250sx carb issue, idles fine, dies if throttle is touched

[gladiator mice]

i got an 85 250sx, just rebuilt the carb with manual in hand, one piece at a time. cleaned it out with air and carb cleaner. reassembled the carb and put everything back on the trike. new gas cap (old ones air vent did not work), and external filter. got it to start up with choke on until warm and had it idling smoothly choke off. had to re adjust throttle stop. gave it some gas sitting there and was ok for the first few times then if you gunned the throttle it would bog down and almost die, if i eased into it it had no problem. took it for a spin got 50 feet and cut out completely. back into neutral and started it up again. idled fine and i touched the throttle and it bogs down quick and dies.

so i got steady gas flowing. the tank fuel filter is clean, the external filter is clean, steady stream to the carb. trike will start and idle fine. cant touch the throttle or it will bog down and die, but will start back up. iv rebuilt the carb correctly. and cleaned the jets and air ways and seats. the float works and does not leak. everything i took off went back on, all replaced parts were replaced properly.

does anyone know what is wrong with this carb not working right. the last thread i wrote was about the bogging down issue. i was told to rebuild the carb. in doing so, i now have more issues.

[tri again]

i got an 85 250sx, just rebuilt the carb with manual in hand, one piece at a time. cleaned it out with air and carb cleaner. reassembled the carb and put everything back on the trike. new gas cap (old ones air vent did not work), and external filter. got it to start up with choke on until warm and had it idling smoothly choke off. had to re adjust throttle stop. gave it some gas sitting there and was ok for the first few times then if you gunned the throttle it would bog down and almost die, if i eased into it it had no problem. took it for a spin got 50 feet and cut out completely. back into neutral and started it up again. idled fine and i touched the throttle and it bogs down quick and dies.

so i got steady gas flowing. the tank fuel filter is clean, the external filter is clean, steady stream to the carb. trike will start and idle fine. cant touch the throttle or it will bog down and die, but will start back up. iv rebuilt the carb correctly. and cleaned the jets and air ways and seats. the float works and does not leak. everything i took off went back on, all replaced parts were replaced properly.

does anyone know what is wrong with this carb not working right. the last thread i wrote was about the bogging down issue. i was told to rebuild the carb. in doing so, i now have more issues.

So you blew out the carb passages too, in addition to the jets? sounds like it.
I had to go into one 3x.
On my 3rd trip in I found some sort of emulsion tube under one of the screw out jets.
About an inch long and full of holes and rustmuck.
Still can't believe I missed it 2x.

Generally, the slow jet clogs and does what you describe.
For a few years, I thought an .008" guitar string was the ticket until I got a good carb and a .010" fit easily.
That jet had some crusty plaque that almost needed a drill to clean it out.

Sorry for your frustration.
We all know what it's like. That's why we're here.
I actually boiled that carb in hot water and vinegar out of sheer desparation since it was hopeless anyway.

I'm sure you did a careful job so makes me wonder if your spark is consistent or maybe you have an intake air leak?

Please keep us posted and you can also try the search key for tons of pages on this and any other topic.

ps - did it ever run good that you know of?
someone may have mixed or swapped jets before you got the machine??

[gladiator mice]

thanks for the input, i know what "tube" under a screw jet your talking about. im going to be pulling the carb again and tearing it down and cleaning it. i also believe the pilot screw is not set properly for some reason. i read that on the pilot screw you turn clockwise till it stops back out two turns start and run the trike, get the throttle stop in correct position and adjust pilot screw inwards until motor stops and back out one turn, and re adjust throttle stop if needed.

as for how it ran before, i couldnt tell you completely. i bought it from the original owner. the trike has never been to a shop or had any work done to it. it sat in a garage its entire life and only came out to do minor yard work. no parts had ever been changed on it except new oil and filter once. guy said it ran ok but he didnt use it more then 20 min here and there when he used it for work.

[tri again]

well that's certainly good news.
Waay better than a pieced together machine.

So it's just gotta be something simple.
I'd spray some carb cleaner around the intake boot and see if you have an air leak.
see if it runs differently.
does it run better with a little choke on?
That would tell me if it was overly lean and where to look next.

any chance the valves have never been checked or adjusted, or possibly adjusted wrong?

Sounds like a super low hour, never abused machine, so you've gotta be really close.

Taking those carbs off and on is not real fun but once you get it,
you'll have a machine that will last forever (again)

They also say that regular ethanol pump gas has a shelf life of a month or 2.
Silly question but you have fresh gas?

yeah, we all need to know what the problem is so please keep us posted.

do you have a

service manual

ps - don't forget the 3 point 3 ounces of gear oil in the rear axle.
They love having every drop.

[gladiator mice]

choke helps when i first started it up, got it warm and was able to shut it off. after the stalling issue the choke didnt make a difference when starting it, once it was running, if i turned the choke on it raised the rpm. i thuroughly checked each valve, seat, and air way, cleaned and aired out. ill try fresh gas tonight after the carb is cleaned and rebuilt. i do have a manual for that year and i used it to rebuild the carb. the gear oil was checked when i did an oil and filter change on the motor.

[Micahdogg]

Do you have steady gas flowing from the line after the screen and inline filter? I've had cases where both filters couldn't keep the bowl full. Otherwise check your timing first and make sure you have good spark before you continue with the fuel side of things. Check the stator bolt too and make sure it didn't loosen and let the stator move out of position. Even though it's keyed, it can move around if the bolt is loose.

[Flyingw]

This problem is all carb. Tri again is right on target. As described, it sounds very much like you still have junk in the carb. As a plan b, i have new looking rebuilt SX carbs for sale. Totally rebuilt and tested on my SX.

[tri again]

Just an odd thought that doesn't add up to your symptoms but
mice Love to make nests in either the frame air intakes.
Main intake is under the gas tank an sorta runs through the frame and also a plugged exhaust can
throw the best of us for a loop.

You're gonna absolutely love that machine.
Sounds like it's barely broken in since new too.
They are amazing.
Don't give up.
You'll get it.
We always do.

and then yer gonna need a couple more.

[gladiator mice]

well, i took out the carb again, opened it up and found the loose jet rolling around in the bowl. hence why it would idle and die when touching the throttle. checked the carb again and out it back together. this time i did not assemble the entire trike. i left the air box out so i could see what was happening while running it. started up nice got it to idle gave it some gas and it runs, BUT im back to square one where you can not gun the throttle, you have to ease into it to get to high rpm. when looking into the carb i can see the throttle needle and slide move freely. when eased into full throttle gas is flowed smoothly, when gunned from idle standpoint, you can see the stream of gas flow up into the carb and thats when the motor bogs down almost as if its enough gas but not getting the air it needs causing the motor to get flooded. also the spark plug is wet and black, TOO much gas not being burned. i guess when sunday comes around i will pull the carb again, clean each piece and see what happens. ALSO, i took off the inline filter, no need for it right now, just the normal set up.

[gladiator mice]

Just an odd thought that doesn't add up to your symptoms but
mice Love to make nests in either the frame air intakes.
Main intake is under the gas tank an sorta runs through the frame and also a plugged exhaust can
throw the best of us for a loop.

You're gonna absolutely love that machine.
Sounds like it's barely broken in since new too.
They are amazing.
Don't give up.
You'll get it.
We always do.

and then yer gonna need a couple more.

ill have to check it later and see whats up inside the air hole in the frame. as for the exhaust, it flows smoothly but shoving a screw driver into it might let me know if something made a house.

[redsox]

just had the same problem on a 86 big red 250. plugged exhaust!!!!!!! what a nightmare. my cousin bought the machine in pristine condition. guy used it moving firewood back and fourth in his yard for a hundred years. always oil changed, always new fuel/stabil etc. very very well taken care of. so, now we get the machine and we start riding. opening it up. next thing you know she dies. starts right back up, little throttle, she dies. so, first thought, she's not getting enough fuel in the bowl to keep up. screw around with the carb. same issue. screw around again, same thing. then, magically, after moving the machine, problem is gone. nw i'm going nuts, because i know something is up. we take her out again, half hour of riding and same issue. this time, after she dies, i hear a long, high pitched squeek coming from the muffler. sounded like the noise you hear when you slowly let the air out of a balloon. over the years, the inside of the muffler had deteriorated, but the machine was never ridden enough to knock the old flakes of crap and or carbon build up out of the muffler. then we came along and boom. plugged up. so, before messing with the carb again, i'd take five minutes and open up the exhaust, see whats in there. there are two bolts on the bottom that open up a little port where you can see if you've got buildup. we had a flake the size of a nickel that was flopping up against the screen and preventing exhaust from escaping. when we moved the beast, it fell back down into the muffler. thats why the problem went away. when we started riding again, it got jared and blocked it again. if it wasn't for the noise, i'd still have the carb off. GOOD LUCK.

[lotust]

Hummm after a card rebuild I'm having a problem a few days after the rebuild. A first it ran like a champ for hours, then all the sudden one morning it's giving me troubles. This exhaust thing sounds like its the easiest thing to try.

[Chunkers101]

I had this same problem with a 1991 trx 200d, it would start, and idle fine, but when i would give it gas, it would die. I found the problem was a jet, You could see tho it fine, but it was stuffed up just enough to make it not work, I rebuilt the carb and it worked fine, But you said you rebuilt yours and are getting the same problem, so i'm not sure =(

[Thorpe]

well, i took out the carb again, opened it up and found the loose jet rolling around in the bowl. hence why it would idle and die when touching the throttle. checked the carb again and out it back together. this time i did not assemble the entire trike. i left the air box out so i could see what was happening while running it. started up nice got it to idle gave it some gas and it runs, BUT im back to square one where you can not gun the throttle, you have to ease into it to get to high rpm. when looking into the carb i can see the throttle needle and slide move freely. when eased into full throttle gas is flowed smoothly, when gunned from idle standpoint, you can see the stream of gas flow up into the carb and thats when the motor bogs down almost as if its enough gas but not getting the air it needs causing the motor to get flooded. also the spark plug is wet and black, TOO much gas not being burned. i guess when sunday comes around i will pull the carb again, clean each piece and see what happens. ALSO, i took off the inline filter, no need for it right now, just the normal set up.

PUT YOUR AIRBOX TOGETHER!!! Without changing your stock jetting, it won't run right without the restriction of the air cleaner and box assembled (with the lid too) Without your box, you are causing the SX to be in a lean condition...

[gladiator mice]

PUT YOUR AIRBOX TOGETHER!!!

I did put the air box back in and assembled the trike. DIDNT MAKE A DIFFERENCE!!!

Also theres no reason to cap me, or anyone FYI.