I got my 87 cbr running tonight. It had a bad cdi and a blown main fuse. I put on a known good cdi and got fire back then I put on another rectifier and cleaned the carbs. It cranks now but as soon as it starts the cdi starts smoking then blows the main fuse again. I only put a 10a fuse in the main so I dont fry my 125.00 cdi. I have looked over the wiring diagrams and looked for fried wires. I am at wits end. Any Help is greatly appreciated. Thanks

 

I would get a volt meter and check some wires out and also some grounds. My 87 is cranking but not turning over.. I checked all my fuses and its fine..
Check your startor solenoid. I changed mine and it worked much better...I would make sure none of your wires are bad or exposed... You can get liquid tape at any auto parts store.
I would chase down why its blowing that fuse and make sure where the fuse is blowing it has the correct fuse bc I read last night if your not putting in the correct fuse you can really screw your bike up and short out other areas if not your entire electrical system.

 

Refer to the drawing but ignore the neutral switch and side stand switch sections as they don't apply to an '87. Also, cylinder numbers are 1,4,2,3 instead of 1,2,3,4. Sounds to me like you have a grounded wire somewhere between the ignition coils and the Spark Unit ( CDI ).Possibly in the Y/Bu or Bu/Y. Reason being current has to flow through the CDI to get to those wires and to ground which could cause the CDI to smoke and the main fuse to blow. It is good that you put only a 10A fuse in the main slot for now as it will limit the amount of damage. I would not however, try to start the bike again until you have found the problem as you might fry the CDI or other components. You must actually check everything on that diagram. You say that the main fuse blows and it starts smoking after the engine is running but it is okay with the key on? If this is true, you have power throughout this entire circuit with the key on. The difference with the engine running is the pulse generators start sending a signal to the CDI which tells it when to fire the ignition coils. This indicates that the problem could be in the pulse generators or those wires. Disconnect the individual components and check it's resistance. If the resistance is not within specs then you have found your problem. If everything checks out, then check of each individual wire to ground. You should have infinite or very high resistance to ground. If not, then that wire is touching the frame somewhere and you will have to find and repair it. It will not always be visibly obvious, i.e. black or frayed. Has the bike been wrecked? When I wrecked mine, it scraped a bunch of wires up at the fuse box. I had to reinsulate them all to prevent grounds. You will have to get an inexpensive multimeter if you don't already have one. They are $10-$15 at your local auto parts store. Download a factory manual of your own here.
http://www.cbrextreme.com/downloads/...manual-54.html
You will find this diagram in the Ignition System section.
Good luck! PM me if you have questions and please post your results.