Bad coil?

[johnhend]

A big thanks to Steve for stoping by and helping with valve adjustments a couple of Saturdays ago.

Now on to my newest problem. Had a problem with cylinder 1 not running. Installed a new spark plug and got it running. After about 10 minutes of driving I lose the cylinder again. Put in another new plug, runs again. After another 10 minute ride I lose the cylinder again, I limp along for another few minutes and then I lose cylinder 4. So I coast into a parking lot, let it cool down for a while and start it back up, with all four cylinders.

I'm thinking that the coil stops working after it heats up. What do you guy's think? I already bought a used set of coils so this time I'm thinking I'll buy a new coil.

[dcil]

sounds logical to me. I'd try switching the 2 coils and see if the problem switches cylinders.

[johnhend]

Does anyone know a good source for a new coil? Should I get a 3 or 5 ohm coil? I've got the dyna s ignition. Ebay has a 5.0 ohm dynatek dual output coil for $69. Can I buy any dual output 3 - 5 ohm coil as long as it'll fit on the bike?

[erch]

Bump cause I'd like to know for my 77 GS750 as well.

[almarconi]

If you have a points ignition system you want 5 ohm, otherwise 3 ohm. Measure your coils to see what you've got in your bike.