DT85 No spark on bottom cylinder

[sethgs]

My 1987 DT85 does not seem to have a spark on the bottom cylinder. The motor runs pretty good otherwise, and when you remove the bottom plug wire, it doesn't effect the performance one way or the other. I took the cover off the box where all the ignition wiring is connected and disconnected the bottom coil wire, and again, no difference. There was a spark arching over where the two wires connect, so it leads me to believe the bottom CDI coil is bad. This seems likely because there is a spark all the way to this point. In addition, the fuel and oil combination from the bottom cylinder, unburnt of course, leaks down the outside of the drive shaft housing, below the lower motor cover. Does anyone know if this is a common/likely problem? Also, does anyone have any idea where I can buy a new one, besides Brown's Point? Thanks.

 

[Yepblaze]

Re: DT85 No spark on bottom cylinder

Not sure about your specific questions, but....<br /><br />Or if it is an actual ignition issue or not?<br /><br />I'll assume it might be three cylinders, and if that's the case.<br />Some of the early three cylinder pressed crankshafts had a tendency to slip, or twist.<br /><br />Check TDC of each piston and assure they still reside 120 degrees apart.<br /><br />I suppose you could try changing coils cylinder for cylinder and see if your issue follows.<br /><br />The goo you see running down the leg might be some carb spitback (somewhat normal), dribble from tilting the motor,(again somewhat normal), or perhaps a powerhead base gasket, in which case might cause poor running with hood on.<br /><br />Or just goo from the non running cylinder which might go away when it gets better.<br /><br />Don't forget a compression check.

 

[sethgs]

Re: DT85 No spark on bottom cylinder

I have good compression on all cylinders. The head gasket is new, and the motor has noticeably more power and runs better after the new gasket. When I pull the bottom plug wire off, I can't see a spark, or even feel one for that matter. I can feel the shock on the other two wires, just not this one. The top two plugs are clean with a little carbon on them, but the bottom one stays wet with fuel/oil. What do you think?

 

[sethgs]

Re: DT85 No spark on bottom cylinder

Is it possible that the bottom cylinder doesn't need to fire all the time? The motor still seems to run good. I can go WOT in my 16' CC (heavy) and it turns between 5000 and 5500 RPM, depending on what kind of mood its in. Even at this, I'm still pushing 40 mph. It would seem that if I was only going on two cylinders, I wouldn't be getting this good of performance. Personally, I get kind of unsure and uneasy about these kind of things and don't really want to go see a mechanic. I wouldn't mind spending the money on a new coil, if I had to. I really appreciate any help I can get with this issue. Thanks.