...To die at highway cruising speed?

I was rolling up the highway the other day, buzzing along in sixth, around 50mph for a mile or two and the bike sounded a little 'off' when I backed off the throttle. I downshifted and went WOT, bike felt fine. Upshifted again, cruised along for another mile at 50mph/6th gear, bike sounded wrong again.

Downshifted and went WOT, bike was bogging hard. No power when I opened the throttle, just "BWAAAHHHhhhh" -- So I screamed at the top of my lungs "We're going DOWN! Brace for impact! Mayday!" and pulled over, where the bike promptly sputtered out.

Wouldn't re-start, smelled fuel all over the place, nothing I could do would make the bike start again.

Bike rode fine for a day or two before that, perhaps it was the long-distance highway speed cruise that caused it. Similar thing happened once before, I diagnosed THAT to be a vacuum forming in the tank not allowing the fuel to siphon out, which was remedied by simply opening the gas cap, turning on the choke, and bike fired right back up after dying. Doesn't sound like the same thing I dealt with a few days ago.

Let's not recommend anything obvious -- running out of gas, main jet that may have fallen out, rode through an electromagnetic field generated by aliens... I've been through everything and ruled out most of the obvious.

Is it possible for a 250r to SLOWLY flood over the course of 3 miles of cruising until one cylinder started misfiring, filled up with gas, puddled in the pipe.. etc?

Bike felt like it was running perfectly on the way to work, not sure what happened on the way home.

Vapor Lock

/moved to new-gen tech area

(this gets a little tedious, can you please start the tech threads there in the first place? :))

bad gas.

Sorry alex, will do. Thanks guys.

Spark plug issue
IC ignitor (CDI) problem
Crankshaft sensor trouble
or
Ignition coil trouble

Is this the same problem as this other thread? http://www.ninjette.org/forums/showthread.php?t=165817

If your IC Ignitor took a dump on you, you've got no spark or the timing may be off. Either way the spinning engine is making a vacuum and drawing in fuel but not igniting it, thus the extreme flooding and the inability to start regardless of what you've done. Do IC ignitors go bad? Yes, they can and have. The fix?... replacement.

Does it only happen when you go several miles at a high speed? Or does it happen at any speed over the course of several miles?

Was the tank low at the time? How long ago did you last fill it?

Will it start now after sitting?

If the fuel was low, gas was old, or had some condensation, it's possible you are just sucking it into the carbs now. Drain the floatbowls and see what comes out.

You could also pull the plugs and take a look - are they black and sooty or light tan? Are they both the same?

Another possibility might be something stuck under the carb needle that didn't let the float close, overflowing the floatbowl and giving way too much gas to that cylinder.

Gas cap isn't venting properly I bet.

Go recreate the issue. Then open the tank and see if it starts up and runs normally

May have been simple vapor lock. I never opened the gas cap before trying to re-start it.

-verified good spark on both cylinders
-switched back to a smaller main jet
-have good plugs in it gapped to 0.7mm
-adjusted float height to 17.00mm (was barely off)
-cleaned the carbs (not dirty)
-drained the tank and filled with fresh 89oct
-replaced a broken throttle cable
-adjusted both cables/choke
-re-verified ALL hoses and vacuum lines are correct as per numerous diagrams

I've got everything back together and I'm about to start the bike and adjust the mixture screws again by listening to the rise/fall of idle while adjusting the screws after the bike has been fully warmed up.

Also read that idle screw adjustment can be tested by blipping the throttle. If it bogs, it's too rich. (Turn screw IN to lean out mixture) If blipping throttle makes idle go high and hang before settling, it's too lean. (Turn screw OUT to richen mixture.)

My next things to try if the bike isn't running right is (in the following order..)
-compression test
-battery test
-sync the carbs
-take apart carbs again and inspect diaphragm for tears/damage

Here we go, hopefully this bitch fires right up....

Was able to start the bike with choke, felt kinda weak -- firing on both cylinders because both pipes were hot.

Put the bike in gear, started moving forward but as soon as I gave it any kind of throttle to get moving it would just die out.

Going to change the oil now that it's hot and get the fuel-flooded-oil out of here.

Pulled a plug and it was nice light tan chocolate.

Bike starts and idles smoothly, but any kind of throttle input and it dies out immediately.

If I crack the throttle it tries to die out. If I open the throttle a tiny miniscule amount, it will pick up speed slowly and climb in RPM. This is with the bike sitting still.

Riding it is impossible for the above mentioned reasons.

Vacuum hoses on properly and sealed? No holes or cracks? It's common to mess that up when you're in and out of the carbs frequently. We all do it, I've done it.

Torn diaphragm maybe?

I'm not looking forward to tearing this all apart again.

No longer doing it for fun or experience..

Once you get it up to 5k or so does it act normal? Might be that the carbs are out sync. Had this problem a while ago and a good carb clean and sync took care of it.

I'm going to take this whole fking thing apart again.

Hello modifications, goodbye OEM reliability, hello finicky race horse.

FML. I'm into this for about the 10th time now.

Captain's Log, Stardate 0800 02.02.14

After draining the float bowls again and checking that both float levels were in sync, more water was discovered in the gas. After 2.56" of rainfall in a 24hr period, this is not surprising. Must've been water in the gas can before I filled it to bring home for the bike.

Drained the float bowls another 5 times apiece, watching water level drop with each flushing. Added seafoam to the gas tank, currently sitting with half-tank of 89octane with estimated water content >3%. DJ106 main is back in.

Bike fires up and idles fine, has re-gained power, minimal bogging upon WOT. Feels like it's 'fixed.'

Waiting for the rain to stop so I can take the bike out and get it up to temp to bring back into shop and adjust mixture screws for the final time. Once I burn through this half-tank of compromised fuel, I'll fill up with e-free 89oct and do some more testing with the DJ108 main.

At this rate I'll have everything dialed in by the time new tires arrive and can mount/balance them and call this bike "Done." :bounce:

Also disassembled gas tank cap, cleaned out some silicone the PO had apparently tried to fix the wheezing sound with, and widened the vent holes slightly. No more singing gas tank thus far.:dancecool:

On to the next project. Thanks guys.

EDIT -- it is now my understanding that when I first had bogging/trouble after extended highway cruising, it was simply vacuum in the fuel tank not allowing the gravity-feed fuel system to operate properly.

nice!!! Glad it was something as simple as a plugged hole and water in the gas. It's always good to know it worked out for someone with minimal work.

Don't worry so much about ruining OEM reliability with an aftermarket intake/exhaust. Once you get the initial rejetting done, the bike will be as reliable (if not more because you know the jetting is correct and you know how to work on it now) as it ever was with the stock setup. I've run exhaust/intake for a long time and never had issues associated with that.

No more singing gas tank thus far.

awwwww.... you muted her mating call. :(

Perhaps the moral here is to put dicking with the carbs down lower on the troubleshooting list.

Yeah but I suspect there is something more sinister going on.

Took the bike for a ride this morning, felt fine. Came back later in the day after a day of rain, didn't feel right. Given -- I am very very anal about running perfectly. Many people probably would have called it 'good enough' by now and given up.

However I live on a mountain -- 1k' elevation and below where I do my normal riding, and the "fun roads" are up near 9k' elevation. So far I haven't taken the bike above 2k', so elevation shouldn't be a factor in my issues. However I want this bike dialed in PERFECTLY before I head up there because I can't afford to cost 20 miles down hill or tow the bike again due to an elevation variable when other things aren't completely and 100% accounted for.

With that said --- there is something more sinister going on.

Bike was parked all day in the GARAGE, but separated only to the rain by a roof and screen door.

Riding this evening felt like the bike would misfire when I let off the throttle and coasted. That's precisely what it felt like going up the highway when all this started.

Then when I'd get back on the throttle, it would still be missing and then "catch", and full power again after a second or two.

What would cause a bike to misfire on one cylinder when I let off the throttle and coasted down from 7krpm?

And also -- is there any more precise way to set mixture screws than with the listening for misfire/adjustment or blipping throttle and listening for hang/bog once the throttle plate closes? I don't feel like I'm nailing the mixture screws like I want to. I wish there was a red light/green light fail-proof method of setting these. It's hard to hear/know when they are correct...

Very tempted to pull my AFR wideband gauge/sensor and stick it in the tailpipe... but that'd be quite a chore and not entirely sure it would help much with carb tuning.

Either I have something else wrong, or I just don't have the 'feel' required for carb tuning. This is starting to get to me.:doh:

I'd pay someone for help at this point but no one does this locally.

Oh and after draining a carb again -- I found a few tiny bubbles (water) condensed in the bottom of my clear fuel-cup. Might be my problem entirely... Wish it would fawking stop raining so I could tune this. 93% humidity today, and 93% humidity/rain every damn day for the entire next week.

Maybe my gas cap just isn't letting air into the tank fast enough.. I drilled the vents out a tiny bit, but every time I take the cap off the tank it sucks in air. Idle for 30 seconds, remove gas cap, and I can hear it suck in air. Not sure if that's normal.

Dear diary...

And also -- is there any more precise way to set mixture screws than with the listening for misfire/adjustment or blipping throttle and listening for hang/bog once the throttle plate closes? I don't feel like I'm nailing the mixture screws like I want to. I wish there was a red light/green light fail-proof method of setting these. It's hard to hear/know when they are correct...

Oh and after draining a carb again -- I found a few tiny bubbles (water) condensed in the bottom of my clear fuel-cup. Might be my problem entirely... Wish it would fawking stop raining so I could tune this. 93% humidity today, and 93% humidity/rain every damn day for the entire next week.

Maybe my gas cap just isn't letting air into the tank fast enough.. I drilled the vents out a tiny bit, but every time I take the cap off the tank it sucks in air. Idle for 30 seconds, remove gas cap, and I can hear it suck in air. Not sure if that's normal.

Dear diary...

Set the screws at 2 1/2 turns out, ride it a while, set them to 3 turns out, ride it a while - better or worse? If worse, go to 2 turns out and ride it a while.

If you didn't drain the tank completely, you can still have water in it. It will sit at the very bottom, and may not get drawn out completely even on reserve. Remove the tank and dump it out, then refill.

It shouldn't have any vacuum in the tank when opening the cap - I'd look into that.

Just pulled the tank, drained the gas, rinsed it twice with methanol, took apart and cleaned the petcock and tank cap again. Waiting for methanol/carb-cleaner to evaporate.

Going to replace the fuel filter and fuel lines with new replacements.

Carb cleaner sprayed into the fuel line on carb, drained float bowls again.

I think water in the fuel system is what's causing these issues. That and a tank cap that wasn't letting air into the tank.

If I put everything back together and still have problems I'm going to look into that "Idle enrichener" that I saw in a diagram with fuel/vacuum lines going to/from it.