Motorcycle Repair: No start/Suzuki, suzuki dr400, suzuki manual

Question
I realize you normally work on Hondas but the same solution may apply to other bikes. I have a Suzuki DR400E dual sport bike. I was riding along with no apparent problems when the bike backfired loudly and died. I changed the sparkplug to no avail. I checked the starter and it spins but does not sound like the engine itself is turning over. I tried rolling it and "popping" the clutch but the bike just sounds like the cylinders are moving but no attempt at firing. Thanks for your help and time.

Answer
Funny, last December I was riding my Honda up in Waimea and came across a Suzuki DR400 rider on the side of the road with the same problem! We stripped off the bodywork, using my toolkit tools, checked all the wiring connectors to the CDI, kill switch, ignition switch and coil. Nothing seemed really obvious, but when we cranked it up again, it had spark where it hadn't had spark before. Battery was too far down to start the bike with e-starter and we tried to push start it, but still didn't fire. Finally, he called his friend to come and gather it up, so I don't know what the final outcome was.

Ya gotta go back to the basics when troubleshooting no start conditions:  Does it have:
COMPRESSION?
SPARK?
FUEL?
AIRFLOW?

The CDI is triggered by a pulser coil under or next to the flywheel, which sends a signal to the CDI box, that generates a signal voltage to the coil, which fires the plug. Gotta check all the components in the chain, to see if some are failing or have died. Pulser coils failures are common, as well as CDI controller boxes. Loose wiring connectors, especially on a thumper can cause electrical failures and sometimes a sudden surge or interruption to the CDI box can blow its circuitry. You have to consult a Suzuki manual for specs and troubleshooting info.

If the motor turns over and has compression, then the problem is probably not mechanical Leave the spark plug out of the head, turn KILL switch to OFF and then spin the motor over and check compression.

You could have had some kind of fuel flow blockage or a type of major vacuum leak due to failed diaphragms or broken vacuum lines.

That's about all I can say about that...

Bill Silver