2n weak spark

[ronztractor]

I know this subject has been bet to death but here goes.
I'm working on a friends 2n he said it started running poorly and has put a lot of parts in it cap,rotor,points,coil,wires.
It has very weak spark 1/8 or less .
I've had the distributor out and went through all the Cks (Bruce va) had suggested everything looks good.
One thing I noticed from other threads is the voltage at the coil is 6.3v after i bump the engine over the low voltage is 5.8v I thought it should be half that.
Any thoughts .
Thanks.

 

[JMOR]

(quoted from post at 23:30:29 09/14/15) I know this subject has been bet to death but here goes.
I'm working on a friends 2n he said it started running poorly and has put a lot of parts in it cap,rotor,points,coil,wires.
It has very weak spark 1/8 or less .
I've had the distributor out and went through all the Cks (Bruce va) had suggested everything looks good.
One thing I noticed from other threads is the voltage at the coil is 6.3v after i bump the engine over the low voltage is 5.8v I thought it should be half that.
Any thoughts .
Thanks.

erhaps a 12v coil in a 6v system?

 

[Dell (WA)]

Ron..........I'll 2nd JMOR suggestion 12-volt coil on 6-volts. Unfortunately, there is NO identification on EITHER the original 6-volt or modern 12-volt square can coil fer the 4-nipple engine. BOTH use the SAME infamous ballast resistor. .......Dell

 

[souNdguy]

Try to figure out your coil, and also make sure you do have a resistor , and good wiring.

Now my guess is possibly this:

Voltage drop is dependent upon current flow.

if the poitns are glazed they may just barely be conducting any current, thus the minimal voltage drop.

clean the points and re-test, after of course making sure you have the correct coil and oem resistor.

 

[ronztractor]

Thanks I'll ask him where he bought the coil maybe the part # will identify the coil type.
Is the primary resistance in the coil the same on 12v as 6v .?
I'll run some emery cloth across the point also.
I did not see much voltage drop across the ballast resister (which is new) what should it be?
Thanks

 

[Bruce (VA)]

" Is the primary resistance in the coil the same on 12v as 6v .?"

No.

.5 to 1.5 ohms for a 6v coil & 2.5 or more for 12v.

Are you sure it's the OEM ballast resistor & not a fixed ceramic resistor?

The OEM ballast resistor is .3 ohms cold & 1.7 ohms red hot.

" I'll run some emery cloth across the point also."

Check point resistance; if you have any, use cardboard or brown paper.
75 Tips