250sx idle/throttle problems

[Sly'85]

I have an '85 250sx that acts really strange. When it's cold it idles ok and runs decent. I can't really snap throttle at any time; warm or cold, it bogs down. I thought the bogging issue was a " lean" condition but after messing with jets for the past couple weeks, it has this issue no matter what jets i put in or what the jet needle position is in.

So, regardless of the bogging issue, I have ridden a couple of times with it running as good as I am able to get it but after it warms up, the idle starts hanging when in neutral, really bad. It hangs when I'm in gear as well and wants to push the trike. Brake is my best friend when this happens.

Anyway, I have been trying to fix this issue by adjusting the carb for lean and rich conditions but no luck. So before I tear my top-end apart, does anyone have any ideas?

[Dirtcrasher]

Easy on the top end!

Why would you even look to the top end??

Low compression, lack of power, noise and or excess oil consumption (smoke)?? Thats about what condemns your top end.........

Why are you playing with jets?? UNLESS you made some changes in the airfilter/open air box?? and or a better flowing exhaust?? ; you shouldn't need to do anything but clean the carb.....

And the idle hanging!??, does that mean sticking?? - Is that the carb, throttle or cable?? You gotta find that out...........

Stock jets, clean carb will run just fine.

It doesn't matter if it's cold or hot.... Use your noggin a bit

[pudge]

clean the carb and lube your throttle cable, its prob about a one hour and free fix

[Sly'85]

Ok, I shoulda stated this in the first post, the stock carb was junked and I replaced it with a 36mm PJ carb that my buddy that races for BBR hooked me up with. He gave me a range of jets to play with but swears that this carb will work just fine with my trike. I took the carb apart, cleaned it up and got a brand new twist throttle and cable for it. As far as taking the top end apart, I heard that a sticky valve could cause some of the symptoms that I am describing. Honestly, I am not sure wether it's my carb or not but I am getting an oem carb sent to me to see if that fixes it.

As far as it being hot or cold, it runs very different cold. No idle hang, idle comes down slowly but doesn't hang. There is a noticable lack of power as well.

[pudge]

sound like you have some tinkering to do with that carb, the fact that it is not stock explains its rough idle, i would just get a stock carb or a 350x carb, i do not know anything about the 35mm PJ

[Sly'85]

I have some hope that an oem carb will help with this issue but a hanging idle only after it's warm doesn't sound like a carb issue. I'm not too knowledgable at diagnosing engines and any other ideas would be greatly appreciated. When I get the new carb on I will update.

[danpalms15]

Put the stock carb on, if you don't have an mod, put teh stock main jet in, adjust the air/fuel screw to stock and the needle to stock position. It will run just fine then.:beer