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Mtd 990 Timing Issues After Changing To Electronic Coil


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#1 Jweavsfarm OFFLINE  

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Posted November 16, 2014 - 06:05 PM

I have a 1976 Mtd that has a 16 hp Briggs in it. It started to act up we it was hot and under load and the local shop told me to try a new electronic coil. When I can get it running it runs great but it is very hard to get running and it kicks back severly. So severly that is has now started sheering the key on the flywheel.

Does anyone have any experience with this issue? I am ready to either get this thing fixed or be done with it and do something different, it is totally redone and has a mower and blade with it so I hate to give up quite yet.

Any help would be appreciated. One thing I thought I would try was offset keys to get the timing right.

Thanks in advance.
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#2 glgrumpy ONLINE  

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Posted November 16, 2014 - 06:39 PM

Not sharp on these, but this is what I heard.  The new magnetos haver reversed polarity and want to make the spark with magnets reversed in the flywheels. Don't think you can change them on flywheel, needs diff one to have reversed polarity. It is setting up spark early then with standard flywheel and it fires before getting to Top Dead Center, or backfires then. I was told to mount the coil reversed from stock original and would be OK.  I didn't try that, not sure if room there to do it even. Looking for a coil w/out electronic may be the answer. They used to make a kit to make your old coil an electronic pick-up one that has gizmo to attach to old coil at a mounting bolt and think that eliminates the points then? Might try to find one of those. I have found most times the area where coil mounts, or the ground screws/wires and the back of points carrier all have to be cleaned off bare and get better ground to make the old parts work.


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#3 superaben OFFLINE  

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Posted November 16, 2014 - 07:59 PM

A couple thoughts here. 

 

By electric coil, I assume you mean an automotive distributor type coil. 

 

I think you are using the wrong condenser.  If you are using the Briggs condenser that was on the tractor, it it setup to handle the old magneto voltage, not the voltage you have now. 

 

Buy a Kohler condenser for battery ignition, Kohler part number 230722 ($6.50 if you want to buy from me) and you will probably solve your problem.  A condenser has to be matched to your coil, otherwise you are shooting yourself in the foot. 

 

If you already are using a different condenser than the original setup, then you might try putting in a hotter spark plug (if you are using the original grade plugs) or convert to the right spark plug (J8C was the original). 

 

You might try replacing the spark plug wire, if you used the old one and put a new end on it.

 

Ben W.


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#4 Sawdust OFFLINE  

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Posted November 16, 2014 - 08:09 PM

Welcome to GTtalk glad to have you aboard. I recently converted my 990 to a Nova II electronic module. I have a 1976 as well. This conversion was very easy. It eliminates the points & condenser. It only took a few minutes to install. It only cranked a couple turns & I had a loud cracking blue spark. I highly recommend. Here is my thread, go down to post #70 to see what I done. In case no one has told you we thrive on pics so don't be shy & don't be a stranger.  :D

http://gardentractor...-mtd-990/page-5

 

Here is the module I bought

http://www.ebay.com/...=item3a66b36755


Edited by Sawdust, November 16, 2014 - 08:11 PM.

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#5 EricFromPa ONLINE  

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Posted November 16, 2014 - 09:20 PM

1st off How many Magnets are on the Flywheel? If it's a 3 magnet flywheel you can Not use a newer style Electronic ignition coil and you can Not use a Nova 2 Ignition Module.

 

Using a 3 magnet flywheel with a Newer Electronic Ignition Module or Magneto will not work.It will start but the timing is WAY to far advancd.It will strip the Starter gear,Shear the flywheel key and will run extremely Hot if run for any length of time.It will burn the valves and cook the rings and possibly burn a hole in the top of the piston.

 

You will either have to Put the Points back on and use the Old style Magneto Or Get another Flywheel with 1 Magnet.

 

Some single Magnet Flywheels are Also Reversed Polarity and you can run into troubles with that also.

 

 

Can you take a Picture of your Flywheel with the New coil Installed?

 

 

 

A briggs Coil will fire if it's on upside down BTW but the timing will be Way off.And if you touch the engine it will shock the crap out of you.Don't ask how I know. :rolling:


Edited by EricFromPa, November 16, 2014 - 09:21 PM.

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#6 Sawdust OFFLINE  

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Posted November 16, 2014 - 10:51 PM

1st off How many Magnets are on the Flywheel? If it's a 3 magnet flywheel you can Not use a newer style Electronic ignition coil and you can Not use a Nova 2 Ignition Module.

 

Using a 3 magnet flywheel with a Newer Electronic Ignition Module or Magneto will not work.It will start but the timing is WAY to far advancd.It will strip the Starter gear,Shear the flywheel key and will run extremely Hot if run for any length of time.It will burn the valves and cook the rings and possibly burn a hole in the top of the piston.

 

You will either have to Put the Points back on and use the Old style Magneto Or Get another Flywheel with 1 Magnet.

 

Some single Magnet Flywheels are Also Reversed Polarity and you can run into troubles with that also.

 

 

Can you take a Picture of your Flywheel with the New coil Installed?

 

 

 

A briggs Coil will fire if it's on upside down BTW but the timing will be Way off.And if you touch the engine it will shock the crap out of you.Don't ask how I know. :rolling:

He stated he had a 1976 shouldn't this only be a two legged coil in which the electronic ignition would work flawlessly like mine. Wasn't the three legged coil along with the three magnet flywheel introduced in the early 80's ? I agree we need pics  :thumbs:



#7 EricFromPa ONLINE  

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Posted November 17, 2014 - 02:15 AM

It's 2 Legged COIL but it May have 3 Magnets on the Flywheel.

 

My MTD Fourteen Hundred And the spare engine that I took off of a rusted apart MTD Fifteen Hundred have 3 magnet Flywheels with 2 Pole Magnetos.1 Strong magnet and 2 weaker smaller magnets.Both are older 4 speed Peerless Gear drive tractors.Both of my big 1976 Gilson 16 Hydro GTs have Single Magnet Flywheels but my slightly newer 1979 Gilson 16 Twin cylinder Hydro has a 3 magnet flywheel.

 

Briggs flywheels came with 1,2 and 3 magnets depending on date code and some times just availability of parts.

 

 

Here's some flywheel Pics for reference only.They are not all 16hp flywheels.

 

$_57.JPG $T2eC16FHJIQE9qUHri6NBQdN9GHv4!~~60_57.JPG 57.JPG

 

 

I'm betting that the Coil is upside down though.That's why I asked for a Pic of his Flywheel with the Coil installed.

 

Alot of the newer $9-$25 Stens Electronic ignition coils that I've ordered have the Ground wire on the Opposite side.Makes it look like it should be installed the way you took the other 1 off but in fact it will be on upside down.I made that mistake myself once or twice with these new Made in Taiwan,China,Korea ect. ect. Coils.

 

Last one I made this mistake on was on my Bolens G11.I did the conversion on it pretty recently.Another Stens Coil with the kill wire on the wrong side,this one was made in Malaysia.

 

All of Stens parts are Cheap aftermarket stuff that's made overseas somewhere.They work but they are cheaply made and in most cases are not identical to any original part.  


Edited by EricFromPa, November 17, 2014 - 02:22 AM.

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#8 EricFromPa ONLINE  

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Posted November 17, 2014 - 02:27 AM

If it's on upside down it will have strong spark through the Plug but very erratic and Way to advanced for it to run correctly.



#9 Sawdust OFFLINE  

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Posted November 17, 2014 - 02:28 AM

Sure are a lot of different combinations. Now I'm thinking the same thing coil backwards which like you said is easy to do. Waiting on pics  :tapping_fingers:



#10 MNGB ONLINE  

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Posted November 29, 2014 - 01:17 PM

Hi, is this a 32XXX series cast iron B&S? An what kind of electronic coil did you install was it a B&S magnetron? If the answer to these two questions is yes it will not work you'll get the results that are indicated, on the cast iron  engines the magnets have reverse polarity vs the newer engines, if you want to go thur the trouble you can remove the flywheel and send it to B&S and they'll change the polarity,  The simplist easy way to correct the ignition problem is to convert it to battery ignition this simple, the points and condenser are needed and a 12 V automotive coil  you may or may not have to replace the ignition switch, the ignition wire on the present switch will not work. I've done this to a number of the B&S engine and they start and run beter the coil I use is a Wells LU800 it is a 12 v coil no need for any resistors.  


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#11 VTXrider ONLINE  

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Posted December 01, 2014 - 07:38 AM

Hi, is this a 32XXX series cast iron B&S? An what kind of electronic coil did you install was it a B&S magnetron? If the answer to these two questions is yes it will not work you'll get the results that are indicated, on the cast iron  engines the magnets have reverse polarity vs the newer engines, if you want to go thur the trouble you can remove the flywheel and send it to B&S and they'll change the polarity,  The simplist easy way to correct the ignition problem is to convert it to battery ignition this simple, the points and condenser are needed and a 12 V automotive coil  you may or may not have to replace the ignition switch, the ignition wire on the present switch will not work. I've done this to a number of the B&S engine and they start and run beter the coil I use is a Wells LU800 it is a 12 v coil no need for any resistors.  

Can you go into a little more detail how you converted to the coil ignition? I have a 16hp BS 32xxx I would like to convert.



#12 Sawdust OFFLINE  

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Posted December 01, 2014 - 12:24 PM

Here is an article that may help...sounds logical & an easy install. Go down to where it talks about coils.

http://gardentractor...om/ignition.htm


Edited by Sawdust, December 01, 2014 - 12:24 PM.

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#13 MNGB ONLINE  

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Posted December 01, 2014 - 01:12 PM

Hi VTXrider, starting from the panel you'll need a 12 V source then a switch (which will the ignition switch)  the switch will be wired on terminal to 12 VDC Can be directly from the battery the other terminal wire will go to the auto coil connect to the + terminal of the coil the - terminal is wired to the points & condenser. the wire coming from the B&S coil can be cut and connected ti the coil - wire or removed and the - coil wire connect directly to the points the mag kill wire is cut/disconnected and removed. Now you just need a spark plug wire from the coil tower to the spark plug and it should be done. Ok the dinner bell rang and I forgot about mounting the coil, I mount it on the blower housing make a simple bracket and screw it on.

If you don't want a separate ignition switch what is needed is a switch that has a terminal that when the key is turned to on there is 12 VDC on that remains on (12 V) when the key is turned to the start position most mag switch will have a terminal for lights but they go off when in the starter position so that will not work.

HPIM1121.JPG HPIM1122.JPG HPIM1124.JPG


Edited by MNGB, December 01, 2014 - 02:03 PM.

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