No start backfire!

Hello it’s me again. I bought this bike as the previous owner said it needed pickup coils no spark. It actually needed a CDI box and the spark issue was resolved as I painfully found out but I got the bike back together went to start it and now it just cranks and cranks then backfires sometimes from the carb other times from the exhaust I took the carb off and cleaned it and didn’t change anything am I missing something? I’m not real familiar with carbs

 

From your other thread so everyone knows a bit of history:

"Well first I replaced both ignition coils then I replaced the pickup coils which gave me about 30 seconds of run time before dying from the same issue before I went through the entire harness even swapped Atari units still nothing then I ripped out the harness did just the most basic wiring to start the bike battery to starter solenoid ignition switch start button regulator/rectifier TCI coils I cleaned the connectors I needed to and still no spark I replaced the spark plug caps the only thing I can think of at this point is the TCI when I started this endeavor the battery was brand new and fully charged now after multiple attempts to start it the battery has dwindled down to 11 volts so when I attempt to start it after checking wire connections I use a battery pack to jump it and check the system to make sure everything is getting a full 12 volts.

So lots done but eventually no spark isolated to the TCI. Sometimes when they backfire it is helpful to know when, such as when I am cranking or when I stop cranking, or maybe when I cycle the key from on to off to on?

 

Thank you! And it’ll backfire after cranking for about 10 seconds at the carb when I stop cranking it backfires out the pipe a lot louder if that helps

 

So backfiring out of the carbs sounds like some really bad timing. Are you sure all four are sparking? Are you sure you have the firing orders wired properly between pickup coils, ignition coils, and TCI. Note that if only one pickup coil is working the TCI will create spark on the opposing cylinders

Backfiring after cranking is that last spark before the TCI shuts down, and usually just means the cylinders / exhaust loaded up with fuel and was then ignited. It also occurs if the key is cycled off to on about two seconds after that if the cylinders are loaded up and the TCI creates that same shut down spark

 

I did make sure all 4 have spark the coils are also brand new but it is entirely possible I have the wires going to the wrong place. The spark plugs are also filthy but I don’t think that would cause a backfire but could cause weak spark I’d imagine I’m picking up after work to try

 

While sitting on the bike: The left plug wires go to cylinders 1 and 4. The right plug wires go to cylinders 2 and 3. The primary hot wire for the left coil is orange, and the primary hot wire for the right coil is grey. The other two primary wires can go to either coil.

 

Plug wires were the problem ha! Now it’s doing a clunk noise everytime I hit the start button and does not start. It did start after I got the plug switched. I’m about to start taking offers and sell this thing.

 

Bad solenoid replaced cranks over again but doesn’t start. WHAT IS WITH THIS BIKE?!

 

@BRA - take a deep breath and check the basics. Fuel, spark, compression.

I am the worst offender, admittedly, but seems like it’s easy to get frustrated and it turns out to be something stupid.

you’ll figure it out.

 

Like Dan said, the basics are where most issues lie. You mention that the PO told you the issue was spark related, the issue with that the PO's are not reliable. You mention there is no spark, so I am assuming you have taken off a wire, held it to a piece of metal, and looked for spark? If you don't see one, maybe do it when its dark out to really make sure (This will also show if the wire is shorting because you will see little sparks where there shouldn't be). If you don't see anything, even after checking all 4 wires, then something is naturally up. I'm not the best at the electrical things on this bike, so defer to someone else for what else can cause a no spark, but I do have one last tidbit. It is possible more than one thing can go bad at the same time. Just because you have spark, doesnt mean you have fuel, doesnt mean you have compression. It can be really hard to diagnose issues as you know if you arnt aware of ALL of the problems. With that in mind, if it were me, along with what I already mentioned above, I would do a compression check on the cylinders (no point continuing if you've got crap compression, refer to other posts on protocol), and I would also give it a few huffs of starting fluid with cranking just to see. Lastly, I would also check the battery/ wires with a multimeter. Make sure you are above that 12V when you get started with diagnosing (anything below 10 and the TCI wont work). There are diagrams and forum posts about people tracking voltages throughout the ignition system, I think you can check it before the coils to see the fluctuations, but youll have to search for that because I can't remember. Again, what Dan said. Check the basics... Hope this helps