Spark out

Practical Sportsbikes (UK) - - What's The Problem -

Over the past few months I stripped my Yamaha TDR250 down to bits and did a com­plete me­chan­i­cal re­build. This in­cluded pow­der­coat­ing the frame, re­build­ing the crank, new pis­tons and con-rods, re­con­di­tion­ing the sus­pen­sion, pow­er­valves, oil pump and carbs, seal­ing the tank and re­pair­ing the speedo. I didn’t paint the rest as it still looks OK.

Ev­ery­thing works ex­cept that there seems to be a prob­lem with the ig­ni­tion and pow­er­valve con­trol. The valve clean­ing cir­cuit works and all the an­cil­lary electrics are fine so I sus­pect the CDI/ECU.

Do you know where I can get one or sug­gest how to go about open­ing it up. Per­haps it’s dry joints on the cir­cuit board. Nei­ther the agents nor Yam­bits can help me. Jo­han En­gel­brecht, South Africa

Fer­ret says: Be­fore sus­pect­ing the CDI, check the re­sis­tance of the ex­citer and pulser coils in the sta­tor as faults in these will pre­vent a spark de­spite ev­ery­thing else ap­par­ently be­ing al­right. Make sure ev­ery­thing that needs an earth is mak­ing good con­tact and not be­ing in­su­lated by your new pow­der­coat­ing. If that all fails bor­row a known good box to try on the bike. Af­ter that, your best op­tion is a re­place­ment sys­tem from the likes of Zeel­tronic.

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