2009 TE310 - Only starts with WOT

Hello - was hoping someone can steer me in the right direction. Troubleshooting my 09 te310. Just cranking the bike will not start. However when I modulate the throttle and hold it wide open - it will sputter to run. Wont idle.

Any ideas.

couple of guesses and suggestions:

• clean the injector (carb spray)
• inspect/check the TPS (mikuni doesn't seem to have a big issue with the tps tho)
• fuel flow? (pump, psi, filter, internal hoses)
• rag in the intake or exhaust. how's the air filter?
• replace the plug- just for grins.
• keep throttle closed; spray starting fluid. does it start?--> fueling issue or TPS. Nope?---> may be electrical or air
• vacuum leak? vac port, cracked manifold, injector seal, MAP leaking.
• bad gas
• coil is going intermittent or bad cap.
• low compression or burnt/stuck valves. timing jump?

Temperature sensor is faulty pull wire of the sensor and it should start.sensor is located at the back of the barrel

good call- 'specially if you have the old black CTS. weird voodoo

it defaults to full-on rich when it fails, IIRC.

Injector - cleaned. The current injector is yellow, but a do have a 4 hole brown/red injector -- is there a difference?
Fuel pump - I do get pressure but it drops off (posted a thread about it).
TPS - Check how? There doesnt seem to be much to it..Also, is there a difference between a 250,310,450 TPS or throttle body for that matter?
Rag In the intake - def - not.
plug - replaced
starting fluid - would need to try.
vacuum leak? vac port - you mean the head vent tube? Map? Where?
gas - fresh.
coil - resistance checks out.
Compression - while i didn't do a specific compression test, I did perform a leakdown which was fine.

Regarding - cts - the sensor is brand new but I can certainly try and unplug it.

..also wouldn't/shouldn't iBeat indicate an issue with the coolant temp sensor - if there was a problem there?

Yellow injector should be stock 4 hole.

I believe all the mikuni TBs are the same 2009-2012
Early bikes have 4pt injectors 2012's have 12pt.

thanks .. so in theory a 450 (mikuni TB) could possibly work on a 250/310? Any idea about the red injector?

crank no-start/super hard to start followed by opening throttle some/playing with throttle then burbles to life somewhat then dies usually indicates tight valves.

if dis-con the cts gets no results check the valves.

Exh .008 r & l
Int .004 l - .006 r

Left intake is on the tighter side - but in spec. I am waiting on the correct shim to get it to .006

Unplugging CTs no change

triad of the combustion process: fuel-compression-spark. if you have properly timed spark + good compression then its gota be missing fuel. prime the chamber through the plug hole. if it lights right up then dies ya got a fuel delivery issue.

get the $1.99 can of starting fluid.
Try carb cleaner as a poor substitute if, for some reason, you're starting fluid adverse.

But if you're losing fuel pressure (btw: how much?) then you have probably found your problem. I'd guess it's a bad pressure regulator, cracked fuel line, cracked filter- or possibly a bad pump. (and I checked your other thread- looks like I said the same thing a last month; so did R_Little)

ill get the starting fluid.

Pressure begins to drop to zero psi after the pump primes. Not sure why I didnt followup on the other thread.

Split in the fuel filter or a split in the fuel hose? loose clamp, (not likely, they are tight at the factory)?

its a new fuel pump (ebay) - using in tank gates fuel line - metal filter. I would need to recheck the clamps ..but I put them on tight with oietiker clamps.
- Pump primes and builds to 43 psi > pump shuts off and will pressure starts to drop back to zero.
- Cranking pump steady at 43 psi
- When modulate the throttle to get it running - pressure is solid and does not fluctuate while running.

I have starting fluid - need to try that, I need to remove the intake boot for that test?

You can spray it anywhere in the intake tract that'll get it to the combustion chamber. Vacuum port, air boot, throttle body, or spark plug. Might not be compatible with a foam filter. Just a short squirt.

Sounds like the check ball in the pump or the regulator is bad. But that may not be a huge issue or the cause of your problems.