coil for ace 90

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any ideas on where to find coil for ace 90? she was up and running great for couple weeks then lost spark,ordered and replaced condenser,points good. is there way to test coil? Thanks in advance. just got title and plates and itching to ride

[rlkarren]

Bruce Young at hodakaparts.com is your best and probably only source.

Test for continuity and ground to make sure your coil has gone bad. Instructions are in the manual.

Roger

[Zyx]

+1. Verify function before ordering a new coil as they are not quite cheap these days. Also consider that the coil may be good, but the spark plug lead may not be. There is a tech article on the SH website regarding replacing the spark lead through minor surgery that anyone with a Dremel can do, should that be your problem. Don't forget to check your spark plug to make sure it is not just fouled. Check ground connections to make sure they are not corroded. Verify that the points are good by isolating the points from the condenser (or take them off the biker) and checking continuity/resistance across the contacts. When the points are clean and closed, resistance should be at or near zero. If they read high, sand them clean with 220 W/D paper and try again. Check your condenser even if it is new, for capacitance which should be 0.25 to 0.27 Mf, plus or minus 10%. I don't believe the battery has anything to do with the ignition, but check it anyway unless you are running without lights and have removed it.

Check the inside surface of the flywheel, where it runs in close proximity to the lighting and primary coils to be sure there is no metal to metal contact, and no rust. I like to clean these surfaces with 220 W/D paper just for the heck of it. If the mounting screws for the coils inside the flywheel are tight, I would not expect them to have moved and changed electrical output, but check anyway. If you find evidence of contact between the flywheel magnets and the coil cores, find out why. It could be worn out crank bearings letting the crankshaft wobble.

There is a stated test regimen for ignition coil on the Ace 90 in the manual. While not difficult at all, if you have never done it, it might be confusing at first. The idea is to supply voltage from the battery to the points rather than from the spinning magneto, to see of you get a spark. If you do, the condenser and points are more or less good, and the problem may be elsewhere. The concept is simple, but you will want to read the instructions more than once. If you don't have a shop manual (as opposed to the owners manual), you might want to get one.

Data for the coil and condenser:

Coil - Primary resistance 0.08 ohm (black coil input lead to ground); secondary resistance 4.8K ohm (spark plug lead to ground).

Hope this helps

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thank you as any and all info helpful.Bruce,Paul have been so much help all the way thru this project as been everyone here. still no spark,points new, condensor new and installed used coil that bench tested little weak but thought mite work but didn't. have checked ign switch and grounds and still nothing.sure would like find new coil but no luck yet. Az Shorty see your in Prescott,I'm in Peoria so if I can ever get this thing running again maybe we can get bikes together for ride.

[Zyx]

Just spoke with Bruce, who told me about your issue with the early 90. The idea was posed that perhaps later 90 or Ace 100 system would cross-fit your bike. I have never seen an Ace 90 up close so I don't know, but I do have a running Ace 100B lighting and ignition system from backing plate to spark plug if you want to compare parts side by side. They are at least dimensionally similar. If the newer parts will fit on the old case and crankshaft, perhaps you could upgrade.

Do you have a multi-meter to use to check your coil? On your bike, the ignition coil is under the magneto, making it harder to get to to test, but once the flywheel is off, you should be able to test it for function, either by doing a resistance check on both primary and secondary windings, or by providing DC power in lieu of the spinning magneto to see if you can raise a spark. I have the explanation for an isolation check on the early coil system if you need instructions to follow. Or, I can pull the electrics off my 100B engine, which I am not using, and you can see if they fit. Perhaps someone out there already knows if the newer parts will retro-fit the early 90.

[rlkarren]

The Ace 100 ignition will fit. However, there are no coil mounting tabs under the tank on an Ace 90 frame. You'll have to get creative. Also, unless it's an early Ace 100 Stator, you'll probably have to replace/modify the keyswitch and harness too

but.. the Ace 90 Manual explains how to test the ignition coil, primary and secondary windings, without removing the flywheel. I don't recall exactly, but I think you test through the black and HT leads to the blue wire.

Let's back up a little... In order to isolate an ignition problem unplug ALL the wires coming from the stator and test for spark. ( On an Ace 90, the key switch is nothing more than a glorified kill switch. Disconnecting those wires isolates the problem specifically to your stator). If you get spark, your problem is that the black wire is grounding at or near the key switch. If you get no spark, the problem exists in your stator assembly.

Since you lost spark and then replaced the condenser, the coil is suspect. But I would carefully inspect your solder joint on the condenser and make sure points are clean and correctly gapped at .013", when the marks line up at 11 O'Clock. Then check for proper operation. Make sure the points actually are opening and closing at the appropriate time. Then make sure the air gap between coil ends and flywheel are .010" You can do all this without removing the flywheel, observing and adjusting through the holes.

Test coil for grounding and continuity. You can still do this without removing the flywheel. The Manual is very good at explaining how to do this.

Make sure your spark plug cap is still good and has good connection to the plug wire. The newer caps have resistors in them that can go bad.

If you have to remove the flywheel, inspect the plastic cog, (the part the rests in the flywheel cam), on the points to make sure it hasn't worn away or broken off, and then clean ALL the contact points for everything; every wire connection, every screw connection, everything, etc. Test for continuity in all the wires and through their connections to other wires. Test for spark again.

I am of the opinion that the Ace 90 coil takes quite a beating before it will go bad. I would approach this as if the coil was good and make sure everything else is in perfect working order before removing/replacing the coil. If you haven't run this bike for awhile and it suddenly stopped getting spark, I would bet it's more likely a bad connection somewhere rather than the coil itself. All of this I've mentioned so far can be done in less than an hour. Time well spent, and very easy to do with the potential to save you lots more time and money.

I apologize for the long post, but ignitions can be extremely frustrating and expensive.

Roger

Here's a tip: If your HT lead is broken, you can replace the high tension lead much easier than for the Ace 100 and later coils. Carefully peel back the varnish impregnated gauze until you reveal the solder joint between the windings and HT lead. Simply solder on a new solid core plug wire, and re-wrap. Black cloth electrical tape or similar will probably work best. The plastic stuff will come off due to heat.

[taber hodaka]

Ace 90 coils were fragile. Ace 100, 100'A and 100'B coils will work and can be mounted under the gas tank. For the ignition coil air gap "between the coil and flywheel" I loosen the screws and bring the coils into center as much as I can and tighten the screws I have never had any problem doing this. Having worked on many of the early ace 90 I would only use the internal early coil in a restoration. I would not trust it out on a long in the hills country ride. It does not like water or moisture at all.. The test in the ace 90 shop manual page 46 Test #4 is the one I use. If you still have a spark problem you can call.---------------- Clarence

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thanks guys so much for everything,i just sent reply but seemed to disappear so if you see a repeat ..... Bruce sending another coil as last one had good secondary of 4800 +/ - but primary was less than .8 tried anyway but no luck,org was dead when tested.yes this has been frustrating.will go back thru all connections and hope to have coil by end of week.i have read each one of your posts over and over and am gaining valuable info with each, thanks again.will update as gain parts.

Larry

Az Shorty,thanks for offer on being able to try 100 parts for fit.Bruce suggested you as valuable asset and bonus we live within couple hours so may indeed hit you up for another set of eyes.

[Zyx]

The early Ace 90 primary coil resistance is 0.08 ohm. Did you see less than 0.8 or less than 0.08?

[[email protected]]

yea....don't remember,work at HD Dealership and had one of techs check. will find out tomorrow

[Bullfrog]

8/100ths of an ohm??? Would you mind double checking that specification? It just seems sufficiently close enough to zero that common volt/ohm meters of the day back in the '60's probably couldn't distinguish between zero and .08 ohms. (of course I could be wrong about that)

Ed

[RichardMott]

My records show that the Ace 100 High-tension coil - primary windings .75 ohms,
Secondary windings 4.8K ohm, the primary exciting coil (down at the
Magneto) should be .6 ohm.
Had this in my files for a while. I think I saved them because I bought a coil on ebay and wanted to be sure it was good. The coil in on my WomAce since 2009. Works!

[Bullfrog]

That sounds more reasonable to me - .75 ohms (very near to 8/10ths of an ohm).

Ed

[Zyx]

8/100ths of an ohm??? Would you mind double checking that specification? It just seems sufficiently close enough to zero that common volt/ohm meters of the day back in the '60's probably couldn't distinguish between zero and .08 ohms. (of course I could be wrong about that)

That's what the book says. Don't have 90 coil in hand to verify, and yes it is very close to no resistance. If someone has an original Ace 90 shop manual, perhaps they can take a look. If the primary coil in the Ace 90 doesn't have a whole lot of windings, or if the wire is stout, I suppose it could be very low resistance. All it has to do is create a large enough magnetic field to induce the larger coil to fire. It is possible to make an electromagnet with just a few windings of wire, and resistance is a function of both length and gauge of wire, so if the windings are not spider web thin and the total length is not so very long, it could be 0.08 and still create the needed magnetic field. Anyway, I just go by the book until it is proved wrong. The reason I asked is that if the original measurement was in the 0.08 ohm range, that is not necessarily a bad coil, and I suspect the problem is elsewhere. From what I am hearing the Ace 90 was not known for a killer spark, so why not 0.08?

Also noted as mentioned that the Ace 100 primary was 0.75 ohm, as was the 100B with the earlier coil (part No. 923008). The later 100 coil (923008A) was completely different, having 1.6 ohms primary and 5,000 secondary, whereas the earlier 100MX had only 0.42 ohm primary resistance, but had higher secondary resistance at 5,300 ohm. There is no real consistency between systems. Seems that as time passed and perhaps as suppliers changed and research progressed, values for the ignition went through changes. But they all worked. One is not necessarily better than the other as long as the parts are reasonably matched. The lower compression and lower top rev limit on the earlier, smaller engines would not have demanded an ultra hot spark, as might a Super Combat turning around 10,000 rpm, so drawing comparisons is a relative sort of thing.

[Dale]

Ace 90 Primary .8 ohms per Workshop Manual.

[taber hodaka]

page47 and150---------------Clarence

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good news is I have spark and believe me its because of you guys.This is where it gets embarrassing,ended up going back to original coil since it read .2 not .8 but as reading posts see very little resistance is needed. replacement coil received and installed must have broken wire as jumped all over as trying to get reading.i think must have overheated new condenser as installing as had pulled black wire from mag and had nothing,put another new in and back to org coil and from post saw to unhook all wires from mag, low and behold spark.more than likely it was bad ign switch the whole time.I took the long way around on this one. Thank you all !! by gleaning info from all your posts I got here in the land of spark.

[Zyx]

Now all you have to do is learn how to rewind coils.

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