS and I haven't needed one yet. He is very partial to these DOHC Hondas.

Scott
 

Similar threads

JNaw
Rotor melted itself 500km after rewind?
Replies
15
Views
368
JNaw
JNaw
N
Odd charging problems on '75 xs650
Replies
8
Views
216
Its been a long time
I
2XSive
Over-charging? Reg/Rec Mod
Replies
5
Views
397
2XSive
2XSive
E
Question about rotor and charging.
2 3
Replies
41
Views
2K
Eric12171
E
I
Pre recommissioning electrical checks?
Replies
13
Views
464
Its been a long time
I
Back
Top