07 Kx250f Won't Start

[Jack19978]

Hey all

 

so i bought this 07 from a friend and it had been sitting a few months, since it didn't have an hour meter and it came with a variety of new parts i did a full engine rebuild so i can keep track of hours on the engine. This is my first bike but i have worked on them and ridden before so ill post everything i know about the bike currently.

 

Valve Clearances (direction if looking from rear of bike)

 

Exhaust Left: 0.20mm

Exhaust Right: 0.20mm

 

Intake Left: 0.12mm

Intake Right: 0.12mm

 

timing is spot on, no spinning on the shafts so it's all okay there

 

Carb

 

fully taken apart and cleaned literally a week ago by myself everything is functioning as normal

all of the jetting is currently stock (cant remember numbers as i was a little silly and didn't right anything down just remember it being stock)

Elevation 650m (2100ft)

Temperature here currently is about 24 Celsius (75 Fahrenheit)

 

Compression

While i haven't been able to get my hands on a compression tester, it certainly feels like there is enough when kicking or generally turning the engine over

tested for a spark and that's all okay too.

 

The weird thing is that if i kick for long enough i can smell the burnt fuel as you would on a bike that's been running so something is happening but i just can't put my finger on it.

 

Any advice would be greatly appreciated, i am new here so a big hello to everyone as well.

 

 

 

 

 

[twowheelbamf]

Hey all

 

so i bought this 07 from a friend and it had been sitting a few months, since it didn't have an hour meter and it came with a variety of new parts i did a full engine rebuild so i can keep track of hours on the engine. This is my first bike but i have worked on them and ridden before so ill post everything i know about the bike currently.

 

Valve Clearances (direction if looking from rear of bike)

 

Exhaust Left: 0.20mm

Exhaust Right: 0.20mm

 

Intake Left: 0.12mm

Intake Right: 0.12mm

 

timing is spot on, no spinning on the shafts so it's all okay there

 

Carb

 

fully taken apart and cleaned literally a week ago by myself everything is functioning as normal

all of the jetting is currently stock (cant remember numbers as i was a little silly and didn't right anything down just remember it being stock)

Elevation 650m (2100ft)

Temperature here currently is about 24 Celsius (75 Fahrenheit)

 

Compression

While i haven't been able to get my hands on a compression tester, it certainly feels like there is enough when kicking or generally turning the engine over

tested for a spark and that's all okay too.

 

The weird thing is that if i kick for long enough i can smell the burnt fuel as you would on a bike that's been running so something is happening but i just can't put my finger on it.

 

Any advice would be greatly appreciated, i am new here so a big hello to everyone

 

it would help to know what jetting you are using and clip height u are running, you are absolutely sure you are running stock jetting? 

 

how many turns out on the fuel screw?

 

will the bike start with choke on?

 

is the pet cock open?

 

is the air filter clean?

 

are you turning the throttle when trying to kick start?

[Jack19978]

I'm positive the jetting is stock, the needle clip is in the third position

The fuel screw is 1 3/4 turns out

Bike won't start with choke or without

Petcock is open

Air filter is clean

Bike won't start no matter the throttle position, no throttle or full doesn't make a difference

[billygildark5007]

May I ask how you cleaned the carb? It's almost impossible to completely clean a pilot jet and its circuit with carb cleaner and an air hose. Did you do the dental floss/fishing line trick on the AF passageway? I've heard around a thousandth of fuel varnish will turn turn a #41jet into a #38ish making starting almost impossible if your sure timing, compression and fire are correct.

[twowheelbamf]

I'm positive the jetting is stock, the needle clip is in the third position

The fuel screw is 1 3/4 turns out

Bike won't start with choke or without

Petcock is open

Air filter is clean

Bike won't start no matter the throttle position, no throttle or full doesn't make a difference

 

new spark plug? what spark plug are you running? CR9? CR8?

 

what was the stator coil resistance reading?

 

what is the coil winding resistance?

 

does the engine even sound like it wants/trying to start? 

[Jack19978]

I cleaned the carb the usual cleaner and compressed air way, didn't know about the floss/fishing line trick so ill have to take the carb apart and try that.

 

Running a Cr8e plug

i didn't check any resistances regarding the coil, but i have tried 2 different coils with no success unless i am unlucky enough to have two bad ones.

It sounds like it tries to fire and i can smell exhaust fumes if i kick for long enough

[nesc103y]

I cleaned the carb the usual cleaner and compressed air way, didn't know about the floss/fishing line trick so ill have to take the carb apart and try that.

 

Running a Cr8e plug

i didn't check any resistances regarding the coil, but i have tried 2 different coils with no success unless i am unlucky enough to have two bad ones.

It sounds like it tries to fire and i can smell exhaust fumes if i kick for long enough

 

Also check the fuel pump diaphragm. Sometimes they dry out and crack, or fill up with dirt

Edited June 9, 2016 by nesc103y

[twowheelbamf]

I cleaned the carb the usual cleaner and compressed air way, didn't know about the floss/fishing line trick so ill have to take the carb apart and try that.

 

Running a Cr8e plug

i didn't check any resistances regarding the coil, but i have tried 2 different coils with no success unless i am unlucky enough to have two bad ones.

It sounds like it tries to fire and i can smell exhaust fumes if i kick for long enough

 

Check the stator

 

If you tried two different ignition coils that were confirmed to be good, then there is no spark or weak spark. No spark, no fire. This could mean a bad stator or magneto.

 

 

Are you running stock exhaust?

[Jack19978]

I'll get out the multimeter and give it all a test, yes I'm running the stock exhaust, I'm getting a spark when testing outside the engine but could the stator or magneto or even just a bad plug prevent it from working under compression?

[Jack19978]

quick update, re cleaned the carb with no luck, new spark plug gave a brilliant spark, but still no luck, then by chance when i turned the engine to TDC to check timing again, as the compression stroke progressed i heard a leaking sound (i'm not sure how i missed it before), pulled the head off and sure enough i have valves that aren't sealing properly, doing the old fuel in the combustion chamber trick showed a very large leak in fact, going to reseat them tomorrow and hopefully get her all back together before i go away on Friday, fingers crossed this is the problem.