cold start issues ignition and coils

I just bought a 83 550 maxim. Great bike. Good compression, carbs rebuilt this year, idles like a p****cat. It runs out of this world. The problem is cold starting. It is not an issue when it runs awhile. Starts fine then. The PO figured carbs thus him forking the bucks for the rebuild.

I figured the battery first. I bought a new one all charged up, and a tender. I checked connections and everything seems good and non corroded. (PO did a great job upgrading the fuse box)

In my diagnosis I found that when it is cold, I get minimal spark. Yellow. When the engine is warm the spark is better but still dim in my opinion. Anyhow, I bought new plugs. Still yellow.

Well I ohmed out the coils. Both primarys in spec at 2.7 ohms. Both secondaries read infinite resistance. So, I take off the NKG boots on the wires and ohm them. 5 ohms each. I then try and check secondaries again, sans the boots in case their happened to be four bad connections. Ha. Still infinite.

Sounds simple enough. Two bad coils right? Well, I am no expert but I have spent a day or two tinkering with hot rod engines and have never had a coil fail when the motor is cold but run good when it is hot. That defies logic or at least what I have seen. I need some help. Has anyone experienced this problem and solved it with new coils?

Am I looking at a possible fried igniter as well?

Any help would be appreciated. Thanks,

 

My pick-up coils have both been temperature sensitive and gave intermittent sparks (one when cold, one when warm!) Wouldn't explain different colours though.

 

I'll bet your difference in spark color is because it pulls more juice to crank cold so you have lower voltage to the coils.

I'd check the starter jets in the carbs before replacing coils. In the front of the float bowl there is a passage with a fixed jet at the bottom which allows fuel in from the bowl. That jet is the first thing that clogs when there is dirt or varnish in the bowls.

 

I had the same problem with my 82 xj750, i went from #5 plug to a #7 and big difference starts no problem now. I am not an expert and have gotten mixed comments about the jump. But i live in Maine and cold mornings are an issue all year.