My Suzuki DRZ400SY is difficult to start from cold. After running for a while it appears to die and surge on a constant throttle opening. This can sometimes be cleared by pulling in the clutch and reving the engine (although it doesn't seem to reach what I feel should be peak revs). Sometimes it just dies. But it starts again imediately. I don't know if the problems are related but it's driving me nuts. I'm reluctant to go poking around aimlessly while the bike is still working. Therefore any help or advice you can give will be very welcome.

surges(no engine told)
hot, and cold engine
any gear, and at idle too. and PARK.?
rpm varies .
surges at cruise,or WOT, wide open throttle?
misfires. ? violent, felt.
scan the PCM when it surges?
lots of causes even cracked brake booster and crazy vacuum leak, now.
and more lots more,

check for problem coil/s and ignition control module
the indications that an electronic component is failing when it gets hot and causing intermittent spark

is it efi engine or carburator ......you may nedd to clean intake throttle body......

To test fuel flow, have a 2nd person stand over air filter (air filter housing open) with a can of starting fluid in one hand. Don't give any throttle, then 2nd person gives 1-second squirt into air filter while you're turning starter motor (no throttle). When engine catches, immediately give one third to one half throttle. Just before it dies, 2nd person should give another short squirt of starting fluid to keep engine from dying. If throttle won't keep engine running and only starting fluid keeps it running, then yes, no fuel is going through fuel lines. Either its a fuel pump issue or maybe there's restriction because of clogged dirty fuel filter. If it starts but runs rough and has black exhaust smoke, then its clogged or dirty fuel injectors.

You first need to buy a carburetor balance tool.

not too cool kick
is check engine light on, at key on and goes out after running?

you forgot to say, does it restart instantly after it dies.
and does it stink of raw gas after or make black smoke.?

when it dies, can you keep it going with a fast right foot>
if it dont start , right after did you try the secret
unflood mode (wide open throttle)

if car wont start , try test fuel
best is instant start in a can (spray)

key test here is car flooding or is it starving for fuel.
those are the top Suzuki tricks.

not sure about Suzuki but when i did my honda cbr they suggest to seat the pilots lightly clockwise and then back it 2 and 1/2 turns out.

DIFFICULT STARTING CAR IN COLD.WOULD BE A THERMO - TIME SWITCH.THE THERMO TIME SWITCH CONTROLS THE AMOUNT OF TIME THE COLD START VALVE IS HELD OPEN BY MEASURING THE COOLANT TEMPERATURE AND UTILIZING A TIME FUNCTION TO PREVENT AN OVER RICH CONDITION.THIS COULD BE MOST OF YOUR PROBLEM.BUT SCAN IT TO SEE WHAT PCM CODE YOU ARE GETTING.

Sounds like you are having a problem with the fuel injection on it. Take it to the dealer.