Dnepr mt11 alternator woes

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Dnepr mt11 alternator woes

Post by Dneprswede » Mon Jul 15, 2019 1:07 pm

Hello fellas

Me and my dad have been rebuilding a 1989 dnepr mt11 during the winter. We got it working and driving beautifully about 2 months ago and have been enjoying some nice rides in our local area, longest ride around 200km.

The bike has only 8700 km on it, and it runs great. However, yesterday when we were riding home from a friend I noticed the charging light was lit. Normally, it will come on on idle, but will go black as soon as you give some revs.

Now, it's constantly on. I checked with a multimeter and there is no charging happening.

The bike has a new electrical system, scratch built after a NOS Ukrainian melted due to shite quality.
Alternator is a 12V 150W G424 with the solid state 33.3702 rectifier.

I have conducted a few tests per the manual, using a test light. All tests gave positive results, apart from the last one.

Page 67. Test of excition circuit.
With test light connected to battery + and alternator W. Battery - to alternator body. Turning the engine/alternator with the kickstart, the test light should glow steadily, mine was black. No glow at all.

Since the other tests where ok, does this still indicate a fault alternator?

Is there any way to test the rectifier? I have access to both analog and digital multimeters and might be able to borrow a oscilloscope.

If rectifier/alternator is faulty. Would it be smarter to upgrade to non Ussr parts? I've read some about using Bosch rectifiers and delco alternators, but need to research this more.

Links to photocopy of manual. Failure on test on page 67.
https://www.dropbox.com/s/yku31zilb7326 ... 3.jpg?dl=0
https://www.dropbox.com/s/zsk44w0lx910n ... 7.jpg?dl=0

Thx
Linus

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Re: Dnepr mt11 alternator woes

Post by brianural » Mon Jul 15, 2019 1:23 pm

Not familiar with the manual your linked. I recently had issues with my MT11, thought is was the 424 gen, ended up being the 33.3702 rectifier. I first replaced 424 with no change in charging. I then replaced rectifier to fix issue. Good luck on your fix. My gen light was not coming on when key turned to on position nor when motor running, I assumed the gen bad, luckily bought both Gen and Rectifier at same time. Once I replaced rectifier, the gen light started to ;ight when key on and charging battery when motor running.
2011 HD RGU
2003 Honda VTX1800 - sold
2005 Honda VTX1300 - sold
Bunch of other metric bikes for last 45 years
"1966 titled" Dnepr MT-11 (reality is a 80-90's)
1956 IMZ M72 (bought in pieces, oh crap what have I done) Hope to have on road in 2018

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Re: Dnepr mt11 alternator woes

Post by Claus » Mon Jul 15, 2019 2:22 pm

I´m not familiar with the solid state regulator, only with the electronic type. The alternator would be the same with both types of regulator.
If you start the engine and after starting excite the alternator direct from battery + (a line from bat + to "shunt", the strange W ) you should hear the gears working louder (the alternator starts charging). You can prove that by connecting a voltmeter to the battery. Attention, no regulating, don´t rev too high.
If the alternator starts charging now, your regulator is defective.

If you want to check the alternator rotor: it should have 10 Ohm resistance between the two copper sliding rings (carbon brush holder taken out ) and no continuity to ground. The three phases of the stator should have all the same resistance below 1 Ohm to each other and no continuity to ground.

The rectifier has three plus and three minus diodes and no pre-exciting diodes. You can check the diodes with a continuity tester for failure.

Most of the times, the rotor is shot or the regulator is defective.
owned bikes: 93 Ural rig domestic model, 01 Ural 750 rig, 92 BMW R100GS, 92 Suzuki GSX1100G rig, 95 BMW R100R rig with Ural sidecar, 98 Ural rig with BMW drivetrain under construction

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Re: Dnepr mt11 alternator woes

Post by Claus » Mon Jul 15, 2019 2:42 pm

brianural wrote:
Mon Jul 15, 2019 1:23 pm
Not familiar with the manual your linked. I recently had issues with my MT11, thought is was the 424 gen, ended up being the 33.3702 rectifier.
Sorry brianural, 33.3702 is the electronic Ural regulator from late 80ies or early 90ies . The rectifier is built in the alternator. This regulator leaves the wave line connector on the alternator empty and operates the generator lamp itself (like a voltmeter, it switches on or off the light without reason sometimes). This regulator can be swapped by Beru reglulator GER 024 https://www.ebay.com/sch/i.html?_from=R ... 4&_sacat=0 , but the generator light would not work lack of pre-exciting diodes in the rectifier. (I used that for ages on my Ural and mounted a volt meter to the handlebar. So I always knew what was on.)

The Beru regulator is connected like this: DF (field) is connected to "shunt" (E lying on it´s back), D- is connected to negative ground and D+ is connected to switched power (it´s hot once the key is turned on).
If you change from solid state regulator to 33.3702 or Beru, let the wave line connector empty on the alternator, the + and the field connector are connected the same way as with the solid state regulator
owned bikes: 93 Ural rig domestic model, 01 Ural 750 rig, 92 BMW R100GS, 92 Suzuki GSX1100G rig, 95 BMW R100R rig with Ural sidecar, 98 Ural rig with BMW drivetrain under construction

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Re: Dnepr mt11 alternator woes

Post by propwash » Mon Jul 15, 2019 4:08 pm

33.3702 regulator testing (Dnepr or Ural with Г424 alternator and solid state regulator)

The "ЛК" terminal on the regulator is the charging light control terminal - "Лamp Кontrol".
Generally, if the charging light does not illuminate when key is switched "on", problem is the regulator, since it is controlling the light.

With a viable power supply (0-15V) and a voltmeter (2 voltmeters easier), two test lamps are good, the basic functionality of the regulator can be checked.

<< insert nanny warnings here >>

Prep
1) Remove regulator from motorcycle.
2) Connected the "+" from the power supply to "+" on regulator and "-" from the power supply to the body/mount point of regulator.
3) Connect "+" from voltmeter to "+" of regulator.
4) Connect "-" from voltmeter to body/mount point of regulator.
5) Vary voltage from 0 - 15V (don't beyond 15V) and make certain the power supply voltage and voltmeter read the same (nice to have one voltmeter on power supply and one on regulator).

Now ready to test
1) Place "+" from voltmeter and connect to the "ЛК" terminal on the regulator.
2) Slowly vary voltage from 0-15V on power supply while monitoring voltage on voltmeter connected to regulator.
3) Between 0-14ish on the power supply, the "ЛК" terminal voltage should read about the same as the power supply (minus 0.5-1V - circuit overhead) (this would illuminate the lamp - simulating low output).
4) Somewhere around 14V but before 15V, the "ЛК" terminal voltage should start to drop off to about 0-1V (this would deactivate the lamp - simulating output/all ok).
5) Repeat steps 1-4 with the "+" from voltmeter and connected to the "Ш" terminal on the regulator and "-" from voltmeter to body/mount point of regulator. Results should be similar to "ЛК" test. This is your excitation line.

<<NOTE>> This is more visual with two test lights or bulbs (12V). Connect test bulb lines to "ЛК" and other to body/mount point of regulator. Connect the other test bulb lines to "Ш" and other to body/mount point of regulator (incandesant bulbs are not polarized).
Repeat test from steps 2-4. The lamps will start to illuminate as voltage gets higher (maybe about 3-5V). After, should get brighter and brighter until somewhere around 14V but before 15V, then it should immediately go dark (above 14.5V, all OK, generator light out and the alternator is no longer energized). Reduce voltage below 14V and the lamps should come back on.

This is a general/basic bench test of the regulator. Once it is active in the charging circuit, it will work but it may be out of spec and not charging the system enough or "lamping" slight off.

If you do find the regulator is bad, order 3-5 if your are getting them from overseas. Since the fall and after the old stock dried up, they have been made elsewhere and questionable quality. It may take a couple to get one that behaves well with your system.

Edited for clarity an one mistake (should never trust a Dnepr schematic) and a mini test diagram.
333702_test.jpg
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Last edited by propwash on Tue Jul 16, 2019 12:25 pm, edited 1 time in total.

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Re: Dnepr mt11 alternator woes

Post by Dneprswede » Mon Jul 15, 2019 5:16 pm

Lots of great suggestions, thanks a bunch. I will read more carefully in the morning. Cheers

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Re: Dnepr mt11 alternator woes

Post by Dneprswede » Tue Jul 16, 2019 10:50 am

Hi. I have now conducted the test described by propwash. It gave positive results according to the guide. This would then indicate that my generator is bad after all.

I shall remove it from the bike to check for wear and do some more tests on it.

Will probably ask more questions later.

One quicky though. I just noticed that the generator has +12V on at all times, regardless if bike is on or off. I do not have a main switch on the bike, I will for sure add one on the positive lead from the battery. Could this be the source of my problems? Have this melted my generator core?

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Re: Dnepr mt11 alternator woes

Post by Claus » Tue Jul 16, 2019 11:09 am

The plus stud on the generator is conected directly to battery plus and to ignition switch, so it has 12V all the time.
If the regulator has 12V all the time as well (and as result the field connector on the generator, too) it would burn your generator rotor core (the field).
In this case I would suggest you should implant a switch that cuts off the plus line of regulator and ignition
owned bikes: 93 Ural rig domestic model, 01 Ural 750 rig, 92 BMW R100GS, 92 Suzuki GSX1100G rig, 95 BMW R100R rig with Ural sidecar, 98 Ural rig with BMW drivetrain under construction

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Re: Dnepr mt11 alternator woes

Post by propwash » Tue Jul 16, 2019 11:34 am

I would do one more quick test of the regulator (with a test light).

1) Connect "+" from voltmeter to "+" of regulator.
2) Connect "-" from voltmeter to body/mount point of regulator.
3) Connect test light - one lead to body/mount point of regulator.
4) Connect test light - other lead to "Ш" of regulator.
5) Vary voltage from 0 - 15V (don't beyond 15V) and watch the test light. It should begin to illuminate as voltage gets higher (maybe about 3-5V). After, should get brighter and brighter until somewhere around 14V but before 15V, then it should immediately go dark.
This is testing if the excite line to the alternator is working properly. The alternator should be "excited" until 14.5V or so. Above 14.5V, the excite line should shut off.

I will edit my first test post for some clarity.

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Re: Dnepr mt11 alternator woes

Post by Dneprswede » Tue Jul 16, 2019 12:16 pm

Thx Propwash, I will try that tomorrow.

Concerning the generator. I found out that the gear was not solid to the axle, it could spin a bit from side to side. Lockwasher was applied, but perhaps poorly. The gear should move I unison with the fan right? Without any play?

I tried to split the generator halves, but can't make the bearings release from the axle. I tried a puller and some sockets to make sure I didn't press on the wrong part of the bearing nothing. I guess I need a hydraulic press to get things to loosen up.

Question 2. The drive gear has a lot of casting flash on it, is it safe or advisable to dress this up with a file?

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Re: Dnepr mt11 alternator woes

Post by propwash » Tue Jul 16, 2019 12:31 pm

If you are speaking of the fold-over lock washer on the front gear - definitely do not trust it. Is the nut a castle nut with spacing for a cotter pin?
Remove bolt and washer and inspect the gear/key and make certain the key is OK. This will also allow you to see if there is a hole in the shaft/axle for a cotter pin. If so, reinstall, with the castle nut, a washer and use a cotter pin to secure.
I have seen instances where the nut loosens, fall of in the gear tower and destroys the front gear set.

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Re: Dnepr mt11 alternator woes

Post by Dneprswede » Tue Jul 16, 2019 12:52 pm

Yes, I'm referring to the fold-over washer. Luckily, I have a castle nut and a box of cotter springs. Will rebuild it with one of those as well.

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Re: Dnepr mt11 alternator woes

Post by brianural » Tue Jul 16, 2019 1:45 pm

this brings up a good point. do the generators use a key on the shaft and gear? When I moved my gear from old to new I noticed key missing, I assumed I had dropped and lost. I made a key from a hardened washer and inserted before putting gear on shaft.
2011 HD RGU
2003 Honda VTX1800 - sold
2005 Honda VTX1300 - sold
Bunch of other metric bikes for last 45 years
"1966 titled" Dnepr MT-11 (reality is a 80-90's)
1956 IMZ M72 (bought in pieces, oh crap what have I done) Hope to have on road in 2018

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Re: Dnepr mt11 alternator woes

Post by Dneprswede » Tue Jul 16, 2019 1:53 pm

Yes, there is a slot in the drive gear and a key on the shaft. Not sure if the key is press fitted or how it's attached. I can take a picture if you like.
Last edited by Dneprswede on Tue Jul 16, 2019 2:40 pm, edited 1 time in total.

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Re: Dnepr mt11 alternator woes

Post by brianural » Tue Jul 16, 2019 2:15 pm

ok I misunderstood, thought you were missing the key..no pic necessary..thanks
2011 HD RGU
2003 Honda VTX1800 - sold
2005 Honda VTX1300 - sold
Bunch of other metric bikes for last 45 years
"1966 titled" Dnepr MT-11 (reality is a 80-90's)
1956 IMZ M72 (bought in pieces, oh crap what have I done) Hope to have on road in 2018

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