Simple Motoplat Testing
Over the years I have seen a lot of test figures to do with testing Motoplat ignition stators and believe me they couldn’t be further away from the truth if they tried, some even go to say they can not be tested and repaired because they are not wire coils they are made up of electronic components. Here are a few simple pointers I can guarantee are correct for I have been testing, repairing these ignitions systems for 20 years.
The motor cycle ignition of which there are over 15 different types but only two different formats, the internal rotor which was purely motocross and the external rotor which had lighting and charging circuits. The internal rotor type of which there are two large Maico and Husky and small KTM. Testing the type for the 250 Maico and Husky, black and blue 3.5 ohms blue to stator body (earth) 600 to 660.For the 440, 490 and 500 black and blue 7 ohms blue to earth 600 to 660 ohms. The small type black to blue 3.5 blue to earth 580 620 ohms .
The external rotor type generally called a mini 6 there are three types of this stator mainly fitted to KTM and Husky. The type fitted to the Husky 500 with one yellow lighting lead, black and blue 17 to 20 blue to earth 300 to 345 ohms. KTM 250 with no light leads black and blue 4.6 blue to earth 385 to 400 ohms. KTM 125 with lighting black and blue 17 to 20 blue to earth 195 to 220.All the early mini 6 type had no ignition curve but the later type fitted to the last of the enduro KTM 125 had about 10 to 12 degrees.
The only way to tell these two apart is the early ones had the timing hole right at the edge of the stator the later one with the advance the timing hole is 5 to 6 mm in from the edge. These are the most common type of Motoplat ignition.
The larger type of mini 6 which were fitted to Bultaco, Montesa and Ossa some of these ran a diode in series to earth so to get an ohms reading is imposable, you can NOT get a proper ohms reading through a semi conductor, but if there is no diode fitted the readings should be black and blue 15 to 17 blue to earth 185 to 200.Another system widely used is the mini4 which was put on Bultacos again the diode was used but not on all stators. Black to blue 4 ohms if no diode is fitted blue to earth 150 to 160, this one type I can enhance the performance of. Another type of system which was fitted to the Beta TR32/33/34, this again runs diodes and resistors in its ignition circuit.
To test the trigger circuit put your meter on the diode setting test between black and blue then reverse you should get a semi conductor reading in both directions if it reads one way only the stator is bad.
Test from blue to earth you should get between 215 and 385 ohms. These test figures are just a few of what Motoplat produced, but I can give many more test figures if required and all so test and repair any motoplat system and HT coils.
This another subject where you find different test figures, basically test between the two spades the reading should be 30 to 33 ohms from the ht lead to the steel bracket 5.6 to 5.8 K ohms. There is talk about black and red leaded coils what will run what, when I talked earlier about diodes in circuit this is where it comes in, all the stators that ran diodes were early stators and ran with a red leaded coil, these red leaded coils will only run with a diode in the stator, but the black leaded coil will run either, but I have had red leaded coils run both as well so watch out.
If you need any other readings which are not mentioned or any other problem you my have just send me an e-mail.
Sherco & Beta REV 3 Triggers
This is another pair of ignitions that are fairly troublesome the main problem with these stators is the triggers pack in. The Rev3 there is no way of checking the triggers so if you test between red and brown the resistance of the charge coil should be 400 to 450 ohms.But the Sherco triggers are different,set your test meter on the diode setting put the black test lead to earth with the red lead test between blue brown black you should get a reading something like 0 – 1018- 1100.Reverse the leads and the reading should be something like 635- 661- 661 your readings might not be the same but should show the same pattern,all different meters have a different internal resistance.In each case I can repair either.