Pe400 Spark Problems

[LWC82PE]

Check wires coming out the coil, epecially the plug lead and check the plug cap. Very often i have found problems with plug leads and caps on old bikes causing ignition problems. Everyone chases other things then eventaually finds out its a plug cap or lead. try and bent/twist/reposition the lead and then check for spark. Also with a multi meter attach one end to plug cap and then the other to a tiny pin and prick the lead in a few places looking to see if theres breaks in the cable. More often that not all you need to do is cutt off the first 10mm of the cable and then re-connect the plug cap and it fixes it. Most restos i do get a new plug lead and cap.It can be harder to replace a lead on a jap type coil but more often that not a whole brand new coil is pretty cheap anyway. The PE coil is common to others across the board and not expensive to buy off ebay.

[lukeb1961]

Just to confuse things more, I thought maybe it was a faulty plug so I got another one and put it in and presto big blue spark! I thought I would put my old plug in to confirm a dead plug and presto again - what the???.
I started reassembling all the bits and refitted tank etc kicked her over and wouldn’t start - no spark...frustrating.

So it worked - FAT AND BLUE and then you reassembled and nothing? mmm.. I hear earth wires, connectors, plug cap. - there just isn't much else!

[Mike52]

Bought a 86 125 KTM a while back.
Real nice looking bike and in good condition too.
After about 10mins it stopped and restarted later when cooler.
Finally found the problem and it was different.
The previous owner had zip tied the kill switch wire to the top radiator hose and the wire was shorting when it got hot.
Found a funny little carbonised/chared patch where they touched.
I am thinking that no one found it and the owner finally got the shits and sold it.
Nice bike that one , cheap too.
Mike

[frostype400]

My 86 ktm isn't in to bad nick but missing the motor so it isn't going anywhere for a while.

[lukeb1961]

I mentioned the kill switch earlier. Does seem odd that everything works fine when apart.
Should be interesting to hear the final solution.

[monaro308]

Almost sounds like what Leith said......a broken plug lead...internally
Do you have another coil to try?

[LWC82PE]

One or two wire kill switch?

[PE MAN]

when mine stuffed up i had a very weak spark. ended up being flywheel. so got coils re wound an new flywheel... now plenty of spark.

[monaro308]

Peter i just re-read my PE250 post

quote author=monaro308 link=topic=16312.msg163357#msg163357 date=1291346086]
Head down bum up time 
Had a play with the bike this morning and cleaned the thread up on the end of the crank and searched  for a woodruff key.
Wanted to see if the flywheel would give any spark with a rooted magnet,bolted it all up and it did have a spark....not a strong one.
Gave it some fuel and a few kicks...nutting!!
Just the occassional big backfire .So i tried an old RM coil,same again.
Then i went through my box of PE175 stuff and tried the whole magneto set up and flywheel....same deal just to see if i had spark (i'm sure Luke said you can modify the 175 plate holes to use on 250's,i'll read up on that later).
No backfire with the 175 set up but has spark.
Pulled the carby off and cleaned and reset the float levels and tried again...same.
Refitted the 250 mag and at least got a backfire again....so i tried the RM cdi off the alphabet bike and after a few kicks it roared into life!!! and idled pretty much straight away
At least i know it runs now,so i'll figure out what to do with the electrics next and may have to run the 175 set up as the 250 flywheel is bastard to find (am i correct Luke and Leith)??

[frostype400]

yeah I think that you have to redrill the holes at 90 degrees from the original two to make the 175 one work on the 250.

[monaro308]

Michael, i was refering to the cdi change as i had a weak-average spark and backfire until i changed the cdi and it fired up on the broken magnet 250 f/wheel.
PE175 82 onwards (haven't checked T,X)electrics bolts straight on and runs ok on the 250,but still needs to be checked with a dial guage and timing light after checking mine as it showed a few degrees off the 175 TDC mark.
 cheers..mario

[lukeb1961]

I am very surprised the CDI was faulty. I have taken a half-dozen apart (a slow tedious process) and they are extremely well protected.

As to fitting the 'early' or 'small' stator and rotor, absolutely true. 33% less mass, but they were fine for the 250 B/C/N and all 175's.

The PE400 ran at 17BTDC, so grab the ( stator, rotor and CDI ) from a PE175T/X - they ran at 17.5 and are still available all over the place. I had a PE400 with all that dropped in and ran fine.

Luke

[ELC hunter]

Back around 85 I had a pe250 t which ran fine for the test run before buying ,then after i bought it.Its performance changed from good starting and performance,to hard starting and slugish running which seemed to variy from one extreme to the other.Changed pulsar coil problem gone,long enough to trade it in.

[lukeb1961]

yes, PE/RM pulsar coils are the usual suspects, way before the CDI.

[LWC82PE]

Probably not on the 400 though. I know quite a few people who had been after 400 CDI's.

I think the problem is the capacitors in the CDI because the they dont last for ever, but the other components are ok, so at some point in their life the CDI's will stop working because of the capacitors. Its just like how a battery doesn't last for ever.