MB5 lost spark

Michael Thomas /
IMAG0077.jpg

So my MB5 died on my son a while back and no spark. Thought it was the coil based on the readings but a new one did not work. Key switch works, neutral light on dash comes on. I am thinking CDI or rectifier but not sure if the rectifier even affects spark. not really done anything with the stator...any thoughts? (edited)

Re: MB5 lost spark

Michael Thomas /

Nothing?

Re: MB5 lost spark

Rectifiers transform a.c. into d.c. within the charging system.

Re: MB5 lost spark

Wish I could help, but mine was dead reliable....looked just like yours, god how I miss that machine. Best of luck with repairs. I have owned many, many bikes, but never enjoyed one as much as that one.

Re: MB5 lost spark

Have you changed the spark plug?

Re: MB5 lost spark

Michael Thomas /

Thanks, yes changed the plug and coil.

The rectifier is supposed to be like a valve and only show continuity one way, mine shows nothing either way, but not sure it affects the spark tho.

Re: MB5 lost spark

Rectifier doesnt affect spark. The cdi is a very common 5 pin pin out, those can be bought for under 10 bucks almost anywhere. 2 stroke 5 pin cdi. They will not make your bike run however, but will spark and at least let you test if the cdi is bad. I'll come back to that.

Look up the 5 pin pin out. You need a pulse in, pulse out, charge in and a ground. 5th is kill.

For starters I'd check all those. 1st easiest, check that the ground is indeed grounded (and that the coil shares the same ground) and check that the kill wire is NOT grounded. You can just disconnect this entirely for testing purposes and checking spark. Also check the engine stator ground wire is actively grounded too.

If those arent your trouble you can continue checking back, Turning the bike over with a drill, measure voltage on the pulse wire from the stator. Should he very low, 1v or less, but measurable. Then check power in from the stator, this is independent of the rec reg. Should be 10-20v range. Then check pulse out to the coil for voltage, should be measurable. In lieu of a volt meter you can also check for small sparking when held to a ground and turning the engine over.

If no pulse outta the stator, you need a pickup coil. If no power outta the stator, likely bad stator coil or engine grounds. If pulse and power get to the cdi, and the box is grounded and kill wire open, but no power out to coil, then it's the box.

And if its pulsing out to the coil but not sparking, its coil, wire boot or plug.

It's not uncommon for the boxes to fail. As I mentioned the 5 pin 2 stroke ones work to spark BUT they mb5 has a timing offset that will fire at very wrong timing with the other cdi boxes. If you're willing you can time it without the woodruff key and get it to work, else a stock mb5 box, if you can find one, runs like 50-80 bucks...

Re: MB5 lost spark

Adding to what Will said, I have seen 80-100VAC off the stator coil for the CDI while kicking over.

Re: MB5 lost spark

Richard Eberline /

If your keyed ignition switch is bad, no spark.

kill switch can be bad, causing no spark.

bypass kill switch by unplugging wires.

ignition switch, unplug both pigtails, the wiring harness connector

jumper the RED wire to the BLACK wire.

Spark ok

no spark, other testing needed.

Re: MB5 lost spark

Check your local lost and found too.

Re: MB5 lost spark

Michael Thomas /

Thanks for the suggestions guys. Is there a way to check the CDI box itself? The manual says I need a specific OHM meter.

Re: MB5 lost spark

> Michael Thomas Wrote:

> -------------------------------------------------------

> Thanks for the suggestions guys. Is there a way to check the CDI box

> itself? The manual says I need a specific OHM meter.

Meh,

Suzuki manual says same thing for Suzuki.

I actually ordered one and purchased it when I worked at the bike shop. Meh

Re: MB5 lost spark

> live ɘvil Wrote:

> -------------------------------------------------------

> > Michael Thomas Wrote:

>

> > -------------------------------------------------------

>

> > Thanks for the suggestions guys. Is there a way to check the CDI box

>

> > itself? The manual says I need a specific OHM meter.

>

> Meh,

>

> Suzuki manual says same thing for Suzuki.

>

> I actually ordered one and purchased it when I worked at the bike shop.

> Meh

Which specific meter would that be ?

I have a regular digital multi meter and it seems to work fine on my FA50 , but ???

Re: MB5 lost spark

> P D Wrote:

> -------------------------------------------------------

> > live ɘvil Wrote:

>

> > -------------------------------------------------------

>

> > > Michael Thomas Wrote:

>

> >

>

> > > -------------------------------------------------------

>

> >

>

> > > Thanks for the suggestions guys. Is there a way to check the CDI box

>

> >

>

> > > itself? The manual says I need a specific OHM meter.

>

> >

>

> > Meh,

>

> >

>

> > Suzuki manual says same thing for Suzuki.

>

> >

>

> > I actually ordered one and purchased it when I worked at the bike

> shop.

>

> > Meh

>

> Which specific meter would that be ?

>

> I have a regular digital multi meter and it seems to work fine on my

> FA50 , but ???

A Suzuki multimeter

Re: MB5 lost spark

Of course . With a special Suzuki part # and Suzuki price to match . ;)

Re: MB5 lost spark

> P D Wrote:

> -------------------------------------------------------

> Of course . With a special Suzuki part # and Suzuki price to match . ;)

Yep.

Go get any good quality mutimeter and get the same results.

Re: MB5 lost spark

Michael Thomas /

Is the NC50 CDI box the same?

Re: MB5 lost spark

Re: MB5 lost spark

Michael Thomas /

Fixed the problem and is now running

Re: MB5 lost spark

> Michael Thomas Wrote:

> -------------------------------------------------------

> Fixed the problem and is now running

After these guys gave you all that help , least you could do is share what the fix was .

Re: MB5 lost spark

Michael Thomas /

I bought the CDI from the link provided by Stephen and it fixed the problem

Re: MB5 lost spark

Great . Thanks . ;)

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