2007 KFX 50
Hard starting when cold. So I crank this bike and it may start but shortly dies after a few minutes and then will take forever to re-start. Once restarted the bike sometimes will die with any press of the throttle, but sometimes I can get it to idle and run correctly if I lift the back up and stab the throttle, ride it around and it will work for the rest of the day. Yesterday it fired right up, idled, died and then would not re-start so I gave up. So the first thing is to clean the carb as it may be dirty in there. Got a carb kit on the way. I’m like the second owner of this and I don’t think the first owner rode it often and it was doing this basically since the day I bought it off him.
The bigger question is the auto choke or Jet Starter or auto bystarter, I have seen various name for the auto choke. The Kawasaki part is labeled as Jet Starter but the repair manual calls it an auto bystarter. The question is, could this be bad, I found a test procedure and have not done it yet. If it is bad, will any one of them work say on E-bay or for a Honda? They all look the same I think. The Kawasaki original I can get for around $70-$80 plus shipping. The e-bay/Honda ones I can get for like $5 - $10 each.
I just figured I would ask in case someone knew the answer before I tore into it.
For anyone else that comes across this,
Test One
The ohms of resistance is 5 ohms, at a minimum of 10 minutes after stopping the engine. If over 5 ohms then it needs to be replaced.
Test Two
After the engine is stopped for 30 minutes, connect a hose to the fuel enriching circuit and blow the hose with a blowing tool. If air cannot be blown into the hose (clogged) the auto bystarter is faulty.
Test Three
Connect the auto bystarter yellow wire to the positive of the battery and the green/black to the negative. Wait 5 minutes. Connect hose to the fuel enriching circuit and blow the hose with a blowing tool. If air can be blown into the hose, then auto bystarter if faulty.

 

I'm adding additional information for all to follow along.

First if you have a manual, the procedure to get to the carb is not the most efficient way of doing it. Yes you can get there but it means doing a lot of unnecessary work. First they have you remove the fuel tank, but to do that you have to remove the handle bars and associated controls. I removed the handlebars and controls and when I got down to the part of removing the front fender I realized that when I removed the right side cover and foot well, everything I needed access to I was able to do through the side easily and not had to do all the other stuff they listed. So good thing I got to that part before I tore it all down. First time tearing this bike down so I wanted to make sure I was doing the right thing. Now I know.

Also for anyone that needs to remove the front brake stop switch wire, do not pull the wire from the back. You will need to disassemble the the break lever and you will need to push it in towards the lever to get it out. I spent probably 40 minutes trying to research how to remove it since the manual does not say. I then instead of detaching the wire there, went under the fender and disconnected the two wires and the whole think (front brake perch and handle bars with the wire ) will lift off. But if you find in the future that you need to remove the cable because it is faulty or broken then push it out of the perch versus pulling it out.

Now for the fun stuff.
Got the carb and Jet Starter out. There was a lot of fuel in the opening of the carb and coming out of the fuel enrichening circuit. Wasn't flowing out but just all sitting there. I started the bike earlier that morning but after a minute of idling it just died.

I pulled the Jet Starter (automatic choke or bystarter) off the carb and ran the test procedures as described above.

1) The omhs I got were 6.2 when it was cold and after step 3 above it was 6.7 just to see what happens. So from here I would assume the Jet Starter is bad since it was over the recommended 5 ohms.

2) I ran the second test and air did pass so now I'm assuming it may not be the Jet Starter.

3) I ran the third test and I was able to get air to blow past, some resistance but it did leak past, so assumed Jet Starter was bad and just not fully doing its job. Assuming fuel was still able to leak by and after warming up it would flood out the carb causing it to stall and then having a hard time to restart it.

So I ordered a small box of parts, Jet Starter, fuel filter, tank screen and another o-ring which goes between the carb spacer plate and the cylinder since when I took that off it looked wet too, so don't know if that was starting to get old and leak.

I'll have another update once I get the parts and everything put back together.

Now for a carb rebuild.
I pre ordered a rebuild kit through Ebay - ***** Out kit. Anyway just want to report that the kit was somewhat of a disappointment. The main jet was the wrong size for what is in the bike. The gaskets are a direct fit and so was the little valve for the float. The slow jet was also correct and so was the gasket at the top of carb. I used the screw assembly adjustment screw but there is no way to use the throttle stop screw unless you have a carb adjustment tool to take the d-shaped headed screw out of the throttle body. As a side note, my screw assembly adjuster was 2 1/4 turns out from stock. It would have been nice if it also came with the o-ring to go between the throttle plate and the cylinder, but it did come with new screws to hold the bowl on in case you mangled yours. Over all it was cheaper to buy the kit versus ordering the few parts I wanted to change anyway, like the seals and o-rings. You can clean jets so no real reason to buy new ones but they were in the kit.

Overall the carb was rather clean and nothing blocking the jets, but since I went through the trouble of getting it out and had the kit for it, I rebuilt it after stripping it down and soaked it in Berrymans chemical dip for an hour, washing it all off and then blowing it all out with compressed air.

 

I messed with the auto choke for years on the Polaris youth models.My two cents is that they're all junk from the old Honda Spree on up. Polaris even came out with a manual choke kit for ours with the auto choke. Some manual chokes worked ok,some didn't. Easiest way to start one when they're cold is to block off the air intake if you can which allows more fuel than air to be sucked into the cylinder a lot faster.

 

If this doesn't work I'll look into some sort of manual choke to to add to it. Looking at the carb looks like it would be easy enough to do.

Would the e-bay generic auto choke or a Honda one work? They were a hell of a lot cheaper. They all look the same to me, but the funny thing is that the specification to the limits of the ohms are different between say a yamaha, honda and this kawaski. So I'm assuming they are all the same but based on jetting and carb the ohms (operating range) could be different? Like this bike is over 5 is bad, yamaha over 10 is bad and Honda the range is between 8 and 16. (I may have the Yamaha and Honda one backwards or not totally right, but just as a comparison)

 

Strange that they show an oem Kawasaki carb with manual choke(up to a 2006 model) on ebay. Don't know if it or the cheap aftermarket one mounts the same as yours.2003-2006 Kawasaki KFX 50 OEM Complete Carburetor Assembly 15003-S004 | eBay New Carburetor Fits 2003 2004 2005 2006 Kawasaki KFX 50 KFX50 ATV Quad Carb | eBay

 

The first carb you reference, Kawasaki turned the mounting flange 90 degrees differently on the 2007 so If I use the one on Ebay, the bowl will be on the side instead of the bottom. Same with the second.

However, it looks as if the manual choke from the 2004 Polaris 90 I have would mount up to the Kawasaki 50. they are both held in a similar fashion where they connect on the carb. Would just need to see if they are the same diameter and if the plungers are the same.

If you were to take a manual choke off the Polaris and look at the carb, it looks very similar to the Kawasaki in that area.

 

Possible that this one would work. Buying the Polaris choke parts piece by piece is expensive.POLARIS SPORTSMAN 90 MANUAL CHOKE CABLE CONVERSION KIT SET 2001-2006 | eBay

 

Adding info for those following this.

Finally got a brand new by starter/jet starter from Kawasaki. I just tested the ohms straight out of the bag and the measured ohms is 5.6/5.8 ohms. The factory manual is saying over 5 you need to replace it, so I have to say I think the factory manual is wrong, or I'm sitting on a bad one from the factory. I just retested the old one out of the bike and it is reading 6.8, but last week it tested out about 6.2 and then 6.7.

So the new one is still over the 5 ohms as the manual states but is better than the old one by an ohm. Will this make a difference? I have no idea. I'll be putting it in the bike later tonight but I need to get some fuel so because I also drained all fuel out of the bike to rule everything out. Maybe tomorrow I'll end up trying to fire it up and see if it works any better.

This will be going on a fresh rebuilt carb too as well as changing the tank filter and the fuel line filter so I know it is all new. The petcock I changed a few months ago as the handle was broken when I bought it. How the "H" do you break a petcock handle??

 

OPT, yeah that one looks like it may work. Thanks. That is the next stop if all this fails.

 

How are you making out with this? I just bought a 07 KFX 50 and somewhat having the same trouble.
The stalling at the press of the throttle. I turned the idle up which fixed that. Now it stalls just about whenever the quad comes to a stop. And stubborn to restart. Something wrong with the electric start so I have to kick quite a few times with the throttle part open.
I was suspecting the jetstart. But at initial start up it seems to start fine and idle high, then after a minute or so the idle kicks down as should.
Thanks for the info since I havent gotten a manual yet