my 1990 model will crank, but not start, and I I believe it has something to do with no spark. going through the manual for the bike, I got to the section where you test the spark unit. my spark unit seems to be different than the one in the images, with only one plug as opposed to the 6 pin and 4 pin ones.



testing the black and white wire to dark green (ground), I get the proper ~12 volts. however, when testing the resistance, blue/yellow to black/ white, as well as yellow/blue to black/white, I get 4.8 ohms of resistance, more than the manual says (2.5-3.1)
after this, I tested the white/yellow to yellow, getting the proper resistance, but I don't have a white/blue or blue to test. I tested the resistance of the light green one , and the one behind it (a light green/black) one but there's no resistance between those two. any assistance would be very helpful.

 

No spark at the plugs I assume?

 

I just did this exact same test last weekend but mine were within spec. I’m not sure what it means if it is higher. I have a 1990 as well and my CDI and plug looks the same as yours with the one plug. In 1990 we only had 1 pulse generator so I think that’s why the blue wires are missing. I never figured out the light green wire. Have to trace it back on the bike since the wiring diagram doesn’t match up well with our bike. The manual accounts for all 4 years but doesn’t show all of the changes for 1990 very well.

To see if you have spark you’ll need to pull the plug and connect it back into the wire. Hold the threads up to the engine block or exposed metal on the frame and crank the bike. You should see a spark at the plug.

if no spark, check the resistance on the 2 coils. Check at the coil (the part that the spark plug wires connect to) and also check at the end of the two spark plug wires without the spark plugs. CDI rarely go bad.

also the resistance at the pulse generator connection plug. It’s easy to get to if the tank is off. It’s the only wire that runs from the left engine cover.

 

May as well check the regulator while you’re at it.

 

No spark at any of the plugs, I had tested by holding them near the case to see if there was anything like you had said ImG2theB. that's what got me to go looking at the spark unit because it looked different than in the manual. Its good to know that it hasn't been changed out for some aftermarket spark unit. I will go back and start checking the regulator and coils then.

sorry for not getting back sooner, ran into some issues with other vehicles that took priority.

 

You don't hold them near the case to check for spark - you need to hold the lower metal part of the plug on something metal to ground it (not the engine case - that's painted) - it needs to be bare metal, like an unpainted bolt top.

 

In addition to what @rockpool said, you can buy a spark fire tester for cheap. it makes the job a bit easier.

 

F1 engine wasn’t painted. If it’s painted now, it’s because someone made it look pretty. Side engine covers were the only parts painted since they were slightly visible with the fairings on.