Yamaha TMAX 500 2003 charging problems

[christoscon]

Hello everybody
My name is Christos and I am from Cyprus. I am a proud owner of a Yamaha TMAX 500, 2003, which I bought used, in 2010. The last couple of years I encountered minor problems in the charging system of the bike, by means that the battery could not get fully charged. The battery was installed on the bike by the previous owner in 2009. Anyway it seemed that the battery was weak. I continued having problems with the charging of the battery of the bike and I decided to replace the battery with a new one, which I did by the end of May of 2015. Since I replaced the battery with a brand new one, made Yuasa YT9B-BS, I had more power on starting the bike but after a few hours of riding the bike, the battery was becoming weaker. So I decided to check the rectifier/regulator of the bike to see if it charges the battery of the bike. I removed all the plastic covers, on both sides of the bike to reveal the rectifier/regulator on the right hand side of the bike and the wirings of the stator (A.C. Magneto), on the left hand side of the bike. I check the rectifier/regulator and it looks that it works well. When the engine of the bike is on and idle the output voltage is at about 12 volts. When I rev the engine up to about 5.000 – 6.000 rpm, the maximum output voltage that I get is about 13.15 volts. In the service manual of the bike, it says that the normal output voltage of the bike, should be 14 Volts at 5.000 rpm. I check it with the multimeter and I believe that it works good. I don’t know if it is weak. Then I tried to check the stator’s wiring. I checked firstly the output of the stator and when the engine is idle, I get a voltage of about 17 – 18 volts AC, max. When I rev the engine up to 5.000 – 6.000 rpm, I get a voltage of about 80 – 85 volts AC. I checked with the multimeter the wirings of the stator and I get a resistance of about 0,2 Ω, between the three phases (in the service manual it says that I should get a stator coil resistance between 0.338 – 0.413 Ω) and there is also a continuity / contact of each three phases with the chassis/frame of the bike of about 0,1 Ω (I don’t know if this should happen). As I see in the specs of the bike, it is equipped, for charging, with A.C. Magneto, manufactured by Mitsubishi, model F4T373, with standard output 14V310W@5.000 rpm. The Stator coil resistance should be 0.375Ω+-10%W-W. The Rectifier/regulator is a Semi conductor short circuit type, manufactured by SHINDENGEN, model SH650A, with no load regulated voltage at 14.5<+->0.4 Volts DC and with rectifier capacity at 18A. Now I desperately want to find out what is going on with my bike. I suspect (I am definitely sure) that the problem is on the stator coil that needs to be replaced. Can anyone help me on this issue. I really don’t know what to do. Can anyone tell me if we can find the full specs on the above mentioned stator coil. What is the normal voltage AC output that I should have with the engine idle and also, with the engine rev up to 5.000 – 6.000 rpm??
Thank you

Christos - Cyprus

[WD Forte]

Christos
the output AC voltages and
the 0.2 ohms between phases sounds ok
but
The 0.1 ohms between any phase and engine/ground sounds bad to me
MY bike for instance will show similar readings until I get to
the resistances between the 3 phase wires and engine case/ground
where its 10s of megaohms or off the scale.
This is usually want you want to see during a stator test

My guess is your stator needs rewinding or renewal

Edit don't get too worried about being exact at such low resistances due to variations in meters, leads, windings.

A basic 3 phases stator resistance test is simple
very low between phases (<1 ohms)
very high between any phase and ground (megaohms)
____________________
bikers smell of wee

[christoscon]

Hi there.

As I realised, the major problem for not charging the bike's battery, is the stator. Most mechanics told me that the best solution to this, if of course, the problem is the stator, is to buy an brand new genuine one from Yamaha. They told me that they don't trust anyone to rewind the wirings of the stator because electronics on bikes are too sensitive and this may cause other problems on the electricals. Is there any other way to test the stator in order to be definitely sure that the problem in this case is the stator?? I don't know any other ways to test the stator and I want to be definetely sure that the problem is the stator, because as you may already know, the stator of the Yamaha TMAX is working in the engine's oil and it needs too much work to be done, before you reveal the stator and remove it from the engine. Please inform me if there is any other place, where I can buy a brand new genuine stator (of Yamaha), because as I found out the genuine one in Cyprus, if I order it, it costs too much and will delay up to three - four weeks to arrive to Cyprus. But firstly, I want to know if this is the problem that make all this mess and not charging the battery.
Thank you
Christos

[WD Forte]

I've told you how to test it above
it how I've diagnosed manys a bad 3 phase bike stator simply and quickly
If you have anything other than very high resistance between the phase coils and ground its new stator time
____________________
bikers smell of wee

[christoscon]

WD Forte

I believe that is time to replace my bike's stator. It needs to be replaced because most of my friends told me is not a good idea to rewind because the electronics of the bike are too sensitive. So Now, I have to look to find a genuine stator for this bike. There is no such a thing in Cyprus, so I have to order it from other country. Any opinion or suggestion from which country should I order this part, would be appreciated.
Thank you[/quote]