Do I need new coils?

[radio one]

I need advice regarding whether or not to purchase new coils. I recently built a bobber using an 1978 XS650 standard as the donor bike. Electrical system includes new battery, brushes, rotor, regulator and rectifier. Battery is fully charged and charging system works well. My problem is bike starts fine when cold and runs great. Then after I shut down, bike is very difficult to start even after a few hours. Runs rough, and misses but gets me home. Next day same thing. I checked the coils (they are original 1978 coils). windings meter at 5 ohms and 9000 ohms primary and secondary windings. The coils appear to spec out ok. Any suggestions would be appreciated. I thought the coils were bad but the ohm meter says otherwise. Is it possible for the coils to check out ok when cold but still fail when hot after running? I don't want to throw money at a problem that may not exist. Thanks for the help. One more thing, I also have new points and new condenser.

 

[fredintoon]

I checked the coils (they are original 1978 coils). - - - windings meter at 5 ohms and 9000 ohms primary and secondary windings. The coils appear to spec out ok. Any suggestions would be appreciated. I thought the coils were bad but the ohm meter says otherwise. Is it possible for the coils to check out ok when cold but still fail when hot after running? - - -

Hi radio one,
There's many, myself included, that fought an ignition problem for weeks before fixing it by cleaning the carbs.
That said, those coils are 34 years old, may well test out OK cold but fail when in use and were el-cheapos to begin with.
Switching to good quality modern coils that put out twice the Voltage will certainly improve the bike's performance.
And if the problem goes away you won't have to clean the carbs.

 

[kopcicle]

50% of carb problems are 90% electrical

Meaning to say eliminate the electrical before allowing the fuel system to drive you crazy
Not that carbs don't get out of wack but get the electrical solid first .

As to the stock coils , I don't use them and haven't for close to 30 years . Read into that whatever you want .

~kop