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Just Purchased Mtd 990


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#46 achomesteader OFFLINE  

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Posted August 05, 2012 - 11:44 AM

First, I'm pretty sure your tractor is not model # 142-990 since that would be a 15 hp tractor. Yours should be a 140-990A and here's the link for your manual as posted before:

770-02531.pdf mtd 990.pdf

To determine whether or not your flywheel has been re-polarized and is magnetron ready, offer a compass to the center fin of the aluminum magnet carrier on the flywheel. If north points toward the flywheel, it has not been re-polarized and is not magnetron ready. If south points toward the flywheel, it has been re-polarized and is magnetron ready.

Below is a pic demonstrating using a compass on a flywheel that is not magnetron ready. Notice that north points toward the flywheel:

Posted Image

That appears to be a magnetron armature that you have on your tractor. Engines with flywheels that are not magnetron ready and have had a magnetron armature installed on them, sometimes won't start or are hard starting, and if they do start, will never run like they should.

If you need to have your flywheel re-polarized, Briggs will do it for free. Just be sure to pack it well to insulate it from damage. Include a short note describing what you need, the Model, Type and Code of the engine, and a return address.

Ship to:

Briggs & Stratton

Menomonee Falls Distribution Center

INBOUND DOCKS 1-13

N83W12529 OLD ORCHARD ROAD

MENOMONEE FALLS WISCONSIN 53051
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#47 Kentrails OFFLINE  

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Posted August 06, 2012 - 07:01 PM

Firstly, thank you very much for your clarification of my most frustrating situation.
Secondly after carefully scraping paint away, I was able to confirm your datum:
DSCF0008 2.JPG 140-990A: right on the money :thumbs:

After performing the compass test, I was able to confirm the wrong polarity as well.
DSCF0008.JPG

The problem was in the manual that I was given, stated it was a: 142-990 with a 16 HP motor
dave:Rx.jpg

I will pull the flywheel off and make it right, Thank you so much for the help!!! :dancingbanana: :yelclap:

One conflict I have found in the manuals is the "Magneto" in the schematic when it was manufactured with points that year. Those kind of incongruences drive me nutz, makes me not trust the data.

Edited by Kentrails, August 06, 2012 - 07:38 PM.


#48 achomesteader OFFLINE  

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Posted August 07, 2012 - 05:14 AM

One conflict I have found in the manuals is the "Magneto" in the schematic when it was manufactured with points that year.


The term "Magneto" in the schematic is correct. A magneto consists of a coil/armature, a switch (either electronic or mechanical breaker points) and the flywheel magnet. In the Briggs Magnetron coil the electronic switch (transistor) is built in.

Hope this helps.

Edited by achomesteader, August 07, 2012 - 05:17 AM.

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#49 Canawler OFFLINE  

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Posted August 07, 2012 - 06:05 PM

That manual (142-990 with the 16 hp) is for an '82. The price of $0.75 agrees with their other manuals from that time frame.

MTD has manuals on their site for 990s up to '83-'84 but there's some question about whether they actually built them that late.

Edited by Canawler, August 07, 2012 - 06:07 PM.

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#50 AverageJoe OFFLINE  

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Posted August 07, 2012 - 07:10 PM

That manual (142-990 with the 16 hp) is for an '82. The price of $0.75 agrees with their other manuals from that time frame.

MTD has manuals on their site for 990s up to '83-'84 but there's some question about whether they actually built them that late.


I remember having that discussion, Jim. Seems like the leftover 82s got badged as 83/84. I would be curious to find one and see if the Briggs engine spec on an 84 model 990 is actually a 1982 engine.

#51 Kentrails OFFLINE  

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Posted August 07, 2012 - 07:11 PM

If any one needs that manual let me know or I can scan it and post it somewhere? Thanks for straightening that out for me, now I can be rid of it.

#52 HALFSCALE ONLINE  

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Posted August 07, 2012 - 10:27 PM

I know Jim [Canawler] and I have had this discussion many times, why mtd offered 990's to some of there chain store vendors when they were building the long frame twin cylinder tractors. Did they have that much in left over parts [ but we know the grille castings and fuel tanks are different ] or was price a factor?

#53 achomesteader OFFLINE  

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Posted August 08, 2012 - 04:47 AM

If any one needs that manual let me know or I can scan it and post it somewhere? Thanks for straightening that out for me, now I can be rid of it.


I would appreciate it, if you would scan it and upload it to the MTD manuals section of the site.

Edited by achomesteader, August 08, 2012 - 04:51 AM.


#54 Kentrails OFFLINE  

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Posted August 08, 2012 - 07:19 PM

I will scan it, and upload it.

I digress ...I was researching the techniques for removing the fly wheel, one mechanic told me to WHACK the nut with a 3lb. hammer, after backing it off slightly, at the same time pry the wheel from behind. Intuitively, I feel I should not do this. When I mentioned that I wanted the B&S tool #19203 wheel puller, and # 19433 strap wrench. they tell me that the wheel puller will crack the flywheel. When I mentioned the re-polarizing of the wheel for the mag, I get the furled brow, squinted eyes and a "I never heard of that"? Can all these mechanics be that out of touch, and what is the correct procedure for removing the fly wheel.
Unfortunately, I still do not have use of my right arm, so... the WHACKING with my non-dominant arm would be disapproved by OSHA
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#55 AverageJoe OFFLINE  

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Posted August 09, 2012 - 03:58 AM

Ken, if you consider this engine is older than most of the mechanics you're talking to, it's not much of a surprise they never heard of heard of the repolarization.

It can be tricky using a puller if the key is even slightly deformed in its passage. You may need to drill it out. Also, there is some merit in "gentle tapping" (but not whacking) the flywheel with a block of wood between the hammer and flywheel.

#56 achomesteader OFFLINE  

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Posted August 09, 2012 - 09:51 AM

When I mentioned the re-polarizing of the wheel for the mag, I get the furled brow, squinted eyes and a "I never heard of that"? Can all these mechanics be that out of touch, and what is the correct procedure for removing the fly wheel.


Now you can teach the mechanics. There certainly are a lot of them that just don't know about re-polarizing.

The correct procedure to remove the flywheel, according to Briggs, is to use the puller, but I've had to use the other method too.

#57 Kentrails OFFLINE  

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Posted August 16, 2012 - 12:55 PM

I removed the Fly-wheel without using my club :thumbs:, The key is steel, I understood it should be aluminium?
I am sending it off.

Attached Thumbnails

  • DSCF0001.JPG
  • DSCF0002.JPG


#58 Kentrails OFFLINE  

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Posted October 16, 2012 - 05:17 PM

The flywheel is on, I turned the key, the motor turned over, and then all the air went out of the magneto. PFFFFFT... and stuff came out. :wallbanging:

I need a new magnito, and a correct wiring schematic.

I was given the B&S part # 398811. Is there one place better than another to purchase this part, or is it proprietary?

Thank you all for your generous support :worshippy1:

Edited by Kentrails, October 16, 2012 - 05:22 PM.


#59 achomesteader OFFLINE  

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Posted October 16, 2012 - 05:37 PM

Found this one on ebay:

http://www.ebay.com/...=item231ffa7169
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#60 Kentrails OFFLINE  

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Posted October 16, 2012 - 06:18 PM

I ordered it. Delivery on the 20th.

Now I noticed there are two wires coming off of the pigtail, which clips on the coil. Where do they terminate, or is only one needed? I don't want to fry another, no more PFFFFFT!

I had one to ground and one to ign?

Thank you once again for the help!




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