KDXRIDER.NET

My bike has always been a bit troublesome to start. It takes a lot of kicking before it will go. I found that if I put a bit of gas directly in the spark plug hole with a small tube it fires right up on the first kick. It revs too high during warm up so I figure extra air is getting in there somehow. Perhaps the left side crank seal?

After the bike has started it will fire up immediately all day long. I've had the carb apart many times in the past year to clean the jets and install leaner jets not so long ago. By the way, changing the jets didn't affect the hard starting (I didn't expect it to, but I just wanted to point that out).

What should I check on the carb to see why the choke isn't working? It may be very obvious next time I get around to removing it, but any tips you all can share would be good.


Chad

More information to add...

The choke does affect the bike when its running. When I pull the choke up it gets really rich. One thing is certain - I need to get more gas in the engine to start the bike.

I don't like throwing parts at a motor until I am reasonably confident its going to fix the issue :) Could it be: Reeds? Worn out piston/rings? leaking crank seal (yes, there was a small little puddle of oil under the stator cover when I removed it last year)?

A combination of all these things?

Have you tried leaning the bike over until it pees a little before starting? Maybe you just need a little more fuel in the bowl. Just a thought. That seems to help me.

Clean the carb(If it hasn't been already), change the spark plug(Check the color), and go from there. Has it ever been jetted correctly?

I would try what Varmint said. You may have a sticky float not letting enough gas in the bowl when you first turn the gas on.

With mine if I turn the gas on, choke it and start kicking right away it will take several kicks to get it to fire up but if I just turn the gas on and walk away for a few minutes than it will start right up first kick.

Tipping the bike would do about the same thing as waiting I would guess. Just a little quicker.

I've tried leaning it over until it drips a bit but I don't do this consistently since it didn't seem to make a difference. I'll pay more attention next time and turn the gas and choke on for a few minutes to see if that makes a difference.

The bike was tough to start before and after cleaning the carb as well so I haven't touched the carb in 6 months or more. I only ride it about once or twice a month if I'm lucky. On the plug... I don't change the spark plug unless its a problem really. Since it starts with a few extra drops of gas in the spark plug hole I haven't suspected an ignition trouble.

I forgot what jets I had in there so I looked up one of my previous posts from June 2011:

"Decided to also pull the carb and check the jets while I had some spare time. There was a 158/45 installed so I put in nice clean 155/45 jets someone from the kdxrider forum was nice enough to mail me a few months ago. When I removed the pilot to check the size I found it was entirely plugged up from what I could tell. Couldn't see any light through it, so I put in the nice clean 45. Started the bike right up and noticed the power was a bit better than before. I still have at least one non functioning kips valve so I'm sure when I get that fixed the bike will have a good deal more power down low. I messed with the air screw but it didn't seem to make a big difference in throttle response just off idle anywhere from 1/2 turn out - 1 1/2 turns out. Even with one of the 3 kips not working I expected more of a change with the air screw adjustment. Fastest idle was less than two turns out so I guess the 45 is the right size pilot if I'm understanding the jetting guide correctly."

I would check compression. Worn rings will make it hard to start. Then once the engine is warm the rings and piston expand from the heat, increasing compression,making it easier to start.

My understanding on a air screw, (I could be wrong here), it's to be adjusted at idle - keep turning the screw in (fine increments) as the engine revs become higher each time. When the engine idle starts to come down, then you know you've gone to far inward, so back it off to the last setting.

At that point, you can rich'en it to your liking for off idle response when cracking the throttle open.

This works on my daughters 4 stroke, not sure it works on a 2 stoke - I've been fortunate enough "not" to have to mess with carb adjustments on my KDX.

I think Velocity Stack is backward on the air screw. From what I understand you need to back it out until the idle goes up to a peak and then play with it from there. I have heard that 2 and 4 strokes are opposite.

Search the jetting guide on here to be sure.

Rbates9 has the best plan, find and read the guide.... I'm headed there now to learn.

Sounds to me that it may not be getting a proper prime. My KDX was doing the same thing until I put a new fuel line on from the petcock to the carb. I couldn't see any leaks b4 but it definitely fixed the prob.

On a 2-Stroke the mixture screw is an "air" screw. Turning it out lets more air in which leans out the idle mixture. On a 4-Stroke the screw is a "fuel" screw. When it's turned out it adds more fuel, making the idle mixture richer.

I had the hardest time remembering which engine had an air screw and which one had a fuel screw until I realized that on 2 strokes, the screw is positioned next to the air intake of the carburetor, thus it's an air screw. 4 strokes have the screw under the float bowl with the fuel, so it's a fuel screw.

Now I can't forget which is which. :)

On a 2-Stroke the mixture screw is an "air" screw. Turning it out lets more air in which leans out the idle mixture. On a 4-Stroke the screw is a "fuel" screw. When it's turned out it adds more fuel, making the idle mixture richer.

be careful there...Plenty of 4T carbs work just like the PWK on the KDX. Plenty of older ones are simply the same carb with an accelerator pump installed....Regardless, you're going to burn it down figuring out which way is which...

I took the carb off the bike today to check out the choke circuit while replacing the seals in the fuel petcock. The tube that pics up gas from the bottom of the bowl to feed the choke was mostly plugged up. I cleaned it out with a needle and carb cleaner then the bike started right up on the first kick with the choke on.

To replace or clean jets I do know the carb can be rotated without fully removing it from the bike... I do like that capability. However, removing and installing the carb is still something I don't enjoy doing. I normally loosen the hose clamps, remove the slide and needle, then work the carb out of the boots. Getting it back in place is harder than removing. It takes a bit of patience to get the carb fit back in the intake boots. Is there a secret way that makes the job easier?

By the way, my jets are 152/42. I have that in my notes now.

well this morning the bike would not start without a shot of gas in the spark plug hole. Guess I'll need to check the compression and condition of the reeds. It must have been the carb cleaner that allowed the bike to start up on the first kick yesterday.

the last few times I've started the bike it has started up after a couple kicks using only the choke. I'm not sure why it didn't start the day after cleaning the choke circuit, but it does look like that was the real cause of the hard starting.