MC5 Coil and other troubleshoot question

[tooclose racing]

If you read my racing thread (from Cato), you will see that I had my bike quit on the last lap in two of the motos. Now - when I say "quit", I mean she would just bog to a stop with no firing,not even mis-firing.   I could see gas in lines and she would tickle okay right there at trackside.  After getting a tow back to the pits, we would pull the plug (relatively dry and light brown) and I would have spark. Put the plug back in and she would start!  

Lots of AHRMA racers standing around and they surmised the first thing I should check (actually just flat out REPLACE) is my coil, providing me an explanation that the coil can behave this way  - it gets hot and "opens up" from a continuity standpoint, cools off and re-establishes continuity.  Also - they pointed to the coil instead of the stator, saying when a stator goes, its GONE, ie it doesn't typically behave on and off AND in fact you would maybe see some sputtering/mis-fire before it is gone.

So- a couple of questions:

1.  They informed me that I needed a "red wire" Motoplat coil for my MC5.  What do they mean AND would any of you fine gentlemen happen to have (a used one) one that I could purchase?

2.  I'm just wondering WHAT ELSE I should or could possibly look at/trouble-shoot.  I pulled and cleaned my Bing as part of my Spring cleaning, hitting it with lots of carb cleaner and air and things like that.  Not seeing any puddles, flooding.  Bike starts right up when cold after a tickle and a couple of kicks.  I guess I can't eliminate that SOMETHING might have occurred to suddenly shut off fuel, but with two petcocks flowing  - it would have to be at the carb.

Feedback is a gift.  Cash or Paypal for the coil.  ; -)

[Kip Kern]

Simple things to check: Coil is grounded well, Ignition is grounded well and engine mounts are grounded well. Look on the Motoplat Flywheel and if the serial number is followed by a (-1), yes you will need a red lead coil, if not, you don't.  The red lead coil will work on both style Motoplats but the black lead coil won't.  You can get a coil on Ebay or contact PVL and they have new ones that will work or can test your original! Good Luck

[454MRW]

First thing. Throw that spark plug away and insert a new Bosch plug. I actually run NGK B8HS plugs in mine when that is all I have, but they don't last like a Bosch plug. When they die, they might re-start cold, but soon die again. Mike
Here is a thread discussing the use of optional plugs:
http://pentonusa.org/forum/topic.asp?TOPIC_ID=13008&SearchTerms=spark,plug

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]

Get a PVL/MZ-B and forget the Motoplat.

Brian

[454MRW]

With using an auxilary ground wire from the engine, or ignition mount plate, to the coil mount I have never had a Motoplat failure with the exception of my 1974 HS 250 original unit that cracked because it got snow in it back in 1978 and froze up and busted. "Knock on Wood". You would be suprised how better the spark looks with the addition of the ground wire, plus I never have to clean paint off of the frame to engine mounts. 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

[tomale]

I would like to second what michael has said. Everytime I get a bike, one of the first things I do is to add an additional ground wire from the coil to the engine head. A stator is much more likely to get cooked due to heat, the thing is covered on all sides and no place for the heat to escape. I have seen them crack due to heat. I had a stator back in the day that did just what you said, when the motor was cool, lots of spark and then after a few minutes, nothing.  Not that a coil does not go bad because they do. My MC 5 still has the stock motoplat on it and I am convinced that the reason is because I am careful to keep it well serviced. periodically I will pull it out and clean all the contact points, this includes where the stator mounts to the engine. I stuggled with a PVL for awhile and they are ok but truth be told, I prefer a Motoplat. I am building a 72 husky 125 and instead of replacing the stock motoplat, I had Vance fix mine. It works great.
One of the other things I did was replace the Magura kill button with a good 2 wire aftermarket one.  I lost more than one race because the stock kill button failed. It about drove me nuts trying to figure out what was going on. They look cool but they are problematic, Great for a show piece, but I would never put it on a race bike. good luck

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
74'250 hare scrambler (project)
74' 1/2 440 maico
78' 440 maico
72' cr125 Husky (project)
93' RMx 250 suzuki

[brian kirby]

I just had my 4th Motoplat fail in October, of course it was the morning of a race. It was the 5th if you count the brand new one in my brand new '82 Husky that never worked right from day 1. If you have a Motoplat it is not IF it will fail, it is WHEN it will fail. I will never depend on a Motoplat again.

Brian

[Kip Kern]

Wow, I have had the opposite luck, never a failure?

[tomale]

Wow, in deed! I am sorry Brian that you have had such luck. I for one, have never had one fail on me. Sure I have seen them and my husky came to me with a dead motoplat. Which really surprised me because the bike really did not have that many hours on it. Based on my conversation with the orginal owner, It was ridden a few times and put away 30+ years ago never to be ridden again. When I realized it did not fire, I took everything apart and began my cleaning regiment. It still did not work. So off to Vance it went. My MC 5 sat in a barn (in high desert) for 20 years and a quick cleaning and she ran great. I still do not know why one worked and the other did not. When I bought the PVL for my Maico, I had nothing but trouble, It struggled to start cold but it did start and then not again until I pulled the ignition cover off, I ended up sending it back to Penton imports to wit they told me it was fine. Once again I clean everything when I put the PVL back on my bike and I added a ground wire, swapped out the Mikuni for a Bing and all my problems went away. That was two years ago and the bike is cold stone reliable. The PVL was easy to mount and time and I really like that. Still I prefer the Motoplat because if I do have a spark issue I can all way tell if I have spark or not.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
74'250 hare scrambler (project)
74' 1/2 440 maico
78' 440 maico
72' cr125 Husky (project)
93' RMx 250 suzuki

[Rob Thatcher]

I am nearing completion on my 72 Jackpiner and have seen a couple of postings about grounding directly to the head.  Does anyone have any pictures of the set up?

[brian kirby]

Like I said, my first bad Motoplat experience was with my brand new '82 Husky 125. If you rode it every weekend, it would start and run fine. If you went two weekends between rides, we had to pull it off behind my Dad's XR200R. It was not flooded, it just wouldnt start unless you pulled it off, then I'd run fine. Husky replaced the Motoplat and the second one did the same thing. The "new" '83 WR175 Husky I just bought last month has a failing Motoplat, but I am going to put an MZ-B on it before it becomes #6.

The first recent one was on the '79 Maico 4 years ago. I did all the things mentioned here, cleaned the frame to case contacts, cleaned behind the stator plate and the cases, cleaned the coil to frame contacts and added another ground wire. Everyone assured me it was not the Motoplat but the jetting or a carb issue or an air leak or something. I tried 3-4 carbs, and jetted them all until I was so frustrated I was about to stop working on it completely, give up and stick it in a corner. Against all the advice of others as a last ditch effort I ordered a PVL and installed it. The bike started on the 2nd kick and has run perfectly since. I had two more fail, and watched probably 4 others fail in bikes my family were riding, then last Oct at Barber the one in the 77 MC5 400 engine which is now in a 74.5 chassis failed Sunday morning of the VMX races after working fine the day before. I'm going to put a PVL or more likely an MZ-B on it before Unadilla. The year before at Barber, the Motoplat in my Cousin's '74 Mag 250 Husky failed in the CC race, but Roger Paris was there that year so we took a PVL off one of his bikes put it on my Cousin Jeff's bike and Ernie sent Roger a new PVL to replace that one.

I read about the experiences of people I trust completely, like the folks here on the POG and elsewhere too, saying they have had great luck with Motoplat ignitions. I have no reason to doubt that, but I personally have not and in fact I have probably lost $2000 in fuel and entry fee costs over the years to Motoplats failing at races. IMO taking a bike with a Motoplat to a race is playing Russian Roulette.

Brian

[brian kirby]

Speaking of PVL/MZ-B, does anyone know why the MZB part number for the 175-400 Pentons are the same, but the 400 has a different number from the rest in the PVL? MZB 40360 for all, PVL 70060 for the 125-250 70177 for the 400, which is also the same for the later 270/350, 420-440-495-500-550. Different timing curve maybe?

Brian

[Big Mac]

I've had 7 Penton/KTMs, 3 Huskys and a bunch of parts bikes and have never found a Motoplat on any of them that DIDN'T work, never had one hiccup or fail...better do some knocking on wood. I even found a used parts-bike CZ Motoplat that was made as an aftermarket item back in the day, put it on a CZ 400 to replace the stock points set up, woke it right up and ran like a champ for several years that way. So far, so good. [8D]

Jon McLean
Lake Grove, OR

[rob w]

Though that is one of the symptoms of a bad coil, which Bob had described.
I was riding an enduro about 6 years ago on my Mint 400. Thought I was in trouble and stuck in the woods when the bike was hot. Would not start. Luckily when it cooled down - it started.

[Steve Minor]

Baub...I had the exact same thing happen to me at an ISDTRR Zink Ranch one year on my 77 400 GS6.

Steve Minor
Wilmington, NC