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2008 TW with 3500 km on it, runs fine, ride at high speed 100 km/h. Pull clutch in, engine dies. Starts right up, runs fine, after a while happens again.

Yes, lots of gas in the tank.

-Never did a valve adjustment on it, but will do one soon

-Never changed the spark plug

It would be really bad to be stuck in the middle of nowhere.

Any ideas, please?

Thank you
 

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Low fuel flow rate from partially blocked petcock, needle and seat, filter, or kinked hose. Stopped up vent.
 

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Discussion Starter #3
Low fuel flow rate from partially blocked petcock, needle and seat, filter, or kinked hose. Stopped up vent.



To start with easy stuff:

-filter? are you referring to the air filter? I washed that about two weeks ago.

Is there a fuel filter on the TW?

-petcock, how do I check /clean that? Do I have to empty the gas tank completely and how do I clean the petcock?

-vent? that would be the tank vent? How do I clean that one?



Sorry for too many questions.

Thanks in advance.
 

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Like Qwerty said



If you take your oem gas cap off and hear a ppssst then vapor lock may be your culprit.



There is a strainer in the fuel tank (may be clogged)







Some grit may have got past this screen and clogged up the petcock valve or the carb In that case you will need to clean one of them out. http://tw200forum.co...-carb-cleaning/



That's why many of us use a 90d inline filter to protect the carb. http://www.rendergre...Fuel_Filter.htm

 

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My bike has started quitting at high speed; I'm thinking vapour lock. How do I check/clean my fuel/tank breather?



Thanks in advance,



Rob.



PS, it isn't fun when it happens on busy roads at around 60mph.....
 

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Rob, The obvious way to check is to immediately loosen the fuel cap. If its vent is blocked and you have negative pressure in the tank, you should 1. hear the whoosh of air entering the tank, or 2. be able to immediately start the bike with not problems.

On the other hand if you have some other fuel restriction (at top speed you may use fuel faster than it can run into the carb, it will be a bit harder to diagnose. I'd check all fuel filter and maybe even check to see if the flow from the petcock seems normal (i.e more than a drip). Thats my best guess for solutions or better symptoms for diagnosis.

Tom
 

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A TW cannot vapor lock. Vapor lock is gasoline evaporating in the fuel lines due to excess heat, then the vapors reach the fuel pump and the pump won't pump. TWs can draw a vacuum with a stopped up fuel vent.
 

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Hmm, interesting.



I might check the fuel tap filter.



Bike would suddenly cut out - not even a pop. First, it happened at an indicated 100km/h on the highway. Slowed, but didn't quite stop. I decided to take it easier, and it again happened at 95km/h; this time it took longer to start. Then 90, and it took a long time to start.



By then, I was almost home. Riding up to km/h the bike was then faultless.



I'm thinking starvation - from where is the question.
 

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Anyone able to provide any further assistance on this issue?



Tonight I finally had the chance to have a look at it, bike even does it after sitting on 65km/h now.



I only got to take the tank off and check fuel pressure. There's plenty, so I can rule out the fuel tap filter. Also, I don't run a fuel filter, so it can't be that.



I'm thinking my floats may have got out of whack, but it seems unlikely.



Anything else to check before I remove the carb and check the float level?



Thanks in advance.



Rob.
 

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Ok, here's how I'm going.



I checked the float level and it's about 10mm below the float gasket level.







When I look in the shop manual, it says to measure whilst the carb is off and upside down. Hopefully someone's measured is correctly when on the bike.



Can anyone confirm before I remove the carb? I wouldn't have thought the level would have been too low to hold half throttle.



Thanks, Rob.
 

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Even with the photo bing blurry I'm sure the fuel level is lower than spec. I think that carb would be sucking air at mid & high speeds.







Edit: Just looked in the maintenance manual... the older carb style spec is 7.5 to 8.5 mm below carb body edge. Still might be getting air in the jet at high speed with 10 mm.
 

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Well, the test was successful. Did maybe 100kms over a few days without a hitch.



Then, suddenly bike wouldn't want to start. Eventually got it to start and it just wants to die. Runs jerky and I have to keep the revs up. Lots of 'popping' from the exhaust.



Any ideas what it could be? I know it's best to look in the last place you touched, but I can't imagine it being the float again? Any help is appreciated.



Cheers, Rob.
 

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A TW cannot vapor lock. Vapor lock is gasoline evaporating in the fuel lines due to excess heat, then the vapors reach the fuel pump and the pump won't pump. TWs can draw a vacuum with a stopped up fuel vent.


On my gravity fed Buell I installed a large metal fuel filter. A short run on the freeway and it stopped. I figured out if I removed the fuel line and let the gas flow through it would run again for a while. Once I removed the metal filter it worked well. Vapor lock can happen w/o a fuel pump in line.



Getting back to the problem at hand, have you opened the idle mixture screw 2.5 turns?
 

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Vapor lock can only occur in a sealed system when fuel vaporizes under pressure. If fuel vaporizes in an open system like on a TW, the vapor is vented. Gravity will continue to pull fuel through any kind of air or vapor as long as the level of fuel in the source is higher than the top of the air or vapor in the system. Simple physics.



Now, if the fuel level in the source is lower than the air or vapor, no flow. That isn't vapor lock, that is air lock, which is different. Air lock occurs when a system is set up with a portion of it dependent on siphoning, and bubbles accumulate at the highest part of the liquid's path. Simple physics. I don't know how your Buell was set up, but if it had an air lock, it's probably because every time the needle opened in the carb a little air bubble made its way up the fuel line into the filter. Given enough little bubbles accumulating, an air bubble could easily break siphoning somewhere in the system. Kind of like a plumbing P-trap under a sink, but in reverse.



Anywho, is the bike in question running lean or rich? If it's running rich, turn the gas off while it is running, it will clean up, run fine for a minute, then die. If it is running lean, turn turn the gas off while it is running, it will not clean up and run fine, but it will still die.
 

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I don't know how your Buell was set up, but if it had an air lock, it's probably because every time the needle opened in the carb a little air bubble made its way up the fuel line into the filter. Given enough little bubbles accumulating, an air bubble could easily break siphoning somewhere in the system. Kind of like a plumbing P-trap under a sink, but in reverse.


Give me a nickel and I will let you have your way.
 
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