headlight tries to kill engine

steve matichuk /

when i turn my light on while riding, my engine wants to die. the power surges up and down until eventually it'll stall out. i have to turn the light off periodically to get the revs up so i can turn it back on again, and if i try to idle while stopped with the light on?- forget it!

also, the horn and light won't work at the same time, kind of perilous at night in the city. the bulb looks like one of the old kind with a really large, elaborate filament inside (compared t the size of the bulb). could these problems be eliminated by replacing the bulb with something more current (pardon the pun), or is there even some newer technology that will fit my 6V bulb socket without rewiring the whole rig? there is no battery on this bike, it's a '75 PC50K1 and runs off a magneto coil.

Re: headlight tries to kill engine

it could be many things. from my limited experience it sounds like you have a bad ground in your headlight or your horn. take your horn off and connect the 2 wires with a piece of metal. if this fixes it its your horn. if that doesnt work try the same thing with your headlight.

Re: headlight tries to kill engine

ok dude, i don't know what a PC50K1 is, but i know this: If you have only one or two wires coming from the engine, then good luck.

but if you have like 5 or 6 wires, disconnect the horn and ground the wire, then reconnect all the wires in the headlight (and if they go to the speedo light, make sure those are solid.) once your headlight works, then put your horn back into the rig. This is just to get one thing working at a time. Doing all the electrics at once is a pain in the ass.

but its probably just what harrold said, a bad ground

Re: headlight tries to kill engine

Isn't a PC50 a Honda Hobbit or Express? K1 would just mean "first year" or "first model".

Re: headlight tries to kill engine

well, it its a honda, then like i said before, good luck. The wirings not so bad man, don't be discouraged. Just hack it and rewire it.

Re: headlight tries to kill engine

steve matichuk /

the original PC50 was only built in 1968-69. in 1970 they continued production of the same PC50 model with a few "upgrades" such as switching the motor from an OHC to an OHV setup. all of these subsequent production years of this model are referred to as K1s up until honda started producing the much uglier (in my opinion) PF50 in 1977-78.

i've been burned in the past buying parts and following manuals for the PC50, so this time i decided to be more specific and include the 'K1' suffix when i asked for some help to avoid confusion. apparently this only caused more.

thanks for the advice. i was hoping it'd be easier than all that though. servicing the electrical system o any PC50 is a bitch as all of the electronics (condensor, harness etc.) are INconveniently sealed inside the frame! getting at them requires dismantling about 5 other major parts.

way to go honda!

Re: headlight tries to kill engine

Lo Steve,

Dont have an PC, but i do have an ss50. The problems you dis cribs are sime lair by an ss50 or any honda. When the condenser on your ignition is broke, she will hardly runs with the lights on. Look on the site for wiring diagram and parts list.


Its an Dutch site, but in English writhen.


Re: headlight tries to kill engine

steve matichuk /

dankiel carel.....

unfortunately, the pc is very difficult to wire. it's all inside the frame and everything else must be removed to access the harness

sorry if i got the dutch part wrong, i only speak german

Re: headlight tries to kill engine

Aber tan sprechen wier doch Deutsch, gibt mir auch wenig problemen. Ja du solst deine moped mussen auskleiden. leider gibt es keine andere muglichheid. nicht ganz natuurlich, nur dahr wo die draht endes sind. Gluklich ist der bobine nicht so swehr su erreichen, ersatz deine condensator und deine problemen sind vorbei.


Re: headlight tries to kill engine

steve matichuk /


Ich habe nuer Ein Jahr in Berlin geleben, und Das war vast vor Viere Jahren. Englisch ist Meine Muettersprache (Ich komme aus Canada) und Ich habe hier Keine Deutsche Freunden bei wem Deutsch zu sprachen. dabei, Mein Gramatik wird echt Sheisse- so Ville Woerter vorlorn, so vill habe Ich vergessen!

es tut Mir echt leid,

freundlich Gruessen aus Toronto,


Re: headlight tries to kill engine

Dont know if it will help but had same prob with my little Melody many moons ago.Problem Rear stop/Brake bulb blew got re/placement but was 6v wrong wattage to high.Changed bulb to correct watts every thing champion

Yorki U.K.

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