GRRRRRR help please

So about a week ago went riding bike ran like a top.. threw out the week all I did was new chain and sprockets.. Went to ride to day bike fired right up and ran great for about 5 min then started acting like it was dying or would just die even if i would try to gas it only some times i could save it and keep it running.( kinda seamed like it was floooding or running out of gas but i could see gas in the fule line going in to carb) It will still start every kick but dies with in one second.. any ideas as i was a 2 smoke guy so no idea where to start.. bike is a 98 yz400f

Unscrew your gas cap and start it and see if that helps, if not drain gas tank and carb, clean your carb with all the jets, add (fresh) gas and try again.

Unscrew your gas cap and start it and see if that helps, if not drain gas tank and carb, clean your carb with all the jets, add (fresh) gas and try again.

Been there. I bought a IMS tank, put it on took the bike out ran then died, ran died. Come to find out the vent hole in the cap wasn't drilled out :smirk:.

I drilled a hole in it and I was good to go.:eek:

that could make sense will try that when i get home thanks guys. Any other ideas?

that could make sense will try that when i get home thanks guys. Any other ideas?

if you're jetted right and the engine has compression and spark - its likely a bad vent hole.

Figured it out yet?

yes I did the pilot screw was in ALL the way somehow.. but the book said to bring out 1 1/2 turns I had to bring out im guessing close to two turns so time to play with the jet my jetting is 175 main 65 starter and 48 pilot to get my pilot screw at 1 1/2 turns out what pilot jet would you switch to ?

Edited by hende
yes I did the pilot screw was in ALL the way somehow.. but the book said to bring out 1 1/2 turns I had to bring out im guessing close to two turns so time to play with the jet my jetting is 175 main 65 starter and 48 pilot to get my pilot screw at 1 1/2 turns out what pilot jet would you switch to ?

If you running good at 2 turns out you are fine. In theory, you should adjust your fuel screw before each ride as the temp, humidity, and elevation changes have a effect on the pilot circuit.

Check this thread for determining if you need to adjust your pilot jetting:

http://www.thumpertalk.com/forum/showthread.php?t=327405

And this one:

http://www.thumperfaq.com/jetting.htm#PJ

This thread will tell you everything you need to know about YZF's:

http://www.thumpertalk.com/forum/showthread.php?t=447989

If you running good at 2 turns out you are fine. In theory, you should adjust your fuel screw before each ride as the temp, humidity, and elevation changes have a effect on the pilot circuit.

Check this thread for determining if you need to adjust your pilot jetting:

http://www.thumpertalk.com/forum/showthread.php?t=327405

And this one:

http://www.thumperfaq.com/jetting.htm#PJ

This thread will tell you everything you need to know about YZF's:

http://www.thumpertalk.com/forum/showthread.php?t=447989

thanks for the info:ride:

got it running descent but it seams like it is running hot have not rode it yet just fired it up in the drive way for 5 min or so and seamed like it was putting off alot of heat. I'm thinking this would be caused from running lean right? so that would mean to turn out the pilot screw somemore? thanks for any and all help :eek:

got it running descent but it seams like it is running hot have not rode it yet just fired it up in the drive way for 5 min or so and seamed like it was putting off alot of heat. I'm thinking this would be caused from running lean right? so that would mean to turn out the pilot screw somemore? thanks for any and all help :smirk:

That's what they do. If you don't have lots of air passing over the radiator they will run hot. If your in a shaded area or somewhat dark area you will see your head pipe glow red also.:eek:

so it is still starting but once it gets warmed up if i give it gas it dies should i come out more with my pilot screw? Sorry for being so clueless first thumper:bonk:

Check to see if the accelerator pump is producing any squirt at all.

When you say "give it gas", how much throttle are you talking about, and how hard/quickly are you twisting?

i have tried to give it gas by rolling on nice and slow and nailing it fast

Read the post in Common Threads regarding adjusting the pilot screw. If that fails to fix your problem, carefully remove the screw altogether. You should find a spring, a washer, and an O-ring. Both the washer and the O-ring may stick in place within the bore, and you might need to extract them with a small pick or a bent paper clip.

If the O-ring is there and in good condition, your pilot jet probably needs cleaning, or you have a major air leak, or the vacuum release plate on the engine side of the slide may be worn or damaged.

It's also possible that something is blocking the main jet and not allowing fuel to rise to the main discharge nozzle as the throttle is opened.

I'm thinking a plugged jet. Even the most microscopic debris will jack things up.

These guys like to run hot at a sit still idle... Best bet tho is to pull the plug to be sure. That is always the best indicator to a lean/rich mixture. Be sure you don't have water in your oil... My bro has a 400 and he had to change the water impeller seal twice because of it overheating. If no signs of this occur I wouldn't be alarmed.

got her running like a rapped ape agian :ride:woot woot.. although I do feel very stupid lol. It was missing the o ring that goes on the pilot screw :eek:

well thought it was running lol back to squar one recleaned carb by shop and is still doing the same thing they are thinking electrical any ideas?

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