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Hi! MC16 no spark issue


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Josho

 
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Hi! MC16 no spark issue

Fri Jul 03, 2015 9:04 pm » Post: #1 » Download Post

Hi there, my names Josh from Kent, UK.

Signed up to ask for some advice and perhaps looking to get a NSR-125 to learn on!

Anyways, I run a mobile car repair business so play around electrical issues on cars all day long, however this is a bike so I am still trying to get my head around it all.

My brother in law purchased a 1987 MC16 NSR 250. Kick start. It's been sat for years (I think 20 odd was mentioned) and he wanted to clean the carbs up and see if it would go.

I suggested a quick dose of easy start/carb cleaner and start from the beggining so we did. Anyways, fast forward, awesome compression but no spark!

We couldn't get the neutral light on so I grounded out the neutral switch to rule that out. There is a slight gear selector issue according to bro in law but I did managed to get it in today and the light lit up on it's own.

I checked the kill switch, fine. There is AC voltage going into the rectifier and there is 12v out. It's a brand new battery.

Anyway, after all these checks it sparked! Checking the coil with a screwdriver that is. The bottom coil didn't do anything though! Plugs in and it spluttered and then nothing. No spark and no matter what I tried I could not get a spark full stop. I temporarily bodged in a Yamaha coil and that did nothing either.

There is 2v at the coils. Resistence is fine on the coils from specs pulled from the net.

He's thinking CDIs. I'm almost with him on that. I do need to load test the wiring but it all seems fine from breif testing.

There is two CDI units together in a rubber boot and one on the tail. Is that right? I am very new to bikes!

I'm sure with a spark it'll run well!

Any pointers would be awesome, I don't 100% how the ignition system works!

Cheers,
Josh
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Andy
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Fri Jul 03, 2015 9:26 pm » Post: #2 » Download Post

Hello Josho, and welcome to NSR-WORLD.

The MC16 does indeed have two CDIs under the rear cowl. They are prone to corrosion and "dry" solder joints, and it's not unheard of for one CDI to fail and the other to work, so try swapping them, and seeing if the spark shifts cylinders.

I wouldn't run the coils without spark plugs, especially given that they can be a bit fragile at 28 years old! Make sure you use the correct spark plugs too; B9ECS.

Although the CDIs can be a bit weak on the MC16, and the spark "look" weak on all NSR250s when the plugs are just grounded and the kickstart operated, you're really fighting against age and exposure to the elements. The last MC16 I had to cut into was so badly corroded, it was virtually impossible to solder joints, as the copper cores were black!

There are some posts here somewhere about MC16 electronics, but you will have to search for them, unless someone else can remember the author. I seem to recall he was able to adapt alternative CDIs from another Honda of the same period, that are more readily available.
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Josho

 
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Fri Jul 03, 2015 10:00 pm » Post: #3 » Download Post

Hi Andy, thank you very much for your advice.

The CDIs were under near the handlebars and one was near battery?

OK so would it be a good idea to take them apart and have a look? I guess try and get the spark back and swap them!

Cheers!
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Andy
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Fri Jul 03, 2015 10:05 pm » Post: #4 » Download Post

Sorry, yeah, the CDI's are under the tank, and the RC Valve controller is under the seat.
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JohnnyAfrica

 
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Sat Jul 04, 2015 12:14 am » Post: #5 » Download Post

Also check the Pick up on the Stator...Multimeter & Ohm them out. I had one go bad and only had spark on 1 cycinder..
Good luck
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Josho

 
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Sat Jul 04, 2015 11:14 am » Post: #6 » Download Post

Hi there's about 10-20 as volts coming from the stator to the rectifier.

Is this right?

Cheers guys, determined to fix this one!
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Josho

 
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Sat Jul 04, 2015 12:43 pm » Post: #7 » Download Post

Ok so again this morning we had spark at the top plug. Put the plug in it ran on one cylinder for about 4 seconds and no more spark.

Found two dry joints on the bottom cylinder CDI but resoldering them has done nothing.

Just going to recheck the stator not quite sure what wires should have what voltage. Three yellow wires and I think some more yellow and some white wires.
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Andy
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Sat Jul 04, 2015 8:58 pm » Post: #8 » Download Post

See if the Electrex fault finder on the main site is helpful:

http://www.nsr-world.com/workshop/
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