COTA66 Posted March 16, 2023 Report Share Posted March 16, 2023 Hoping someone can help diagnose a no spark Cota 248. I have tried 4 old stators plus one brand new one, 2 flywheels, 3 coils, various new points, new condenser, new woodruff key on flywheel, new plug caps, direct earth of coil to the engine, various contact gap settings Absolutely refuses to spark although I can feel a weak shock from the HT lead if I hold the plug business end. Current setup is brand new stator and wiring, new points, new condenser, new plug, all gapped correctly but absolutely nothing. Only things left to replace are the coil (just ordered a new replacement from InMotion) and the flywheel. Has anyone ever heard of a flywheel losing its magnetic charge? It still holds steel parts to the magnets so I find it hard to believe it could fail, plus I have a second flywheel I have swapped in with no effect. The various HT coil circuits both show resistances so are not open circuit, can anyone advise what the low tension and high tension coil resistances should be? I get about 13.5K ohms on the high tension side, and about 10 ohms on the low tension side. Is there anything I am missing? Checked all the continuity and earths and all look OK. It's driving me absolutely nuts!!!! On the upside I could now probably change out the whole ignition system with my eyes closed! In my experience of other engines I should be able to see a spark of some sort to have a chance of it starting, or does the Montesa have a magic invisible spark?!! Any help appreciated. Quote Link to comment Share on other sites More sharing options...
COTA66 Posted March 16, 2023 Author Report Share Posted March 16, 2023 I have also disconnected the kill switch completely and left the green, pink, and yellow wires disconnected. I have read that on Bultaco's which use the same Motoplat system, the green wire needs to be earthed to get a spark. Does anyone know whether this is the same on a Montesa? Also, does anyone know where I could get a manual? I have an engine in bits to rebuild, difficult without a manual! Quote Link to comment Share on other sites More sharing options...
kurtas Posted March 16, 2023 Report Share Posted March 16, 2023 Have you set the points gap correctly? If you can feel a charge at the spark plug you mustn't have too much wrong. Quote Link to comment Share on other sites More sharing options...
COTA66 Posted March 16, 2023 Author Report Share Posted March 16, 2023 Thanks for the reply. Stripped it all down again tonight and cleaned the engine cases behind the stator plate to get a better earth. Looked at the new points and saw that the nylon rocker bush was too big for the shaft and would affect gap. Changed to a better set of points, gapped them as best I could and hey presto BIG FAT SPARK!! Might have been some of those changes, or perhaps the bottle of Spanish wine I bought to help calm my nerves and the Spanish prayers! 2 Quote Link to comment Share on other sites More sharing options...
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