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. ; -)
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
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
Get a PVL/MZ-B and forget the Motoplat.
Brian
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
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
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
Wow, I have had the opposite luck, never a failure?
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
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?
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
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
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
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.
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
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
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
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
Quotequote: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
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
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