Misfiring

[orbital]

I have an 83 XS650 Heritage Special. The bike starts but misfires. I changed the ignition coil, new plugs and plug wires. I disconnected the reg/rectifier to see if it would still misfire and it did. I read PamcoPete suggest that. I had recently cleaned the carbs. I'm not sure as to whether it's an electrical or a fuel issue. Bike is stock still has the stock air filter. I need help on better diagnosing the problem.

 

[650Dave]

Make sure that your battery has a full charge before you do anything else. A weak battery can affect the way the engine runs. If it is low, recharge it (if it will take a charge) and check the alternator output. If this all checks out, let us know and we will go from there. Dave

 

[orbital]

I bought the AGM battery from Mikes. Charged it, put it on the bike and it's still misfiring. I even cleaned the carbs again. Bike still has stock air cleaners, stock carbs. It's still misfiring. Now I'm thinking it's the TCI that's defective. How can I check this?

 

[xjwmx]

Now I'm thinking it's the TCI that's defective. How can I check this?

I don't know of any check except by substitution, and it's good to have a spare around to do that with. If the TCI starts acting up it will usually turn the bike off, from what I gather, but anything's possible. One thing you can do maybe to see if it's the ignition is put a timing light on it and see if the misfire corresponds to the absence of a flash.

People have reported misfiring that they attribute to a weak magnet in the rotor, but it seems like that doesn't start until around 3k rpm or higher. And I think pulling the regrect is a test for that problem and you already did that.

 

[osteoderm]

It seems almost too obvious to ask, but you didn't mention it in your original post... have you already checked/set the timing, cam chain tension, and valves? Also a good idea to check for clean fuel flow. People have been caught off-guard by stupid simple things like clogged gas cap vents, faulty vacuum petcocks, etc.