November 12th, 2019, 12:09 PM | #1 |
ninjette.org member
Name: Tom
Location: Kentucky
Join Date: Jun 2009 Motorcycle(s): None yet Posts: 13
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Ninja 250 Gas Petcock Use
A little background - I'm thinking about getting back into motorcycling after a hiatus of around 50 years! My last experience riding a motorcycle was as a teenager on a friend's 2-stroke "scrambler", which we rode on his grand-dad's farm. My plan is to take the MSF course, then, presuming I pass, go buy a low-powered motorcycle. I've sort of narrowed my selection down to either a 2008 - 2012 Ninja 250, or a 1988 - 2007 Ninja 250. Honestly, I'm leaning towards the pre-gen, as there are several features that I prefer over the newer model - center stand, valve adjustments by setscrew/lock-nut, temperature gauge, and the traditional gas petcock. (Really, the only thing that the newer ninja has going for it, in my opinion, is the styling of the bodywork.)
I've been looking at a BUNCH of YouTube videos, and have yet to see anyone explain how to use the fuel petcock on the pre-gen Ninja to manage the gas supply. Universally, everyone extols the virtue of the gas gauge on the new Ninja, and complain about visually opening the fill cap to verify their remaining fuel. The gas petcock is intended to provide the means to keep track of fuel usage, so if you don't know this works, it goes like this: 1. Before you start the bike up, presuming it has a full or mostly-full tank, turn the petcock to the "run" position. In "run", the taller of the two fuel pickup tubes in the tank is selected. 2. As you ride, eventually the level of gas in the tank will go down, until finally the top of the "run" fuel pickup tube will begin to uncover (intermittently due to the sloshing of fuel within the tank). At the time this happens the engine will begin to "sputter" as the supply of gas to the carburetor float bowls can't keep up with the demands of the engine. 3. Now, reach down by your left knee and switch the petcock to "reserve". This will de-select the "run" fuel pickup tube, and will instead select the "reserve" pickup tube, which is shorter. Now the engine can draw on the remaining fuel, maybe a quart or more, that is below the "run" pickup but still above the "reserve" pickup. This should be worth maybe 15 or 20 miles of riding - enough to get you to a gas station. It's good practice, whenever you shut off the engine, to switch the petcock to "off". Yes, I know that the petcock has a vacuum valve that will shut the fuel off when the engine stops, but this might fail and possibly overflow the carburetor float bowls, which could cause gasoline to eventually contaminate the crankcase oil and cause serious damage to the engine. So getting in the habit of switching the petcock to "off" on shut-down is a good habit to acquire. |
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November 12th, 2019, 12:22 PM | #2 |
Certifiable nontundrum
Name: Harper
Location: NC Milkshake stand
Join Date: Mar 2013 Motorcycle(s): 2013 SE NINJA 300 Posts: Too much.
MOTM - Sep '13, Sep '16
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Sweet post; welcome back to two wheels
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November 12th, 2019, 01:34 PM | #3 |
ninjette.org member
Name: Sergey
Location: Ontario, GTA
Join Date: Oct 2019 Motorcycle(s): Ninja ZZR250 (EX250H) Posts: 213
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On mine ZZR250 (EX250H7) I have no way of completely turn the petcock off as it seems. There are 3 positions On, PRI, Res. The first and third will allow the fuel through when the vacuum is present. The second will let it through without vacuum (priming). I am really missing the manual on, off, reserve thpe of valve.
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November 12th, 2019, 07:52 PM | #4 |
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MOTY - 2018, MOTM - Nov '17
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I use fully automatic new-gen petcock on my pre-gen. No gas-gauge, no reserve!
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November 13th, 2019, 01:10 PM | #5 | |
ninjette.org member
Name: Tom
Location: Kentucky
Join Date: Jun 2009 Motorcycle(s): None yet Posts: 13
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Quote:
I could see where the Prime position would be handy - just don't ever leave it in PRI after the engine starts. |
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November 13th, 2019, 02:18 PM | #6 | |
ninjette.org member
Name: Sergey
Location: Ontario, GTA
Join Date: Oct 2019 Motorcycle(s): Ninja ZZR250 (EX250H) Posts: 213
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Quote:
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November 14th, 2019, 04:33 PM | #7 |
Lucid, yet unaware.
Name: Gregg
Location: Virginia
Join Date: Aug 2011 Motorcycle(s): 2006 Goldwing; 2009 KLR-650; 2011 Ninja 250; 2010 FJR-1300 Posts: 173
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On my 2011, the petcock is has a setting for on and pri. If you turn it to pri, the petcock will bypass the vacuum and use the vent hose for air. You would do this to initially fill the bowls after draining them. In my case I have the carbs out to clean them because I let the bike sit too long. When I put the carbs back in I will fill the bowls using this method. After just a few seconds on pri (the fuel comes out pretty quick) switch to on. If the vacuum every failed, the carb has an overflow vent hose (the same air hose used when on pri) to vent the fuel out to the ground. I don’t see how it could end up in the crank case using this method. Also if you want to drain the tank (as in your are taking the tank off and you don’t want to manage the weight) remove the supply line from the carb and route the hose to a catch container. Switch the petcock to pri and out comes the fuel from the tank. If you open the gas cap and really let it breathe the fuel will come out pretty fast.
Hope this helps.
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2011 Ninja 250, 2010 FJR-1300, 2009 KLR-650, and 2006 Goldwing IBA #485, Goldwing Darkside #646 http://va-ldrider.blogspot.com |
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November 15th, 2019, 09:27 AM | #8 | |
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MOTY - 2018, MOTM - Nov '17
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Huh?!???
Quote:
1. remove tank from bike 2. disconnect ALL hoses from petcock, vacuum & fuel 3. turn petcock to PRI What happens? It flows fuel out fuel-port no matter what! No hoses, no vacuum needed. What Tom and Sergey was pointing out is that in cases where float-valves leak and not stop fuel-flow, having petcock on PRI and flowing fuel constantly can cause fuel to leak out carbs and down into crankcase. That's how my 2008 got hydro-locked and snapped couple of teeth off starter ring-gear. https://www.ninjette.org/forums/showthread.php?t=300194 |
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November 15th, 2019, 02:52 PM | #9 | |
ninjette.org member
Name: Sergey
Location: Ontario, GTA
Join Date: Oct 2019 Motorcycle(s): Ninja ZZR250 (EX250H) Posts: 213
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Quote:
If so I do not think it's an overflow vent hose. It is the atmospheric pressure sensor and it's level is above the jets in the venturi. If the petcock flows gas and the float valves are messed up the fuel will flow through the jets (pilot and needle) into the intake, then down into the cylinders and into the crankcase. I could be wrong but I am not aware of any alternative overflow vent hoses. |
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November 15th, 2019, 04:22 PM | #10 |
Lucid, yet unaware.
Name: Gregg
Location: Virginia
Join Date: Aug 2011 Motorcycle(s): 2006 Goldwing; 2009 KLR-650; 2011 Ninja 250; 2010 FJR-1300 Posts: 173
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In the Kawasaki Service Manual for my model (2011), under the appendix for house routing pages 17-28 and 29 it states “Run the carburetor vent hose between the air cleaner box and battery”. That is my reference for it being a vent hose. If it isn’t venting fuel to ground, what is it venting?
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2011 Ninja 250, 2010 FJR-1300, 2009 KLR-650, and 2006 Goldwing IBA #485, Goldwing Darkside #646 http://va-ldrider.blogspot.com |
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November 15th, 2019, 06:07 PM | #11 |
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It’s vent hose for pressure and vapour. But liquid fuel can’t possibly flow out of that hose unless bike is upside down. It’s similar to tank vent hose where it’s well above fuel level and its main purpose is to vent away fuel-vapour on hot days to prevent pressure build-up. And that vent-hose doesn’t connect to petcock in any way.
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November 15th, 2019, 07:48 PM | #12 | |
ninjette.org member
Name: Sergey
Location: Ontario, GTA
Join Date: Oct 2019 Motorcycle(s): Ninja ZZR250 (EX250H) Posts: 213
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Quote:
If the was no equalizing hose provided the pressure above the bowls would depend on the temperature of the gas a lot. That would mess up all the tuning of the carb and the richness of the mixture would go up due to temperature increase and down with the temperature decrease. The carb tuning would be all over the place. |
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November 16th, 2019, 02:01 PM | #13 |
Lucid, yet unaware.
Name: Gregg
Location: Virginia
Join Date: Aug 2011 Motorcycle(s): 2006 Goldwing; 2009 KLR-650; 2011 Ninja 250; 2010 FJR-1300 Posts: 173
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Got it. That makes a lot of sense. Thanks for setting me straight.
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2011 Ninja 250, 2010 FJR-1300, 2009 KLR-650, and 2006 Goldwing IBA #485, Goldwing Darkside #646 http://va-ldrider.blogspot.com |
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November 17th, 2019, 07:06 AM | #14 |
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in most simple terms....the vent hose is venting to atmosphere.....think of your finger over the end of a liquid filled straw, liquid unable to flow with gravity. Same basic concept.
Also doubles as "overflow" hose too, a more extreme duty....we won't even go there.
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gordon@customcarbservices.com Custom Carb Service www.customcarbservices.com |
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November 17th, 2019, 02:06 PM | #15 |
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Mechanical computer, heh, heh...
Hundreds of years later we developed technology to actually build Babbage's machine... and it worked perfectly! |
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November 18th, 2019, 10:23 AM | #16 | |
ninjette.org member
Name: Brian
Location: Blacksburg
Join Date: Jul 2017 Motorcycle(s): 2003 Ninja 250R Posts: 32
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Quote:
I don't understand your second point about oil contamination though. The only way it could get into the oil is through a combination of bad rings/seals and gas accumulating in the cylinders via a chronically over-rich condition, but the latter would be unlikely as the excess gas would get blown out of the exhaust at the completion of each power stroke. If the former happened, the bike would run poorly and would show outward signs of that. Maybe I'm missing something though. |
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November 18th, 2019, 08:05 PM | #17 |
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The second effect takes place over time when bike is not running and I’ve seen it numerous times.
With petcock not off for whatever reason, combined with leaky float valves, petrol level fills up float bowl and continues to rise upwards. It flows out of jets, fuel-circuits and out into venturi of carbs. It dribbles down throat of carbs and down intake tract of engine. Due to extreme duration of cams, it’s very likely intake valves will be slightly or fully open. Petrol is much, much less viscous than oil, so it has no problems getting past rings. And since there’s no combustion-pressure pushing rings outwards, ring-seal against cylinder wall isn’t that tight in non-running engine. So overnight, or over course of days, petrol continues to flow from carbs past rings and into crankcase. It continues to rise and displaces air until entire crankcase is full. You’ve got hydro-locked engine because pistons can’t move down and compress fluid. There’s many cases of this happening, just do web search. I had it happen to my 2008 250. I picked up an ‘86 Interceptor for free in ‘88 because owner though he seized engine. Starter just buzzed and complained. Pushing-starting just dragged back wheel and left skidmark, yup seized engine. I started removing engine to swap in another. When I opened oil-drain to make it lighter, over 3-gallons of oil & petrol mix rushed out and overflowed my 3-gal drain pan. So yes, leaky petcock combined with leaky float valves can hydro-lock engine. If you’re unlucky enough to have cylinders halfway down, they may be able to complete 1/2 compression stroke and actually ignite. Then they stop suddenly halfway down and snap some rods and shove remnants through side of engine! |
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December 10th, 2019, 02:15 PM | #18 |
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Name: Kyle
Location: Kansas city
Join Date: Apr 2014 Motorcycle(s): 02 Aprilia RS70 97 Ninja 250 Posts: 53
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December 10th, 2019, 03:04 PM | #19 |
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New-gen petcock is vacuum-operated just like pre-gen. Has PRI position for draining tank easily. It's also compact and fits fully under tank. Doesn't have knob to bump into tank like aftermarket petcocks that are too short to clear side of tank.
However, lack of reserve means you don't get warning when running low. I use mileage of 230-250 miles as time to fill up depending upon how hard I've been riding. |
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