Another motoplat question

[Lloyd Boland]

I have both an MC5 250 and a 1974 CZ400 with a motoplat.  Last week, while riding the CZ in practice (it was running fine), it all of a suddon it started missing and just stopped running. (not like seizing but more like the flywheel key gave way and spun a flywheel)  I tried kicking it over but it wouldn't start.  I put it on the trailer and rode my '72 that a take to the races as a back-up bike.  The next day I checked the timing and eveything looked good.  It had good spark.  I kicked it over and it started right up but after about 20-30 second it started running rough again and stalled.  I kicked it over again and it started up again but only ran for 5-10 seconds.  I tried to start it again but it wouldn't start.  Pulled the plug and now no spark.  Changed plugs (new) still no spark.  Checked the timing and the timing is still good.

My thought is something is warming up and going bad electrically.  Any other thoughts, (the timing has not changed) suggestions?

[tomale]

Lloyd, that was my thought too. I have never had that happen to a motoplat but I did have that happen to a Fenzna? Bultaco ignition. I pulled off the flywheel and pulled off the Magneto and to my amazement. there was a crack in the plastic that covered the electronics. At that time there was nothing that we could buy to repair the crack but somekind of seal might work today. Still if that is the problem I am not so sure how long it would last and how reliable it would be. As I understand it the plastic acts as a insulator to keep the electronics for overheating. When the bike warms up the ignition shuts down. Hate to say it but you may have to pull the whole unit to find out for sure. I doubt that it is the coil. They seem to either work or they don't. When they go out they go out. But that does not happen very often. I am sure that Dane or one of the other guys would be of more help here than I.  I hope I am wrong.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
78' 400 MC5

[Lloyd Boland]

Thanks Thom.  My next option was to pull the ignition and send it to PVL to get tested.  Wanted to avoid pulling the entire ignition and sending it out if I was missing something.  I'm going to wait to see if any of the really bright guys around here have any suggestions.  Thanks again.

[Larry Perkins]

Llloyd

I have seen quite a few Motoplats do that and I bet Dane will send it back as suspect.  Is it a black lead coil wire Motoplat?

Larry P

[Lloyd Boland]

Larry, I don't remember the lead color. I'll have to look tonight. Thanks.  I'm out of town tomerrow so I'll report back on Wed.

[Lloyd Boland]

The consensus from other sources is that it is a stater gone bad.  Dane, what do you think, is it terminal?

[herman]

I had the same problem on my 74 250 .My problem turned out to be the coil had a hair line crack in it.I would look at that real good . Herm

Herm

[Rain Man]

resistance is futile, check your grounded And grounding conductors:)

Raymond
 Down East Pentons

[TGTech]

The fact that the spark has come and gone is usually an indicator that there is a ground problem. If after you have worked over the grounding, (stator to cases, cases to frame, and coil to frame, and you still don't have spark, I would suspect that the stator is toast. The coils are normally pretty good, and only about one out of twenty that I test are actually bad.

Dane

[Lloyd Boland]

Thanks everyone for the input.  I actually always run a separate ground wire from the coil to the cases trying to avoid the possibility of a bad contact.  I will double check all grounds including the additional ground wire to make sure it is grounded properly.  I will also look closely to see if there are any visible cracks, etc.

Dane, if the ground appears to be OK, should I send in the entire electrics to be tested or is there a way of determining the problem?  If the stator is "toast", is there any fix for it?

Thanks again to everyone.  It is these suggestions that remind us of the obvious things that are sometimes forgotten.  The follow-up will have to wait until the weekend when I have some free time. I will let you know the results.