Author Topic: Maico 490 1981 Mega 2 - starting issues  (Read 4268 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.

Offline peely_14

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Re: Maico 490 1981 Mega 2 - starting issues
« Reply #49 on: November 28, 2017, 10:52:18 PM »
Hey guys,

Sorry to be back here asking more questions but I feel im getting closer to resolving the problem.

Last friday I attempted to start my bike after having to replace the kickstarter shaft after it snapped. On the 3rd kick she was alive. I kept it alive for 5mins, before deciding it's time to take it out to finally run it in. I turned her off and immediately attempted to start again, on the 2nd/3rd kick she was alive again. Loaded her up and took her out bush. Started 3rd/4th kick and rode for 5mins before having to turn her off and make some adjustments to brakes. Started once again after 6 kicks and rode on stop for 40mins. She ran superbly, every now and then she would bog down a little but never stalled. The old man decided to stall it and that was it day was done, she would not kick
Over again. I put a timing light on plug lead and failed to get any light. Loaded her up and headed home.

Next morning I tried starting again, with no joy and again timing light indicated no light when kicking.

Thoughts? Faulty coil?

Can't wait to have some consistency.

Cheers, Josh.

Offline sleepy

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Re: Maico 490 1981 Mega 2 - starting issues
« Reply #50 on: November 29, 2017, 09:57:55 AM »
Atleast with no spark you have a chance of diagnosis.
First check kill switch and all wiring for shorts or open circuits. I have a Bosch ignition on my 81 400 that the insulation on the wires coming out of the trigger coil had perished and was intermittently shorting. It only started to cause a problem after I adjusted the timing last time.
Next you could swap the coil with your fathers for a test.
When you are checking for spark, have you tried with the plug out so as to check at higher kick speed?

Offline peely_14

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Re: Maico 490 1981 Mega 2 - starting issues
« Reply #51 on: December 01, 2017, 12:01:14 AM »
Thanks sleepy, yes hopefully narrowing it down. Will do some more tests when I'm home in a couple  of weeks and see what we get. Cheers.