Author Topic: Maico 490 1981 Mega 2 - starting issues  (Read 3836 times)

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HeavenVMX

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Re: Maico 490 1981 Mega 2 - starting issues
« Reply #45 on: September 06, 2017, 05:17:48 PM »
I guess someone (I am not going back three pages) has told you that the motoplat system must have non resistor plug caps and non resistor plugs. The motoplat ignitions will not drive a resistor in the system unless in absolutely perfect and even then only just. The top HT ignition coil in the motoplat system have some of the electronics in them an SCR and one of the capacitors from memory.

The stators in motoplat system rarely die outright they just get weaker and weaker as more and more winding turns fail by shorting out. The first sign is poor starting followed by fouled plugs and finally they are hard to start even by pushing.

The HT coil however do fail outright. I assume you have the correct HT Coil (red plug lead). The points ignition HT coils looks almost the same but has a black HT lead.

The largest gap that a motoplat will jump under compression reliably is 0.6mm (0.024") which is much less than modern or period Japanese CDIs. Motoplats don't seem to like iridium plugs from my experience B7/8/9EGV all the way. Gapped at 0.56mm B8EGV plugs last all year.

Attaching a wire directly from the stator backing plate and earth bracket of the HT coil is an excellent idea. All my Motoplat systems (5 off) have that as a permanent fixture.

As mentioned the flywheel and stator must match (there are dozens and dozens of versions including clockwise and counter clockwise rotation). They do not mix as it throws the timing out significantly as pointed out.

This is a long shot but I have seen the wires attached to the HT coil reversed this happens when people cut wires etc. The two spades on the HT LV side are different sizes but it could be wired up incorrectly. This means the charging wired cooks the trigger circuit in the HT coil. This may account for now having two dead bikes.

Pack the whole lot up and send them to Small Coil Rewinds (Vic) or Betta Bikes (SA) who will test them in real time as a complete system. They can also rewind stators or remagnetise flywheels etc. PVL make a replacement HT coil although I have never tried one. There are NOS HT coils on EBay US sometimes usually as Harley Davision parts (from the Italian Harleys).
« Last Edit: September 06, 2017, 09:33:17 PM by HeavenVMX »

Offline peely_14

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Re: Maico 490 1981 Mega 2 - starting issues
« Reply #46 on: September 27, 2017, 01:48:11 PM »
Hi guys, I finally have some good news!

The reason for old mans bike not running was a faulty kill switch.

My bike: We conducted a series of bench tests on my ignition system and discovered results were all within the limits and were therefore confident that ignition shouldn't be a player and running out of ideas convinced that timing must have been responsible. Matching the timing as per the book proved to be insufficient for a start (showed no signs of life), along with matching the old mans setup. Instead we advanced it as much as we could so we had kickbacks, then retarded until no kick backs until BANG she was alive first kick. All I need to do now is service my bing carby.

Now with the enduro season over, I can have time to run her in and get her ready to rock n roll for next season. Thank you once again to everyone that has helped me along the way sharing years of wisdom.

Regards Peely_14

Offline tony27

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Re: Maico 490 1981 Mega 2 - starting issues
« Reply #47 on: September 27, 2017, 05:39:13 PM »
Are you saying the timing marks were out?

Offline peely_14

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Re: Maico 490 1981 Mega 2 - starting issues
« Reply #48 on: September 28, 2017, 11:39:27 PM »
Yeah tony27 timing marks are out. Started 2nd kick today and rode well for 10minutes. After parking it up to make some adjustments to brakes etc she didn't want to start again haha.