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1975 DT175 No Spark. Please Help


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Hello everyone.

So i just picked up a 1975 dt175 for my wife to cruse around on. It worked great when i picked it up a few days ago. Took it around the neighborhood a few times since then and was really impressed with how it ran.

The PO had some crappy turn signals on it that looked horrible, so i removed them.

The battery was not holding a charge, so i had the battery out sitting in my truck so i could get the replacement.

Today my wife and i went on a little ride, and about 10 min in she "stalled" the bike. From what i can tell it felt like it ran out of gas.

Tried and tried to get it started again with no luck. Got back to the house and found no spark at the plug.

So what did i mess up by just removing the turn signals and running it without the battery? I thought the battery was for the lights only, and since i did not have turns on, no need for the battery. Did i fry a rectifier or regulator or something? I tried a new plug and still no spark. Everything else seems to work fine. kicks over great, and wants to start, but just no ignition spark.

Thank you for your help in advance.

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  • Moderator

Tried another plug?

Tis the first rule of 2stroke. Unless its got electric start it will run fine without a battery although the lighting will be weak.

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It's more than likely a simple problem................

Has the 'kill switch' been grounded?

Did removing the turn signals disturb the wiring to the kill switch itself?

Does the kill switch wiring go into the headlight bowl and has it become disconnected there?

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  • Moderator

Nope. The dt uses a self contained ig system. Im not saying the coil hasnt failed. Unlikely as that is.

Next stop for me if the plug is ok would be checking the points and condenser.

For my money if you broke anything doing the battery or indicators it would not have started at all.

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yip" am with cynic" it ran after battery& turns[ usa for indicators :rolleyes: ] were removed, i think points gap will have closed , as its been layed up for years, the dry rotor will have worn the bacalite down,, resulting in narrow points gap. :icon_idea:

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points look great. new plug. tested ignition coil resistance at 2oms and secondary at 11k. (think the coil is good with those specs) tested the kill switch working fine. looked over as may wires as possible and all looks good. Im almost sure it is the rectifier, but dont know for sure.

found the rectifier, and its tiny! only has two prongs and the bolt to the bike for ground. how do i test the rectifier?

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  • Moderator

Ok said slowly....

THE RECTIFIER PLAYS NO PART IN THE IGNITION. NOR DOES THE VOLTAGE RECTIFIER THEY ARE SEPARATE.

Your ig system consists of primary coil, points, condenser, secondary coil then the plug and thats it. Spluttering to a halt is 90per cent plug or points and condenser.

Have you checked the points and condenser esp the gap.. Condensers are not all that reliable. On my old points bike i fitted mine outside the mag.

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Aye salvage" try cutting 1 inch of the HT lead , and refit plug cap,, :eusa_think: ,

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