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400/4 no spark

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adriangsmith:
Hi All,
I can't get a spark out of my newly built 400/4.
have fitted new points and condensers, set gaps and timing.
Get spark at the points but not from the plugs.
Have checked 12v at black white wire on coils, earthing from coils to frame and continuity of the blue and yellow wires to the points. checked and changed plug caps to no effect. Have also checked engine kill circuit and neutral switch. Starter motor works OK.
Coils are getting warm so assume they are getting power.
Apart from this i do not know how to check the coils themselves.

What am I missing??
TIA
Adrian

hairygit:
Sounds like you have assembled the wiring to the points wrongly. The wire that attaches to each set of points should have insulating washers either side of the terminal on the wire. The terminal MUST NOT be in contact with the body of the points, ONLY the spring, otherwise you have the coils permanently grounded and they wont spark!. Also, did you clean the faces of the points? They are coated with an anti corrosion grease/gunge which must be cleaned off.

mike the bike:
Assuming the 12v on the coils is ok (black/white), unplug the blue and yellow wires by the brake switch.  If you momentarily earth the negative end of the coil,  you should get a spark.  I'm thinking the same as Hairy: you've got a permanent ground on the points,  which  is why the coils are getting hot.

ogri211:
To check the coils you need to disconnect them then take a primary and a secondary reading with an ohm meter I don't know the exact figures but the primary which is taken between the 2 thin leads should be about 4-7 ohms and the secondary taken between the 2 ht leads should be somewhere between about 25000 to 35000 ohms if you check both of them they should be roughly the same , usulay if the coil is knackered you will have an open circuit between one of them.

adriangsmith:

--- Quote from: ogri211 on April 14, 2018, 04:42:19 AM ---To check the coils you need to disconnect them then take a primary and a secondary reading with an ohm meter I don't know the exact figures but the primary which is taken between the 2 thin leads should be about 4-7 ohms and the secondary taken between the 2 ht leads should be somewhere between about 25000 to 35000 ohms if you check both of them they should be roughly the same , usulay if the coil is knackered you will have an open circuit between one of them.

--- End quote ---
Hi all.
Problem solved. Forgot to clean the points contacts!
Always the simple things that get missed!
Fired up first time.

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