Rewound Rotor 4.70 Ohms - is this good enough

[LTGTR]

I have got my undies in a twist over this spec.
My Yamaha workshop manual (74-77) has a specification table in the front which says rotor resistance 5.15 +- 10% which equates to a low of 4.63.
This is the spec that I sent to the guy who rewound my rotor. It looks like a good job and cost was ok at $110 Aust and it measures 4.70 Ohms which is technically within spec.
But at the end of the manual (77 supplement) it says 5.25 +- 10% which equates to 4.73 - which technically mine is below.
My mistake was quoting him the spec and the tolerance - I should have just told him a spec like 5.2 Ohms (no tolerance).
This tolerance is obviously on the low side and I would like some comments from the guys on the forum.
Will it work okay.
Jim - I took your advise and using Skulls info (from ages ago) was able to find a guy her in Aus to do the job - the job looks good, done in quick time and trusted me to pay with an invoice with the returned goods - its the low reading that give me the shits.
Regards Ray.

 

[jetmechmarty]

I’ve been running a rewind for over 20 years. If memory serves, it measured under four ohms when I got it. It has been functioning just fine all these years.

 

[nj1639]

If the rotor measured 2 ohms then you should be concerned.
I'm with Marty, I've run a rewind with under 5ohm, closer to 4 than five and never had a problem.
.....though sometimes I'll run my tire pressure a little above or a little below suggested spec just to challenge the norm, I'm that rebellious.
You'll be fine.

 

[gggGary]

@Jim
The resistance is a function of wire diameter and length. Sooo fatter wire makes for less length as there's only so much room. Both fatter and shorter than OEM will lead to a coil with lower resistance. The wire coating thickness will factor in a bit, then the ability to make windings that efficiently fill the space available.
A bit of a rub is the lower the resistance the higher the coil draw and I'm doubting this higher draw translates into much higher output.
all that waffling aside run it. and see how it works. The good news is you have a recorded baseline resistance, so checks later will easily verify the coil remains intact with no shorting.
It's been pretty consistent that few rewinds match OEM spec most falling closer to 5 than 5.7 ohms

 

[nj1639]

.....another good reason to have a mounted voltmeter for watching charging health......l

 

[Jim]

Like everyone says, you'll be fine Ray.
Fwiw, Honda specs their big 4 rotors at about 4.0Ω, and they're basically the same rotor. Actually I should say, that's what the Honda boys want to see on their rewinds.
Another thing to keep in mind is that once your engine is warmed up, resistance will be all the way up to about 7Ω, give or take an ohm.
It's not as critical as Yamaha makes it out to be.

 

[jetmechmarty]

As long as I’ve been on these boards or email groups, I’ve not heard of a rewound rotor failure. Not by @Jim, not by Custom Rewind in Alabama. The one I sourced from @DonebySunday has been going 21 years and I don’t know who rewound it. Guys overseas aren’t posting complaints that I’ve seen.

 

[BACK SHIFT]

From all the rewound rotors out there that are available, I recently bought one of Jim's, and it works quite well, the time frame was fantastic also. All his several rewound rotor reviews will always read 100% satisfied buyers. I would highly recommend hooking up with Jim!
back shift

 

[LTGTR]

Many thanks to all who replied and untangled the twist in my undies.
The rotor is a spare because as per the advice of the forum the original charging system, with some improvements, is a good system because it only produces what it needs. These bikes are getting old and I like my "spares".
I have fitted the VR115 and Windy Nations rectifier and my voltage sits steady between 14.1 and 14.3.
For all the Ozzys, here is the guy who did my rewind - thanks originally to Skull.

S & K Parts and Service
29 Albyn Road
Sunnybank
Queensland 4109
0412462149

The guys name is Sal
Regards - Ray.

 

[jetmechmarty]

The rotor is a spare because as per the advice of the forum the original charging system, with some improvements, is a good system because it only produces what it needs. These bikes are getting old and I like my "spares".

I like spares too. Here’s what I’m about to do and I suggest you do the same. My XS650SH is low miles and running the OE rotor that’s working fine. I’m going to install my rewound rotor and keep the OE as spare. The rewound rotor is less likely to fail. Typical fail mode is shorted. When that happens, it takes the battery with it.