Jump to content

Why does the "hand grenade" alternator blow up?


MTRRAD
 Share

Recommended Posts

Ok, why does the Dnepr MT16 alternator blow up? If it's the bearings, I'll replace mine this winter, and will show how it's done, or rather, how I do it.

Link to comment
Share on other sites

If you are referring to the 35a/500w alternator, the front bearing siezes without warning and takes out the rest of the timing gears before you have a chance to react. There appears to be no known way to rebuild this alternator, and if you did it would still fail without warning. People have been known to use this alternator for many 10,000s of kms without problems. I have almost 20,000 kms on mine, but just replaced it with the German Denso adaptor. I'm not sure about the use of this alternator on a MT16 - I'm talking about on a Ural but imagine it would be the same case. You don't state your location, but if you would like to play with a good one that was removed in fear, I'll send you one for shipping costs.

Link to comment
Share on other sites

Send me a picture of it. If it's like mine I'll redo it and post it here. I am kinda like an uber-mechanic. Or at least I have no fear. If the electics are good, I am sure I can find a way to make the mechanicals work.

Link to comment
Share on other sites

Some caveats about the 35 amp alternator. My wife used to work at Worldwide Automotive, the largest rebuilder of alternators. She took one of these units in and there are several problems that can cascade.

 

Mechanicals - the shaft for the rotor is too soft and tends to bend. Once it bends it's out of balance and stress is added to the bearings which hastens mechanical failure. The seal on the front bearing is so-so, sometimes it lets in engine oil which washes out the grease and the bearing fails.

 

Electricals - the stator wiring is iffy. A common failure is for one of the 3 windings to burn open, and the alternator tries to compensate by running the other 2 harder. This leads to escape of magic smoke and wonderful odors.

 

The regulator is sensitive to voltage spikes. The brushes are harder than normal, and on some units they bounce on the commutator causing arcing. This causes voltage spikes which eventually kills the regulator. A Bosch regulator can be made to work.

 

These things vary enormously in quality. I had one go for 20,000 km and was still working when I traded the bike. My 2000 Tourist went through a bunch of them, including 1 that grenaded.

 

I'm not trying to discourage you. The design of the alternator is actually pretty good, but the execution is spotty. The shaft hardness varied from unit to unit. If the slot machine of fate gave you one with all good parts you had a winner, if not, then poof!

 

Let us know what you find out on the one you examine!

Link to comment
Share on other sites

My mt16 has a 424 alternator don't think that is the hand grenade It is just a lower amp alt but not aware they are bad just don't overload it with acc. Mine actually works ok the odd thing I noticed (at least to me) is if for some reason I run the battery low like when it is flooded and I grind on the starter and run bat down some when it starts my alt light stays on even at speed for 5 or 6 miles and only goes off and back to normal when bat is up on charge. That is how mine works don't know about the rest of them and all auto mechanics that I have asked just shake their head. By the way mine has 16000 km on it and I don't intend to change unless it gives trouble. Also back about the 5000 km mark I took it to the best rebuild shop in west Illinois and they said the bearings were ok so if it fails so be it I have found ther are a lot of little things to address with out worry about my alt. good luck. This info may not be agreeable to all so take it for what it is worth. I think you will,enjoy the 16 just a little slow. Dennis

Link to comment
Share on other sites

This post really belongs in the 'Late Urals,2002 and up' section.

 

Stop reading information about Urals if you want your MT16 to run ok. No Dnepr has never been fitted with the 'hand grenade' alternator from the factory so where did you get the idea they are?

 

As Denis says, the standard alternator is a 3phase L424 unit which is a copy of a 1960's Bosch unit as used on some German cars of the period. The Russian units are mostly poorly made and can be damaged by trying to charge a flat battery with them if here is insufficient voltage available to excite the third phase. I have seen many fail, but never seen one 'hand grenade'

 

If you wish to upgrade the alternator, there are several good alternatives without having to rely on the expensive crap that Ural supply

 

It would be nice if you edit out your references to the MT16, to avoid others being misled.

Link to comment
Share on other sites

Thanks for the clarification. I thought it was more than a bit unusual. The adaptor that I referred to works on a Dnepr also and fits a cheaper Kawasaki Denso alternator. The 35a alternator was fitted to Urals from 1998 1/2 to about 2004, so probably this is the best place since it crosses over both the other sections.

Link to comment
Share on other sites

the 35A/500W Russian alternator will fit on a Dnepr provided you use the Dnepr alt gear,

exactly like the 14A 424 alternator that was standard until the early 90ties on Dnepr and Ural alike.

 

I had a 35 A for about 3000 miles till i sold the bike, a 2002 750 Ural in total the alt had run 10000miles, it was noisy but didn't fail, the subsequent owner fitted the later Ural equipment for big $$ just to be safe.

 

the 424s I've had for many years and miles and they lasted not more than 10000miles on average, all 5 of them rotor interuption.

Most of them had come to the front bearing too loose in the casing potentially shorting the rotor to the stator and many of them had been run on bad batteries ( thus overloaded) and on sidecars (thus low speed less cooling first gear revving, shocks back and forth from city stop and go all of which fatigues an alt).

But none died instantaneously. They were cheap and readily available. second hand made in USSR, dunno how the Chineese of today are...

 

I do like the 424, it looks as if it belongs to the Dnepr or Ural, it doesn't put much stress on the drivetrain. The Victor alt which uses the front housing of the 424 is even more compact, I run it on the IMZ M-61 (after the last 424 failure made me come back from a ride drawing juice from a car battery ) has been working OK for 2 years, output is great, more electrodynamic resistance(make sure the pinnion is tight) but I do not use this old motorcycle too much in big city traffic and preferr to be gentle on the throttle.

 

When the next 424 alt goes bad on one of my other machine (though I'll monitor the batteries better) I'll change it for a Victor.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
×
  • Create New...