Need advice - Electrical (Stator / RR ) problems

Hey guys!

First post here. Tried to find some, but no one had the same situation as me.
Here's my problem. My brand new Yuasa battery (2 weeks old now) won't seem to get charged by the stator.

Here's my tests so far.

I charged the battery again to 12.8V and when I start the bike, it drops to 11.5 (normal for now).
Now starts the fun. I can't check the rectifier since the plug on the yellow cables have been soldered there. I tried to pull the heatshrink and check the resistance between them, got less then 100 ohm between them (which seems to be ok?)

When the engine is running, on idle i get around 12.5v-12.7v. When I rev to 3k, I get between 13v-13.4v. Over 3k rpm, the voltage drops to 13v and stays there over the rpm range (tried to ~7k)

I don't know how to check the stator since the yellow cables are soldered. My only option right now in my head is to cut everything and install a female plug on it.

I have a feeling it's the stator because of the 13v at 5k rpm, but could be the r/r aswell...

Unless anyone has a better idea for further tests, I guess I'll have to install a new plug for further tests.

PS : Is a mosfet r/r worth the 50$ increase (CAD) ? Thanks all in advance!

 

Here's a picture of the sleeping beast :')

Sexybeast by ERKanis posted Aug 16, 2018 at 5:59 PM

 

I had similar readings on mine. As the RPM's rose, the charging voltage would drop. The highest voltage I could get was at about 3500 RPM, and that was only 13.2 volts.

With a used mosfet rr from a Fleabay dealer I now have a consistant 14.0 - 14.4 volts at all RPM's above 2K.

 

You need to test the stator, it takes two minutes to resolder the wires.
If you don't do that, you're only guessing.
A charged battery is 13.1v
Stator output is AC, 25 to 50vac is about right.

 

Hi and welcome to the MadHouse.

To be honest 5th Gens can have a heap of electrical system gremlins so its a process of inspection, testing and elimination.

http://vfrworld.com/threads/how-to-fix-common-regulator-stator-failures.39277/


The above thread (post # 9 sets out the basic tests to do) covers all the usual suspects. But the tests need to be done twice once with the bike cold and then again after the bike has been for a 20 minutes plus trip as stuff may test OK when cold but diodes or insulation on stator windings can fail when hot causing the battery to be drained.

A quick and cheap check for the stator is to just buy a replacement Honda gasket and then remove the stator cover. If you are greeted by the sight or smell of burnt electrical windings you will need a new stator. However do not assume that is it. Sometimes a fault with one component can kill others in the charging system. As those voltage figures look low it seems quite likely your RR is faulty. If you need replacements please fit an OEM stator but always go for a Shindengen RR - the sort routinely installed on Yamaha models or sold by www.Roadstercycle.com . Be wary of other cheap alternatives - plenty of bad ones to avoid mentioned in that very extensive thread linked above.

Take care and let us know how you get on.

SkiMad

 

Hello all! Thanks for the advices and tips.

So Saturday, removed the rear cowl and started doing some tests with my trusty voltmeter. Managed to find that my stator / alternator was going strong. Had a quick 20 min ride close after charging my battery, cut the soldered wires and checked the stator values. Going between 15-65v on each phases. I had the OEM upgraded RR installed already. The one ending with SH. But after removal, ive found a few bubbles on the plastic side underneath. So I went ahead and ordered a brand new R/R MOSFET from a local company (RmStator, seen a few good reviews so why not...).

I will probably install it tomorrow and add another update then!