My second newbie off the wall question.

I have a 1975 DT 250B. The bike has been stripped by the previous owner of all wiring, lighting, gauges etc. It has 4 wires coming from the points/magneto. The green, yellow, green/red are cut and taped and then shoved under the tank. The black wire goes to the coil. I'll be adding a kill switch into this equation soon (the P.O. used a screwdriver to the sparkplug terminal as an off switch).

I started the bike yesterday and it ran for about 30 seconds and then the dreaded no spark issue. I checked for spark at the plug and nothing, then with a new plug and nothing. At this point with the hokey wiring I traced each wire to the case looking for any possible grounding and couldn't see any so off with the flywheel cover and no spark at the points??? I removed the flywheel only to discover it looks like a nasty home-brew solder of wires and jumpers. After looking at the rats nest I figured out what was stock and what was not. Actually it was easy as whoever went in there with a soldering gun used insulated solid core wire, it looks like doorbell wiring.

It was at this point I started to wonder if I really need the lighting coil at all? Can I eliminate the lighting coil completely? This would eliminate the 3 wires I already have no use for (I will not be adding lights on later) and at the same time clean up the magneto/points/condenser area. I also see where there is a jumper wire that goes from the source coil to the lighting coil and wondered if this is a common shared ground or something more than a ground.

Thanks in advance,
Doug "Curly"

the lighting coil is there for the headlight. if it is going to be a off road only bike with no headlight to be used,it can be disconnected and ran that way.

on the no spark issue,it could be a fouled plug or the points got dirty or the wiring is messed up. there should be no spark at all at the points,this points to a bad condenser.

I would get a known good spark plug and see if there is spark,if there still is no spark,I would take a look at the points,make sure the open and close and dress them with a little sand paper.

if you get it running,might look through the apetures on the spinning flywheel in the area where the points are and make sure you don't see any sparking there. if there is sparking,it will foul the points again in short order,it would be wise to replace the points and condenser

Sudco still makes points and condensers for this bike should you need them.

Some of the "off road" Yamaha's came with lighting coils (not connected to anything) or a "dummy" lighting coil that was basically just the core without the windings...

That leads me to believe leaving the coil in place is a good idea... even if you don't use it.



.

Spelled DUMMY LOAD?
Leave it,will keep the voltage in the designed range.

I went through everything, fresh plug=no spark, all the way down to the points and still no spark. Pulled the flywheel and I thought the points might be worn down just from how they were at the end of the adjusting slot and the felt was missing so I ordered points and condenser. Sure enough the part of the points that runs on the hub is extremely worn.Wait for a new felt to arrive. I decided to clean up the multitude of splices and crack insulation in the wiring. Soldered all connections and everything got treated to heat shrink to minimize any accidental wire exposures. It looks from the cuts and splices someone has already swapped out the source coil.

Thanks for the info.

Still waiting for the felt wiper to arrive. I have a question on a jumper wire while I wait for parts. The source coil is wired in with one lead going to the lighting coil and the other going to the condenser as I have seen in countless illustrations so I'm confident that portion is correct. However on the lighting coil it appears as someone has placed a jumper from the upper and outer lead of the lighting coil to the points. So at the points I have a wire that goes to the condenser + a wire that goes to the lighting coil. Any ideas on what someone was attempting here? Every diagram and parts manual shows only one wire going to the points and that is the one from the condenser.

I would talk to the guy you got it from. If he had it running and shut it off with a screwdriver then maybe he can explain the logic behind the wiring. Anyone else would just have to guess.

the screwdriver was doing the exact same job as the kill switch i rekon, grounding out the spark which kills the motor. It works every time, just watch out for the zap.

been going through the "how do i wire my magneto correct" currently... but i think i got it or at least pretty close, still gotta wire in the lights. i have a 75 dt250 .. so i ran one wire off the ignition coil, to the condenser the other wire outta the ig coil i ran to the lighting/charging coil... the L/C coil has to be there weather it works or not, im 92% sure at least. i tried pulling it because it had melted and was arcing to ground at a certain rpm and acting like a kill switch. reluctant to spend 120$ for a bike i paid 350$ for was hard at first so i tried everything i could think of first... with out it there i couldnt get spark. finally spent the money and now i have hot spark that starts first kick... still working on the lights and tuning but at least its headed the right direction... learning everyday..slowly....and always the hard way, but still learning none the less.

Just a matter of personal preference. Dave Rymal likes to keep everything stock and leaves them in. I believe a part that is not there cannot cause me any problems and pull them out. Fact is that the ignition and lighting are 2 separate systems so keep it or leave it, totally up to you. Jeff