MC5 Coil and other troubleshoot question

[brian kirby]

At the really wet White Lightning race in SC '09 Ernie's MC5 did something similar. With a brand new plug it would go about .5 a mile then stop. Even hot, if you put another brand new plug in it, it started right up and went another .5/.75 miles and quit. I ran out of plugs before I made even one lap. Forgot about that one, there's another $50 I can add to my "lost to Motoplat ignition" costs.

Brian

[Ernie Phillips]

Hold on Kirby - Fact Check:

1.  Jeffery's Husky stator was poorly grounded - lots of corrosion.  Later bench test indicated that the 'splat was fine.
2.  Part of the Maico problem is yo butt is too puny, and yo legs is to short, to get a good kick on the Big Tall Maico.  
3.  The MC 5 has never been shook down properly, much less race tested. Period. To say it has a bad 'splat is not a fair evaluation.  In fact when I got it home and washed it up (you left it very muddy buddy boy) it fired right up.  The main bearings are a tad loose and that's why I haven't done much with it.  Plus if I did get it sorted out, you and Christopher will just go out and hammer it.  No thanks.

The early generation 'splats with the diode in the stator was not a good idea.  Later generation (red wire - diode in coil) seem to be much more reliable.  Now, this stuff is very old - it's going to fail!   PVL on small bore Sachs: yes.  Big bore KTM's start, run and deliver power best with a 'splat -imho.

I think the 'splats poor reputation is exaggerated.  Sorta like the Bing carbs.  Folks hate'm.
My experience is otherwise.  I do know this; for maximum enjoyment and reliability: KKOYB - Keep Kirby Off Your Bike

Ernie P.
Chattanooga, TN

[brian kirby]

The Maico's Motoplat failed, it was not lack of Butt. Lack of butt or carb jetting does not cause popping and backfiring. The 400's failed. Ed's 175 Husky's failed. The one in the "John Deere" Penton failed. My new '82 Husky's failed. The one in my '83 Husky 175 has failed. One of my Can-Am's has an internal rotor Motoplat that failed after working for a bit. On your MC5, you are right all it might have needed was making sure everything was grounded and clean, but the fact remains, a Motoplat ignition was in the bike and it failed.

BTW, I need to call to order an MZ-B for the Mint.

Brian

[Ernie Phillips]

quote:but the fact remains, a Motoplat ignition was in the bike and it failed.

No failure, you just did not carry enough spark plugs!  Do you have a part #?  MZB $$$  Why not try a Vance rebuild, lots of good testimonials?  Or, PVL with added flywheel?

Ernie P.
Chattanooga, TN

[454MRW]

It is common knowledge that if a Motoplat becomes ungrounded it will burn out. That is why they always tell you not to kick your bike over with the plug wire off. Poor grounding is the same: Motoplats burn out because of lack of ground. An additional wire run from the stator plate to the coil mount just gives some extra insurance from becoming ungrounded due to corrosion or poor frame mount ground. That is what I attribute to why mine haven't failed. Just my $.02 Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R

[brian kirby]

Ernie, the applications list shows #40360 for the MZ-B 400 which is the same number for the 125-250 KTMs but the PVL number is different for the 400 only so maybe double check that number is correct. PVL has a more aggressive timing curve, the MZ-B has the external rotor and milder timing curve. Not interested in a Vance rebuilt.

Mike, you are correct and the first thing I do when I get a new/old bike is clean all those contact points and add a ground wire so there is a good solid ground. On all the Motoplats I have had fail, the stator epoxy coating was cracked which I believe allows moisture to get into the windings and eventually raises the resistance to where the stator fails. Not really a fault of the Motoplat per se, and probably why the Vance rebuilts work so well since he fixes that and recovers the windings with new epoxy.

Brian