alternator or diode board or what?

[GrimReaper]

the voltmeter shows that the alternator charge the system only in high RPM.in around 4k rpm it shows 14 volts,but when idling only 8-9 and after a 20-30 seconds engine died.I opened the alternator and check the brushes(looks OK)I spoke with the local dealer and they told me that the alternator is pretty reliable and usualy the diode board or some other relay is the reason for that.I hope someone can help me with this problem.

    Best GR

[Barry]

8 or 9 volts at idle is not right at all and maybe low enough not to provide a decent spark which is maybe why the engine died. What state is the battery in? Voltage tests of the charging system are only really valid if you start with a good battery that is fully charged. Also is the charging light illuminated with the ignition on and before you start the engine ? If the bulb has failed there will be no current flow to the alternator field windings which can result in the symtoms you descibe i.e. no charge until the engine is at high revs.  Best to check the basics first before assuming you have a problem with the diode board.  

[Bob_Roller]

I agree with Barry, check to see if the 'GEN' comes on when you turn the key to the run position .

If it doesn't, you need to do a bit of simple troubleshooting .

If the "GEN' light doesn't come on, here's the troubleshooting steps .

First, remove the positive lead from the battery, and secure it so it doesn't spring back and touch the positive terminal of the battery .

The reason for this, is that there are 'hot' terminals under the front engine cover, they have power to them regardless if the ignition switch is in the off position or not .

You can damage the diode board if the cover touches one of these hot terminals .

Remove the front cover from the engine .

Reconnect the positive lead to the battery .

Place a wire, or other metal object between the slip rings on the alternator rotor, with the ignition switch in the on position, the light should come on .

This checks the wiring and the bulb, if it's good, this test is done .

If the light doesn't come on, you need to open the back of the tachometer, and check the bulb to see if it is good, or just maybe loose in it's socket or possibly the wiring or bulb socket is faulty .

If the bulb is at fault, it's a common SAE 168, 194 type bulb, available from an auto parts store, get the incandescent type bulb, not an LED type, the LED bulb will not pass enough current to properly operate the charging system .

If the test for the bulb circuit checks good, you need to check the alternator rotor for continuity of the windings .

Turn the ignition key to the off position, or remove the positive battery cable again .

Place small pieces of paper between the brushes and the slip rings, place the leads from the multimeter on each of the rotor slip rings, you should get around 2.8 ohms .

If you get infinite resistance, the rotor is bad .

[montmil]

Bob, that's an excellent, well written and easy to understand diagnostic. [smiley=thumbup.gif]

In my opinion, this thread should be considered as an addition to the FAQs Section; after all input from the R65 crew has been received.

Both my R65s have a Generator Light Auxillary Circuit that keeps the charging system doing its job if the GEN bulb fails. Mandatory on the '81 as the actual light and instrumentation was replaced with the digital TrailTech product. Rick Jones has a kit or you can roll your own as I've done on the '83 Mexico Bike.

http://www.motoelekt.com/genlightacc.htm

Monte

[Bob_Roller]

Only thing I didn't like about the Motorrad Elektrik kit, was the type of connectors that are provided  .

They cut the insulation of the wire, I personally didn't use them .

[Semper Gumby]

I bet the battery is bad and there is nothing wrong with your charging system.  Check out the battery first.

[GrimReaper]

the Gen light iluminated with ignition on and when the bike runs on rpm above 2k comes off.When idling iluminate again and after while the engine dies.
 If the charging system works then i think it does matter how good is the battery.The alternator should provide ehough voltage to charge the battery and to keep bike runnin,
  
 Bob i will run the test for the rotor tonight.The gen light seems to be OK.

[Semper Gumby]

Sounds like a normal Bosch charging system to me.  Really.  With my Omega 400 watt system the light doesn't go out till about 2700 RPMs.  It comes back on on the way back to idle at about 1700 RPM.  At idle the battery is the only thing powering the electrical system with the Bosch Alternator.
I would check the battery and all the connections that connect the battery to the frame (ground) and the rest of the electrical system.  I think the positive lead runs up under the top cover to the starter solinoid.  Make sure these connections and the battery connections are goodntight.

If your system is putting out 14 volts at speed then your charging system is probably AOK.

[Bob_Roller]

If the light comes on, with the switch in the run position, and goes out like Bill has said, doesn't sound like the charging system is at fault .

Battery is a likely suspect now .

Is your battery a sealed type, or can you add distilled water to it ?

If it is a serviceable type, remove the caps, and see if the plates are exposed .

Like Las Vegas, the Phoenix heat is pretty tough on batteries .

I've gone to sealed AGM type batteries on the bikes .

[GrimReaper]

Battery is low for sure,but Bob isn,t the alternator suppose to provide enough volts and sparks to keep the bike runnin even when idling,or maybe not because the bike is not desined to idle for a long term?

[Semper Gumby]

No.  Not on the Bosch system.  The GEN light is on which means the battery and the battery alone is powering the system.

Now if you had the Enduralast Alternator system...maybe?

[Bob_Roller]

Unfortunately, this charging system doesn't start producing more power than the bike is consuming, below the 2500-3000 rpm area .

If you ride in a lot of 'city' type riding, the battery will get discharged .

When I lived in Chicago, when the weather was conducive to riding, if I took the bike to work, I had 5.5 miles and 13 stop lights, if I didn't charge the battery on my weekend, or take the bike out for a good highway speed ride, the battery would be discharged enough in 7 workdays, that the battery wouldn't operate the starter .

A float charger connected to the battery when the bike is not in regular use, or your riding style is mostly city traffic,  is probably a good idea .

[GrimReaper]

 Yes i ride the bike only in the city for a 5-6 miles a day with a lot of traffic lights.Sounds exactly like what happened to me.I will start with recharging battery first

[Bob_Roller]

If you need to replace the battery, I don't know what kind of sources you have for batteries, but the R65 takes a non-standard battery size .

Three of us here have installed a generic AGM type battery .

www.staabbattery.com/product/UB12220-v.html

Don't know what kind of service life to expect, but the price was quite reasonable .

[Barry]

Batteries tend to get taken for granted. Like Bob I have a short commute to work that takes 10 or 12 mins. How much charge is a battery going to get in 10 mins especially in the winter with brake lights and indicators and headlights on the go all the time.  The answer is none in fact it will discharge. Even in the summer it will get no more than if you put it on charge in the garage for 10mins which amounts to next to nothing. Riding a bike does not charge the battery faster than a normal garage charger. If it did it would damage the battery.

Use of a battery tender or regular charging is not being fussy its essential unless the bike gets regular long runs and I mean long runs like hours.