I need to pic your brain again

[Dale Sonnenschein]

Hi all,
I'm pulling my hair out over this and maybe someone can help. The bike is a 75 250 penton. Last winter I rebuilt this bike to ride. This spring I started it for the first time. It ran ok, but the bing carb was shot. I put a new mikuni on it and it would start and run for less than a minute and die. Seemed like it was running out of gas. I messed around with it for a few weeks here and there but no difference.I thought the float needle was hanging up but it seemed fine.  I gave up.
Tonight I got it back out and tried again.It started up and stalled after about 30 or 40 seconds. same game. But this time I pulled the plug and it was wet.I checked for spark (New plug) but had none. I put in a new plug and it fired up and died the same way. Again no spark. Tried another plug and it showed spark. Seems like the plugs are losing spark, but what would make this happen? I'm using NGK b8hs plugs.

Thanks

Dale

74 puch 175 SD
73 Husky 360 WR/RT
75 Penton 250
10 ktm 250xc
02 bmw r1150r

[brian kirby]

Motoplat.

Brian

[Big Mac]

or grounding Motoplat to motor to frame to coil. Easy to run wire from motor mount to coil mount to trouble shoot first.

[Dale Sonnenschein]

I have a ground wire from the coil to the motor. It is a motoplat.

74 puch 175 SD
73 Husky 360 WR/RT
75 Penton 250
10 ktm 250xc
02 bmw r1150r

[gooddirt]

start with the kill button ( a short) then spark plug cap ( loose) then the other grounds . next  do  a upper Moto-P coil Ohm  check or change it out  with another for test . next do a lower stator Ohm reading. google for test specs [|)]

[Dale Sonnenschein]

I did swap the coil with another good one. No difference. The cap is on the worn side.maybe i'll try that.

Thanks for the help. I'll keep you posted.

74 puch 175 SD
73 Husky 360 WR/RT
75 Penton 250
10 ktm 250xc
02 bmw r1150r

[454MRW]

I recently sold my 1980 MC 250 and it ran exactly the same way. Starts when cold or with a new plug, then after warm would not start. Same with a ground wire from the engine to the coil mount and without the kill switch, the original Bing or a good known Lectron carb, and even a different coil. I wound up sending the buyer the Motoplat off a good running bike with the coil and flywheel. Problem solved. It may have been weak magnets in the flywheel or a tired motoplat, but it runs consistently now.
Dale BTW, I have healed up from surgery enough to finish sanding your tank and will update you this weekend. 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

[Dale Sonnenschein]

Sounds good Mike. Glad to see your on the mend.  

Can a motoplat be repaired or do I shop for another one?

74 puch 175 SD
73 Husky 360 WR/RT
75 Penton 250
10 ktm 250xc
02 bmw r1150r

[Mick Milakovic]

Same thing to me, replaced the Motoplat ran fine.

Mick

[3putt]

M-P can be repaired, and the guy to contact is Vance Smith,  [email protected]
but you need to do it ASAP, cause he is leaving for FL very soon.  He does very good work.  We have a number of them in use.   Nelson McCullough

[Dale Sonnenschein]

thank you Nelson.

74 puch 175 SD
73 Husky 360 WR/RT
75 Penton 250
10 ktm 250xc
02 bmw r1150r

[Dale Sonnenschein]

He must have left for Fla.  He didn't return my email.I'll have to try in the spring.

74 puch 175 SD
73 Husky 360 WR/RT
75 Penton 250
10 ktm 250xc
02 bmw r1150r

[3putt]

Dale, Were you able to make contact with Vance to get M-P working ?   Nelson

[pklinck]

Dale,

I have had the same problem on my 73 penton 125 with the motoplat system.  I believe, if someone didn't already mention that the dioid is bad in the stator.  After extensively hot temperatures, they become faulty.   If you change to a later model motoplat spark coil with the Red Wire lead, not the black spark wire, I bet the bike would run just fine.  On the Red lead wirers, the dioid is in the spark coil so the dioid that is not functional in the stator anymore, it will now run.  That would be the cheapest route and relatively reliable. Try it. A NOS red lead motoplat spark coil will cost about 40-80 bucks on ebay.  Call me if you have a question  pms 6-8 at 802/889-3585 EST. Good luck.

peter klinck

[Dale Sonnenschein]

Nelson, No I haven't contacted him yet this year. I have been working on the bike some lately. I had put a new mikuni on it last year and I'm sure the jetting is off along with what ever else ale's this bike. I did ride it for a few minutes a couple weeks ago and it quit and wouldn't start again. I think it may have fouled the plug. It was black when I pulled it out.

Peter, I'll look for a coil and give that a shot. I really would like to get it running right as it's been a project for me that I would like to finish.
I'll also email Vance and see what he has to say.
Thanks for the help

74 puch 175 SD
73 Husky 360 WR/RT
76 Husky WR360
75 Penton 250
10 ktm 250xc
02 bmw r1150r