Found substitute for TCI Ignition Coils

[pauln]

I found these TCI Coils on Ebay for a Yamaha MZ360 generator engine and they looked close enough in the photo that I thought I would take a chance on them for my YT6700 ($20 each plus $11 shipping):

http://www.ebay.com/itm/YAMAHA-MZ360-Engine-Replacement-Ignition-Coil-TCI-Unit-7WG-85640-00-00-/181756114171



They work FINE!  There is a "catch" - you will need to file/grind out the coil slots more toward the flywheel side in order for them to fit with enough clearance.  The hole width is fine, it is just that the length needs to be longer on the flywheel side.  I used a rat tail file, but a Dremel with a cutter/grinder would be a lot faster (I did not have these for my Dremel).  You don't have to remove much, but the steel plates that are riveted together are about 1/2" thick, so it took me around an hour total of filing to get both where they would fit.

Here is a pic of one of my original JE8-85630-00-00 (on the left) along with one of the Ebay ones:



Here is a pic of one of the new coils where I lengthened the slots (on the left) along with an unmodified one:



Hope this helps keep some of these old Yamahas going

I know some people have used the 7LY-85640-01-00 as a direct replacement of the JE8-85630-00-00 with no modifications needed, but man, these things go for $150+ each.  The Ebay ones I bought are obviously not Yamaha OEM (most likely from China), but for $51 total and an hour of filing, they fit the bill for me.

The coil wires on my Ebay coils are shorter than my originals.  However, unless you are set on routing them the same as the originals, they are plenty long enough to go on the plugs.  I had to do away with those rubber covers on the original plug wires that slot into the plastic engine cover - I don't think they matter, but I may put some duct tape over the openings just in case those were needed to make the cooling work properly.  I mowed with the new coils and the plug wire slots open for about an hour last night and everything seemed fine.

My ignition coils went bad gradually, actually over a number of years.  First it was hard starting, then fouling plugs, then finally only running on one cylinder.   I actually let it sit in the garage unused for a couple of years.  I was going to set it out front and sell it for a few dollars, but I thought instead I would give it one more try to figure out what was wrong - glad I did!

One question - does anyone have the actual spec for the air gap between the coils and the flywheel?  I used an index card that measures out to about .007" and that seems fine, but it would be nice to know what Yamaha recommends so I could set them exactly.

Thanks to whoever started this forum so that we have a place to share info about these "dinosaurs".  It has helped me a lot.

Paul from Ohio

[Jeff S]

Nice fix!

I was looking for a replacement for 1 of mine last year. Now I'm probably gonna get 2 of these for spares! Lol

Like you, I knew there had to be a cheap $20 coil that would work, I just didnt have time and went $$$ Yamaha.

[Tommy Jordan]

 Thanks for taking the time to post this! Maby we can keep these Mowers going a few more years.

[rattosh51]

Great find Paul, have been looking for something that would be close for a long time.

[dmiller90]

Great Find.  I have the Service Manual, but it does not indicate the Air Gap for the coils.  Does anyone know the correct gap?

Thanks.

[pauln]

Thanks everyone for the nice comments.  I did not think I would be able to find any substitutes for the TCI coils.  But, I took some time searching and found the Ebay ones and they LOOKED very similar.  It wasn't until I got them and tried mounting them that I found they were basically identical except for the slot length.  Even the curve of the coil against the flywheel is the same (which must mean they are for the same size flywheel).  Then, when I cranked the engine it turned about two rolls and fired right up and ran perfectly - I knew these coils would work.  I guess the only question is how long will they last?  No telling, but the same can be said for any coils, even Yamaha OEM.

It took me a while to understand how these operate.  The last time I messed with lawn mower ignition coils they had breaker points to trigger them!  I originally thought the connector on the Yamaha coils must go to some sort of electronic breaker maybe under the flywheel.  But, the wiring diagram shows that that connector is open when the ignition is on and goes to ground when the ignition is off (to shut off the coils).  So, the TCI part must mean there is a transistor inside the coil itself that opens the primary winding when the voltage gets to a certain level to induce a high voltage in the secondary winding and make the spark.  I guess you do learn something new every day

As far as the air gap goes, as I indicated I used an index card that I measured at about .007" and pushed the coil up against that and the flywheel and tightened it up.  So, .007" seems to be working fine.  I was just curious if Yamaha had a spec.

I like to try to share info if it will help others out.  These are interesting mowers and I would like to keep mine running as long as possible.  They have lots of attention to detail (the low fuel light being one example) and they make a good conversation piece (neighbor: "I didn't know Yamaha made lawn mowers").  I bought it brand new in early 1994 ($2,000) and I know it has a lot of life left in it.  I have a J.D. zero turn as my main mower, but the Yamaha makes a good backup and trailer-tower.  For 10 years the Yamaha was our only mower (other than push mowers) for our 2 acres.

[cr250]

Just use a business card for the air gap,

[rattosh51]

Agree with cr250-the business card gap is a basic measurement for all lawn mower coil gaps.
Paul--you are correct on how the point-less coils work...got rid of one of the biggest pains in the ignition system!
You are one of the few original owners around.
Welcome to the Forum, and glad you contributed!

[dmiller90]

Spoke with a Lawn Mower repair Shop and this is what they advised me.  

The gap should be between .006 and .010 if it has aluminum cylinders.
The gap should be between .010 and .014 if it has cast iron cylinders.

I am not sure if the YT6800 has aluminum or cast iron.  Thoughts?

[Jerry]

Thanks for your info.  

It worked great on my YT6700 tractor. I picked it up last fall for $200. Excellent condition.
It ran fine till under load, then seemed to have no power.  One cylinder only working part time.

 Nice tractor, I like it better than my almost new Cub Cadet.  

The plug wires were fine for me, I used the original spark plug cap, the spark plug caps unscrew from the wire, and the rubber grommet works in the original slot in the plastic cover.  took about 5 minutes with a 7/32 chain saw file to lengthen the slots.

Great Find!

[pauln]

Jerry wrote

The plug wires were fine for me, I used the original spark plug cap, the spark plug caps unscrew from the wire, and the rubber grommet works in the original slot in the plastic cover.  took about 5 minutes with a 7/32 chain saw file to lengthen the slots.

Jerry, glad the coils worked out.  I never thought about taking the plug caps off to be able to slide the rubber grommets on - duh.  Good thinking   I was sort-of in a hurry when I did mine because I wanted to see if the coils would work - the only file I had was an old, dull one that was too small, which is why it took me so long to file them out.  Glad to hear that it is not a big deal if you have a good file.

Paul from Ohio

[dmiller90]

Was able to get a Actual Yamaha Manual.  I have enclosed a pic of  Manual that gives the TCI (coil) air Gap Settings.  Sorry for the horrible pic.

[pauln]

dmiller90, thanks for the information about the coil air gap.  Wow, 016" to .024" seems like a pretty large gap, but Yamaha should know what the specs should be - lol.  Mine are set to about .007" and have been working fine.  I might try to set them to the correct specs after the mowing season is over and see if it changes anything about how it runs.  Right now I want to leave well-enough alone   Thanks again for posting up the manual page.

[dmiller90]

Yes I thought the same thing with the gap being so large.  I changed mine to the manual specs, and seems fine.  I think it actually has something to do with the advanced/retard of the timing.  

[Jerry]

Another one on Ebay, may not need filing?  Looks like the arms are a little shorter.

YAMAHA MZ175 Engine Replacement Ignition Coil TCI Unit 7NJ-85640-00-00

http://www.ebay.com/itm/YAMAHA-MZ175-Engine-Replacement-Ignition-Coil-TCI-Unit-7NJ-85640-00-00/161744087014?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D32474%26meid%3Dbdbda9a69eba479ab24bb751a29c3d4d%26pid%3D100011%26rk%3D2%26rkt%3D2%26sd%3D181756114171

[pauln]

Jerry, thanks  Yes, I saw the MZ175 coils when I was looking.  I just picked the MZ360 coils because they looked similar to the OEM - the MZ175 ones might be a better fit.  That ebay site has coils for other Yamaha engines as well (although the pictures all look like either the MZ175 or MZ360 coils).  The problem is we have to "buy-em and try-em" to see if they will work.

The mowing season is about over and my MZ360 coils are still working fine (although I probably only put about 30 hours on my YT6700 since I put the coils on it).

[Playfair]

I just installed an MZ175 coil because it was cheaper than the other now, and though not exactly like the OEM, it fits with no mods set to the correct gap.

[rattosh51]

Nice to have that confirmed...Thanks

[gsxrhayabusa]

I can second that these coils work great on my 6800. The plug wires are a little shorter than OEM but still long enough to work.  Thanks a million for the Information!

[Ytee5700]

I also installed the MZ 175 coils, and they work fine after a bit of head scratching.  I originally had the right coil go gradually, so I ordered a replacement. I replaced the right coil, and it ran better, not great. It would miss on start up, and tend to miss after restarting hot for about 10 mins.,  so thinking I had a left coil breaking down also, I ordered and replaced the left side a few weeks latter. It did not change the problem. Finally the other day I took a close look at things, and changed coils side to side, installed correct new spark plugs, with no change in performance. The right coil spark appeared slightly weaker than the left.I made sure the coil air gaps where identical. What I had done wrong was I installed the right coil in the wrong direction, thus, the induced voltage was not as great as it should have been, creating my built in performance issue. Starts & runs great now.