I have a later model 80 in evo bored .020 but basicly stock, cam info unkown at this time. running a compufire single fire 20600 ign idles great revs fine but as it warms up and gets hot it acts like a misfire or droping a cylender but i can rev out of it. carb has been cleaned and rebuilt. compression checked found bad head gasket replaced that and problem still happens so leads me to ign dont know much about the evo style engines. thinking module or coil dont really want to throw parts at it but dont have a problem with it i guess but what parts to start with and what parts are there lol. where should with i begin or are there tests to rule out certian things. if i start cheep it will be the most expensive part or if i start expenxive it will be the cheap part .thanks for any help

 

It sounds to me like the cam sensor. Located behind the derby cover.

A couple of tests for it are heating it with a heat gun and seeing if that recreates the fault. Or you can use a chiller spray to test it when hot and see if runs smoothly as you cool it down. You'd take off the derby cover for both tests.

I recently replaced one. The newer part is better made than the original design in my '86.

My issue turned out to be the module. The updated ignition module really improved my Evo's performance.

 

As JC says as well how old is the gas in the tank?

 

gas was drained and new premium was put in sorry i neglected to put that in my origonal post

 

1986 didnt have cam sensor

 

Mine is a much later one and can sensor is on left front side of lower case I believe not sure tho some sensor is there attached to the voltage regulator

 

Your right!

The ignition sensor on EVOs is referred to as a crank sensor.

On The T/C is a cam sensor.

 

I assume that sensor is the one on the lowerleft side of engine

 

OK lets try it this way I believe ign sensor, ign module, coil, and voltage regulator are the parts I should be looking at are there tests I can perform to check any of them or am I best to just start replacing them I do not have a bike I can rob parts from to check or rule one out

 

Since you have a nose cone ignition (and not the separate module deal) try running the bike without the timing cover in place. This may tell you if it's a heat issue with the programmable ignition itself. It seems the biggest failure mode with nose cone ignitions are heat related. And the first guy who designs a louvered timing cover that rams in cool air but keeps rain water out will make a million bucks! LOL!