wtf? wont start until the second i pop the gas cap!!

when i first started it this morning it wouldn't start wouldn't start wouldnt start for like ten minutes, then it finally started on choke, throttle full off. ran till it warmed up at low rpm. this thing is really just mystifying me. we were thinking maybe the electronics heated up too hot and messed with them some how. man this just kicked my can today. my bike has been running fine, then the tach starts to be way off or die while the motor runs smoothly. after a five minuter trip, whenever i get going slow the motor will sputter and then die. then not start. it has done this about thirty times in the last two days. i can punch it when it sputters and it goes better and accelerates, but slow down and sputter and die. wont start. unless and until i pop the gas tank cap and then it starts instantly!!! i tightened a kinda loose nut on the smaller pos. post on the relay or whatever that is by the battery and thought it went away. I DRILLED A HOLE STRAIGHT THRU THE BACK OF MY CAPS CHECK VALVE THRU THE TOP. And then i REMOVED THE CHECK VALVE ALTHOUGHTER, and it STILL did the SAME thing!!!! the metalic o-ring spring on the rubber gasket of my tank cap is shot, the metal spring is gone. since last week. It CANT be any kind of vacuum from gas disappearing from the tank as i have a complete opening to outer space now. Then AFTER a stall at two miles out, an instant start in the street as soon as i popped the cap, it ran great with the cap off for five more. turned it off, drank a beer, got back on cap on tight, drove 20 miles at about 55 with NO ISSUES AT ALL. not even with the tach!!! then another 10 with no issues. got home and it's like nothing ever happened. amazing. what in the hell would tie or be a connection between my gas cap and starting right up? (on Pri)

 

Noooooo drilling. Just take cap apart and remove check ball and clean then all should be good. Now with hole through cap it will spill gas every time you stop fast with full tank! Unless you like roasting you nuts on an open fire!!

 

spills aready w/o that spring around the gasket. so not so full no big deal. i'm only asking what the connection is.
also want to mention i read the sticky on the gas cap rebuild. i pried the chrome back, over the 'hinges' but then no matter how hard i stuck a giant screwdriver inside btwn the chrome and the inside steel, it WOULD NOT COME OFF. i don't give a crap i drilled a hole. so pressure is WITHOUT DOUBT the same inside the tank as out, so HOW could removing the cap DO ANYTHING???? Unless i did it, the bike WOULD NOT START.

I was wondering if the gasket got pushed up far enough when it was shut, without that spring in there, to do whatever it is supposed to do, like allow air inside that little notch under the spacer things while the check ball was in there. i took it out to get around that. without the check ball in there, it shouldn't have been able to do anything.

 

If the cap won't vent air then gas won't come out of tank ergo no gas no go

 

you access the ball from the bottom of the cap the only thing you remove the crome part for is to change the oring at the top of the lock.


didn't you post about petcock problems a few days ago?

 

Sounds to me like you need to get a replacement gas cap, or rebuild the one you have (if it hasnt' been drilled to death). Stalling, and restarting when the gas cap is open may just be a coincidence.
I don't know what "sticky" you read about rebuilding the gas cap, but this is the definitive guide: http://www.xj4ever.com/gas cap.pdf

 

yep, the one with the pizza. yes that was my petcock post too. and i'm pretty sure you gave me or someone else the link to that pizza.
Re-reading it now, i realize i screwed up big time by NOT removing the lock cylinder BEFORE i tried prying off the chome outer part. oh well. it just started up alittle finikyly, ?, but started. it had been sitting in the sun all morning tho. i am going on another shake down cruise. other than the one time it died after i drilled the hole, it ran great. so man if it was a coincidence then i wish i would have been rolling dice instead, and betting on craps or not come line. i can't see it. btw i also got my hands on a full face brain bucket.

i suppose, that if drilling the cap took care of the why's of the first 30 times it started when i popped the cap, then there was only one time that it didn't, and THAT one time could have very well been a coincidence. having no further stalling would prove that. but before that last time it stalled after the drill out, the tach was playing it's usual trick. i still wonder if coils or electronic module, or something (what?) got too hot. temp gage only read medium, not hot, tho.

On page 11 of the gas cap rebuild, they show a pic of 'the other side of the vent hole'. i am guessing that is what was clogged up and i shoulda took the lock cylinder out. but i wasn't near a 'puter at the time at my bro in laws.

 

Is the stalling sudden, or is it gradual as if it were about to need to be switched to reserve?

 

DAAAAAMMITTTTT! just went about ten miles, no probs. stopped, talked, ten minutes later starts and goes. go another ten miles, and now the tank is half empty, not almost full like start of yesterday, so i am thinking i am going to write my problem is gone, NO, just a block away, i didn't notice the tach tho, i stop at a stop sign, and DEAD. try to start, no. try again, no. try again, cause i got this thread going. no! pop the cap and it starts right up like nothin. i mean right now too, all these times it's done this, the split second that cap is popped, the motor starts right up. before, while i was under power, i would be cruising along and you could feel some hesitation starting, yes, alot like having to switch to reserve... till when you get going slow enough, it just dies. the last time just now, no hesitations, and like i said, i wasn't looking at the tach either.

 

did you ever look at the screen filter inside the tank over the fuel pick-up. Take the fuel valve out, you'll find it

 

And he might find some crud in the bottom of the tank as well.

 

yes, that was the first thing i did. i replaced the filter when i rebuilt the petcock and also had to put a dimple on the back of the plunger inside it. see my petcock thread. anyway, my filter was perfectly clean. to bring you up to speed i also cleaned all the rust that was in the tank out and coated it with plastic tank liner at that time, carbs were removed and new valve/seat/filters installed in the bowls when they were ultrasonically cleaned. also installed a new inline filter in the gas line. i have not, however, been able to get my bike up there to sync the carbs yet. cant see how that would solve this issue, but.....

 

lets just say for a minute that the carbs are the best in the land. The tach seems to be tied to the problem too. There's a gray wire that goes from the tci to one of the coils, then splits and goes to the tach. What if something is bad on that gray wire or even inside the tach and it stops one of the coils from working. It feels like you're running out of gas and stalls at low rpm because you only have two cylinders
this is where it gets ugly.
find the gray wire at the coil, identify what end goes to the tci and the other that goes to the tach. In close to the coil, where you could splice it back together, cut the gray wire to the tach
you don't need it to run and if it has a intermittent ground on it, it will stop one coil. Just don't cut the side that goes to the tci

 

How long between opening the cap and the bike starts? Are you waiting a bit or is it right away? When it is at the point where it dies, and when trying to start and opening the cap, do you have a clear fuel filter where you can see if gas is flowing and filling what appears to be empty carbs?

So, when you open the tank cap, you push on the tank on one side. If electrical, perhaps there is a chaffed wire under the tank on one of the harnesses, and the very slight movement is enough to temporarily remove the short. Or, things like the kill switch connectors from the right control assembly are under the tank and if loose / corroded that slight movement of the tank pushing against a harness might correct an issue. Try gently rocking the tank side to side when the bike is in a running mode and observe the tach or maybe the engine will suddenly die.

Just to be sure the motor is turning over just not starting?

 

replace your gas cap. I think that your tank is not venting

 

That has been covered. Apparently he drilled a hole straight through the cap.

 

not venting ANYWAY!!! i filled it up and reduced the air space in the tank and i'll be damned right away i can hear the little hole i drilled WHISTLING!! it's playing to beat the band!!! not as free flowing as i thought!! i need to order a new $30 gasket and take it from there. in the meantime, i can deal with it, but that whistling tells me one thing fo sho....VAPOR LOCK.
A new cap would be nice, but not for $85.

 

Snag a used one on Ebay and rebuild it if needed. At some point water is going to find its way into the tank so long as you have a hole through the cap. What you have isn't vapor lock (fuel boiling to vapor in a fuel line), but negative pressure forming as the fuel exits the tank.

 

the reason it whistles is it doesn't know the words..........that's a old one
but really it draws air the same if the tank is full or empty......drill a 3/8 hole in it, then you'll know for sure

 

yeah....Potaytoe, potahtoe.

i had already drilled a small 1/6" hole in the green metal piece that holds the gasket on. but i did it on the opposite side of the check ball. that made it whistle. so i then rotated it 180 and put it right next to the check ball and that stopped the whistling. actually i just bought it the lyric sheet! i still need a new gasket from chacal tho. it will leak on my new paint job if i fill it up to the bottom of the filler tube, but i have to lean it over or gun it for that to happen