Weak Spark Problem

  • Hello, I'm new to this forum and looking for some help regarding a 1991DTR build I'm nearly finished on. Problem is it aint running due to a suspected electrical issue. The bike has its original stator and CDI yet no wiring loom, this i have made up myself by carefully copying the diagram (excluding the bits i will no longer be running. side stand switch, dash lights, oil lever sensor etc...). the engine has had a full rebuild and everything there is as should be. compression is excellent and crank seals spot on.

    the problem i am having is an exceptionally weak spark. the best i have had when trying to start the bike is a brief coughing sound from the motor and a rather pathetic puff of smoke from the exhaust. After loosing my patience i have taken it to my local and trusted shop to have them look over the bike and they too have concluded the problem lies with the weak spark and to go right through the electrical system.

    my question is, has anyone experienced this problem before and offer direction on what to to start replacing first? the obvious place to start would be the loom as its fabricated by myself but i am quietly confident I've got that correct. my (limited) understanding would suggest if i hadn't correctly wired it up then i would have no spark. it is essentially a very basic loom (does anyone have a diagram know to work of a loom so basic its all the bike needs to run? i can figure this out myself but have no way to confirm it to be working thereby ruling the loom out as a problem). Both the CDI and stator are very pricey to source if you can find them at all. Is either of these more likely to be the culprit than the other? is there anything else i could try? kind of at a loss with it now so any input would be greatly appreciated.


  • @thomas-dance ignition coil?

  • oh yeah thanks, i forgot to mention that the coil was tested with the multimeters and resistance checked out. this could however be a cheap enough item to replace just to rule out

  • @thomas-dance I've had problems with the "spark cap" (no idea what it's called on English).
    That's also a cheap item to change.

  • just ordered a coil ht lead and cap. can't hurt having a new one on there for peace of mind

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