250sx ran great then radomly bogs down..

[ChevyAndVW]

i drove my 250sx for like 2 hrs today. ran great and then randomly bogged down and died. it happened twice and started back up? i havent looked into it too far. but i had 3/4 full tank. clean gas and tank. new carb. clean air filter. new fuel filter. it happened when i was driving quick and not putting around. it never did this before and every part of the fuel, air, and spark is fine. is this a common problem or...? any ideas of what i should look for?

[tri again]

Almost sounds like the gas tank vent isn't venting but also sounds like you checked the gas level
which would allow air into the tank.
Screen in the petcock plugged?
So it bogged like it was running out of gas? or died instantly like spark?

[ChevyAndVW]

tank isnt venting? i know the top seal leaks a little so i think its venting. the fuel filter is installed correctly. and it also has a brand new petcock and screen. i had it in prob 4th cruising right along on a straight flat service and it bogged down and lost power and rolled to a stop. someone was saying somthing about a wire in the back that always comes loose on the SXs but isnt the important wires in the front? (sparkplug wire, ignition, etc)

[tri again]

tank isnt venting? i know the top seal leaks a little so i think its venting. the fuel filter is installed correctly. and it also has a brand new petcock and screen. i had it in prob 4th cruising right along on a straight flat service and it bogged down and lost power and rolled to a stop. someone was saying somthing about a wire in the back that always comes loose on the SXs but isnt the important wires in the front? (sparkplug wire, ignition, etc)

That's exactly why I logged back on.
All I know is it's some wire near the battery that flexes with the suspension.
and maybe some wire tape wrapping needs to be pulled back.

Can you get the search key to work?
Dirtcrasher seems to know exactly what it is.
A problem I guess I should look forward to.

Your gas cap should say off and on.
and they don't always work and often stays a problem because they feel like they're
running out of gas, kinda funny, so we check the gas, it's Not empty and the sucker runs again for a while.
because more air got in.

It's easy to pull the line off the carb and see if it really flows, messy but eliminates one problem at least.
But ya gotta let it run until a vacuum is created in the tank and it stops flowing IF that's the problem.

If someone else logs on, that mystery wire will surely get honorable mention.

[Tippmann98]

I would put money on it being the gas tank vent. Mine was bad and always did that. I normally just turned the cap on about a quarter turn, just tight enough that it wouldn't leak but not too tight so it would still vent.

[ChevyAndVW]

im not sure. what is the "on" and "off" cuz mine seems to do nothing hah. it leaks on different angles not matter what. im going to check the bowl on the carb and try messing around with the gas cap. any options on other gas caps? like a dirtbike style 1?

[Tippmann98]

They get plugged up so it wouldn't matter if it's on or off. Some people drill a little pinhole in the edge of the cap to let it breathe.

[3wheely]

Funny I just got a 250sx 2 weeks ago. I haven't rode it until today because I re-coated the tank. Wouldn't you know I hit 4th gear and it bogged down. I read this post earlier so it was helpful in figuring out the problem. I took the cap off and put it back on just enough to hold it in place and ran like a champ. Might try the drill a hole trick.

[tri again]

some people have had luck soaking them in carb cleaner but who know what's inside there?

rubber that will melt?
new caps are avail but 1/2 the price of a parts trike.

[ChevyAndVW]

same. i was in 4th i think as well. well next time i ride i will def mess with the cap and see what happens. i know its breathing tho cuz it leaks on big angles like wheelies. but mabe ill drill a hole. weld a little nub thing and put a breather tube on it like a dirtbike. but what is inside of the gas cap? and the on and off thing? whats that suposed to do?

[ChevyAndVW]

ttt
bump
ttt
bump
ttt

[ChevyAndVW]

still doing it after long runs... seems like it isnt the cap and needs to cool down or somthing.

[WJG1000W]

my cap leaks in wheelies or hill climbs too in the off position but put it on the road in 5th and in less then a mile it will bog and die put it back in the on position it will run many miles and all day
also bring some water and throw it on the engine and it should cool it down quick to see if thats why but if it is heat then it shouldnt start right back up it should take a while to cool
did you pull the hose of the carburetor to check flow

[tri again]

I'd start it and hit a few different components one at a time with a hairdryer
and see if heat kills something.

Heat the coil, then the cdi and so on.

Compressed air will also cool stuff off enough to diagnose.

Face it, we ALL need to know what the problem is.

Good luck and please keep us posted.

[Big Mike]

There is a fuse holder at the back of the SX that if it get even a little bit lose it will die, Mine used to do that all the time till I cut out the glass fuse holder and put one in for a standard blade-style fuse.

[ChevyAndVW]

i dont think its a fuse. it only does it when it gets hot. i wanna try the hairdryer on things but i dont wanna break anything. it happens after a long ride and usualy when im going fast just cruising. so it should be getting nice cool air... idk

[Keepah Rolln]

Make sure your getting good air she will heat up quick and bog. Sounds like a wire or air problem. But make sure you don't have it on reserve tank...lol

[AbusedBigRed]

EASY! My friend has the same problem with his 250SX, The problem is your gas cap, There is a thing that i don't know the name in english on it that can turn, I can goes to the ON position, Or the OFF positon, Well all you have to do is put the thing between the On and Off , At 75 degres angle and it'll run fine!

[ChevyAndVW]

it has a uni filter which is clean so its getting good air. and i tried the gas cap trick and still the same... it mostly happens at high speeds when it has been ran for a while. does anyone segust but drilling a hole straight thru the center of the cap. removing the on/off knob and adding a short beather. like off a dirtbike??

[greenhollow12]

This happend to me to. I will be riding in 4th gear and it will start to sput and bog and then die. If i try to start to start it right back up it wont start. I will let it sit for a minute or 2 then it will crank over.