Weak spark 85' 700X

Newbie on board.
1st off, this is an excellent source of info for the Yamaha Maxim, it might have kept me from buying a manual even! Too long to cheap for sure. I am buying the factory manual. Is this the best choice for this bike?
It all starts innocently enough. Free motorcycle, come pick it up. Overall great bike better give the guy at least $100 so he produced the title. Thus starts the longest trouble shooting process on a bike to date. Many Yamaha Viragos restored so confidence was high.

My issue is weak spark when turning over (blue but a thin line jumping from electrode). Tried all tests I could find here. Except battery load test.
New Dyna coils, wires, plugs, and battery. Checked stator brushes and voltage regulator, to spec. Voltage when turning over, 10.78 at battery. Tried with starter curcuit on a seperate battery, still weak spark. Checked timing (looks good). Currently checking pulse coils for ohms (need ohms for an 85), mine check out at 110 ohms, read that they should be 700 onhere. The pulse cover was left off bike for a while while it was parked outdoors. Seems that both coils lost resistance, but they are still close to the same ohms within 10. Checked for voltage drops and connections thru bike and haven't found anything major in voltage drop, assuming the light will pull 1 volt with ignition on.
I have fuel to plugs and cleaned carbs to start. The only time it has fired is when letting off the starter button.
Any advice on direction will be appreciated.
Thanks!! 8)

 

If you have Dyna coils, they SHOULD be OK
Did you measure the resistance in the spark plug caps? If you pull the rubber boot off the bottom, the center conductor unscrews and will allow you to clean it up, check the spring, and check the resistor.

Firing when you let off the starter button leads me to guess you have a poor connection somewhere. 10.78V is very low.
Once you let off the starter button, the voltage spikes (due to no load) and will finally give you enough power to the coils.

You probably double checked the ground already.

What is the voltage at the coils? (and when cranking)

I've read other discussion about starter brushes and alternator brushes doing ugly things to available voltage at start up but I haven't had any experience (knock on wood)

You might just need a new battery too. If you can "borrow" one from a different bike and give it a try (or simply cart it down to NAPA for a quick test).

Welcome aboard from a previous Minnesotan now in Pennsylvania
You NEED to get the XJCD ordered. For $10 it is priceless.

HAP has a lot of X specific information on his web-site www.maxim-x.com

 

Since putting the starter on a different battery didn't help, I wouldn't think low voltage from the battery is the problem. My bike drops to about 10.5 -10.8 volts when cranking as well, so that doesn't sound too unreasonable.

Are you sure these are the correct dyna coils for your bike? If their primary impedance is not pretty close to the stock coils they might be getting underdwelled. If that's the problem, there won't be much you can do without changing coils.

 

Thanks for the quick response guys. I ordered the dyna coils per their website and the Maxim-X recommendation. I'll installed the new wires and plug caps , they were per recommendation also. I'll double check the ohms on the caps. They are 5K caps and measured that.
I resorted to jumping the battery with a running 4wheeler to see if spark would improve, no luck. Trying to overcome weak battery
I've double checked the grounds, even added a ground to the dyna coil grounding bar without results.
Battery voltage 12.3 sitting, ignition on 11.7
Voltage to the coils (at connector before Dyna) ignition on, 10.7. cranking 9.6. Sounds weak I know. I did have the signal coils disconnected at test, but it sounds the same as when I measured it before.
I have removed headlight for additional cranking voltage, it doesn't cut out when starting.
Battery out going for a test tommorow.

 

Battery not carrying FULL AMPERAGE LOAD, it can show 12 volts, but have enough dead cells to not fire up the coils GET NEW BATTERY AND TRY IT.. OR JUMP YOUR CAR BATTERY ON IT, then see what happens..