81 440 ltd

Purchased a bike from a neighbor. He had the bike sitting a good five years or more non running. I got it to the garage, to kers around a bit. Bypassed the ignition switch as there is no key. Cleaned carbs a bit tested electrical system with 12v test light. Seems to check out. Problem I'm having is no spark once the bike warms up. Any advice/tips things to check for. Wiring looks to be in good shape and when the bike is cold/warming up has all the ponies I do notice it misfires a bit when coming back down from WOT.

How do you know there is no spark? 
The problem could be that it runs out of fuel due to a clogged or improper filter, improper fuel level in the carbs, a malfunctioning fuel valve (petcock), a clogged fuel tank cap vent, and such.

I tested spark with test light as well as placing them on the heads while cranking. Fuel delivery is fine, carbs seem to be in time with each other as well. Once the bike is to op temp it just cuts out it doesn't bog or miss or lack power it just dies. When that happens I pull plugs and test for spark gives off nothing. Let the bike cool and spark is back. I have continuity from the positive and ground circuits. Voltage readings are at or above 12v.

If you have close to battery voltage at the coil positive and the negative side of the coil is being pulsed by the CDI/Points and you still have no spark I would suspect either the HT leads or coil itself is breaking down when hot

Wookie58 wrote:

I came in here to say it's almost certainly the coil. As it continues to fail, the bike will probably run for less and less time before losing spark.

 

In that case, I too will vote for a bad coil.