What's the deal with no gas for 4-T's

Hey guys, I'm just wondering what's the deal with not giving it gas to start a 4-stroke? I'm learning how to start my KX250f and I can get it cranked but then it shuts off. Last week I HAD to twist the throttle while I was kicking in order to start it.

This weekend I had to twist the throttle just as soon as it started. I realize I'm starting it wrong and I"m learning but I was just wondering what's the deal with NO gas when starting a 4-stroke? Thanks guys.

Hey guys, I'm just wondering what's the deal with not giving it gas to start a 4-stroke? I'm learning how to start my KX250f and I can get it cranked but then it shuts off. Last week I HAD to twist the throttle while I was kicking in order to start it.

This weekend I had to twist the throttle just as soon as it started. I realize I'm starting it wrong and I"m learning but I was just wondering what's the deal with NO gas when starting a 4-stroke? Thanks guys.

Assuming of course that this is not a 2011 you're talking about...

Simply put, 4t carbs have an accelerator pump in order to avoid starving for fuel when you open the throttle. Twisting the throttle activates the pump and when you're at a dead stop, this floods the engine.

I would venture to guess that your pilot jet needs a cleaning and/or valves needs a clearance check.

4-strokes can idle really well, in fact they need to to stop from stalling.

And they are really finicky about the fuel mixture, mostly because they only fire every other revolution.

So you start it to idle basically.

When cold, I always put the choke on + give it 2 twists of the throttle. This loads extra gas into the engine. Which is what it needs when cold.

Then find top dead center, return the kick pedal all the way up, then slowly but firmly kick all the way down.

The key is to move the kick pedal long enough, not fast enough.

When it´s warm/hot, it gets even more finicky about mixture. That´s why you have the hotstart lever.

Pull the lever, find tdc and then repeat the kicking procedure. Release it as soon as it starts.

Pulling the hotstart essentially does the same as opening the throttle slightly, it just does it very precise and does not add any extra gasoline from the accelerator pump.

If you try starting it by opening the throttle, you will probably get it to fire, but it will be inconsistent.

Learn to like the methodical approach.

Sounds like your idle may be set too low. Turn your idle adjuster in a few turns then start the bike. This should create a high idle. Back out on the adjuster 1/4 turn, give the throttle a quick "snap", and see where the idle lands. Repeat if it's still too high.

To add: If on cold start, the bike fires and then stalls and this happens several times in a row, chances are, the starter jet is too small. Ging up a size or two will resolve that.

Using the hotstart is not like cracking the throttle. If you crack the throttle, you will expose part of the needle and fuel wil be added. The AP not squirt if you very slowly move the thottle.

Hot start only adds air.

does it very precise and does not add any extra gasoline

that is hair splitting

Thanks for the tips guys. I know the carb isn't adjusted just right yet so the fuel screw and air screw needs to be adjusted. I have already thought about going up a size on the pilot jet, it's a 40 and I've got a full exhaust on there. Any suggestions for the needle and main jet?

Thanks for the tips guys. I know the carb isn't adjusted just right yet so the fuel screw and air screw needs to be adjusted. I have already thought about going up a size on the pilot jet, it's a 40 and I've got a full exhaust on there. Any suggestions for the needle and main jet?

What year and pipe brand?

Thanks for the tips guys. I know the carb isn't adjusted just right yet so the fuel screw and air screw needs to be adjusted. I have already thought about going up a size on the pilot jet, it's a 40 and I've got a full exhaust on there. Any suggestions for the needle and main jet?

Should have included that bit of info in the orignal post. Yep, time to get into the carb. 42 pilot should be your starting point.

What year and pipe brand?

Sorry, it's a 07 250f and it's Pro Circuit T-4 muffler and pipe.

Sorry, it's a 07 250f and it's Pro Circuit T-4 muffler and pipe.

Stock 182 main, 40 pilot, NHJT needle in clip 4, 1 3/4 turns fuel screw, 55 leak

Pro Circuit 170 main, 42 pilot, NCYS needle in clip 3, 2 1/2 turns fuel screw, 50 leak

Thanks for the tip, I'm having trouble finding the needle being listed however I did find one on CRFsonly.com. Since it's still a Keihin carb it would still be OK right?

Thanks for the tip, I'm having trouble finding the needle being listed however I did find one on CRFsonly.com. Since it's still a Keihin carb it would still be OK right?

Yep. I got mine from a honda dealer as well. I think it's in the '08 450f?

its a honda needle. with the weather now you can run a 45 pilot and up to 178 main, also you can run the ncyr needle just put one in a friends bike runs great. its one richer of the bottom than the nycs.

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