Starts only on choke but revs to the moon

[TX21]

Just finished a re-build on an unfamilar bike. I replaced the crank, top end, got the cylinde fixed by Millinum Tech.. I got it all back together and could not start it. I pull the choke and kick it a few times then it just goes crazy to crazy. I have no idea why but I have spent a lot of time on this bike to give up now. I did a compression test and got 205 - 210 psi, pulled the plug and it looked fine. What does the the sensor on the carb do? Where should I set the carb screws for a base line? 1 1/2 out? There are two screws on the side I only assume one is a fuel/air screw and the other a idle screw? I have no experiance with anything but a Yz125 so this bike is weird to me. HELP!!

1998 Kx250 stock

[kargo27]

Are you running lean? Did you set your carb's air screw in to seated and then back it out 1.5 turns (or whatever your manual says)?

I have a 99 KX250 and mine revs really high on choke, too, but once I turn the choke off it's good.

Karl

[TX21]

Are you running lean? Did you set your carb's air screw in to seated and then back it out 1.5 turns (or whatever your manual says)?

I have a 99 KX250 and mine revs really high on choke, too, but once I turn the choke off it's good.

Karl

I am flying with no book I screwd the plastic one with the spring all the way in and backed it out 2 turns. It was screwed about 4 turns out. When I turn the choke off the bikes dies.

[kargo27]

OK, the one with the spring is the idle.

But the idle/air/fuel mix screw is recessed and kind of hidden behind the breather lines. It's small.

Did you check to make sure that your pilot jet isn't clogged and that all the rubber intake parts are secure and not letting any air in?

Karl

PS Where are you in TX? I'm in Ft. Worth

[TX21]

OK, the one with the spring is the idle.

But the idle/air/fuel screw is recessed and kind of hidden behind the breather lines. It's small.

Did you check to make sure that your pilot jet isn't clogged and that all the rubber intake parts are secure and not letting any air in?

Karl

PS Where are you in TX? I'm in Ft. Worth

I screwd the fuel/idle/air out 1 1/2 . I cleaned the carb out real good. The rubber boot on the motor side of the carb looks a little worn. I do suspect the case might be letting in some air. The rod poked a hole in the bottom, something I didn't see when I bought it? but I got it fixed and it seemed to mate up with the other half fine. I guess I need to do a leak down test. I am in Euless (HEB)

[no1clyde]

You need to pressure test the cases. You may need to watch ebay and get another set, alot of years work 94-01 are about the same 02 works also but has larger main bearing OD and the same ID. Any back out the screw with the spring on it to slow the idle. Ed

[TX21]

You need to pressure test the cases. You may need to watch ebay and get another set, alot of years work 94-01 are about the same 02 works also but has larger main bearing OD and the same ID. Any back out the screw with the spring on it to slow the idle. Ed

Opps guess I need to back it out a lil bit then. Man I hope I don't have to take that thing appart again

[rally 224]

I had this problem also. I fixed it by taking the carb out and just doing a full clean down on it. Finish it off by blowing everything out with compressed air. It will do wonders some times.

[avisdo]

Does the throttle seem normal? maybe the cable is kinked or pinched. Check your cable routing.

[TX21]

Does the throttle seem normal? maybe the cable is kinked or pinched. Check your cable routing.

The slide functions normal but I do hear a pop of the spring on the carb slide about half throttle. I have heard the same pop on a yz125 and it ran fine. I took it all apart and could not see where it was making this noise.

[AWDBooSTiN90]

my yz125 does the same pop thing and works fine. check to see if the slide goes all the way down when you relaease the throtle only like a crack should be open. take the back boot off from where it goes to the air filter and look at the slide to see if your cable is pinches somewhere. also try to move the idle screw around. you said when you got it was 4 turns out maybe put it back to the way you got it and try it. if that doesnt work. fully clean the carb with carb cleaner and compressed air.

[TX21]

my yz125 does the same pop thing and works fine. check to see if the slide goes all the way down when you relaease the throtle only like a crack should be open. take the back boot off from where it goes to the air filter and look at the slide to see if your cable is pinches somewhere. also try to move the idle screw around. you said when you got it was 4 turns out maybe put it back to the way you got it and try it. if that doesnt work. fully clean the carb with carb cleaner and compressed air.

Yes the slide closes fully. When I first started the bike before I changed anything it still reeved to the moon. I think its all air because it wont run with the choke off.

[TX21]

Well I didnt want to post this but ...

I fabed up a leakdown tester with some car shock mounts and a tire valve stem (works awesome!) and found my air leak. In my hurry up and put it together mode I left part of the old gasket on the reeds where it seals to the case. At that point I realized I hadent even put the new gasket on. So I get to wear the dunce hat all day today

[kargo27]

Excellent! No dunce hat, just the opposite. You successfully located the leak and fixed it.

Now, if someone else other than you had found the problem then you'd have to wear the hat. :-)

Karl