hello, i have a 98 ex and i am getting pissed. it was running rough when cold and barely would idle when hot. and when cold it was hard to start. so i took it apart to clean and found nothing dirty. i took all the jets out. now it won't start and shoots flames from the pipe. so i screwed with the mixture or something. what is the jet that goes in between the floats supposed to be set at. i did not put it exactly where it was set at and now i am screwed. also there is a screw on the bottom of the carb that has a needle that points out into the throttle bore. what is this and what does it need to be set at. i have a new timing chain on it and i know it is in time. it sparks nicely as well and has good compression.

 

That screw with a point on it, in the bottom of the carb, is the mixture screw. It needs to be treated lightly, as it will deform easily. Pull it out all the way, and make sure the point part isnt deformed or mushed. If its mishapened, youll need a new one. Then lightly screw it in all the way, til you feel resistance, and then unscrew it about two turns...this should be a good starting point for that. The mixture screw only controls idle mixture, the midrange and main circuits are controlled by the needle and main jet.
Theres supposed to be a couple of o rings on that mixture screw (one may still be inside the hole), if one or the other is missing or out of place, itll make for difficult running.

How long has it been since the valve clearance was checked? Sounds to me like the intake could be a bit tight.

 

i adjusted the exhaust valves when i put the timing chain on but i don't think i did the intakes. what are the specs for that. the pointy needle is in good shape. do you know what the big jet in the middle is supposed to be at because i know i did not put that back where it was. it has the lock nut on it to hold it in place. also has that plastic piece that goes between the floats. i think that is a big problem. thanks.

 

Go to a shop, order a Haynes book. it will answer all the questions you have, if it doesnt it will give you a better idea then just guessing.

 

carb diagram

If you go here, theres a diagram of the carb. If youre referring to the main jet, #32, then tighten it snug to the #23, which is the needle jet holder. You cant really go wrong. The plastic piece is just a baffle to keep gas around the main jet, when the gas is sloshing around.

I think the clearance is supposed to be .005" intake and .006" ex. But i dont have the service manual handy, so if someone else has the manual, and its wrong, please correct me.

 

i am talking about that part but there is a nut that is used to set # 23 piece to the carb itself, setting it at a certain adjustment. that part does not screw flush to the carb body because it is supposed to be set with that nut somehow. the nut is on the diagram you showed me. thanks for the help though. i have not been able to work on it yet though.

 

I was trying to find a photo on line for that, best i could do is this article
300ex hopup
Theres one pic that shows the bottom of the carb, and youll see the needle jet holder sticking up.
It only bottoms out, inside the center hole, and there will be threads sticking back up into the float bowl area. Its been machined to the proper demensions, and it loctaes simply by bottoming out. Dont get real physical with it, it only needs to be snug. Then the nut threads to the carb body and acts as a lock nut, keeping the needle jet holder from unscrewing. Then the main jet screws to the end of that. Everything gets tightened down snug...theres no spacing or adjustment..everything gets bottomed.

 

the needle that runs through the middle of your carb is the slide needle and it determines how much gas your carb will get you can take it off, take the spring off of it and there should be about 5 adjustments normally the clip is in the middle of it. take the clip to the top to get less gas and to bottom to get more gas. but you would probably be better off not messing with it.