wanted jdm-74 TESTER

[JDT]

My guess is the Skiroule tester is a different version of the JD tester.

I also assume the stimultor/simulator is used to test the external coils by suppiling a pulse to check for spark at the plug.
120 volts is more than enough. I typically use a 9v battery for such a test.

The tester Rob is sending me appears to have just four fixed switch positions while the JD one has a pot.
I bet there are internal resistors on the switch to match the settings with the pot model.

Will find that out when I get my hands on it.
Obviouly these things did work or they would have not been offered to all these different sled manufactors.

[JDT]

Greg thanks for checking the harness.

I still would like to get a copy or scan of the instructions that JD had with their tester.

[TOYMECH]

Todd,

If you want, i can wander over to the neighbor's place with it. He is an electronics engineer and is well versed with that sort of thing. I can open it up and he can have a look at the gizzards of the JDM-74 and identify all the pieces for you.
I will take a look in my library of JD shop manuals and training books - somewhere in there, i remember where the simulator was used for testing. Offhand, i think it was for Cyclone and early Liquifire models...

What Rob is sending you used to be available from Mercury Marine as well. Merc-O-Tronic is still around:

http://www.mercotronic.com/mercotronics.php

THE best test instrument for ignition systems in the small engine and marine field was the old Model 98. It put ignition coils to the TRUE test. It was not for testing CDI however:

http://www.ebay.com/itm/MERC-O-TRONIC-C ... 1157721062


Greg

[harleysportster]

Greg thanks for checking the harness.

I still would like to get a copy or scan of the instructions that JD had with their tester.

There are instructions in the 76-78 Cyclone/Liquifire service manual.

[JDT]

That Ole 98 looks pretty cool.

Does it go back to the late 50's?

[TOYMECH]

Todd,

I'm not too sure how far they date back to be honest with you. I know that they were available up until not that long ago (10 years ago or so). I used one when i worked as a marine mechanic at a Merc dealer in the 80's and then when i was teaching small engine and marine mechanics at a local community college back in the early 90's we bought one new from Mercury Marine. They're a great tool to have in the shop to sniff out suspected ignition coil problems as they will put the coil right on it's knees as far as load. If the coil has a problem with external voltage leakage or low secondary voltage output due to an internal short, it will show up for sure. They are deadly accurate. I'm actually keeping 1/2 an eye peeled for one as they are very reliable when sniffing out a problem.

I had a look at my Cyclone and Liquifire shop manual and found in section 40, Page 10-3 (page 119 on link to .pdf file below), a more detailed description of the JDM-74 tester and it's accessories. Seems the simulator is only used to determine whether or not the test equipment including the batteries are funtioning correctly:

http://www.vintagesnow.com/John_Deere_f ... one_SM.pdf

Greg

[JDT]

Thank you for that link Greg.

[TOYMECH]

Hey, not a problem, Todd!

[tieszo6]

Could someone post a picture or diagram of the test harness called out in the test procedure?

Thanks
Mark

[JDGuy]

Tieszo6: Here are some pics, hope it helps. I bought this from a JD dealer a few years ago. He had not used any of it for years, but when he learned I was interested, his obsolete stuff became gold plated!!

[JDGuy]

JDM-74-6 was missing, so I made my own from shop manual info, 80/84LF. It worked. See above post

[JDGuy]

Testing the Tester instructions via Kawasaki manual. See above. This is everything I have. Hope it helps.

[tieszo6]

Thanks for all the info. Is there anything special about the JDM-74-6 harness or is it really just two wires?

Mark

[JDGuy]

2 wires

[jdrob]

Well an update to my search ! Ask and ye shall receive. A HUGE thank you to a fellow member here on the site He found me a testor on ebay for a downright "STEAL OF A DEAL" He could have easily said nothing to me and bought it for himself and re-sold it for a profit, but he called me and gave me the heads up on it ! You never know what and where your gonna find something listed on EBAY. We'll just keep it at that ! My Hats off to John from NY this is a "GOOD GUY ALERT" thank you So very much !