I set up my brand new 26cc zenoah mod engine on a rigger with propwest 7017/2 prop. The engine stall after few laps of running and i found out that the red coil is not functioning so i put on a brand new one. The engine stall again after few laps and still the problem with the red coil. The plug won't spark anymore. Please tell me why my new red coil get spoil/broken so easily.

Is the coil rubbing the flywheel? Have you also checked for proper grounding?


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The red coil and grey coil are proper grounding and the flywheel is not rubbing the coil. Gap between red coil and flywheel is 0.37 - 0.40mm. Will it caused by high rpm due to the lifting and small prop? Those red coil are brand new.

Are you sure it's the red coil ? In over 15 years I have only had one fail and i own six zenoah motors and race them most weekends ! if you have a multi meter check that you have resistance of 185 ohms or 255 ohms between the red and black leads there are two different red coils both do the same job ! Set air gap with a bit of post card with the magnets away from pick up, make sure that both coils are grounded, if you have relocated the Gray coil then check that the coil inside the red spark plug cap is making a good contact with the HT lead some times when you twist the cap the spike pulls out and doesn't make contact especially with vibration of the motor

All good info. I have to agree I have never really had much problems with the red coils. The spark does weaken as rpm get higher... You can try a smaller plug gap to see if that changes anything. Are you sure it is the coil ( spark) that is giving out though? Could be something ales altogether...??? How are you confirming that it is the coil ?

i'm pretty sure is the red coil that caused the engine stall. I replaced with a new red coil today and it works fine at the beginning but the engine stall again after around one tank of gas . No spark at all on the spark plug and it is 3rd for this week. Feel So fed up and frustrated. I will ship the coil back to the local Zenoah supplier and they will send it to Japan for inspection.

So after the engine stalls, you bring it in, and test for spark and it is dead? No more spark at all? That's interesting to say the least...

Yes, i try to start the engine but it can't be started because there isn't spark at all. That's rare right. I've been involved myself into the rc gas boat racing for 8 years and this is the first time having this crazy problem. Spoil 3 red coil in a week, funny huh!

This is certainly very strange as i said first I would test the Resistance of the coil's before sending them off I have found the motor will run with air gap smaller or larger I cant think of much you can do that would blow them as all they do is send a timed low volt pulse via the red lead to the gray ignition coil which turns low volts into high volts for the spark plug the magnets on the fly wheel prejudice the low volts and the timing of the pulse to the gray coil ! The gray one can be damaged by turning the motor over with out the plug being grounded ( I use two crocodile clips and a short bit of wire to ground the plug body ) that way you can pull it over as much as you like handy if it takes a big gulp of water which mine often do as we race in the sea.

Thank you for all the suggestiion. I just checked the resistance with the meter this morning and the three spoiled red coil indicated different reading with the brand new one. Once again i confirmed it was the problem of red coil . So, i will return the red coil back to local Zenoah supplier. Again, thank you for all the information.